text:
Diffusion magnetic resonance HE MAGNETIC resonance application that the rest of this thesis will be concerned with is that
Clayden, Jonathan D.
4 Diffusion magnetic resonance imaging T HE MAGNETIC resonance application that the rest of this thesis will be concerned with is that of diffusion magnetic resonance imaging (dMRI). This chapter provides a brief description of diffusion and how it can be examined in the brain with dMRI. Mathematical
Four-Dimensional Magnetic Resonance Imaging Using Axial Body Area as Respiratory Surrogate: Initial Patient Results
Yang, Juan; Cai, Jing; Wang, Hongjun; Chang, Zheng; Czito, Brian G.; Bashir, Mustafa R.; Yin, Fang-Fang
Purpose To evaluate the feasibility of a retrospective binning technique for 4-dimensional magnetic resonance imaging (4D-MRI) using body area (BA) as a respiratory surrogate. Methods and Materials Seven patients with hepatocellular carcinoma (4 of 7) or liver metastases (3 of 7) were enrolled in an institutional review board-approved prospective study. All patients were simulated with both computed tomography (CT) and MRI to acquire 3-dimensinal and 4D images for treatment planning. Multiple-slice multiple-phase cine-MR images were acquired in the axial plane for 4D-MRI reconstruction. Image acquisition time per slice was set to 10-15 seconds. Single-slice 2-dimensinal cine-MR images were also acquired across the center of the tumor in orthogonal planes. Tumor motion trajectories from 4D-MRI, cine-MRI, and 4D-CT were analyzed in the superior–inferior (SI), anterior–posterior (AP), and medial–lateral (ML) directions, respectively. Their correlation coefficients (CC) and differences in tumor motion amplitude were determined. Tumor-to-liver contrast-to-noise ratio (CNR) was measured and compared between 4D-CT, 4D-MRI, and conventional T2-weighted fast spin echo MRI. Results The means (±standard deviations) of CC comparing 4D-MRI with cine-MRI were 0.97 ± 0.03, 0.97 ± 0.02, and 0.99 ± 0.04 in SI, AP, and ML directions, respectively. The mean differences were 0.61 ± 0.17 mm, 0.32 ± 0.17 mm, and 0.14 ± 0.06 mm in SI, AP, and ML directions, respectively. The means of CC comparing 4D-MRI and 4D-CT were 0.95 ± 0.02, 0.94 ± 0.02, and 0.96 ± 0.02 in SI, AP, and ML directions, respectively. The mean differences were 0.74 ± 0.02 mm, 0.33 ± 0.13 mm, and 0.18 ± 0.07 mm in SI, AP, and ML directions, respectively. The mean tumor-to-tissue CNRs were 2.94 ± 1.51, 19.44 ± 14.63, and 39.47 ± 20.81 in 4D-CT, 4D-MRI, and T2-weighted MRI, respectively. Conclusions The preliminary evaluation of our 4D-MRI technique results in oncologic patients demonstrates its potential usefulness to accurately measure tumor respiratory motion with improved tumor CNR compared with 4D-CT. PMID:24444759
Pediatric magnetic resonance imaging
Cohen, M.D.
This book defines the current clinical potential of magnetic resonance imaging and focuses on direct clinical work with pediatric patients. A section dealing with the physics of magnetic resonance imaging provides an introduction to enable clinicians to utilize the machine and interpret the images. Magnetic resonance imaging is presented as an appropriate imaging modality for pediatric patients utilizing no radiation.
Magnetic resonance imaging: prologue
Jacobson, H.G.
Magnetic resonance imaging is becoming an increasingly important method of diagnostic imaging. This new method can compete with computed tomography for several applications, especially those involving the central nervous system. Magnetic resonance imaging is rapidly evolving, and several advances can be anticipated in the near future.
SU-E-J-192: Verification of 4D-MRI Internal Target Volume Using Cine MRI
Lafata, K; Czito, B; Palta, M; Bashir, M; Yin, F; Cai, J [Duke University Medical Center, Durham, NC (United States)
Purpose: To investigate the accuracy of 4D-MRI in determining the Internal Target Volume (ITV) used in radiation oncology treatment planning of liver cancers. Cine MRI is used as the standard baseline in establishing the feasibility and accuracy of 4D-MRI tumor motion within the liver. Methods: IRB approval was obtained for this retrospective study. Analysis was performed on MR images from four patients receiving external beam radiation therapy for liver cancer at our institution. Eligible patients received both Cine and 4D-MRI scans before treatment. Cine images were acquired sagittally in real time at a slice bisecting the tumor, while 4D images were acquired volumetrically. Cine MR DICOM headers were manipulated such that each respiratory frame was assigned a unique slice location. This approach permitted the treatment planning system (Eclipse, Varian Medical Systems) to recognize a complete respiratory cycle as a "volume", where the gross tumor was contoured temporally. Software was developed to calculate the union of all frame contours in the structure set, resulting in the corresponding plane of the ITV projecting through the middle of the tumor, defined as the Internal Target Area (ITA). This was repeated for 4D-MRI, at the corresponding slice location, allowing a direct comparison of ITAs obtained from each modality. Results: Four patients have been analyzed. ITAs contoured from 4D-MRI correlate with contours from Cine MRI. The mean error of 4D values relative to Cine values is 7.67 +/? 2.55 %. No single ITA contoured from 4D-MRI demonstrated more than 10.5 % error compared to its Cine MRI counterpart. Conclusion: Motion management is a significant aspect of treatment planning within dynamic environments such as the liver, where diaphragmatic and cardiac activity influence plan accuracy. This small pilot study suggests that 4D-MRI based ITA measurements agree with Cine MRI based measurements, an important step towards clinical implementation. NIH 1R21CA165384-01A1.
Stark, D.D.; Bradley, W.G. Jr.
The authors present a review of magnetic resonance imaging. Many topics are explored from instrumentation, spectroscopy, blood flow and sodium imaging to detailed clinical applications such as the differential diagnosis of multiple sclerosis or adrenal adenoma. The emphasis throughout is on descriptions of normal multiplanar anatomy and pathology as displayed by MRI.
Breast magnetic resonance imaging.
Johnson, Marlene M
Mammography has long been considered the gold standard for screening breast cancer. Although it reduces the risk of breast cancer mortality by enabling early diagnosis, it does not detect all breast cancers. Numerous breast imaging technologies are emerging as effective adjunctive diagnostic tools when mammography results are negative or inconclusive. Contrast-enhanced magnetic resonance (CE-MR) imaging, in particular, has demonstrated a high sensitivity and has proven to be most effective, especially with patients at high risk for developing breast cancer. This article discusses the clinical applications for breast MR imaging, use of CE-MR for breast cancer detection, and other emerging breast imaging technologies. PMID:22267704
Magnetic resonance imaging methodology
Ewald Moser; Andreas Stadlbauer; Christian Windischberger; Harald H. Quick; Mark E. Ladd
Introduction Magnetic resonance (MR) methods are non-invasive techniques to provide detailed, multi-parametric information on human anatomy,\\u000a function and metabolism. Sensitivity, specificity, spatial and temporal resolution may, however, vary depending on hardware\\u000a (e.g., field strength, gradient strength and speed) and software (optimised measurement protocols and parameters for the various\\u000a techniques). Furthermore, multi-modality imaging may enhance specificity to better characterise complex disease patterns.
Diffusion MRI simulation with the Virtual Imaging Platform Lihui Wang, Sorina Camarasu-Pop, Tristan Glatard, Yue-Min Zhu, Isabelle E. Magnin
Paris-Sud XI, Université de
1 Diffusion MRI simulation with the Virtual Imaging Platform Lihui Wang, Sorina Camarasu of in vivo human heart. Diffusion magnetic resonance imaging (dMRI) is one of the most potential techniques and with influence of MRI scanner noise and artifacts, it is difficult to evaluate how well the diffusion
Molecular magnetic resonance imaging
Hengerer, A; Grimm, J
Molecular MRI (mMRI) is a special implementation of Molecular Imaging for the non-invasive visualisation of biological processes at the cellular and molecular level. More specifically, mMRI comprises the contrast agent-mediated alteration of tissue relaxation times for the detection and localisation of molecular disease markers (such as cell surface receptors, enzymes or signaling molecules), cells (e.g. lymphocytes, stem cells) or therapeutic drugs (e.g. liposomes, viral particles). MRI yields topographical, anatomical maps; functional MRI (fMRI) provides rendering of physiologic functions and magnetic resonance spectroscopy (MRS) reveals the distribution patterns of some specific metabolites. mMRI provides an additional level of information at the molecular or cellular level, thus extending MRI further beyond the anatomical and physiological level. These advances brought by mMRI are mandatory for MRI to be competitive in the age of molecular medicine. mMRI is already today increasingly used for research purposes, e.g. to facilitate the examination of cell migration, angiogenesis, apoptosis or gene expression in living organisms. In medical diagnostics, mMRI will pave the way toward a significant improvement in early detection of disease, therapy planning or monitoring of outcome and will therefore bring significant improvement in the medical treatment for patients. In general, Molecular Imaging demands high sensitivity equipment, capable of quantitative measurements to detect probes that interact with targets at the pico- or nanomolar level. The challenge to detect such sparse targets can be exemplified with cell surface receptors, a common target for molecular imaging. At high expression levels (bigger than 106 per cell) the receptor concentration is approx. 1015 per ml, i.e. the concentration is in the micromole range. Many targets, however, are expressed in even considerably lower concentrations. Therefore the most sensitive modalities, namely nuclear imaging (PET and SPECT) have always been at the forefront of Molecular Imaging, and many nuclear probes in clinical use today are already designed to detect molecular mechanisms (such as FDG, detecting high glucose metabolism). In recent years however, Molecular Imaging has commanded attention from beyond the field of nuclear medicine. Further imaging modalities to be considered for molecular imaging primarily include optical imaging, MRI and ultrasound. PMID:21614236
Stray Field Magnetic Resonance Imaging
K. Zick
In many applications of magnetic resonance imaging large linewidths means that to achieve useful resolution in the image large magnetic field gradients should be employed. This paper outlines the principles of stray field imaging that utilises the large gradients intrinsic to the fringe field of superconducting solenoidal magnets. Examples of images from strongly broadened everyday objects are given.
MRI (Magnetic Resonance Imaging)
... Criteria for Significant Risk Investigations of Magnetic Resonance Diagnostic Devices - Guidance for Industry and Food and Drug Administration ... the Submission Of Premarket Notifications for Magnetic Resonance Diagnostic Devices (Withdrawn) A Primer on Medical Device Interactions with ...
Breast Magnetic Resonance Imaging Techniques
Nola M. Hylton
Magnetic resonance imaging (MRI) of the breast is finding wider clinical application as an adjunct diagnostic procedure to mammography and ultrasound. Because of its high sensitivity and effectiveness in dense breast tissue, MRI can be a valuable addition to the diagnostic work up of a patient with a breast abnormality or biopsy-proven cancer. The major limitation of breast MRI is
Low field magnetic resonance imaging
Pines, Alexander (Berkeley, CA); Sakellariou, Dimitrios (Billancourt, FR); Meriles, Carlos A. (Fort Lee, NJ); Trabesinger, Andreas H. (London, GB)
A method and system of magnetic resonance imaging does not need a large homogenous field to truncate a gradient field. Spatial information is encoded into the spin magnetization by allowing the magnetization to evolve in a non-truncated gradient field and inducing a set of 180 degree rotations prior to signal acquisition.
Magnetic Resonance Imaging of Electrolysis.
Meir, Arie; Hjouj, Mohammad; Rubinsky, Liel; Rubinsky, Boris
This study explores the hypothesis that Magnetic Resonance Imaging (MRI) can image the process of electrolysis by detecting pH fronts. The study has relevance to real time control of cell ablation with electrolysis. To investigate the hypothesis we compare the following MR imaging sequences: T1 weighted, T2 weighted and Proton Density (PD), with optical images acquired using pH-sensitive dyes embedded in a physiological saline agar solution phantom treated with electrolysis and discrete measurements with a pH microprobe. We further demonstrate the biological relevance of our work using a bacterial E. Coli model, grown on the phantom. The results demonstrate the ability of MRI to image electrolysis produced pH changes in a physiological saline phantom and show that these changes correlate with cell death in the E. Coli model grown on the phantom. The results are promising and invite further experimental research. PMID:25659942
Interventional Cardiovascular Magnetic Resonance Imaging
Saikus, Christina E.; Lederman, Robert J.
Cardiovascular magnetic resonance (CMR) combines excellent soft-tissue contrast, multiplanar views, and dynamic imaging of cardiac function without ionizing radiation exposure. Interventional cardiovascular magnetic resonance (iCMR) leverages these features to enhance conventional interventional procedures or to enable novel ones. Although still awaiting clinical deployment, this young field has tremendous potential. We survey promising clinical applications for iCMR. Next, we discuss the technologies that allow CMR-guided interventions and, finally, what still needs to be done to bring them to the clinic. PMID:19909937
Magnetic Resonance Imaging and Magnetic Resonance Spectroscopy in Dementias
Hsu, Yuan-Yu; Du, An-Tao; Schuff, Norbert; Weiner, Michael W.
This article reviews recent studies of magnetic resonance imaging and magnetic resonance spectroscopy in dementia, including Alzheimer's disease, frontotemporal dementia, dementia with Lewy bodies, idiopathic Parkinson's disease, Huntington's disease, and vascular dementia. Magnetic resonance imaging and magnetic resonance spectroscopy can detect structural alteration and biochemical abnormalities in the brain of demented subjects and may help in the differential diagnosis and early detection of affected individuals, monitoring disease progression, and evaluation of therapeutic effect. PMID:11563438
Magnetic resonance imaging of acquired cardiac disease.
Carrol, C L; Higgins, C B; Caputo, G R
Over the last 15 years, advances in magnetic resonance imaging techniques have increased the accuracy and applicability of cardiovascular magnetic resonance imaging. These advances have improved the utility of magnetic resonance imaging in evaluating cardiac morphology, blood flow, and myocardial contractility, all significant diagnostic features in the evaluation of the patient with acquired heart disease. Utilization of cardiovascular magnetic resonance imaging has been limited, primarily due to clinical reliance upon nuclear scintigraphy and echocardiography. Recent developments in fast and ultrafast imaging should continue to enhance the significance of magnetic resonance imaging in this field. Widespread use of magnetic resonance imaging in the evaluation of the cardiovascular system will ultimately depend upon its maturation into a comprehensive, noninvasive imaging technique for the varying manifestations of acquired heart disease, including cardiomyopathy, ischemic heart disease, and acquired valvular disease. Images PMID:8792545
Basics of magnetic resonance imaging
Oldendorf, W.; Oldendorf, W. Jr.
Beginning with the behavior of a compass needle in a magnetic field, this text uses analogies from everyday experience to explain the phenomenon of nuclear magnetic resonance and how it is used for imaging. Using a minimum of scientific abbreviations and symbols, the basics of tissue visualization and characterization are presented. A description of the various types of magnets and scanners is followed by the practical advantages and limitations of MRI relative to x-ray CT scanning.
Instrumentation for parallel magnetic resonance imaging
Brown, David Gerald
Parallel magnetic resonance (MR) imaging may be used to increase either the throughput or the speed of the MR imaging experiment. As such, parallel imaging may be accomplished either through a "parallelization" of the MR experiment, or by the use...
Image-relayed corner cube ring resonator
C. C. Shih; G. J. Linford; S. W. Quon; A. J. Schmit
An image-relayed corner-cube ring free electron laser (FEL) resonator has been investigated theoretically and experimentally. The laser beam is outcoupled from the resonator by using an annular 'scraper' mirror which is image-relayed to the FEL wiggler by two intracavity telescopes of unequal magnifications. The resulting FEL resonator has significant advantages over both conventional and grazing incidence resonators owing to drastically
Magnetic resonance imaging: Principles and applications
Kean, D.; Smith, M.
This text covers the physics underlying magnetic resonance (MR) imaging; pulse sequences; image production; equipment; aspects of clinical imaging; and the imaging of the head and neck, thorax, abdomen and pelvis, and musculoskeletal system; and MR imaging. The book provides about 150 examples of MR images that give an overview of the pathologic conditions imaged. There is a discussion of the physics of MR imaging and also on the spin echo.
Nitinol in magnetic resonance imaging.
Melzer; Michitsch; Konak; Schaefers; Bertsch, Th
Surgical and interventional instruments as well as implants can cause significant magnetic resonance image (MRI) artifacts. The artifacts can be used to visualize instruments, cannulae, guide wires, catheters during interventional MRI and Nitinol devices have proven to be useful for MRI procedures. Diagnostic imaging is often compromised in the area of an implant. Complete vanishing of signals occurs in close proximity or inside implants. The paper presents a fundamental evaluation of MRI artifact of Nitinol devices such as Stents, Vena Cava Filter, heart defect closure devices, cannulae, guide wire, localizer, anastomosis device, etc. in a 1.0 Tesla magnetic field. The American Society for Testing Materials (ASTM) recommendations for selection of sequences and test setup were used but the results of this paper are not sufficient for FDA approval. PMID:16754135
Localized diffusion magnetic resonance micro-imaging of the live mouse brain.
Wu, Dan; Reisinger, Dominik; Xu, Jiadi; Fatemi, S Ali; van Zijl, Peter C M; Mori, Susumu; Zhang, Jiangyang
High-resolution diffusion MRI (dMRI) is useful for resolving complex microstructures in the mouse brain, but technically challenging for in vivo studies due to the long scan time. In this study, selective excitation and a three-dimensional fast imaging sequence were used to achieve in vivo high-resolution dMRI of the mouse brain at 11.7Tesla. By reducing the field of view using spatially selective radio frequency pulses, we were able to focus on targeted brain structures and acquire high angular resolution diffusion imaging (HARDI) data at an isotropic resolution of 0.1mm and 30 diffusion encoding directions in approximately 1h. We investigated the complex tissue microstructures of the mouse hippocampus, cerebellum, and several cortical areas using this localized dMRI approach, and compared the results with histological sections stained with several axonal and dendritic markers. In the mouse visual cortex, the results showed predominately radially arranged structures in an outer layer and tangentially arranged structures in an inner layer, similar to observations from postmortem human brain specimens. PMID:24440780
Artifacts in magnetic resonance imaging.
Krupa, Katarzyna; Bekiesi?ska-Figatowska, Monika
Artifacts in magnetic resonance imaging and foreign bodies within the patient's body may be confused with a pathology or may reduce the quality of examinations. Radiologists are frequently not informed about the medical history of patients and face postoperative/other images they are not familiar with. A gallery of such images was presented in this manuscript. A truncation artifact in the spinal cord could be misinterpreted as a syrinx. Motion artifacts caused by breathing, cardiac movement, CSF pulsation/blood flow create a ghost artifact which can be reduced by patient immobilization, or cardiac/respiratory gating. Aliasing artifacts can be eliminated by increasing the field of view. An artificially hyperintense signal on FLAIR images can result from magnetic susceptibility artifacts, CSF/vascular pulsation, motion, but can also be found in patients undergoing MRI examinations while receiving supplemental oxygen. Metallic and other foreign bodies which may be found on and in patients' bodies are the main group of artifacts and these are the focus of this study: e.g. make-up, tattoos, hairbands, clothes, endovascular embolization, prostheses, surgical clips, intraorbital and other medical implants, etc. Knowledge of different types of artifacts and their origin, and of possible foreign bodies is necessary to eliminate them or to reduce their negative influence on MR images by adjusting acquisition parameters. It is also necessary to take them into consideration when interpreting the images. Some proposals of reducing artifacts have been mentioned. Describing in detail the procedures to avoid or limit the artifacts would go beyond the scope of this paper but technical ways to reduce them can be found in the cited literature. PMID:25745524
Contrast-enhanced dynamic magnetic resonance imaging of the rat kidney.
Fransen, R; Muller, H J; Boer, W H; Nicolay, K; Koomans, H A
This study was designed to assess whether contrast-enhanced dynamic 1H magnetic resonance imaging (DMRI) can be used to detect the effects of the loop diuretic furosemide and the vasoactive peptide angiotensin II on tubular water reabsorption in the rat kidney. A bolus of gadolinium-DTPA-dimeglumine (Gd-DTPA) (0.025 or 0.1 mmol/kg) was used as a contrast agent. The signal intensity in the magnetic resonance images relative to the precontrast signal intensity (RSI) was assessed as a function of time in the cortex and medulla. In the cortex, no differences were observed between high and low bolus injection, and between different treatment groups and controls. In the medulla, RSI patterns were different between high and low bolus, with the high bolus showing lower RSI values, because of T2 shortening at high Gd-DTPA concentrations. No difference was observed between controls and angiotensin II-infused animals. This is in line with the finding that angiotensin II did not alter medullary water reabsorption, as evidenced by unchanged urine flow and osmolality compared with controls. Medullary RSI patterns during furosemide infusion differed markedly from controls, in a manner suggesting that a lower concentration of Gd-DTPA was present compared with controls. This agrees with the well-known inhibiting effect of furosemide on medullary water reabsorption. It was concluded that, with the method used, small concentration differences of Gd-DTPA in the cortex resulting from small changes of plus or minus 20% in tubular water reabsorption, previously found to be present by direct micropuncture measurements, cannot be detected in rats. However, large changes in renal concentrating ability do result in different RSI patterns in the medulla. PMID:8704108
Near Infrared Surface Plasmon Resonance Phase Imaging and Nanoparticle-Enhanced Surface Plasmon Resonance Phase Imaging
Near Infrared Surface Plasmon Resonance Phase Imaging and Nanoparticle-Enhanced Surface Plasmon: The techniques of surface plasmon resonance-phase imaging (SPR-PI) and nanoparticle-enhanced SPR-PI have been tool for biological researchers throughout the world.1,2 Surface plasmon resonance imaging (SPRI
Ferromagnetic Resonance Imaging with Magnetic Resonance Force Microscopy
NASA Astrophysics Data System (ADS)
Pelekhov, Denis
Magnetic resonance force microscopy achieves very high resolution three-dimensional imaging capabilities of magnetic resonance imaging by taking advantage of very high sensitivity mechanical force detection. This enables non-contacting, microscopic studies and imaging of a broad range of materials. As a consequence of the strong interactions between spins, the assumptions underlying conventional MRI are not applicable to FMR imaging. However, using a new approach to localizing the resonant volume in an FMR measurement founded on the strong, nonuniform magnetic field of the micromagnetic probe tip, we have demonstrated scanned probe Ferromagnetic Resonance (FMR) imaging [1]. The scanned probe FMR images obtained in patterned ferromagnetic films are well explained by detailed numerical modeling. In addition to illuminating the mechanisms underlying localized FMR, the model provides the basis for submicron scanned probe FMR imaging of films and buried ferromagnetic elements. This work was supported by the U.S. Department of Energy through Grant No. DE-FG02-03ER46054. [1] ``Local Ferromagnetic Resonance Imaging with Magnetic Resonance Force Microscopy,'' Yu. Obukhov, D.V. Pelekhov, J. Kim, P. Banerjee, I. Martin, E. Nazaretski, R. Movshovich, S. An, T.J. Gramila, S. Batra, and P. C. Hammel, Phys. Rev. Lett. 100(19), 197601 (2008).
Gradient characterization in magnetic resonance imaging
Cheng, Joseph Yitan
Special magnetic resonance (MR) scans, such as spiral imaging and echo-planar imaging, require speed and gradient accuracy while putting high demands on the MR gradient system that may cause gradient distortion. Additionally, ...
Manual of clinical magnetic resonance imaging
Heiken, J.P.; Glazer, H.S.; Lee, J.K.T.; Murphy, W.A.; Gado, M.
This work is a guide to conducting magnetic resonance imaging (MRI) examinations. The manual presents specific imaging protocols for various MRI examinations of the body. An introductory section describes the physical principles and techniques of magnetic resonance imaging and describes the most commonly encountered artifacts. Guidelines are offered for selecting imaging protocols and conducting examinations of the head, spine, neck, chest, cardiovascular system, abdomen, pelvis, musculoskeletal system, and breast.
Functional Magnetic Resonance Imaging and Pediatric Anxiety
ERIC Educational Resources Information Center
Pine, Daniel S.; Guyer, Amanda E.; Leibenluft, Ellen; Peterson, Bradley S.; Gerber, Andrew
The use of functional magnetic resonance imaging in investigating pediatric anxiety disorders is studied. Functional magnetic resonance imaging can be utilized in demonstrating parallels between the neural architecture of difference in anxiety of humans and the neural architecture of attention-orienting behavior in nonhuman primates or rodents.…
Polarimetric surface plasmon resonance imaging biosensor
Paris-Sud XI, Université de
Polarimetric surface plasmon resonance imaging biosensor Aurélien Duval,1, * Aude Laisné,2 Denis.6680, 310.6860, 110.5405. Surface plasmon resonance (SPR) biosensors are be- ing increasingly used of capturing TM-polarized images of the biosensor's surface, fol- lowing two orthogonal planes of incidence
Imaging agents for in vivo magnetic resonance and scintigraphic imaging
Engelstad, Barry L. (Orinda, CA); Raymond, Kenneth N. (Berkeley, CA); Huberty, John P. (Corte Madera, CA); White, David L. (Oakland, CA)
Methods are provided for in vivo magnetic resonance imaging and/or scintigraphic imaging of a subject using chelated transition metal and lanthanide metal complexes. Novel ligands for these complexes are provided.
Imaging agents for in vivo magnetic resonance and scintigraphic imaging
Engelstad, B.L.; Raymond, K.N.; Huberty, J.P.; White, D.L.
Methods are provided for in vivo magnetic resonance imaging and/or scintigraphic imaging of a subject using chelated transition metal and lanthanide metal complexes. Novel ligands for these complexes are provided. No Drawings
Parallel magnetic resonance imaging: characterization and comparison
Rane, Swati Dnyandeo
. Echo Planar Imaging (EPI) . . . . . . . . . . . . 11 b.FastSpinEcho(FSE) ............... 12 c. OtherPulseSequences ............... 14 2. ParallelImaging ..................... 14 III PARALLEL MAGNETIC RESONANCE IMAGING ....... 15 A...-SMASH (VD-AUTO-SMASH) . . 22 H.GRAPPA ........................... 23 I. SPACERIP.......................... 24 J. SingleEchoAcquisition(SEA)................ 24 IV CHARACTERIZATION AND COMPARISON OF PARAL- LEL MRI TECHNIQUES ..................... 26 vi CHAPTER...
Stepped Impedance Resonators for High Field Magnetic Resonance Imaging
Akgun, Can E.; DelaBarre, Lance; Yoo, Hyoungsuk; Sohn, Sung-Min; Snyder, Carl J.; Adriany, Gregor; Ugurbil, Kamil; Gopinath, Anand; Vaughan, J. Thomas
Multi-element volume radio-frequency (RF) coils are an integral aspect of the growing field of high field magnetic resonance imaging (MRI). In these systems, a popular volume coil of choice has become the transverse electromagnetic (TEM) multi-element transceiver coil consisting of microstrip resonators. In this paper, to further advance this design approach, a new microstrip resonator strategy in which the transmission line is segmented into alternating impedance sections referred to as stepped impedance resonators (SIRs) is investigated. Single element simulation results in free space and in a phantom at 7 tesla (298 MHz) demonstrate the rationale and feasibility of the SIR design strategy. Simulation and image results at 7 tesla in a phantom and human head illustrate the improvements in transmit magnetic field, as well as, RF efficiency (transmit magnetic field versus SAR) when two different SIR designs are incorporated in 8-element volume coil configurations and compared to a volume coil consisting of microstrip elements. PMID:23508243
Surface Plasmon Resonance Imaging Measurements of Electrostatic Biopolymer
Surface Plasmon Resonance Imaging Measurements of Electrostatic Biopolymer Adsorption onto surface plasmon resonance (SPR) imaging experiments is used to charac- terize the differential/RAS) and surface plasmon resonance (SPR) thickness mea- surements. A schematic diagram of the scanning SPR
Array combination for parallel imaging in Magnetic Resonance Imaging
Spence, Dan Kenrick
In Magnetic Resonance Imaging, the time required to generate an image is proportional to the number of steps used to encode the spatial information. In rapid imaging, an array of coil elements and receivers are used to reduce the number of encoding...
Magnetic resonance imaging of Morgagni hernia
Bradford A. Yeager; Gwen E. Guglielmi; Mark L. Schiebler; Warren B. Gefter; Herbert Y. Kressel
A case of a Morgagni hernia is demonstrated by magnetic resonance imaging (MRI). The correct diagnosis was facilitated by the ability to image directly the anteromedial diaphragmatic defect in the coronal and sagittal planes. The findings from MRI, computed tomography, and radiographic studies are correlated.
Quantitative cardiovascular magnetic resonance for molecular imaging
Patrick M Winter; Shelton D Caruthers; Gregory M Lanza; Samuel A Wickline
Cardiovascular magnetic resonance (CMR) molecular imaging aims to identify and map the expression of important biomarkers on a cellular scale utilizing contrast agents that are specifically targeted to the biochemical signatures of disease and are capable of generating sufficient image contrast. In some cases, the contrast agents may be designed to carry a drug payload or to be sensitive to
Magnetic resonance images of tuberous sclerosis
Y. Inoue; S. Nakajima; T. Fukuda; Y. Nemoto; M. Shakudo; R. Murata; O. Matsuoka; K. Takemoto; Y. Matsumura; Y. Onoyama
The cerebral lesions in tuberous sclerosis are of three kinds: subependymal nodules, cortical tubers, and cluster of heterotopic cells in the white matter. Understanding of these hamartomas is still incomplete even with modern imaging modalities. Magnetic resonance (MR) images of ten patients with tuberous sclerosis were reviewed and compared to computed tomographic (CT) scans and to the clinical severity of
Magnetic resonance imaging of the knee
Mink, J.H.; Reicher, M.A.; Crues, J.V.
Introducing a comprehensive, practical guide to the use of magnetic resonance imaging (MRI) in detecting and evaluating knee disorders and planning arthroscopic surgery) This book integrates MRI findings with pertinent anatomy, physiology, and clinical signs to assist radiologists in selecting imaging protocols and interpreting scans. Detailed chapters focus on magnetic resonance imaging of the menisci and ligaments and evaluation of osteonecrosis, osteochondrosis, and osteochondritis. The authors demonstrate the potential of MRI for diagnosing various knee disorders such as arthritis, fractures, popliteal cysts, synovial disease, plicae, popliteal artery aneurysms, tumors, and bone marrow disorders.
Structural magnetic resonance imaging in epilepsy
Karel Deblaere; Eric Achten
Because of its sensitivity and high tissue contrast, magnetic resonance imaging (MRI) is the technique of choice for structural\\u000a imaging in epilepsy. In this review the effect of using optimised scanning protocols and the use of high field MR systems\\u000a on detection sensitivity is discussed. Also, the clinical relevance of adequate imaging in patients with focal epilepsy is\\u000a highlighted. The
Magnetic Resonance Imaging of the Retina
Duong, Timothy Q.; Muir, Eric R.
This paper reviews recent developments in high-resolution magnetic resonance imaging (MRI) and its application to image anatomy, physiology, and function in the retina of animals. It describes technical issues and solutions in performing retinal MRI, anatomical MRI, blood oxygenation level-dependent functional MRI (fMRI), and blood-flow MRI both of normal retinas and of retinal degeneration. MRI offers unique advantages over existing retinal imaging techniques, including the ability to image multiple layers without depth limitation and to provide multiple clinically relevant data in a single setting. Retinal MRI has the potential to complement existing retinal imaging techniques. PMID:19763752
Musculoskeletal applications of magnetic resonance imaging: Council on Scientific Affairs
Harms, S.E.; Fisher, C.F.; Fulmer, J.M. (American Medical Association, Chicago, IL (USA))
Magnetic resonance imaging provides superior contrast, resolution, and multiplanar imaging capability, allowing excellent definition of soft-tissue and bone marrow abnormalities. For these reasons, magnetic resonance imaging has become a major diagnostic imaging method for the evaluation of many musculoskeletal disorders. The applications of magnetic resonance imaging for musculoskeletal diagnosis are summarized and examples of common clinical situations are given. General guidelines are suggested for the musculoskeletal applications of magnetic resonance imaging.
Magnetic resonance imaging of atherosclerosis
T. Leiner; S. Gerretsen; R. Botnar; E. Lutgens; V. Cappendijk; E. Kooi; J. van Engelshoven
Abundant data now link composition of the vascular wall, rather than the degree of luminal narrowing, with the risk for acute ischemic syndromes in the coronary, central nervous system, and peripheral arterial beds. Over the past few years, magnetic resonance angiography has evolved as a well-established method to determine the location and severity of advanced, lumen-encroaching atherosclerotic lesions. In addition,
Magnetic resonance imaging of breast implants.
Shah, Mala; Tanna, Neil; Margolies, Laurie
Silicone breast implants have significantly evolved since their introduction half a century ago, yet implant rupture remains a common and expected complication, especially in patients with earlier-generation implants. Magnetic resonance imaging is the primary modality for assessing the integrity of silicone implants and has excellent sensitivity and specificity, and the Food and Drug Administration currently recommends periodic magnetic resonance imaging screening for silent silicone breast implant rupture. Familiarity with the types of silicone implants and potential complications is essential for the radiologist. Signs of intracapsular rupture include the noose, droplet, subcapsular line, and linguine signs. Signs of extracapsular rupture include herniation of silicone with a capsular defect and extruded silicone material. Specific sequences including water and silicone suppression are essential for distinguishing rupture from other pathologies and artifacts. Magnetic resonance imaging provides valuable information about the integrity of silicone implants and associated complications. PMID:25463409
Magnetic resonance imaging safety: principles and guidelines.
Stikova, E
(Full text is available at http://www.manu.edu.mk/prilozi). This paper provides an overview of the published literature regarding magnetic resonance imaging (MRI) safety. It gives basic information about the electromagnetic fields that are generated during the MRI diagnostic procedure, followed by a description of the biological effects of those fields on humans. It concludes with a discussion of the safety issues related to MRI use in clinical practice, highlighting the existing MRI standards and guidelines. Key words: magnetic resonance imaging, biological effects of electromagnetic radiation, MRI standards, safety guidelines. PMID:23037190
Review: Magnetic resonance imaging techniques in ophthalmology
Fagan, Andrew J.
Imaging the eye with magnetic resonance imaging (MRI) has proved difficult due to the eye's propensity to move involuntarily over typical imaging timescales, obscuring the fine structure in the eye due to the resulting motion artifacts. However, advances in MRI technology help to mitigate such drawbacks, enabling the acquisition of high spatiotemporal resolution images with a variety of contrast mechanisms. This review aims to classify the MRI techniques used to date in clinical and preclinical ophthalmologic studies, describing the qualitative and quantitative information that may be extracted and how this may inform on ocular pathophysiology. PMID:23112569
Stepped impedance resonators for high-field magnetic resonance imaging.
Akgun, Can E; DelaBarre, Lance; Yoo, Hyoungsuk; Sohn, Sung-Min; Snyder, Carl J; Adriany, Gregor; Ugurbil, Kamil; Gopinath, Anand; Vaughan, J Thomas
Multi-element volume radio-frequency (RF) coils are an integral aspect of the growing field of high-field magnetic resonance imaging. In these systems, a popular volume coil of choice has become the transverse electromagnetic (TEM) transceiver coil consisting of microstrip resonators. In this paper, to further advance this design approach, a new microstrip resonator strategy in which the transmission line is segmented into alternating impedance sections, referred to as stepped impedance resonators (SIRs), is investigated. Single-element simulation results in free space and in a phantom at 7 T (298 MHz) demonstrate the rationale and feasibility of the SIR design strategy. Simulation and image results at 7 T in a phantom and human head illustrate the improvements in a transmit magnetic field, as well as RF efficiency (transmit magnetic field versus specific absorption rate) when two different SIR designs are incorporated in 8-element volume coil configurations and compared to a volume coil consisting of microstrip elements. PMID:23508243
Cardiovascular magnetic resonance imaging in small animals.
Botnar, René M; Makowski, Marcus R
Noninvasive imaging studies involving small animals are becoming increasingly important in preclinical pharmacological, genetic, and biomedical cardiovascular research. Especially small animal magnetic resonance imaging (MRI) using high field and clinical MRI systems has gained significant importance in recent years. Compared to other imaging modalities, like computer tomography, MRI can provide an excellent soft tissue contrast, which enables the characterization of different kinds of tissues without the use of contrast agents. In addition, imaging can be performed with high spatial and temporal resolution. Small animal MRI cannot only provide anatomical information about the beating murine heart; it can also provide functional and molecular information, which makes it a unique imaging modality. Compared to clinical MRI examinations in humans, small animal MRI is associated with additional challenges. These included a smaller size of all cardiovascular structures and a up to ten times higher heart rate. Dedicated small animal monitoring devices make a reliable cardiac triggering and respiratory gating feasible. MRI in combination with molecular probes enables the noninvasive imaging of biological processes at a molecular level. Different kinds of iron oxide or gadolinium-based contrast agents can be used for this purpose. Compared to other molecular imaging modalities, like single photon emission computed tomography (SPECT) and positron emission tomography (PET), MRI can also provide imaging with high spatial resolution, which is of high importance for the assessment of the cardiovascular system. The sensitivity for detection of MRI contrast agents is however lower compared to sensitivity of radiation associated techniques like PET and SPECT. This chapter is divided into the following sections: (1) "Introduction," (2) "Principals of Magnetic Resonance Imaging," (3) "MRI Systems for Preclinical Imaging and Experimental Setup," and (4) "Cardiovascular Magnetic Resonance Imaging." PMID:22137434
Surface plasmon resonance imaging for biosensing.
Paul, S; Vadgama, P; Ray, A K
Surface plasmon resonance imaging (SPRI) is a useful tool for the study of surface biomolecular interactions allowing for label-free detection and elegant instrumentation. SPRI imaging system is described in this review with an emphasis on recent applications with examples of different biological interactions and high throughput analysis. Signal amplification in SPRI using nanoparticle and waveguide-based optical coupling is introduced. Finally the detection sensitivity of the SPRI system is examined in terms of other competitive methods. PMID:19640160
Magnetic resonance imaging in Mexico
NASA Astrophysics Data System (ADS)
Rodriguez, A. O.; Rojas, R.; Barrios, F. A.
MR imaging has experienced an important growth worldwide and in particular in the USA and Japan. This imaging technique has also shown an important rise in the number of MR imagers in Mexico. However, the development of MRI has followed a typical way of Latin American countries, which is very different from the path shown in the industrialised countries. Despite the fact that Mexico was one the very first countries to install and operate MR imagers in the world, it still lacks of qualified clinical and technical personnel. Since the first MR scanner started to operate, the number of units has grown at a moderate space that now sums up approximately 60 system installed nationwide. Nevertheless, there are no official records of the number of MR units operating, physicians and technicians involved in this imaging modality. The MRI market is dominated by two important companies: General Electric (approximately 51%) and Siemens (approximately 17.5%), the rest is shared by other five companies. According to the field intensity, medium-field systems (0.5 Tesla) represent 60% while a further 35% are 1.0 T or higher. Almost all of these units are in private hospitals and clinics: there is no high-field MR imagers in any public hospital. Because the political changes in the country, a new public plan for health care is still in the process and will be published soon this year. This plan will be determined by the new Congress. North American Free Trade Agreement (NAFTA) and president Fox. Experience acquired in the past shows that the demand for qualified professionals will grow in the new future. Therefore, systematic training of clinical and technical professionals will be in high demand to meet the needs of this technique. The National University (UNAM) and the Metropolitan University (UAM-Iztapalapa) are collaborating with diverse clinical groups in private facilities to create a systematic training program and carry out research and development in MRI
Focal renal masses: magnetic resonance imaging
Choyke, P.L.; Kressel, H.Y.; Pollack, H.M.; Arger, P.M.; Axel, L.; Mamourian, A.C.
Thirty patients with focal renal masses were evaluated on a .12-Tesla resistive magnetic resonance unit using partial saturation and spin echo pulse sequence. Fifteen patients had cystic lesions, nine patients had renal cell carcinoma, two had metastatic lesions, one had an angiomyolipoma, and three had focal bacterial infection. Renal cell carcinomas demonstrated areas of increased signal using a partial saturation sequence. Magnetic resonance imaging accurately detected perinephric extension and vascular invasion in all patients. Metastatic disease to the kidney was uniformly low in signal, in contrast to primary renal cell carcinoma; an angiomyolipoma demonstrated very high signal intensity. Two masses resulting from acute focal bacterial nephritis were uniformly low in signal. Magnetic resonance imaging appears to be an accurate way of detecting, identifying, and staging focal renal masses.
Prenatal magnetic resonance imaging enhances fetal diagnosis
Theresa M Quinn; Anne M Hubbard; N. Scott Adzick
Background: Ultrasound (US) evaluation of some fetal anomalies provides limited information. Anatomic details that affect prognosis and selection for fetal therapy, such as liver herniation and pulmonary hypoplasia in congenital diaphragmatic hernia (CDH) and airway patency in giant neck masses, may be difficult to delineate using conventional sonographic methods. The authors evaluated the utility of prenatal magnetic resonance imaging (MRI)
Magnetic resonance imaging in acute tendon ruptures
Richard H. Daffner; Barry L. Riemer; Anthony R. Lupetin; Nilima Dash
The diagnosis of acute tendon ruptures of the extensor mechanism of the knee or the Achilles tendon of the ankle may usually be made by clinical means. Massive soft tissue swelling accompanying these injuries often obscures the findings, however. Magnetic resonance imaging (MRI) can rapidly demonstrate these tendon ruptures. Examples of the use of MRI for quadriceps tendon, and Achilles
Reducing Field Distortion in Magnetic Resonance Imaging
NASA Technical Reports Server (NTRS)
Eom, Byeong Ho; Penanen, Konstantin; Hahn, Inseob
A concept for a magnetic resonance imaging (MRI) system that would utilize a relatively weak magnetic field provides for several design features that differ significantly from the corresponding features of conventional MRI systems. Notable among these features are a magnetic-field configuration that reduces (relative to the conventional configuration) distortion and blurring of the image, the use of a superconducting quantum interference device (SQUID) magnetometer as the detector, and an imaging procedure suited for the unconventional field configuration and sensor. In a typical application of MRI, a radio-frequency pulse is used to excite precession of the magnetic moments of protons in an applied magnetic field, and the decaying precession is detected for a short time following the pulse. The precession occurs at a resonance frequency proportional to the strengths of the magnetic field and the proton magnetic moment. The magnetic field is configured to vary with position in a known way; hence, by virtue of the aforesaid proportionality, the resonance frequency varies with position in a known way. In other words, position is encoded as resonance frequency. MRI using magnetic fields weaker than those of conventional MRI offers several advantages, including cheaper and smaller equipment, greater compatibility with metallic objects, and higher image quality because of low susceptibility distortion and enhanced spin-lattice-relaxation- time contrast. SQUID MRI is being developed into a practical MRI method for applied magnetic flux densities of the order of only 100 T
Slatton, Clint
A NEW CLUSTERING ALGORITHM FOR SEGMENTATION OF MAGNETIC RESONANCE IMAGES By ERHAN GOKCAY which improved the quality of this dissertation. I also wish to thank my wife Didem and my son Tugra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 Magnetic Resonance Image Segmentation
Magnetic resonance imaging of cartilage repair procedures.
Forney, Michael C; Gupta, Amit; Minas, Tom; Winalski, Carl S
Cartilage injuries in the knee are common and can be a persistent source of pain or dysfunction. Many new surgical strategies have been developed to treat these lesions. It is important for the radiologist to have an understanding of these procedures and their appearance on magnetic resonance (MR) imaging. This article provides the radiologist with an overview of the surgical strategies for repairing cartilage lesions in the knee followed by a discussion of their postoperative appearance on MR imaging in normal and abnormal cases. Guidelines for adequate reporting of the MR imaging findings after cartilage repair in the knee are also included. PMID:25442028
Magnetic Resonance Image Example Based Contrast Synthesis
Roy, Snehashis; Carass, Aaron; Prince, Jerry L.
The performance of image analysis algorithms applied to magnetic resonance images is strongly influenced by the pulse sequences used to acquire the images. Algorithms are typically optimized for a targeted tissue contrast obtained from a particular implementation of a pulse sequence on a specific scanner. There are many practical situations, including multi-institution trials, rapid emergency scans, and scientific use of historical data, where the images are not acquired according to an optimal protocol or the desired tissue contrast is entirely missing. This paper introduces an image restoration technique that recovers images with both the desired tissue contrast and a normalized intensity profile. This is done using patches in the acquired images and an atlas containing patches of the acquired and desired tissue contrasts. The method is an example-based approach relying on sparse reconstruction from image patches. Its performance in demonstrated using several examples, including image intensity normalization, missing tissue contrast recovery, automatic segmentation, and multimodal registration. These examples demonstrate potential practical uses and also illustrate limitations of our approach. PMID:24058022
INVITED TOPICAL REVIEW: Parallel magnetic resonance imaging
NASA Astrophysics Data System (ADS)
Larkman, David J.; Nunes, Rita G.
Parallel imaging has been the single biggest innovation in magnetic resonance imaging in the last decade. The use of multiple receiver coils to augment the time consuming Fourier encoding has reduced acquisition times significantly. This increase in speed comes at a time when other approaches to acquisition time reduction were reaching engineering and human limits. A brief summary of spatial encoding in MRI is followed by an introduction to the problem parallel imaging is designed to solve. There are a large number of parallel reconstruction algorithms; this article reviews a cross-section, SENSE, SMASH, g-SMASH and GRAPPA, selected to demonstrate the different approaches. Theoretical (the g-factor) and practical (coil design) limits to acquisition speed are reviewed. The practical implementation of parallel imaging is also discussed, in particular coil calibration. How to recognize potential failure modes and their associated artefacts are shown. Well-established applications including angiography, cardiac imaging and applications using echo planar imaging are reviewed and we discuss what makes a good application for parallel imaging. Finally, active research areas where parallel imaging is being used to improve data quality by repairing artefacted images are also reviewed.
Magnetic Resonance Imaging of Dendrite Currents
NASA Astrophysics Data System (ADS)
Jay, William; Dolasinski, Brian; Wijesinghe, Ranjith; Roth, Bradley
The action currents of active dendrites generate their own magnetic field, which can cause the phase of the spins to change. Many investigators have attempted to detect neural and dendritic currents directly using magnetic resonance imaging. Such a measurement of action currents would be remarkable, since it would allow functional imaging of neural activity using the high spatial resolution of MRI and avoid an ill-posed inverse problem to determine the current sources. Measurement of the magnetic field of neural currents would better follow the distribution of neural activity in time and space. Our goal in this presentation is to use the calculated magnetic field of a dendrite to estimate the resulting phase shift in the magnetic resonance signal. We find the phase shift produced by a collection of simultaneously active dendrites is below the threshold for detection using current MRI technology.
Magnetic resonance imaging of pancreatitis: An update
Manikkavasakar, Sriluxayini; AlObaidy, Mamdoh; Busireddy, Kiran K; Ramalho, Miguel; Nilmini, Viragi; Alagiyawanna, Madhavi; Semelka, Richard C
Magnetic resonance (MR) imaging plays an important role in the diagnosis and staging of acute and chronic pancreatitis and may represent the best imaging technique in the setting of pancreatitis due to its unmatched soft tissue contrast resolution as well as non-ionizing nature and higher safety profile of intravascular contrast media, making it particularly valuable in radiosensitive populations such as pregnant patients, and patients with recurrent pancreatitis requiring multiple follow-up examinations. Additional advantages include the ability to detect early forms of chronic pancreatitis and to better differentiate adenocarcinoma from focal chronic pancreatitis. This review addresses new trends in clinical pancreatic MR imaging emphasizing its role in imaging all types of acute and chronic pancreatitis, pancreatitis complications and other important differential diagnoses that mimic pancreatitis. PMID:25356038
Magnetic resonance imaging in gynecological oncology.
Harry, Vanessa N; Deans, Heather; Ramage, Emma; Parkin, David E; Gilbert, Fiona J
Magnetic resonance imaging (MRI) has become an indispensable tool in the assessment of malignant disease. With increasingly sophisticated systems and technical advancements, MRI has continued to expand its role in providing crucial information regarding cancer diagnosis and management. In gynecological malignancies, this modality has assumed greater responsibility, particularly in the evaluation of cervical and endometrial cancers. In addition to conventional imaging, innovative techniques such as dynamic contrast-enhanced MRI and diffusion-weighted MRI show promise in offering early assessment of tumor response. This paper reviews the current role of MRI in gynecological cancers and highlights the potential of novel techniques in improving patient care. PMID:19395992
Magnetic resonance imaging of perianal fistulas.
Vanbeckevoort, Dirk; Bielen, Didier; Vanslembrouck, Ragna; Van Assche, Gert
Perianal fistulization is the result of a chronic inflammation of the perianal tissues. A wide spectrum of clinical manifestations, ranging from simple to complex fistulas, can be seen, the latter especially in patients with Crohn disease. Failure to detect secondary tracks and hidden abscesses may lead to therapeutic failure, such as insufficient response to medical treatment and relapse after surgery. Currently, magnetic resonance (MR) imaging is the preferred technique for evaluating perianal fistulas and associated complications. Initially used most often in the preoperative setting, MR imaging now also plays an important role in evaluating the response to medical therapy. PMID:24238135
Magnetic resonance imaging features of allografts
S. V. Kattapuram; M. S. Rosol; D. I. Rosenthal; W. E. Palmer; H. J. Mankin
Objective. To investigate the magnetic resonance imaging (MRI) features of allografts at various time intervals after surgery in patients\\u000a with osteoarticular allografts.\\u000a \\u000a \\u000a Design and patients. Sixteen patients who were treated with osteoarticular allografts and who were followed over time with MRI studies as part\\u000a of their long-term follow-up were retrospectively selected for this study. T1-weighted images were obtained both before
Sensorineural Hearing Loss after Magnetic Resonance Imaging
Mollasadeghi, Abolfazl; Mehrparvar, Amir Houshang; Atighechi, Saeid; Mostaghaci, Mehrdad
Magnetic resonance imaging (MRI) devices produce noise, which may affect patient's or operators' hearing. Some cases of hearing impairment after MRI procedure have been reported with different patterns (temporary or permanent, unilateral or bilateral, with or without other symptoms like tinnitus). In this report, a case of bilateral sensorineural hearing loss in an otherwise healthy patient underwent brain MRI was described. The patient's hearing loss was accompanied with tinnitus and was not improved after 3 months of followup. PMID:23844303
Alkali lasers for magnetic resonance imaging
Boris V. Zhdanov; Randall J. Knize
Spin-polarized nuclei of such gases as 3He and 129Xe are successfully used for magnetic resonance imaging of lungs and other organs of human body. To produce large numbers\\u000a of spin-polarized nuclei required for this medical application, a high power narrowband tunable laser source is required.\\u000a Diode pumped alkali lasers, developed during last several years can be an ideal source for
Polarimetric surface plasmon resonance imaging biosensor
A. Duval; F. Bardin; J. Moreau; A. Aide; A. Bellemain; M. Canva
We report the realization of a surface plasmon resonance imaging biosensor potentially capable of dynamically characterizing optical anisotropy by means of polarimetric measurements. Our approach relies on a light beam propagating through a high refractive index glass-prism (Kretschmann-Raether configuration) in order to excite a surface plasmon wave along a metal-dielectric interface. This evanescent wave probes the metal-dielectric vicinities with subnanometer
Magnetic resonance imaging. Application to family practice.
Goh, R. H.; Somers, S.; Jurriaans, E.; Yu, J.
OBJECTIVE: To review indications, contraindications, and risks of using magnetic resonance imaging (MRI) in order to help primary care physicians refer patients appropriately for MRI, screen for contraindications to using MRI, and educate patients about MRI. QUALITY OF EVIDENCE: Recommendations are based on classic textbooks, the policies of our MRI group, and a literature search using MEDLINE with the MeSH headings magnetic resonance imaging, brain, musculoskeletal, and spine. The search was limited to human, English-language, and review articles. Evidence in favour of using MRI for imaging the head, spine, and joints is well established. For cardiac, abdominal, and pelvic conditions, MRI has been shown useful for certain indications, usually to complement other modalities. MAIN MESSAGE: For demonstrating soft tissue conditions, MRI is better than computed tomography (CT), but CT shows bone and acute bleeding better. Therefore, patients with trauma or suspected intracranial bleeding should have CT. Tumours, congenital abnormalities, vascular structures, and the cervical or thoracic spine show better on MRI. Either modality can be used for lower back pain. Cardiac, abdominal, and pelvic abnormalities should be imaged with ultrasound or CT before MRI. Contraindications for MRI are mainly metallic implants or shrapnel, severe claustrophobia, or obesity. CONCLUSIONS: With the increasing availability of MRI scanners in Canada, better understanding of the indications, contraindications, and risks will be helpful for family physicians and their patients. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 PMID:10509224
Magnetic resonance imaging: present and future applications
Johnston, Donald L.; Liu, Peter; Wismer, Gary L.; Rosen, Bruce R.; Stark, David D.; New, Paul F.J.; Okada, Robert D.; Brady, Thomas J.
Magnetic resonance (MR) imaging has created considerable excitement in the medical community, largely because of its great potential to diagnose and characterize many different disease processes. However, it is becoming increasingly evident that, because MR imaging is similar to computed tomography (CT) scanning in identifying structural disorders and because it is more costly and difficult to use, this highly useful technique must be judged against CT before it can become an accepted investigative tool. At present MR imaging has demonstrated diagnostic superiority over CT in a limited number of important, mostly neurologic, disorders and is complementary to CT in the diagnosis of certain other disorders. For most of the remaining organ systems its usefulness is not clear, but the lack of ionizing radiation and MR's ability to produce images in any tomographic plane may eventually prove to be advantageous. The potential of MR imaging to display in-vivo spectra, multinuclear images and blood-flow data makes it an exciting investigative technique. At present, however, MR imaging units should be installed only in medical centres equipped with the clinical and basic research facilities that are essential to evaluate the ultimate role of this technique in the care of patients. ImagesFig. 5Fig. 6Fig. 7Fig. 8Fig. 9Fig. 10Fig. 11Fig. 12Fig. 13Fig. 14 PMID:3884120
Gastrointestinal imaging-practical magnetic resonance imaging approach
Liu, Baodong; Ramalho, Miguel; AlObaidy, Mamdoh; Busireddy, Kiran K; Altun, Ersan; Kalubowila, Janaka; Semelka, Richard C
Over the past two decades, advances in cross-sectional imaging such as computed tomography and magnetic resonance imaging (MRI) have dramatically changed the concept of gastrointestinal imaging. MR is playing an increasing role in the evaluation of gastrointestinal disorders. MRI combines the advantages of excellent soft-tissue contrast, noninvasiveness, functional information and lack of ionizing radiation. Furthermore, recent developments of MRI have led to improved spatial and temporal resolution as well as decreased motion artifacts. In this article we describe the technical aspects of gastrointestinal MRI and present a practical approach for a well-known spectrum of gastrointestinal disease processes. PMID:25170393
Quantitative Pulmonary Imaging Using Computed Tomography and Magnetic Resonance Imaging
Washko, George R.; Parraga, Grace; Coxson, Harvey O.
Measurements of lung function, including spirometry and body plethesmography, are easy to perform and are the current clinical standard for assessing disease severity. However, these lung functional techniques do not adequately explain the observed variability in clinical manifestations of disease and offer little insight into the relationship of lung structure and function. Lung imaging and the image based assessment of lung disease has matured to the extent that it is common for clinical, epidemiologic, and genetic investigation to have a component dedicated to image analysis. There are several exciting imaging modalities currently being used for the non-invasive study of lung anatomy and function. In this review we will focus on two of them, x-ray computed tomography and magnetic resonance imaging. Following a brief introduction of each method we detail some of the most recent work being done to characterize smoking-related lung disease and the clinical applications of such knowledge. PMID:22142490
Interventional and intraoperative magnetic resonance imaging.
Kettenbach, J; Kacher, D F; Koskinen, S K; Silverman, S G; Nabavi, A; Gering, D; Tempany, C M; Schwartz, R B; Kikinis, R; Black, P M; Jolesz, F A
The goal of the Image Guided Therapy Program, as the name implies, is to develop the use of imaging to guide minimally invasive therapy. The program combines interventional and intraoperative magnetic resonance imaging (MRI) with high-performance computing and novel therapeutic devices. In clinical practice the multidisciplinary program provides for the investigation of a wide range of interventional and surgical procedures. The Signa SP 0.5 T superconducting MRI system (GE Medical Systems, Milwaukee, WI) has a 56-cm-wide vertical gap, allowing access to the patient and permitting the execution of interactive MRI-guided procedures. This system is integrated with an optical tracking system and utilizes flexible surface coils and MRI-compatible displays to facilitate procedures. Images are obtained with routine pulse sequences. Nearly real-time imaging, with fast gradient-recalled echo sequences, may be acquired at a rate of one image every 1.5 s with interactive image plane selection. Since 1994, more than 800 of these procedures, including various percutaneous procedures and open surgeries, have been successfully performed at Brigham and Women's Hospital (Boston, MA). PMID:11701527
Model-based reconstruction of magnetic resonance spectroscopic imaging
Chatnuntawech, Itthi
Magnetic resonance imaging (MRI) is a medical imaging technique that is used to obtain images of soft tissue throughout the body. Since its development in the 1970s, MRI has gained tremendous importance in clinical practice ...
Magnetic resonance imaging in acute mastoiditis
Kitzler, Hagen H; Gudziol, Volker; Laniado, Michael; Hahn, Gabriele
Background In cases of suspected mastoiditis, imaging is used to evaluate the extent of mastoid destruction and possible complications. The role of magnetic resonance imaging (MRI) in mastoiditis has not been systematically evaluated. Purpose To assess the diagnostic performance of MRI in patients with suspected acute mastoiditis. Material and Methods Twenty-three patients with suspected acute mastoiditis were included in this retrospective study (15 boys, 8 girls; mean age, 2 years 11 months). All patients were examined on a 1.5?T MRI system. The MRI examination included both enhanced and non-enhanced turbo spin echo (TSE), diffusion-weighted images, and venous time-of-flight magnetic resonance angiography (TOF MRA) for the evaluation of the venous sinuses. Surgical findings, as well as clinical and imaging follow-up were used as the standard of reference. The sensitivity and accuracy of MRI for mastoiditis and subperiosteal abscesses was calculated. Results Twenty (87%) of 23 patients had mastoiditis, and 12 (52%) of 23 patients had a subperiosteal abscess in addition to mastoiditis. Mastoiditis and subperiosteal abscesses were identified by MRI in all cases. Sensitivity for mastoiditis was 100%, specificity was 66%, and accuracy was 86%. Sensitivity for subperiosteal abscesses was 100% and accuracy was 100%. Conclusion Multiparametric MRI has high accuracy for mastoiditis and subperiosteal abscesses. PMID:24778805
The magnetic resonance imaging-linac system.
Lagendijk, Jan J W; Raaymakers, Bas W; van Vulpen, Marco
The current image-guided radiotherapy systems are suboptimal in the esophagus, pancreas, kidney, rectum, lymph node, etc. These locations in the body are not easily accessible for fiducials and cannot be visualized sufficiently on cone-beam computed tomographies, making daily patient set-up prone to geometrical uncertainties and hinder dose optimization. Additional interfraction and intrafraction uncertainties for those locations arise from motion with breathing and organ filling. To allow real-time imaging of all patient tumor locations at the actual treatment position a fully integrated 1.5-T, diagnostic quality, magnetic resonance imaging with a 6-MV linear accelerator is presented. This system must enable detailed dose painting at all body locations. PMID:24931095
Cardiovascular Magnetic Resonance Imaging in Experimental Models
Price, Anthony N.; Cheung, King K.; Cleary, Jon O; Campbell, Adrienne E; Riegler, Johannes; Lythgoe, Mark F
Cardiovascular magnetic resonance (CMR) imaging is the modality of choice for clinical studies of the heart and vasculature, offering detailed images of both structure and function with high temporal resolution. Small animals are increasingly used for genetic and translational research, in conjunction with models of common pathologies such as myocardial infarction. In all cases, effective methods for characterising a wide range of functional and anatomical parameters are crucial for robust studies. CMR is the gold-standard for the non-invasive examination of these models, although physiological differences, such as rapid heart rate, make this a greater challenge than conventional clinical imaging. However, with the help of specialised magnetic resonance (MR) systems, novel gating strategies and optimised pulse sequences, high-quality images can be obtained in these animals despite their small size. In this review, we provide an overview of the principal CMR techniques for small animals for example cine, angiography and perfusion imaging, which can provide measures such as ejection fraction, vessel anatomy and local blood flow, respectively. In combination with MR contrast agents, regional dysfunction in the heart can also be identified and assessed. We also discuss optimal methods for analysing CMR data, particularly the use of semi-automated tools for parameter measurement to reduce analysis time. Finally, we describe current and emerging methods for imaging the developing heart, aiding characterisation of congenital cardiovascular defects. Advanced small animal CMR now offers an unparalleled range of cardiovascular assessments. Employing these methods should allow new insights into the structural, functional and molecular basis of the cardiovascular system. PMID:21331311
Novel Magnetic Resonance Imaging Techniques in Brain Tumors.
Nechifor, Ruben E; Harris, Robert J; Ellingson, Benjamin M
Magnetic resonance imaging is a powerful, noninvasive imaging technique with exquisite sensitivity to soft tissue composition. Magnetic resonance imaging is primary tool for brain tumor diagnosis, evaluation of drug response assessment, and clinical monitoring of the patient during the course of their disease. The flexibility of magnetic resonance imaging pulse sequence design allows for a variety of image contrasts to be acquired, including information about magnetic resonance-specific tissue characteristics, molecular dynamics, microstructural organization, vascular composition, and biochemical status. The current review highlights recent advancements and novel approaches in MR characterization of brain tumors. PMID:26049817
76 FR 58281 - Magnetic Resonance Imaging Safety; Public Workshop
Federal Register 2010, 2011, 2012, 2013, 2014
...factors affecting the safe use of magnetic resonance imaging (MRI) and approaches...the International Society for Magnetic Resonance in Medicine (ISMRM...implants include the static magnetic field, maximum spatial gradient,...
Magnetic resonance imaging of thyroid nodules
Kroop, S.A.; Margouleff, D.; Stein, H.L.; Zanzi, I.; Susin, M.; Goldman, M.A.
The capacity of Magnetic Resonance (MR) imaging to characterize the nature of palpable thyroid nodules was prospectively evaluated in 9 patients. Seven nodules were nonfunctioning and 2 showed function on radio-iodine Nuclear Medicine (NM) scans. Each patient underwent high-resolution real time ultrasound (US) examination followed by MR imaging with a 0.6 Tesla superconducting whole body coil utilizing T/sub 1/ and T/sub 2/ weighted inversion recovery and spin-echo pulse sequences in coronal, transverse and sagittal planes. All NM, US and MR studies were evaluated independently by each of two physicians. Diagnoses were established by surgical pathology (n=7) or by radiologic and clinical correlation (n=2). There were 3 cases of solitary adenoma, 4 cases of adenomatous goiter, 1 case of papillary carcinoma and 1 case of epidermoid carcinoma. Lesions demonstrated variable signal intensity on T/sub 1/ weighted images. All lesions demonstrated nonspecific increased signal intensity on T/sub 2/ weighted images. One malignancy was correctly diagnosed by the identification of adjacent cervical lymph nodes of increased signal intensity and another by demonstration of tracheal invasion on MR images, both not visible by other imaging modalities. Regions of hemorrhage and cystic degeneration as well as additional non-palpable thyroid nodules could be detected on MR images. Vascular displacement, tracheal compression and deviation, and substernal thyroid extension were also well demonstrated. The findings suggest that qualitative assessment of MR signal intensity alone cannot reliably differentiate benign from malignant thyroid lesions, but that MR images can provide other useful information to aid in this differentiation.
Tools for cardiovascular magnetic resonance imaging
Krishnamurthy, Ramkumar; Cheong, Benjamin
In less than fifteen years, as a non-invasive imaging option, cardiovascular MR has grown from a being a mere curiosity to becoming a widely used clinical tool for evaluating cardiovascular disease. Cardiovascular magnetic resonance imaging (CMRI) is now routinely used to study myocardial structure, cardiac function, macro vascular blood flow, myocardial perfusion, and myocardial viability. For someone entering the field of cardiac MR, this rapid pace of development in the field of CMRI might make it difficult to identify a cohesive starting point. In this brief review, we have attempted to summarize the key cardiovascular imaging techniques that have found widespread clinical acceptance. In particular, we describe the essential cardiac and respiratory gating techniques that form the backbone of all cardiovascular imaging methods. It is followed by four sections that discuss: (I) the gradient echo techniques that are used to assess ventricular function; (II) black-blood turbo spin echo (SE) methods used for morphologic assessment of the heart; (III) phase-contrast based techniques for the assessment of blood flow; and (IV) CMR methods for the assessment of myocardial ischemia and viability. In each section, we briefly summarize technical considerations relevant to the clinical use of these techniques, followed by practical information for its clinical implementation. In each of those four areas, CMRI is considered either as the benchmark imaging modality against which the diagnostic performance of other imaging modalities are compared against, or provides a complementary capability to existing imaging techniques. We have deliberately avoided including cutting-edge CMR imaging techniques practiced at few academic centers, and restricted our discussion to methods that are widely used and are likely to be available in a clinical setting. Our hope is that this review would propel an interested reader toward more comprehensive reviews in the literature. PMID:24834409
Sodium Magnetic Resonance Imaging: From Research to Clinical Use
Ouwerkerk, Ronald
Sodium Magnetic Resonance Imaging: From Research to Clinical Use Ronald Ouwerkerk, PhD INTRODUCTION. Sodium MRI is no longer a stand- alone modality with 1 H MRI used only as a scout image. Instead, 23 Na the properties of this nu- cleus and what imaging techniques can be used to observe it. SODIUM-MAGNETIC RESONANCE
Diagnosis of hematogenous pyogenic vertebral osteomyelitis by magnetic resonance imaging
S. P. Meyers; S. N. Wiener
The clinical information and imaging data from 27 patients with hematogenous pyogenic vertebral osteomyelitis were reviewed. All patients had roentgenographic and magnetic resonance imaging examinations. Seventeen patients had computed tomograms; 17 had technetium Tc 99m medronate bone scans; and seven had gallium citrate Ga 67 scans. Magnetic resonance imaging, when used as a part of the initial radiologic evaluation, detected
Cardiac imaging using gated magnetic resonance
Lanzer, P.; Botvinick, E.H.; Schiller, N.B.
To overcome the limitations of magnetic resonance (MR) cardiac imaging using nongated data acquisition, three methods for acquiring a gating signal, which could be applied in the presence of a magnetic field, were tested; an air-filled plethysmograph, a laser-Doppler capillary perfusion flowmeter, and an electrocardiographic gating device. The gating signal was used for timing of MR imaging sequences (IS). Application of each gating method yielded significant improvements in structural MR image resolution of the beating heart, although with both plethysmography and laser-Doppler velocimetry it was difficult to obtain cardiac images from the early portion of the cardiac cycle due to an intrinsic delay between the ECG R wave and peripheral detection of the gating signal. Variations in the temporal relationship between the R wave and plethysmographic and laser-Doppler signals produced inconsistencies in the timing of IS. Since the ECG signal is virtually free of these problems, the preferable gating technique is IS synchronization with an electrocardiogram. The gated images acquired with this method provide sharp definition of internal cardiac morphology and can be temporarily referenced to end diastole and end systole or intermediate points.
Developments in boron magnetic resonance imaging (MRI)
Schweizer, M.
This report summarizes progress during the past year on maturing Boron-11 magnetic resonance imaging (MRI) methodology for noninvasive determination of BNCT agents (BSH) spatially in time. Three major areas are excerpted: (1) Boron-11 MRI of BSH distributions in a canine intracranial tumor model and the first human glioblastoma patient, (2) whole body Boron-11 MRI of BSH pharmacokinetics in a rat flank tumor model, and (3) penetration of gadolinium salts through the BBB as a function of tumor growth in the canine brain.
Clinical applications of cardiovascular magnetic resonance imaging
Marcu, Constantin B.; Beek, Aernout M.; van Rossum, Albert C.
Cardiovascular magnetic resonance imaging (MRI) has evolved from an effective research tool into a clinically proven, safe and comprehensive imaging modality. It provides anatomic and functional information in acquired and congenital heart disease and is the most precise technique for quantification of ventricular volumes, function and mass. Owing to its excellent interstudy reproducibility, cardiovascular MRI is the optimal method for assessment of changes in ventricular parameters after therapeutic intervention. Delayed contrast enhancement is an accurate and robust method used in the diagnosis of ischemic and nonischemic cardiomyopathies and less common diseases, such as cardiac sarcoidosis and myocarditis. First-pass magnetic contrast myocardial perfusion is becoming an alternative to radionuclide techniques for the detection of coronary atherosclerotic disease. In this review we outline the techniques used in cardiovascular MRI and discuss the most common clinical applications. PMID:17030942
In vivo nuclear magnetic resonance imaging
NASA Technical Reports Server (NTRS)
Leblanc, A.; Evans, H.; Bryan, R. N.; Johnson, P.; Schonfeld, E.; Jhingran, S. G.
A number of physiological changes have been demonstrated in bone, muscle and blood after exposure of humans and animals to microgravity. Determining mechanisms and the development of effective countermeasures for long duration space missions is an important NASA goal. The advent of tomographic nuclear magnetic resonance imaging (NMR or MRI) gives NASA a way to greatly extend early studies of this phenomena in ways not previously possible; NMR is also noninvasive and safe. NMR provides both superb anatomical images for volume assessments of individual organs and quantification of chemical/physical changes induced in the examined tissues. The feasibility of NMR as a tool for human physiological research as it is affected by microgravity is demonstrated. The animal studies employed the rear limb suspended rat as a model of mucle atrophy that results from microgravity. And bedrest of normal male subjects was used to simulate the effects of microgravity on bone and muscle.
3D-Computerized facial reconstructions from 3D-MRI of human heads using deformable model approach
Adel Kermi; S. Marniche-Kermi; M. T. Laskri
The aim of facial reconstruction is to estimate the face of an unknown individual from the shape of his\\/her skull to aid in recognition and identification. In this paper a 3D computerized facial reconstruction method from 3D-MRI of human heads is presented. It based on a model deformable approach constrained by the knowledge of soft tissues thicknesses, at a certain
LASER-POLARIZED 129Xe MAGNETIC RESONANCE SPECTROSCOPY AND IMAGING;
Rosen, Matthew S
LASER-POLARIZED 129Xe MAGNETIC RESONANCE SPECTROSCOPY AND IMAGING; THE DEVELOPMENT OF A METHOD ............................................................................38 3.2 Laser System and Optics
Contrast mechanisms in magnetic resonance imaging
NASA Astrophysics Data System (ADS)
Lepage, M.; Gore, J. C.
The first publications describing gel dosimetry used magnetic resonance imaging to detect changes in the proton longitudinal relaxation rate of a gel infused with ferrous ions and irradiated with ionizing radiation. Later, different gel dosimeter systems were proposed that are based on the free-radical polymerization of monomers dispersed in a gel matrix. In these polymer gels, changes in transverse relaxation rates were shown to be dependent on the absorbed dose. More recently, contrast in MR images based on the exchange of magnetization between polymer and water protons, following saturation of the polymer protons, has been exploited in polymer gel dosimeters. In addition, variations in relaxation times in the rotating frame (T1?) have been shown to produce contrast in MR images of irradiated polymer gel dosimeters. The signal and contrast in MR images may be manipulated to reflect a variety of these and other processes within an irradiated sample, An attempt is made here to provide an overview of the main different types of MRI contrast that may be used in gel dosimetry and, where possible, to relate this contrast to the nature of the chemical processes and structural changes that occur within the gels following the absorption of ionizing radiation.
Magnetic Resonance Imaging of the Living Brain
Rosenbloom, Margaret J.; Pfefferbaum, Adolf
Magnetic resonance imaging (MRI) provides a safe, noninvasive method to examine the brain's macrostructure, microstructure, and some aspects of how the living brain functions. MRI is capable of detecting abnormalities that can occur with alcoholism as well as changes that can occur with sobriety and relapse. The brain pathology associated with chronic excessive alcohol consumption is well documented with imaging of the living body (i.e., in vivo imaging). Consistent findings include shrinkage of the frontal cortex,1 underlying white matter, and cerebellum and expansion of the ventricles. Some of these changes are reversible with abstinence, but some appear to be enduring. Research showing correlations between brain structure and quantitative neuropsychological testing demonstrates the functional consequences of the pathology. In addition, functional imaging studies provide evidence that the brain compensates for cognitive deficits. The myriad concomitants of alcoholism, the antecedents, and the consumption patterns each may influence the observed brain changes associated with alcoholism, which tend to be more deleterious with increasing age. The multifaceted nature of alcoholism presents unique challenges and opportunities to understand the mechanisms underlying alcoholism-induced neuropathology and its recovery. Longitudinal MRI studies of animal models of alcoholism, however, can address questions about the development and course of alcohol dependence and the scope and limits of in vivo degeneration and recovery of brain structure and concomitant function that may not be readily addressed in clinical studies. PMID:23584010
Magnetic Resonance Imaging–guided Vascular Interventions
Ozturk, Cengizhan; Guttman, Michael; McVeigh, Elliot R.; Lederman, Robert J.
Magnetic resonance imaging (MRI), which provides superior soft-tissue imaging and no known harmful effects, has the potential as an alternative modality to guide various medical interventions. This review will focus on MR-guided endovascular interventions and present its current state and future outlook. In the first technical part, enabling technologies such as developments in fast imaging, catheter devices, and visualization techniques are examined. This is followed by a clinical survey that includes proof-of-concept procedures in animals and initial experience in human subjects. In preclinical experiments, MRI has already proven to be valuable. For example, MRI has been used to guide and track targeted cell delivery into or around myocardial infarctions, to guide atrial septal puncture, and to guide the connection of portal and systemic venous circulations. Several investigational MR-guided procedures have already been reported in patients, such as MR-guided cardiac catheterization, invasive imaging of peripheral artery atheromata, selective intraarterial MR angiography, and preliminary angioplasty and stent placement. In addition, MR-assisted transjugular intrahepatic portosystemic shunt procedures in patients have been shown in a novel hybrid double-doughnut x-ray/MRI system. Numerous additional investigational human MR-guided endovascular procedures are now underway in several medical centers around the world. There are also significant hurdles: availability of clinical-grade devices, device-related safety issues, challenges to patient monitoring, and acoustic noise during imaging. The potential of endovascular interventional MRI is great because as a single modality, it combines 3-dimensional anatomic imaging, device localization, hemodynamics, tissue composition, and function. PMID:16924170
Use of contrast agents in oncological imaging: magnetic resonance imaging
Cugini, Christian; Scatto, Giuliano; Zanato, Riccardo; Fusaro, Michele; Dorigo, Alberto
Abstract Magnetic resonance plays a leading role in the management of oncology patients, providing superior contrast resolution and greater sensitivity compared with other techniques, which enables more accurate tumor identification, characterization and staging. Contrast agents are widely used in clinical magnetic resonance imaging; approximately 40–50% of clinical scans are contrast enhanced. Most contrast agents are based on the paramagnetic gadolinium ion Gd3+, which is chelated to avoid the toxic effects of free gadolinium. Multiple factors such as molecule structure, molecule concentration, dose, field strength and temperature determine the longitudinal and transverse relaxation rates (R1 and R2, respectively) and thus the T1- and T2-relaxivities of these chelates. These T1- and T2-relaxivities, together with their pharmacokinetic properties (i.e. distribution and concentration in the area of interest), determine the radiologic efficacy of the gadolinium-based contrast agents. PMID:24060901
Use of contrast agents in oncological imaging: magnetic resonance imaging.
Morana, Giovanni; Cugini, Christian; Scatto, Giuliano; Zanato, Riccardo; Fusaro, Michele; Dorigo, Alberto
Magnetic resonance plays a leading role in the management of oncology patients, providing superior contrast resolution and greater sensitivity compared with other techniques, which enables more accurate tumor identification, characterization and staging. Contrast agents are widely used in clinical magnetic resonance imaging; approximately 40-50% of clinical scans are contrast enhanced. Most contrast agents are based on the paramagnetic gadolinium ion Gd3+, which is chelated to avoid the toxic effects of free gadolinium. Multiple factors such as molecule structure, molecule concentration, dose, field strength and temperature determine the longitudinal and transverse relaxation rates (R1 and R2, respectively) and thus the T1- and T2-relaxivities of these chelates. These T1- and T2-relaxivities, together with their pharmacokinetic properties (i.e. distribution and concentration in the area of interest), determine the radiologic efficacy of the gadolinium-based contrast agents. PMID:24060901
Designing and characterizing hyperpolarizable silicon nanoparticles for magnetic resonance imaging
Anahtar, Melis Nuray
Magnetic Resonance Imaging (MRI) is one of the most powerful noninvasive tools for diagnosing human disease, but its utility is limited because current contrast agents are ineffective when imaging air-tissue interfaces, ...
Mapping motion from 4D-MRI to 3D-CT for use in 4D dose calculations: A technical feasibility study
Boye, Dirk [Center for Proton Therapy, Paul Scherrer Institut, 5232 Villigen-PSI (Switzerland); Computer Vision Laboratory, ETH Zuerich, 8092 Zuerich (Switzerland); Lomax, Tony [Center for Proton Therapy, Paul Scherrer Institut, 5232 Villigen-PSI (Switzerland); ETH Zuerich, 8092 Zuerich (Switzerland); Knopf, Antje [Center for Proton Therapy, Paul Scherrer Institut, 5232 Villigen-PSI (Switzerland)
Purpose: Target sites affected by organ motion require a time resolved (4D) dose calculation. Typical 4D dose calculations use 4D-CT as a basis. Unfortunately, 4D-CT images have the disadvantage of being a 'snap-shot' of the motion during acquisition and of assuming regularity of breathing. In addition, 4D-CT acquisitions involve a substantial additional dose burden to the patient making many, repeated 4D-CT acquisitions undesirable. Here the authors test the feasibility of an alternative approach to generate patient specific 4D-CT data sets. Methods: In this approach motion information is extracted from 4D-MRI. Simulated 4D-CT data sets [which the authors call 4D-CT(MRI)] are created by warping extracted deformation fields to a static 3D-CT data set. The employment of 4D-MRI sequences for this has the advantage that no assumptions on breathing regularity are made, irregularities in breathing can be studied and, if necessary, many repeat imaging studies (and consequently simulated 4D-CT data sets) can be performed on patients and/or volunteers. The accuracy of 4D-CT(MRI)s has been validated by 4D proton dose calculations. Our 4D dose algorithm takes into account displacements as well as deformations on the originating 4D-CT/4D-CT(MRI) by calculating the dose of each pencil beam based on an individual time stamp of when that pencil beam is applied. According to corresponding displacement and density-variation-maps the position and the water equivalent range of the dose grid points is adjusted at each time instance. Results: 4D dose distributions, using 4D-CT(MRI) data sets as input were compared to results based on a reference conventional 4D-CT data set capturing similar motion characteristics. Almost identical 4D dose distributions could be achieved, even though scanned proton beams are very sensitive to small differences in the patient geometry. In addition, 4D dose calculations have been performed on the same patient, but using 4D-CT(MRI) data sets based on variable breathing patterns to show the effect of possible irregular breathing on active scanned proton therapy. Using a 4D-CT(MRI), including motion irregularities, resulted in significantly different proton dose distributions. Conclusions: The authors have demonstrated that motion information from 4D-MRI can be used to generate realistic 4D-CT data sets on the basis of a single static 3D-CT data set. 4D-CT(MRI) presents a novel approach to test the robustness of treatment plans in the circumstance of patient motion.
Thoracic magnetic resonance imaging: pulmonary thromboembolism.
Fink, Christian; Henzler, Thomas; Shirinova, Aysel; Apfaltrer, Paul; Wasser, Klaus
Ongoing technical developments have substantially improved the potential of magnetic resonance imaging (MRI) in the assessment of the pulmonary circulation. These developments includes improved magnet and hardware design, new k-space sampling techniques (ie, parallel imaging), and alternative contrast materials. With these techniques, not only can pulmonary vessels be visualized by MR angiography with high spatial resolution but also the perfusion of the lungs and its changes in relation to pulmonary thromboembolism (PE) can be assessed. Considering venous thromboembolism as a systemic disease, MR venography might be added for the diagnosis of underlying deep venous thrombosis. A unique advantage of MRI over other imaging tests is its potential to evaluate changes in cardiac function as a result of obstruction of the pulmonary circulation, which may have a significant impact on patient monitoring and treatment. Finally, MRI does not involve radiation, which is advantageous, especially in young patients. Over the years, a number of studies have shown promising results not only for MR angiography but also for MRI of lung perfusion and for MR venography. This review article summarizes and discusses the current evidence on pulmonary MRI for patients with suspected PE. PMID:23545949
TOPICAL REVIEW: Endovascular interventional magnetic resonance imaging
NASA Astrophysics Data System (ADS)
Bartels, L. W.; Bakker, C. J. G.
Minimally invasive interventional radiological procedures, such as balloon angioplasty, stent placement or coiling of aneurysms, play an increasingly important role in the treatment of patients suffering from vascular disease. The non-destructive nature of magnetic resonance imaging (MRI), its ability to combine the acquisition of high quality anatomical images and functional information, such as blood flow velocities, perfusion and diffusion, together with its inherent three dimensionality and tomographic imaging capacities, have been advocated as advantages of using the MRI technique for guidance of endovascular radiological interventions. Within this light, endovascular interventional MRI has emerged as an interesting and promising new branch of interventional radiology. In this review article, the authors will give an overview of the most important issues related to this field. In this context, we will focus on the prerequisites for endovascular interventional MRI to come to maturity. In particular, the various approaches for device tracking that were proposed will be discussed and categorized. Furthermore, dedicated MRI systems, safety and compatibility issues and promising applications that could become clinical practice in the future will be discussed.
Improvements in Magnetic Resonance Imaging Excitation Pulse Design
Improvements in Magnetic Resonance Imaging Excitation Pulse Design by Adam Charles Zelinski;#12;Improvements in Magnetic Resonance Imaging Excitation Pulse Design by Adam Charles Zelinski Submitted inhomogeneity limitations. When magnetic spins are tilted by only a small amount, pulse transmission may
Long-Range Surface Plasmon Resonance Imaging for Bioaffinity Sensors
Long-Range Surface Plasmon Resonance Imaging for Bioaffinity Sensors Alastair W. Wark, Hye Jin Lee A novel bioaffinity sensor based on surface plasmon resonance (SPR) imaging measurements of a multiple- layered structure that supports the generation of long- range surface plasmons (LRSPs) at the water
Surface Plasmon Resonance Imaging Studies of Protein-Carbohydrate Interactions
Surface Plasmon Resonance Imaging Studies of Protein-Carbohydrate Interactions Emily A. Smith; E-mail: email@example.com; firstname.lastname@example.com Abstract: Carbohydrate arrays fabricated on gold films were used to study carbohydrate-protein interactions with surface plasmon resonance (SPR) imaging
Behavioral/Systems/Cognitive Functional Magnetic Resonance Imaging Reveals the
Murray, Scott
magnetic resonance imaging (fMRI) has been extensively used to study the neural sub- strates of the handBehavioral/Systems/Cognitive Functional Magnetic Resonance Imaging Reveals the Neural Substrates the everyday act of reaching out to pick up a coffee cup seems like a single fluid action, arguably
Understanding Understanding Source Code with Functional Magnetic Resonance Imaging
Kaestner, Christian
Understanding Understanding Source Code with Functional Magnetic Resonance Imaging Janet Siegmund languages, tools, or coding conventions to support developers in their everyday work. In this paper, we explore whether functional magnetic resonance imaging (fMRI), which is well established in cognitive
Lie detection by functional magnetic resonance imaging.
Lee, Tatia M C; Liu, Ho-Ling; Tan, Li-Hai; Chan, Chetwyn C H; Mahankali, Srikanth; Feng, Ching-Mei; Hou, Jinwen; Fox, Peter T; Gao, Jia-Hong
The accurate detection of deception or lying is a challenge to experts in many scientific disciplines. To investigate if specific cerebral activation characterized feigned memory impairment, six healthy male volunteers underwent functional magnetic resonance imaging with a block-design paradigm while they performed forced-choice memory tasks involving both simulated malingering and under normal control conditions. Malingering that demonstrated the existence and involvement of a prefrontal-parietal-sub-cortical circuit with feigned memory impairment produced distinct patterns of neural activation. Because astute liars feign memory impairment successfully in testing once they understand the design of the measure being employed, our study represents an extremely significant preliminary step towards the development of valid and sensitive methods for the detection of deception. PMID:11835606
Magnetic Resonance Imaging of the Knee
Hash, Thomas W.
Context: Magnetic resonance imaging (MRI) affords high-resolution visualization of the soft tissue structures (menisci, ligaments, cartilage, etc) and bone marrow of the knee. Evidence Acquisition: Pertinent clinical and research articles in the orthopaedic and radiology literature over the past 30 years using PubMed. Results: Ligament tears can be accurately assessed with MRI, but distinguishing partial tears from ruptures of the anterior cruciate ligament (ACL) can be challenging. Determining the extent of a partial tear is often extremely difficult to accurately assess. The status of the posterolateral corner structures, menisci, and cartilage can be accurately evaluated, although limitations in the evaluation of certain structures exist. Patellofemoral joint, marrow, tibiofibular joint, and synovial pathology can supplement physical examination findings and provide definitive diagnosis. Conclusions: MRI provides an accurate noninvasive assessment of knee pathology. PMID:24381701
Burn injury by nuclear magnetic resonance imaging.
Eising, Ernst G; Hughes, Justin; Nolte, Frank; Jentzen, Walter; Bockisch, Andreas
Nuclear magnetic resonance imaging has become a standard diagnostic procedure in clinical medicine and is well known to have hazards for patients with pacemaker or metallic foreign bodies. Compared to CT, the frequency of MRI examinations is increasing due to the missing exposure of the patients by X-rays. Furthermore, high-field magnetic resonance tomograph (MRT) with 3 T has entered clinical practice, and 7-T systems are installed in multiple scientific institutions. On the other hand, the possibility of burn injuries has been reported only in very few cases. Based on a clinical finding of a burn injury in a 31-year-old male patient during a routine MRI of the lumbar spine with standard protocol, the MR scanner was checked and the examination was simulated in an animal model. The patient received a third-degree burn injury of the skin of the right hand and pelvis in a small region of skin contact. The subsequent control of the MRI scanner indicated no abnormal values for radiofrequency (RF) and power. In the subsequent animal experiment, comparable injuries could only be obtained by high RF power in a microwave stove. It is concluded that 'tissue loops' resulting from a contact between hand and pelvis must be avoided. With regard to forensic aspects, the need to inform patients of such a minimal risk can be avoided if the patients are adequately positioned using an isolating material between the hands and pelvis. These facts must be emphasized more in the future, if high-field MRI with stronger RF gradients is available in routine imaging. PMID:20630342
Bioengineering 208: Magnetic Resonance Imaging Laboratory Winter 2008
California at San Diego, University of
coil design Classes of coils Design criteria Reciprocity Coil loading Dielectric resonance Build your Basic scan parameters Image contrast: T1, T2, PD Image SNR TBA 3 Gradient echo imaging SPGR vs FLASH vs 5 Parallel Imaging Collect data with coil array and reconstruct 6 Artifacts and SNR TBA 7 MR
Small Animal Imaging with Magnetic Resonance Microscopy
Driehuys, Bastiaan; Nouls, John; Badea, Alexandra; Bucholz, Elizabeth; Ghaghada, Ketan; Petiet, Alexandra; Hedlund, Laurence W.
Small animal magnetic resonance microscopy (MRM) has evolved significantly from testing the boundaries of imaging physics to its expanding use today as a tool in non-invasive biomedical investigations. This review is intended to capture the state-of-the-art in MRM for scientists who may be unfamiliar with this modality, but who want to apply its capabilities to their research. We therefore include a brief review of MR concepts and methods of animal handling and support before covering a range of MRM applications including the heart, lung, brain, and the emerging field of MR histology. High-resolution anatomical imaging reveals increasingly exquisite detail in healthy animals and subtle architectural aberrations that occur in genetically altered models. Resolution of 100 µm in all dimensions is now routinely attained in living animals, and 10 µm3 is feasible in fixed specimens. Such images almost rival conventional histology while allowing the object to be viewed interactively in any plane. MRM is now increasingly used to provide functional information in living animals. Images of the beating heart, breathing lung, and functioning brain can be recorded. While clinical MRI focuses on diagnosis, MRM is used to reveal fundamental biology or to non-invasively measure subtle changes in the structure or function of organs during disease progression or in response to experimental therapies. The ability of MRM to provide a detailed functional and anatomical picture in rats and mice, and to track this picture over time, makes it a promising platform with broad applications in biomedical research. PMID:18172332
Magnetic resonance imaging of the central nervous system
Brant-Zawadzki, M.; Norman, D.
This book provides an introduction to magnetic resonance imaging (MRI) of disorders of the central nervous system, spine, neck, and nasopharynx. The book provides guidance in performing and interpreting MRI studies for specific clinical problems. Images showing pathologic findings for various disorders and demonstrating how abnormalities detected in MRI scans can aid both in differential diagnosis and clinical staging are shown. The book summarizes the basic principles of MRI and describes equipment components and contrast agents. Explanations of common artifacts and pitfalls in image interpretation and of pathophysiologic correlates of signal alterations in magnetic resonance imaging are given. A review of the principles and potential applications of magnetic resonance spectroscopy is also included.
Diagnosis of hematogenous pyogenic vertebral osteomyelitis by magnetic resonance imaging
Meyers, S.P.; Wiener, S.N. (Mt Sinai Medical Center, Cleveland, OH (USA))
The clinical information and imaging data from 27 patients with hematogenous pyogenic vertebral osteomyelitis were reviewed. All patients had roentgenographic and magnetic resonance imaging examinations. Seventeen patients had computed tomograms; 17 had technetium Tc 99m medronate bone scans; and seven had gallium citrate Ga 67 scans. Magnetic resonance imaging, when used as a part of the initial radiologic evaluation, detected abnormalities consistent with osteomyelitis in all 27 patients. Magnetic resonance imaging also demonstrated paravertebral and/or epidural extension of infection in 14 patients, including seven patients who had neurologic signs of lower-extremity weakness. Roentgenograms, computed tomograms, technetium bone scans, and gallium scans had findings suggestive of the diagnosis in 48%, 65%, 71%, and 86% of the patients, respectively. We recommend magnetic resonance imaging as an important and perhaps critical imaging modality for detection of pyogenic vertebral osteomyelitis.
Use of magnetic resonance imaging in pharmacogenomics.
Viviani, Roberto; Lehmann, Marie-Louise; Stingl, Julia C
Because of the large variation in the response to psychoactive medication, many studies have attempted to uncover genetic factors that determine response. While considerable knowledge exists on the large effects of genetic polymorphisms on pharmacokinetics and plasma concentrations of drugs, effects of the concentration at the target site and pharmacodynamic effects on brain functions in disease are much less known. This article reviews the role of magnetic resonance imaging (MRI) to visualize response to medication in brain behaviour circuits in vivo in humans and assess the influence of pharmacogenetic factors. Two types of studies have been used to characterize effects of medication and genetic variation. In task-related activation studies the focus is on changes in the activity of a neural circuit associated with a specific psychological process. The second type of study investigates resting state perfusion. These studies provide an assessment of vascular changes associated with bioavailability of drugs in the brain, but may also assess changes in neural activity after binding of centrally active agents. Task-related pharmacogenetic studies of cognitive function have characterized the effects in the prefrontal cortex of genetic polymorphisms of dopamine receptors (DRD2), metabolic enzymes (COMT) and in the post-synaptic signalling cascade under the administration of dopamine agonists and antagonists. In contrast, pharmacogenetic imaging with resting state perfusion is still in its infancy. However, the quantitative nature of perfusion imaging, its non-invasive character and its repeatability might be crucial assets in visualizing the effects of medication in vivo in man during therapy. PMID:23802603
Use of magnetic resonance imaging in pharmacogenomics
Viviani, Roberto; Lehmann, Marie-Louise; Stingl, Julia C
Because of the large variation in the response to psychoactive medication, many studies have attempted to uncover genetic factors that determine response. While considerable knowledge exists on the large effects of genetic polymorphisms on pharmacokinetics and plasma concentrations of drugs, effects of the concentration at the target site and pharmacodynamic effects on brain functions in disease are much less known. This article reviews the role of magnetic resonance imaging (MRI) to visualize response to medication in brain behaviour circuits in vivo in humans and assess the influence of pharmacogenetic factors. Two types of studies have been used to characterize effects of medication and genetic variation. In task-related activation studies the focus is on changes in the activity of a neural circuit associated with a specific psychological process. The second type of study investigates resting state perfusion. These studies provide an assessment of vascular changes associated with bioavailability of drugs in the brain, but may also assess changes in neural activity after binding of centrally active agents. Task-related pharmacogenetic studies of cognitive function have characterized the effects in the prefrontal cortex of genetic polymorphisms of dopamine receptors (DRD2), metabolic enzymes (COMT) and in the post-synaptic signalling cascade under the administration of dopamine agonists and antagonists. In contrast, pharmacogenetic imaging with resting state perfusion is still in its infancy. However, the quantitative nature of perfusion imaging, its non-invasive character and its repeatability might be crucial assets in visualizing the effects of medication in vivo in man during therapy. PMID:23802603
Magnetic Resonance Imaging Part II—Clinical Applications
Hendee, William R.; Morgan, Christopher J.
Magnetic resonance (MR) imaging is the most promising new technology to appear in the clinical imaging arena since the advent of x-ray transmission computed tomography in the early 1970s. Five independent tissue characteristics (spin density, spin-lattice and spin-spin relaxation times, flow and spectral shift information) are accessible to MR imaging, and their relative influence in the magnetic resonance image can be varied by appropriate selection of pulse sequences and pulse times. All major organ systems appear to be amenable to MR imaging, and some are revealed with superior definition compared with their appearance in images obtained by alternate imaging technologies. Of particular interest is the superior contrast resolution in MR images of the brain and spinal cord, and the absence of bone- and motion-induced artifacts in images of the abdomen and pelvis. Applications of MR imaging to the heart and great vessels are just developing, as are new types of contrast agents for use in MR imaging. In vivo chemical spectroscopic measurements by magnetic resonance are heralded by some investigators as the most significant contribution that magnetic resonance will make ultimately to clinical diagnosis. At present, the number of MR imaging units is extremely low, and clinical studies are proceeding at a slow rate. Nevertheless, it is possible to provide a preliminary evaluation of the usefulness of MR imaging in a variety of clinical applications. This article is such an evaluation, tempered by the acknowledgement that much additional work remains to be done. Images PMID:6516335
Imaging of tophaceous gout: computed tomography provides specific images compared with magnetic resonance imaging and ultrasonography
J C Gerster; M Landry; L Dufresne; J Y Meuwly
Objective: To determine the usefulness of computed tomography (CT), magnetic resonance imaging (MRI), and Doppler ultrasonography (US) in providing specific images of gouty tophi.Methods: Four male patients with chronic gout with tophi affecting the knee joints (three cases) or the olecranon processes of the elbows (one case) were assessed. Crystallographic analyses of the synovial fluid or tissue aspirates of the
Cost effectiveness of magnetic resonance imaging in the neurosciences.
Szczepura, A K; Fletcher, J; Fitz-Patrick, J D
OBJECTIVES--To measure, in a service setting, the effect of magnetic resonance imaging on diagnosis, diagnostic certainty, and patient management in the neurosciences; to measure the cost per patient scanned; to estimate the marginal cost of imaging and compare this with its diagnostic impact; to measure changes in patients' quality of life; and to record the diagnostic pathway leading to magnetic resonance imaging. DESIGN--Controlled observational study using questionnaires on diagnosis and patient management before and after imaging. Detailed costing study. Quality of life questionnaires at the time of imaging and six months later. Diagnostic pathways extracted from medical records for a representative sample. SETTING--Regional superconducting 1.5 T magnetic resonance service. SUBJECTS--782 consecutive neuroscience patients referred by consultants for magnetic resonance imaging during June 1988-9; diagnostic pathways recorded for 158 cases. MAIN OUTCOME MEASURES--Costs of magnetic resonance imaging and preliminary investigations; changes in planned management and resulting savings; changes in principal diagnosis and diagnostic certainty; changes in patients' quality of life. RESULTS--Average cost of magnetic resonance imaging was estimated at 206.20/patient pounds (throughput 2250 patients/year, 1989-90 prices including contrast and upgrading). Before magnetic resonance imaging diagnostic procedures cost 164.40/patient pounds (including inpatient stays). Management changed after imaging in 208 (27%) cases; saving an estimated 80.90/patient pounds. Confidence in planned management increased in a further 226 (29%) referrals. Consultants' principal diagnosis changed in 159 of 782 (20%) referrals; marginal cost per diagnostic change was 626 pounds. Confidence in diagnosis increased in 236 (30%) referrals. No improvement in patients' quality of life at six month assessment. CONCLUSIONS--Any improvement in diagnosis with magnetic resonance imaging is achieved at a higher cost. Techniques for monitoring the cost effectiveness of this technology need to be developed. PMID:1819260
Low field strength magnetic resonance imaging of the neonatal brain
Whitby, E; Paley, M; Smith, M; Sprigg, A; Woodhouse, N; Griffiths, P
Background: Magnetic resonance (MR) imaging of the neonate has been restricted by the need to transport the sick baby to the large magnetic resonance scanners and often the need for sedation or anaesthesia in order to obtain good quality images. Ultrasound is the reference standard for neonatal imaging. Objective: To establish a dedicated neonatal MR system and compare the clinical usefulness of MR imaging with ultrasound imaging. Design: Prospective double blind trial. Setting: Neonatal intensive care unit, Sheffield. Main outcome measures: Imaging reports. Patients: 134 premature and term babies. Results: In 56% of infants with pathology suspected on clinical grounds, MR provided additional useful clinical information over and above that obtained with ultrasound. Conclusion: Infants can be safely imaged by dedicated low field magnetic resonance on the neonatal intensive care unit without the need for sedation at a cost equivalent to ultrasound. PMID:12719393
Magnetic resonance imaging: Review of imaging techniques and overview of liver imaging
Maniam, Santhi; Szklaruk, Janio
Magnetic resonance imaging (MRI) of the liver is slowly transitioning from a problem solving imaging modality to a first line imaging modality for many diseases of the liver. The well established advantages of MRI over other cross sectional imaging modalities may be the basis for this transition. Technological advancements in MRI that focus on producing high quality images and fast imaging, increasing diagnostic accuracy and developing newer function-specific contrast agents are essential in ensuring that MRI succeeds as a first line imaging modality. Newer imaging techniques, such as parallel imaging, are widely utilized to shorten scanning time. Diffusion weighted echo planar imaging, an adaptation from neuroimaging, is fast becoming a routine part of the MRI liver protocol to improve lesion detection and characterization of focal liver lesions. Contrast enhanced dynamic T1 weighted imaging is crucial in complete evaluation of diseases and the merit of this dynamic imaging relies heavily on the appropriate timing of the contrast injection. Newer techniques that include fluoro-triggered contrast enhanced MRI, an adaptation from 3D MRA imaging, are utilized to achieve good bolus timing that will allow for optimum scanning. For accurate interpretation of liver diseases, good understanding of the newer imaging techniques and familiarity with typical imaging features of liver diseases are essential. In this review, MR sequences for a time efficient liver MRI protocol utilizing newer imaging techniques are discussed and an overview of imaging features of selected common focal and diffuse liver diseases are presented. PMID:21160685
Realization of magnetic resonance current density imaging at 3 tesla.
Goksu, C; Sadighi, M; Eroglu, H H; Eyuboglu, M
Magnetic Resonance Current Density Imaging (MRCDI) is an imaging modality, which reconstructs electrical current density distribution inside a material by using Magnetic Resonance Imaging (MRI) techniques. In this study, a current source with maximum current injection capability of 224.7mA, under 1k? resistive load is used. Experiments are performed with a 2D uniform phantom, in which a current steering insulator is inserted. Magnetic flux density distributions are measured, and current density images are reconstructed. The reconstructed images are in agreement with the reconstructions obtained with simulated measurements. PMID:25570158
Magnetic resonance imaging of oscillating electrical currents.
Halpern-Manners, Nicholas W; Bajaj, Vikram S; Teisseyre, Thomas Z; Pines, Alexander
Functional MRI has become an important tool of researchers and clinicians who seek to understand patterns of neuronal activation that accompany sensory and cognitive processes. However, the interpretation of fMRI images rests on assumptions about the relationship between neuronal firing and hemodynamic response that are not firmly grounded in rigorous theory or experimental evidence. Further, the blood-oxygen-level-dependent effect, which correlates an MRI observable to neuronal firing, evolves over a period that is 2 orders of magnitude longer than the underlying processes that are thought to cause it. Here, we instead demonstrate experiments to directly image oscillating currents by MRI. The approach rests on a resonant interaction between an applied rf field and an oscillating magnetic field in the sample and, as such, permits quantitative, frequency-selective measurements of current density without spatial or temporal cancellation. We apply this method in a current loop phantom, mapping its magnetic field and achieving a detection sensitivity near the threshold required for the detection of neuronal currents. Because the contrast mechanism is under spectroscopic control, we are able to demonstrate how ramped and phase-modulated spin-lock radiation can enhance the sensitivity and robustness of the experiment. We further demonstrate the combination of these methods with remote detection, a technique in which the encoding and detection of an MRI experiment are separated by sample flow or translation. We illustrate that remotely detected MRI permits the measurement of currents in small volumes of flowing water with high sensitivity and spatial resolution. PMID:20421504
Magnetic Resonance Imaging in Postprostatectomy Radiotherapy Planning
Sefrova, Jana, E-mail: email@example.com [Department of Oncology and Radiotherapy, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic); Odrazka, Karel [Department of Clinical and Radiation Oncology, Multiscan and Pardubice Regional Hospital, Pardubice (Czech Republic); First and Third Faculty of Medicine, Charles University in Prague, Prague (Czech Republic); Paluska, Petr [Department of Oncology and Radiotherapy, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic); Belobradek, Zdenek [Department of Radiology, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic); Brodak, Milos [Department of Urology, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic); Dolezel, Martin [Department of Clinical and Radiation Oncology, Multiscan and Pardubice Regional Hospital, Pardubice (Czech Republic); First and Third Faculty of Medicine, Charles University in Prague, Prague (Czech Republic); Prosvic, Petr [Department of Urology, Regional Hospital Nachod, Nachod (Czech Republic); Macingova, Zuzana; Vosmik, Milan [Department of Oncology and Radiotherapy, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic); Hoffmann, Petr [Department of Radiology, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic); Louda, Miroslav [Department of Urology, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic); Nejedla, Anna [Department of Oncology and Radiotherapy, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic)
Purpose: To investigate whether the use of magnetic resonance imaging (MRI) in prostate bed treatment planning could influence definition of the clinical target volume (CTV) and organs at risk. Methods and Materials: A total of 21 consecutive patients referred for prostate bed radiotherapy were included in the present retrospective study. The CTV was delineated according to the European Organization for Research and Treatment of Cancer recommendations on computed tomography (CT) and T{sub 1}-weighted (T{sub 1}w) and T{sub 2}-weighted (T{sub 2}w) MRI. The CTV magnitude, agreement, and spatial differences were evaluated on the planning CT scan after registration with the MRI scans. Results: The CTV was significantly reduced on the T{sub 1}w and T{sub 2}w MRI scans (13% and 9%, respectively) compared with the CT scans. The urinary bladder was drawn smaller on the CT scans and the rectum was smaller on the MRI scans. On T{sub 1}w MRI, the rectum and urinary bladder were delineated larger than on T{sub 2}w MRI. Minimal agreement was observed between the CT and T{sub 2}w images. The main spatial differences were measured in the superior and superolateral directions in which the CTV on the MRI scans was 1.8-2.9 mm smaller. In the posterior and inferior border, no difference was seen between the CT and T{sub 1}w MRI scans. On the T{sub 2}w MRI scans, the CTV was larger in these directions (by 1.3 and 1.7 mm, respectively). Conclusions: The use of MRI in postprostatectomy radiotherapy planning resulted in a reduction of the CTV. The main differences were found in the superior part of the prostate bed. We believe T{sub 2}w MRI enables more precise definition of prostate bed CTV than conventional planning CT.
Satashu Goel; Jerry Tsai; Narayan Krishnamurthy
Magnetic resonance (MR) images are routinely used for med- ical diagnosis. Denoising of these images to enhance their clinical usability has been an active area of research. This paper considers the thresholding based appproaches for im- age denoising. The paper investigates the use of appropriate basis for image representation and the choice of an appro- priate threshold. The use of
Magnetic resonance microwave absorption imaging: initial experimental results in phantoms
Bin Xie; John Weaver; Paul Meaney; Keith Paulsen
We have used phase contrast magnetic resonance gradients to image small displacements induced by a pulsed 434 MHz microwave field. Thermoelastic expansions, which are related to the tissues' local microwave absorption properties and the applied microwave field distribution are encoded into the phase of MR images. The imaging principles are applicable to other irradiation sources. Initial efforts to develop the
Gegenbauer High Resolution Reconstruction of Magnetic Resonance Imaging
Renaut, Rosemary
Gegenbauer High Resolution Reconstruction of Magnetic Resonance Imaging Jim Estipona and Prasanna K or dark rings seen at the borders of abrupt intensity change on the images. Gegenbauer High Resolution Velamuru Advisors: Dr. Rick Archibald, Dr. Rosemary Renaut Abstract- A variety of image artifacts
Whole-body magnetic resonance imaging: assessment of skeletal metastases.
Moynagh, Michael R; Colleran, Gabrielle C; Tavernaraki, Katarina; Eustace, Stephen J; Kavanagh, Eoin C
The concept of a rapid whole-body imaging technique with high resolution and the absence of ionizing radiation for the assessment of osseous metastatic disease is a desirable tool. This review article outlines the current perspective of whole-body magnetic resonance imaging in the assessment of skeletal metastatic disease, with comparisons made to alternative whole-body imaging modalities. PMID:20229438
D. Ferrario; M. Bach Cuadra; M. Schaer; N. Houhou; D. Zosso; S. Eliez; L. Guibaud
In this work we present a method for the image anal- ysis of Magnetic Resonance Imaging (MRI) of fetuses. Our goal is to segment the brain surface from multiple volumes (axial, coronal and sagittal acquisitions) of a fe- tus. To this end we propose a two-step approach: first, a Finite Gaussian Mixture Model (FGMM) will segment the image into 3
Magnetic resonance imaging of the kidneys
Leung, A.W.L.; Bydder, G.M.; Steinter, R.E.; Bryant, D.J.; Young, I.R.
A study of the magnetic resonance imaging (MRI) appearance of the kidneys in six normal volunteers and 52 patients is reported. Corticomedullary differentiation was seen with the inversion-recovery (IR 1400/400) sequence in the normal volunteers and in patients with functioning transplanted kidneys and acute tubular necrosis. Partial or total loss of corticomedullary differentiation was seen in glomerulonephritis, acute and chronic renal failure, renal artery stenosis, and transplant rejection. The T1 of the kidneys was increased in glomerulonephritis with neuphrotic syndrome, but the T1 was within the normal range for renal medulla in glomerulonephritis without nephrotic syndrome, renal artery stenosis, and chronic renal failure. A large staghorn calculus was demonstrated with MRI, but small calculi were not seen. Fluid within the hydonephrosis, simple renal cysts, and polycystic kidneys displayed very low signal intensity and long T1 values. Tumors displayed varied appearances. Hypernephromas were shown to be hypo- or hyperintense with the renal medulla on the IR 1400/400 sequence. After intravenous injection of gadolinium-DTPA, there was marked decrease in the tumor T1.
Magnetic Resonance Imaging of Cartilage Repair
Trattnig, Siegfried; Winalski, Carl S.; Marlovits, Stephan; Jurvelin, Jukka S.; Welsch, Goetz H.; Potter, Hollis G.
Articular cartilage lesions are a common pathology of the knee joint, and many patients may benefit from cartilage repair surgeries that offer the chance to avoid the development of osteoarthritis or delay its progression. Cartilage repair surgery, no matter the technique, requires a noninvasive, standardized, and high-quality longitudinal method to assess the structure of the repair tissue. This goal is best fulfilled by magnetic resonance imaging (MRI). The present article provides an overview of the current state of the art of MRI of cartilage repair. In the first 2 sections, preclinical and clinical MRI of cartilage repair tissue are described with a focus on morphological depiction of cartilage and the use of functional (biochemical) MR methodologies for the visualization of the ultrastructure of cartilage repair. In the third section, a short overview is provided on the regulatory issues of the United States Food and Drug Administration (FDA) and the European Medicines Agency (EMEA) regarding MR follow-up studies of patients after cartilage repair surgeries.
Design algorithms for parallel transmission in magnetic resonance imaging
Setsompop, Kawin
The focus of this dissertation is on the algorithm design, implementation, and validation of parallel transmission technology in Magnetic Resonance Imaging (MRI). Novel algorithms are proposed which yield excellent excitation ...
Improvements in magnetic resonance imaging excitation pulse design
Zelinski, Adam Charles
This thesis focuses on the design of magnetic resonance imaging (MRI) radio-frequency (RF) excitation pulses, and its primary contributions are made through connections with the novel multiple-system single-output (MSSO) ...
Microfluidically Cryo-Cooled Planar Coils for Magnetic Resonance Imaging
Koo, Chiwan
High signal-to-noise ratio (SNR) is typically required for higher resolution and faster speed in magnetic resonance imaging (MRI). Planar microcoils as receiver probes in MRI systems offer the potential to be configured into array elements for fast...
A Bayesian time course model for functional magnetic resonance imaging
Worsley, Keith
to a small number of pre-selected isolated regions (`plots'), such as Broca's or Wernicke's areas Magnetic Resonance Imaging (fMRI), and brain mapping in general, presents statisticians with new challenges
Magnetic resonance imaging contrast agents for chemical sensing
Liu, Vincent Hok
Magnetic resonance imaging (MRI) is frequently used for examining the human body. MRI contrast agents currently used in the clinic assist physicians in locating problematic areas, but other tools are needed to interrogate ...
FY08 Annual Report for Nuclear Resonance Fluorescence Imaging
Warren, Glen A.; Caggiano, Joseph A.
FY08 annual report for project the "Nuclear Resonance Fluorescence Imaging" project. Reviews accomplishments of last 3 years, including U-235 signature search, comparison of different photon sources, and examination of NRF measurements using monochromatic photon source.
The Nobel Prize in Medicine for Magnetic Resonance Imaging
ERIC Educational Resources Information Center
Fry, Charles G.
Nobel Prize in Medicine awarded in December 2003 to chemist Paul C. Lauterbur and physicist Peter Mansfield for the development of magnetic resonance imaging (MRI), a long overdue recognition of the huge impact MRI has had in medical diagnostics and research is mentioned. MRI was derived, and remains an extension of nuclear magnetic resonance…
Reduction of motion artifacts in magnetic resonance diffusion imaging
Archie Chih-Ching Chu
Nuclear magnetic resonance (NMR) diffusion is capable of probing molecular displacement in vivo in a micrometer range. The clinical application of diffusion magnetic resonance imaging (MRI) is used for early detecting acute stroke, and it may be a sensitive monitor of early response to cancer treatments. NMR diffusion techniques are sensitive to Brownian motion, but also enhance bulk-motion artifacts in
An electrochemical surface plasmon resonance imaging system targeting cell analysis
NASA Astrophysics Data System (ADS)
Zhang, L. L.; Chen, X.; Wei, H. T.; Li, H.; Sun, J. H.; Cai, H. Y.; Chen, J. L.; Cui, D. F.
This paper presents an electrochemical-surface plasmon resonance imaging (EC-SPRI) system, enabling the characterization of optical and electrical properties of cells, simultaneously. The developed surface plasmon resonance (SPR) imaging system was capable of imaging micro cavities with a dimension of 10 ?m × 10 ?m and differentiated glycerol solutions with a group of refractive indices (RIs). Furthermore, the EC-SPRI system was used to image A549 cells, suggesting corresponding RI and morphology changes during the cell death process. In the end, electrochemical and SPR methods were used in combination, recording oxidation peaks of A549 cells in the cyclic voltage curves and SPR response unit increase, simultaneously.
Towards magnetic resonance imaging guided radiation therapy (MRIgRT)
Teodor Marius Stanescu
The goal of this work is to address key aspects of the magnetic resonance imaging guided radiation therapy (MRIgRT) process of cancer sites. MRIgRT is implemented by using a system comprised of a magnetic resonance imaging (MRI) scanner coupled with a radiation source, in our case a radiotherapy accelerator (Linac). The potential benefits of MRIgRT are the real-time tracking of
Magnetic resonance imaging appearance of hypertensive encephalopathy in a dog.
Bowman, Chloe A; Witham, Adrian; Tyrrell, Dayle; Long, Sam N
A 16-year-old female spayed English Staffordshire terrier was presented for evaluation of a 10-month history of intermittent myoclonic episodes, and a one weeks history of short episodes of altered mentation, ataxia and collapse. Magnetic resonance imaging identified subcortical oedema, predominately in the parietal and temporal lobes and multiple cerebral microbleeds. Serum biochemistry, indirect blood pressure measurements and magnetic resonance imaging abnormalities were consistent with hypertensive encephalopathy secondary to chronic kidney disease. PMID:25949801
Proton magnetic resonance imaging of lipid in pecan embryos
John M. Halloina; Thomas G. Cooper; E. James Potchen; Tommy E. Thompson
Magnetic resonance images of plant tissues typically are manifestations of water protons in tissues. Within oilseeds, however,\\u000a lipids contain a major portion of the mobile protons, which should enable specific imaging of lipids. In this study, experiments\\u000a were done to demonstrate spin-echo imaging (SEI) and chemical-shift imaging (CSI) of lipid within nonimbibed and imbibed embryos\\u000a of pecan (Carya illinoensis), a
Silicon Nanoparticles as Hyperpolarized Magnetic Resonance Imaging Agents
Aptekar, Jacob W.; Cassidy, Maja C.; Johnson, Alexander C.; Barton, Robert A.; Lee, Menyoung; Ogier, Alexander C.; Vo, Chinh; Anahtar, Melis N.; Ren, Yin; Bhatia, Sangeeta N.; Ramanathan, Chandrasekhar; Cory, David G.; Hill, Alison L.; Mair, Ross W.; Rosen, Matthew S.; Walsworth, Ronald L.
Magnetic resonance imaging of hyperpolarized nuclei provides high image contrast with little or no background signal. To date, in-vivo applications of pre-hyperpolarized materials have been limited by relatively short nuclear spin relaxation times. Here, we investigate silicon nanoparticles as a new type of hyperpolarized magnetic resonance imaging agent. Nuclear spin relaxation times for a variety of Si nanoparticles are found to be remarkably long, ranging from many minutes to hours at room temperature, allowing hyperpolarized nanoparticles to be transported, administered, and imaged on practical time scales. Additionally, we demonstrate that Si nanoparticles can be surface functionalized using techniques common to other biologically targeted nanoparticle systems. These results suggest that Si nanoparticles can be used as a targetable, hyperpolarized magnetic resonance imaging agent with a large range of potential applications. PMID:19950973
Detection of Entorhinal Layer II Using Tesla Magnetic Resonance Imaging
Fischl, Bruce
scanner using a solenoid coil. In 70 and 100 m isotropic data, the entorhinal islands were clearly visible lobe were robustly detected using the magnetic resonance images. Our ex vivo results could break ground used a human whole-body 7T scanner, obtaining images with 100 m isotropic voxels, and were able
Design of a dynamic heart phantom for magnetic resonance imaging
E. Gullans; E. Ollinick; S. Rein; C. Saffos; J. Shilling; K. C. Yan; J. J. Pilla; Chun Xu
Extensive research in the field of magnetic resonance imaging has been done to improve diagnosis of cardiovascular diseases. Using a dynamic heart phantom (DHP) is vital to improve and validate MR imaging techniques and protocols. We have developed an innovative DHP design using a motor driven hydraulic system that delivers XYZ translational motion, rotation of the gel and internal pressure
Applications of functional magnetic resonance imaging for market research
Peter Kenning; Hilke Plassmann; Dieter Ahlert
Purpose – The purpose of this paper is to provide a brief overview of the methodology of several brain imaging techniques and in particular, functional magnetic resonance imaging (fMRI) and its potential implications for market research. The aim is to enable the reader both to understand this emerging methodology and to conduct independent research in the area. Design\\/methodology\\/approach – A
The accuracy of magnetic resonance imaging for stereotactic localization
Cheng Yu; M. L. J. Apuzzo; Chi-Shing Zee; G. Luxton; Z. Petrovich
Stereotactic radiosurgery is based on the precise definition of intracranial target in relation to an extracranial reference system. A special plexiglas phantom for both magnetic resonance imaging (MRI) and computed tomography (CT) was built to test the spatial accuracy of MR images using the Leksell stereotactic head frame and localizer system. The phantom was constructed in a shape of cube,
Automatic Segmentation of Adipose Tissue from Thigh Magnetic Resonance Images
Li, Baihua
of fuzzy C-means clustering with spatial connectivity constraints to guide segmentation [4]. This methodAutomatic Segmentation of Adipose Tissue from Thigh Magnetic Resonance Images Senthil Purushwalkam1 segmentation. Existing image processing software such as Osyrix, Corresponding author: firstname.lastname@example.com #12
Acquisition of electrophysiologic signals during magnetic resonance imaging.
Parker, J M; Alger, J R; Woo, M A; Spriggs, D; Harper, R M
We describe a low cost system for acquiring electrophysiological signals during magnetic resonance imaging. The system consists of high common-mode-rejection and low noise operational amplifiers, coupled by fiber optic cables to a receiver located at the periphery of the magnetic field. The system minimizes noise introduction which would contaminate image signals. PMID:10617174
Safety Guidelines for Conducting Magnetic Resonance Imaging (MRI) Experiments Involving
Squire, Larry R.
Safety Guidelines for Conducting Magnetic Resonance Imaging (MRI) Experiments Involving Human Risks 7 Risk Management 14 Emergencies 18 Contact With Body Fluids 20 Visitors 20 Summary of Safety imaging (MRI) experiments involving human subjects and biomedical studies at the UCSD Functional MRI
Voriconazole-related periostitis presenting on magnetic resonance imaging
Davis, Derik L.
Summary Painful periostitis is a complication of long-term antifungal therapy with voriconazole. A high clinical suspicion coupled with imaging and laboratory assessment is useful to establish the diagnosis. Prompt discontinuance of voriconazole typically results in the resolution of symptoms and signs. This report describes the presentation of voriconazole-related periostitis on magnetic resonance imaging. PMID:26136804
Bright and Dark Field Imaging of Plasmon Resonance in Nanoparticles
Anlage, Steven
Bright and Dark Field Imaging of Plasmon Resonance in Nanoparticles Armand Rundquist, Chad Ropp information about the structure of the particle. Introduction Optical Setup Dark Field Imaging Acknowledgments alone, an axicon (conical lens) is used to focus the white light source into a ring, which
Magnetic resonance imaging of knee injuries in children
S. J. King; H. M. L. Carty; O. Brady
The purpose of this study was to evaluate the significance of meniscal appearances and determine the frequency of abnormalities seen on magnetic resonance (MR) imaging in children with knee injuries. We reviewed 78 consecutive MR imaging studies of 74 children aged 5–16 years with unfused epiphyses. Menisci were evaluated using conventional grading techniques. We used ?2 to compare the frequencies
Reconstruction of pulse noisy images via stochastic resonance
Han, Jing; Liu, Hongjun; Sun, Qibing; Huang, Nan
We investigate a practical technology for reconstructing nanosecond pulse noisy images via stochastic resonance, which is based on the modulation instability. A theoretical model of this method for optical pulse signal is built to effectively recover the pulse image. The nanosecond noise-hidden images grow at the expense of noise during the stochastic resonance process in a photorefractive medium. The properties of output images are mainly determined by the input signal-to-noise intensity ratio, the applied voltage across the medium, and the correlation length of noise background. A high cross-correlation gain is obtained by optimizing these parameters. This provides a potential method for detecting low-level or hidden pulse images in various imaging applications. PMID:26067911
Reconstruction of pulse noisy images via stochastic resonance.
Han, Jing; Liu, Hongjun; Sun, Qibing; Huang, Nan
We investigate a practical technology for reconstructing nanosecond pulse noisy images via stochastic resonance, which is based on the modulation instability. A theoretical model of this method for optical pulse signal is built to effectively recover the pulse image. The nanosecond noise-hidden images grow at the expense of noise during the stochastic resonance process in a photorefractive medium. The properties of output images are mainly determined by the input signal-to-noise intensity ratio, the applied voltage across the medium, and the correlation length of noise background. A high cross-correlation gain is obtained by optimizing these parameters. This provides a potential method for detecting low-level or hidden pulse images in various imaging applications. PMID:26067911
Instrumentation for parallel magnetic resonance imaging
Brown, David Gerald
of small animal research and education. A 64-channel receiver for parallel MR imaging with arrays of sensors was also developed. The receiver prototype was characterized through both bench-top tests and phantom imaging. The parallel receiver is capable...
Denoising by Averaging Reconstructed Images: Application to Magnetic Resonance Images
Jianhua Luo; Yuemin Zhu; Isabelle E. Magnin
A novel denoising approach is proposed that is based on averaging reconstructed images. The approach first divides the spectrum of the image to be denoised into different parts. From every such partial spectrum is then reconstructed an image using a 2-D singularity function analysis model. By expressing each of the reconstructed images as the sum of the same noise-free image
Atypical magnetic resonance imaging findings in hepatocellular carcinoma.
Roumanis, Panayota S; Bhargava, Puneet; Kimia Aubin, Golnaz; Choi, Joon-Il; Demirjian, Aram N; Thayer, David A; Lall, Chandana
Magnetic resonance imaging (MRI) is currently the modality of choice to evaluate liver lesions in patients with cirrhosis and hepatitis B and C. Hepatocellular carcinoma demonstrates typical imaging findings on contrast-enhanced MRI, which are usually diagnostic. Unfortunately, a subgroup of hepatocellular carcinoma presents with atypical imaging features, and awareness of these atypical presentations is important in ensuring early diagnosis and optimal patient outcomes. Herein, we review some of the more common atypical presentations with a focus on MRI. PMID:25823550
Optically Detected Scanned Probe Magnetic Resonance Imaging
NASA Astrophysics Data System (ADS)
Wolfe, Christopher; Bhallamudi, Vidya; Wang, Hailong; Du, Chunhui; Manuilov, Sergei; Adur, Rohan; Yang, Fengyuan; Hammel, P. Chris
Magnetic resonance is a powerful tool for studying magnetic properties and dynamics of spin systems. Scanned magnetic probes can induce spatially localized resonance due to the strong magnetic field and gradient near the magnetic tip., Nitrogen vacancy centers (NV) in diamond provide a sensitive means of measuring magnetic fields at the nanoscale. We report preliminary results towards using the high sensitivity of NV detection with a scanned magnetic probe to study local magnetic phenomena. This work is supported by the Center for Emergent Materials at The Ohio State University, a NSF Materials Research Science and Engineering Center (DMR-0820414).
Magnetic resonance imaging protocols for paediatric neuroradiology
Dawn E. Saunders; Clare Thompson; Roxanne Gunny; Rod Jones; Tim Cox; Wui Khean Chong
Increasingly, radiologists are encouraged to have protocols for all imaging studies and to include imaging guidelines in care\\u000a pathways set up by the referring clinicians. This is particularly advantageous in MRI where magnet time is limited and a radiologist's\\u000a review of each patient's images often results in additional sequences and longer scanning times without the advantage of improvement\\u000a in diagnostic
Basic Principles of Magnetic Resonance Imaging—An Update
Scherzinger, Ann L.; Hendee, William R.
Magnetic resonance (MR) imaging technology has undergone many technologic advances over the past few years. Many of these advances were stimulated by the wealth of information emerging from nuclear magnetic resonance research in the areas of new and optimal scanning methods and radio-frequency coil design. Other changes arose from the desire to improve image quality, ease siting restrictions and generally facilitate the clinical use of MR equipment. Many questions, however, remain unanswered. Perhaps the most controversial technologic question involves the optimal field strength required for imaging or spectroscopic applications or both. Other issues include safety and clinical efficacy. Technologic issues affect all aspects of MR use including the choice of equipment, examination procedure and image interpretation. Thus, an understanding of recent changes and their theoretic basis is necessary. ImagesFigure 9. PMID:3911591
Single echo acquisition magnetic resonance imaging
McDougall, Mary Preston
at speeds limited only by the time it takes to acquire a single echo Â? is presented with a discussion of extremely high frame rate imaging. The contribution to the field of medical imaging is the first implementation, characterization, and demonstration...
Parallel magnetic resonance imaging: characterization and comparison
Rane, Swati Dnyandeo
parameters selected by the pulse sequences, the subject being imaged and the RF hardware system in operation. New pulse sequences have been developed in order to decrease the imaging time by a faster k-space scan. However, they may not be fast enough...
Method for nuclear magnetic resonance imaging
Kehayias, J.J.; Joel, D.D.; Adams, W.H.; Stein, H.L.
A method for in vivo NMR imaging of the blood vessels and organs of a patient characterized by using a dark dye-like imaging substance consisting essentially of a stable, high-purity concentration of D/sub 2/O in a solution with water.
Raman-induced resonance imaging of trapped atoms
NASA Astrophysics Data System (ADS)
Savard, Thomas Alan
This dissertation describes the development of the first neutral atom trapping apparatus at Duke University and Raman induced resonance imaging of trapped atoms-an imaging technique which provides three-dimensional information about the atomic spatial distribution in the trap. The design and operating principles of the 6Li atom source, laser sources, multi-coil Zeeman slower, and magneto-optic trap used in the experiment are explained. Using Raman induced resonance imaging, the atomic spatial distribution in the magneto-optic trap is imaged with 12 ?m resolution. Changes to the experiment will yield a resolution of 5 ?m-rivaling the best resolution achieved in previous two-dimensional imaging experiments-without the expense of large aperture optics and high resolution cameras. The position distribution of atoms is acquired by inducing Raman transitions between lithium's ground state hyperfine levels. The quadrupole magnetic field of the MOT causes the Raman transition strength and Raman resonance frequency to vary with position. By measuring the response of the atomic distribution at different Raman pulse frequencies, a spectrum is obtained which depends on the position distribution of the atoms. Previous images of trapped atoms used CCD cameras to record fluorescence or phase contrast images of the atomic spatial distribution. Because the CCD camera measures only two-dimensional information, the entire depth of the trap was averaged onto a single plane. In Raman induced resonance imaging of the MOT, the number of atoms in concentric ellipsoidal shells is measured. Consequently, Raman induced resonance imaging is ideally suited for probing small centrally located density variations within high density atomic spatial distributions, a regime in which two-dimensional imaging with a camera is unsuitable. In this dissertation, Raman induced resonance imaging is used to determine the size of the atomic distribution and it's offset relative to the MOT's magnetic field zero point. The center of the atomic cloud is found to be substantially shifted from the magnetic field zero point of the trap. In addition, the work presented here significantly advances the development of single-shot Raman transient imaging techniques that will have wide applications to fundamental measurements of ultracold trapped atoms.
Gradient Moment Compensated Magnetic Resonance Spectroscopic Imaging
Kim, Dong-Hyun; Gu, Meng; Spielman, Daniel M.
Spectroscopic imaging applications outside of the brain can suffer from artifacts due to inherent long scan times and susceptibility to motion. A fast spectroscopic imaging sequence has been devised with reduced sensitivity to motion. The sequence uses oscillating readout gradients and acquires k-space data in a spiral out–in fashion, which allows fast k-space coverage. We show that a spiral out–in readout acquisition is characterized by small gradient moments, reducing sensitivity to motion-induced artifacts. Data are acquired comparing the sequence to normal phase encoded spectroscopic imaging and conventional spiral spectroscopic imaging protocols. In addition, in vivo data are acquired from the liver, demonstrating potential usage as a multivoxel fat/water spectroscopic imaging tool. Results indicate that in the presence of motion, ghosting effects are reduced while metabolite signal increases of approximately 10% can be achieved. PMID:19161164
Magnetic resonance imaging of interstitial laser photocoagulation
NASA Astrophysics Data System (ADS)
Bleier, Alan R.; Higuchi, Nobuya; Panych, Lawrence P.; Jakab, Peter D.; Hrovat, Mirko I.; Jolesz, Ferenc A.
We have previously demonstrated the detection of reversible and irreversible changes on MR images oflaser energy deposition and tissue heating and cooling1. It is possible to monitor and control energy deposition during interstitial laser therapy. This presentation describes some first steps toward optimizing the power and total energy deposited in various tissues in vivo, by analyzing the irreversible tissue changes and their spatial distribution as revealed by spin echo imaging. We used various power settings of an Nd.YAG laser delivered by a fiber optic inserted into several tissues (brain, muscle, liver) of anesthetized rats and rabbits. MR imaging was performed at 1.9 T. Photothermally-produced lesions were seen on both T1- and Ta-weighted images. The overall size of the lesions correlated with the magnitude of the energy applied. The MR image appearance depended not only on the laser energy but also on the way it was delivered, on the type of tissue, and the MR pulse sequence applied. While Ti-weighted images adequately demonstrated an area of tissue destruction, T2- weighted images showed a more heterogeneous and more extensive lesion which could be better correlated with the complex histological representation of these lesions. Typically, when rabbit brain, liver, and muscle had been exposed to laser power of 2.5 Watts for a range of 55 to 120 seconds, depending on the tissue, a central area of signal void was surrounded by an inner hypointensity and an outer hyperintensity on T2-weighted images. The 3D extent of the lesions was well demonstrated on multislice images, providing correlation of the affected volumes seen on MRI with volumes seen in histological or histochemical preparations. We are developing an analytical model of laser heating and its effect on MR images to assess whether heating during imaging will produce unacceptable artifacts during surgery. The effect of heating is modeled as a change in magnetization during image acquisition. The region in which the change occurs is blurred by the Fourier transform of the change in magnetization as a function of time. Thus, blurring is minimized when changes occur slowly, compared to image acquisition times. We conclude that MRI can demonstrate the 3D extent of the lesions induced by lasers and can be used to investigate and optimize the control of induced tissue change within the affected volume.
Magnetic resonance imaging of the central nervous system
Brant-Zawadzki, M.; Norman, D.
This text provides an introduction to magnetic resonance imaging (MRI) of disorders of the central nervous system, spine, neck, and nasopharynx. The book offers guidance in performing and interpreting MRI studies for specific clinical problems. Included are more than 800 images showing pathologic findings for various disorders and demonstrating how abnormalities detected in MRI scans can aid both in differential diagnosis and in clinical staging. The book summarizes the basic principles of MRI and describes the major equipment components and contrast agents. A review of the principles and potential applications of magnetic resonance spectroscopy is also included.
Field map reconstruction in magnetic resonance imaging using Bayesian estimation.
Baselice, Fabio; Ferraioli, Giampaolo; Shabou, Aymen
Field inhomogeneities in Magnetic Resonance Imaging (MRI) can cause blur or image distortion as they produce off-resonance frequency at each voxel. These effects can be corrected if an accurate field map is available. Field maps can be estimated starting from the phase of multiple complex MRI data sets. In this paper we present a technique based on statistical estimation in order to reconstruct a field map exploiting two or more scans. The proposed approach implements a Bayesian estimator in conjunction with the Graph Cuts optimization method. The effectiveness of the method has been proven on simulated and real data. PMID:22315539
Roadmap: Radiologic Imaging Sciences -Magnetic Resonance Imaging (with AAS Radiologic Technology) -
Sheridan, Scott
Roadmap: Radiologic Imaging Sciences - Magnetic Resonance Imaging (with AAS Radiologic Technology) - Bachelor of Radiologic and Imaging Sciences Technology [RE-BRIT-RIS-MRRT] Regional College Catalog Year Hours] Note: Students must have earned an AAS degree in Radiologic Technology (43 semester credits
Roadmap: Radiologic Imaging Sciences -Magnetic Resonance Imaging (with AAS Radiologic Technology) -
Sheridan, Scott
Roadmap: Radiologic Imaging Sciences - Magnetic Resonance Imaging (with AAS Radiologic Technology) - Bachelor of Radiologic and Imaging Sciences Technology [RE-BRIT-RIS-MRRT] Regional College Catalog Year Hours] Note: Students must have earned an AAS degree in Radiologic Technology (69-71 semester credits
High resolution resonance ionization imaging detector and method
Winefordner, James D. (Gainesville, FL); Matveev, Oleg I. (Gainesville, FL); Smith, Benjamin W. (Gainesville, FL)
A resonance ionization imaging device (RIID) and method for imaging objects using the RIID are provided, the RIID system including a RIID cell containing an ionizable vapor including monoisotopic atoms or molecules, the cell being positioned to intercept scattered radiation of a resonance wavelength .lambda..sub.1 from the object which is to be detected or imaged, a laser source disposed to illuminate the RIID cell with laser radiation having a wavelength .lambda..sub.2 or wavelengths .lambda..sub.2, .lambda..sub.3 selected to ionize atoms in the cell that are in an excited state by virtue of having absorbed the scattered resonance laser radiation, and a luminescent screen at the back surface of the RIID cell which presents an image of the number and position of charged particles present in the RIID cell as a result of the ionization of the excited state atoms. The method of the invention further includes the step of initially illuminating the object to be detected or imaged with a laser having a wavelength selected such that the object will scatter laser radiation having the resonance wavelength .lambda..sub.1.
Travelling Wave Magnetic Resonance Imaging at 3 Tesla
Vazquez, F; Marrufo, O; Rodriguez, A O
Waveguides have been successfully used to generate magnetic resonance images at 7 T with whole-body systems. The bore limits the magnetic resonance signal transmitted because its specific cut-off frequency is greater than the majority of resonant frequencies. This restriction can be overcome by using a parallel-plate waveguide whose cut-off frequency is zero for the transversal electric modes and it can propagate any frequency. To investigate the potential benefits for whole-body imaging at 3 T, we compare numerical simulations at 1.5 T, 3 T, 7 T, and 9 T via the propagation of the parallel-plate waveguide principal mode filled with a cylindrical phantom and two surface coils. B1 mapping was computed to investigate the feasibility of this approach at 3T. The point spread function method was used to measure the imager performance for the traveling-wave magnetic resonance imaging experiment. Human leg images were acquired to experimentally validate this approach. The principal mode shows very little field magni...
Magnetic resonance imaging of the cirrhotic liver: An update.
Watanabe, Agnes; Ramalho, Miguel; AlObaidy, Mamdoh; Kim, Hye Jin; Velloni, Fernanda G; Semelka, Richard C
Noninvasive imaging has become the standard for hepatocellular carcinoma (HCC) diagnosis in cirrhotic livers. In this review paper, we go over the basics of MR imaging in cirrhotic livers and describe the imaging appearance of a spectrum of hepatic nodules marking the progression from regenerative nodules to low- and high-grade dysplastic nodules, and ultimately to HCCs. We detail and illustrate the typical imaging appearances of different types of HCC including focal, multi-focal, massive, diffuse/infiltrative, and intra-hepatic metastases; with emphasis on the diagnostic value of MR in imaging these lesions. We also shed some light on liver imaging reporting and data system, and the role of different magnetic resonance imaging (MRI) contrast agents and future MRI techniques including the use of advanced MR pulse sequences and utilization of hepatocyte-specific MRI contrast agents, and how they might contribute to improving the diagnostic performance of MRI in early stage HCC diagnosis. PMID:25848471
Single echo acquisition magnetic resonance imaging
McDougall, Mary Preston
limitations are already being approached. Parallel imaging methods (using multiple receiver coils to partially encode k-space) have offered some relief in the efforts and are rapidly becoming the focus of current endeavors to decrease scan time. Ideally...
Centric scan SPRITE magnetic resonance imaging
Meghan Halse; David J. Goodyear; Bryce MacMillan; Pavol Szomolanyi; David Matheson; Bruce J. Balcom
Two rapid, pure phase encode, centric scan, Single Point Ramped Imaging with T1-Enhancement (SPRITE) MRI methods are described. Each retains the benefits of the standard SPRITE method, most notably the ability to image short T2* systems, while increasing the sensitivity and generality of the technique. The Spiral-SPRITE method utilizes a modified Archimedean spiral k-space trajectory. The Conical-SPRITE method utilizes a
Brain magnetic resonance imaging with contrast dependent on blood oxygenation
Ogawa, S.; Lee, T.M.; Kay, A.R.; Tank, D.W. (AT and T Bell Laboratories, Murray Hill, NJ (United States))
Paramagnetic deoxyhemoglobin in venous blood is a naturally occurring contrast agent for magnetic resonance imaging (MRI). By accentuating the effects of this agent through the use of gradient-echo techniques in high yields, the authors demonstrate in vivo images of brain microvasculature with image contrast reflecting the blood oxygen level. This blood oxygenation level-dependent (BOLD) contrast follows blood oxygen changes induced by anesthetics, by insulin-induced hypoglycemia, and by inhaled gas mixtures that alter metabolic demand or blood flow. The results suggest that BOLD contrast can be used to provide in vivo real-time maps of blood oxygenation in the brain under normal physiological conditions. BOLD contrast adds an additional feature to magnetic resonance imaging and complement other techniques that are attempting to provide position emission tomography-like measurements related to regional neural activity.
Magnetic resonance imaging for prostate cancer clinical application
Li, Bing; Du, Yong; Huang, Yayong; Meng, Jun; Xiao, Dongmei
As prostate cancer is a biologically heterogeneous disease for which a variety of treatment options are available, the major objective of prostate cancer imaging is to achieve more precise disease characterization. In clinical practice, magnetic resonance imaging (MRI) is one of the imaging tools for the evaluation of prostate cancer, the fusion of MRI or dynamic contrast-enhanced MRI (DCE-MRI) with magnetic resonance spectroscopic imaging (MRSI) is improving the evaluation of cancer location, size, and extent, while providing an indication of tumor aggressiveness. This review summarizes the role of MRI in the application of prostate cancer and describes molecular MRI techniques (including MRSI and DCE-MRI) for aiding prostate cancer management. PMID:23592906
Surface plasmon resonance imaging by holographic enhanced mapping.
Mandracchia, B; Pagliarulo, V; Paturzo, M; Ferraro, P
We designed, constructed and tested a holographic surface plasmon resonance (HoloSPR) objective-based microscope for simultaneous amplitude-contrast and phase-contrast surface plasmon resonance imaging (SPRi). SPRi is a widely spread tool for label-free detection of changes in refractive index and concentration, as well as mapping of thin films. Currently, most of the SPR sensors rely on the detection of amplitude or phase changes of light. Despite the high sensitivities achieved so far, each technique alone has a limited detection range with optimal sensitivity. Here we use a high numerical aperture objective that avoids all the limitations due to the use of a prism-based configuration, yielding highly magnified and distortion-free images. Holographic reconstructions of SPR images and real-time kinetic measurements are presented to show the capability of HoloSPR to provide a versatile imaging method for high-throughput SPR detection complementary to conventional SPR techniques. PMID:25816225
Magnetic resonance imaging with an optical atomic magnetometer.
Xu, Shoujun; Yashchuk, Valeriy V; Donaldson, Marcus H; Rochester, Simon M; Budker, Dmitry; Pines, Alexander
We report an approach for the detection of magnetic resonance imaging without superconducting magnets and cryogenics: optical atomic magnetometry. This technique possesses a high sensitivity independent of the strength of the static magnetic field, extending the applicability of magnetic resonance imaging to low magnetic fields and eliminating imaging artifacts associated with high fields. By coupling with a remote-detection scheme, thereby improving the filling factor of the sample, we obtained time-resolved flow images of water with a temporal resolution of 0.1 s and spatial resolutions of 1.6 mm perpendicular to the flow and 4.5 mm along the flow. Potentially inexpensive, compact, and mobile, our technique provides a viable alternative for MRI detection with substantially enhanced sensitivity and time resolution for various situations where traditional MRI is not optimal. PMID:16885210
Magnetic resonance imaging with an optical atomic magnetometer
Xu, Shoujun; Yashchuk, Valeriy V.; Donaldson, Marcus H.; Rochester, Simon M.; Budker, Dmitry; Pines, Alexander
We report an approach for the detection of magnetic resonance imaging without superconducting magnets and cryogenics: optical atomic magnetometry. This technique possesses a high sensitivity independent of the strength of the static magnetic field, extending the applicability of magnetic resonance imaging to low magnetic fields and eliminating imaging artifacts associated with high fields. By coupling with a remote-detection scheme, thereby improving the filling factor of the sample, we obtained time-resolved flow images of water with a temporal resolution of 0.1 s and spatial resolutions of 1.6 mm perpendicular to the flow and 4.5 mm along the flow. Potentially inexpensive, compact, and mobile, our technique provides a viable alternative for MRI detection with substantially enhanced sensitivity and time resolution for various situations where traditional MRI is not optimal. PMID:16885210
Portal biliopathy, magnetic resonance imaging and magnetic resonance cholangiopancreatography findings: a case series.
Baskan, Ozdil; Erol, Cengiz; Sahingoz, Yusuf
Portal biliopathy (PB) is a rare disorder, characterized by biliary ductal and gallbladder wall abnormalities seen in patients with portal hypertension. It most commonly occurs due to idiopathic extrahepatic portal vein obstruction (EHPVO). The abnormalities consist mainly of bile duct compression, stenoses, fibrotic strictures and dilation of both extrahepatic and intrahepatic bile ducts, as well as gallbladder varices. PB may mimic cholangiocarcinoma, sclerosing cholangitis, or choledocholithiasis. Misdiagnosis can be avoided using appropriate imaging modalities to prevent complications. We present the magnetic resonance imaging (MRI) and magnetic resonance cholangiography (MRCP) features of three patients with PB. PMID:25216728
Efficient bias correction for magnetic resonance image denoising.
Mukherjee, Partha Sarathi; Qiu, Peihua
Magnetic resonance imaging (MRI) is a popular radiology technique that is used for visualizing detailed internal structure of the body. Observed MRI images are generated by the inverse Fourier transformation from received frequency signals of a magnetic resonance scanner system. Previous research has demonstrated that random noise involved in the observed MRI images can be described adequately by the so-called Rician noise model. Under that model, the observed image intensity at a given pixel is a nonlinear function of the true image intensity and of two independent zero-mean random variables with the same normal distribution. Because of such a complicated noise structure in the observed MRI images, denoised images by conventional denoising methods are usually biased, and the bias could reduce image contrast and negatively affect subsequent image analysis. Therefore, it is important to address the bias issue properly. To this end, several bias-correction procedures have been proposed in the literature. In this paper, we study the Rician noise model and the corresponding bias-correction problem systematically and propose a new and more effective bias-correction formula based on the regression analysis and Monte Carlo simulation. Numerical studies show that our proposed method works well in various applications. PMID:23074149
Magnetic resonance imaging for lung cancer screen.
Wang, Yi-Xiang J; Lo, Gladys G; Yuan, Jing; Larson, Peder E Z; Zhang, Xiaoliang
Lung cancer is the leading cause of cancer related death throughout the world. Lung cancer is an example of a disease for which a large percentage of the high-risk population can be easily identified via a smoking history. This has led to the investigation of lung cancer screening with low-dose helical/multi-detector CT. Evidences suggest that early detection of lung cancer allow more timely therapeutic intervention and thus a more favorable prognosis for the patient. The positive relationship of lesion size to likelihood of malignancy has been demonstrated previously, at least 99% of all nodules 4 mm or smaller are benign, while noncalcified nodules larger than 8 mm diameter bear a substantial risk of malignancy. In the recent years, the availability of high-performance gradient systems, in conjunction with phased-array receiver coils and optimized imaging sequences, has made MR imaging of the lung feasible. It can now be assumed a threshold size of 3-4 mm for detection of lung nodules with MRI under the optimal conditions of successful breath-holds with reliable gating or triggering. In these conditions, 90% of all 3-mm nodules can be correctly diagnosed and that nodules 5 mm and larger are detected with 100% sensitivity. Parallel imaging can significantly shorten the imaging acquisition time by utilizing the diversity of sensitivity profile of individual coil elements in multi-channel radiofrequency receive coil arrays or transmit/receive coil arrays to reduce the number of phase encoding steps required in imaging procedure. Compressed sensing technique accelerates imaging acquisition from dramatically undersampled data set by exploiting the sparsity of the images in an appropriate transform domain. With the combined imaging algorithm of parallel imaging and compressed sensing and advanced 32-channel or 64-channel RF hardware, overall imaging acceleration of 20 folds or higher can then be expected, ultimately achieve free-breathing and no ECG gating acquisitions in lung cancer MRI screening. Further development of protocols, more clinical trials and the use of advanced analysis tools will further evaluate the real significance of lung MRI. PMID:25276380
Image restoration and spatial resolution in 7-tesla magnetic resonance imaging.
Lohmann, Gabriele; Bohn, Stefan; Müller, Karsten; Trampel, Robert; Turner, Robert
A good spatial resolution is essential for high precision segmentations of small structures in magnetic resonance images. However, any increase in the spatial resolution results in a decrease of the signal-to-noise ratio (SNR). In this article, this problem is addressed by a new image restoration technique that is used to partly compensate for the loss in SNR. Specifically, a two-stage hybrid image restoration procedure is proposed where the first stage is a Wiener wavelet filter for an initial denoising. The artifacts that will inevitably be produced by this step are subsequently reduced using a recent variant of anisotropic diffusion. The method is applied to magnetic resonance imaging data acquired on a 7-T magnetic resonance imaging scanner and compared with averaged multiple measurements of the same subject. It was found that the effect of image restoration procedure roughly corresponds to averaging across three repeated measurements. PMID:20577978
Osteoid osteoma of the scaphoid: magnetic resonance imaging vessel sign.
Kussman, Steven R; Thompson, Michael; Chang, Eric Y
Osteoid osteomas can be a challenging diagnosis, especially in smaller bones and, particularly, in the carpus. Clinical and imaging diagnosis may both be delayed due to other, more common, post-traumatic or inflammatory pathology in the same area. We present a case of a pathologically proven scaphoid osteoid osteoma with a feeding vessel sign on magnetic resonance imaging, previously described in long bones with computed tomography, as a helpful sign for accurate diagnosis in the scaphoid. PMID:25721711
Very low field magnetic resonance imaging with spintronic sensors
NASA Astrophysics Data System (ADS)
Herreros, Q.; Dyvorne, H.; Campiglio, P.; Jasmin-Lebras, G.; Demonti, A.; Pannetier-Lecoeur, M.; Fermon, C.
A very low field magnetic resonance imaging (MRI) setup based on magnetoresistive-superconducting mixed sensors is presented. A flux transformer is used to achieve coupling between the sample to image and the mixed sensor. The novel detector was implemented in a spin echo MRI experiment, exposing the mixed sensor to RF pulses without use of any RF switch. The performance of the novel detector is given in terms of signal-to-noise ratio and is compared with classical tuned coils.
Functional Magnetic Resonance Imaging and Radiosurgical Dose Planning
Michael Schulder; Jose Vega; Venkat Narra; Alexander Jacobs; Andrew Kalnin; Gudrun Lange; Wen-Ching Liu
Objective: To assess the effect of functional magnetic resonance imaging (fMRI) on stereotactic radiosurgical (SRS) dose planning. Methods: Patients included those undergoing SRS whose lesions were in or near areas that could be identified with fMRI. After processing, an fMR scan was registered to the anatomic scan, and this dataset was registered to a stereotactic CT scan. The imaged functional
Imaging of ventricular function by cardiovascular magnetic resonance
Vikas K. Rathi; Robert W. W. Biederman
Over the past 15 years, cardiac magnetic resonance imaging (CMR) has vaulted to the forefront as the ideal diagnostic modality\\u000a for the evaluation of both left and right ventricular function. The accumulated literature supports this contention for the\\u000a left ventricle. However, for the right ventricle, typically poorly visualized accurately by traditional imaging techniques,\\u000a CMR has emerged as the test of
Automated Analysis of Craniofacial Morphology Using Magnetic Resonance Images
M. Mallar Chakravarty; Rosanne Aleong; Gabriel Leonard; Michel Perron; G. Bruce Pike; Louis Richer; Suzanne Veillette; Zdenka Pausova; Tomás Paus; Tianzi Jiang
Quantitative analysis of craniofacial morphology is of interest to scholars working in a wide variety of disciplines, such as anthropology, developmental biology, and medicine. T1-weighted (anatomical) magnetic resonance images (MRI) provide excellent contrast between soft tissues. Given its three-dimensional nature, MRI represents an ideal imaging modality for the analysis of craniofacial structure in living individuals. Here we describe how T1-weighted
Magnetic Resonance Imaging of Anatomic Defects in Fecal Incontinence
Jaap Stoker; Andrew P. Zbar
Endoanal probe technology provides high-resolution soft-tissue imaging for periluminal anal and rectal disease, most notably\\u000a in complex perirectal sepsis and in patients presenting with fecal incontinence and sphincter damage. The trend is a movement\\u000a away from direct sphincter repair toward sacral neuromodulation in external anal sphincter (EAS) injury. However, endoanal\\u000a magnetic resonance imaging (EAMRI) has shown clear accuracy in the
Applications of Magnetic Resonance Imaging in Cardiac Disease
M. Y. Desai; D. A. Bluemke
Magnetic resonance (MR) imaging is widely recognized as providung an accurate and reliable means of assessing the function\\u000a and anatomy of the heart and great vessels. Previously, the means to obtain images of the cardiovascular system were compromised\\u000a by extremely long examination times and software that was available only at specialized centers. With the recent development\\u000a of specialized cardiovascular MR
Stiffness-weighted magnetic resonance imaging.
Glaser, Kevin J; Felmlee, Joel P; Manduca, Armando; Kannan Mariappan, Yogesh; Ehman, Richard L
An imaging method is introduced in which the signal in MR images is affected by the stiffness distribution in the object being imaged. Intravoxel phase dispersion (IVPD) that occurs during MR elastography (MRE) acquisitions decreases the signal in soft regions more than in stiff regions due to changes in shear wave amplitude and wavelength. The IVPD effect is enhanced by lowpass filtering the MR k-space data with a circular Gaussian lowpass filter. A processing method is introduced to take the time series of MRE magnitude images with IVPD and produce a final stiffness-weighted image (SWI) by calculating the minimum signal at each pixel from a small number of temporal samples. The SWI technique is demonstrated in phantom studies as well as in the case of a preserved postmortem breast tissue specimen with a stiff lesion created by focused ultrasound ablation to mimic a breast cancer. When free of significant sources of depth-dependent wave attenuation, interference, and boundary effects, SWI is a simple, fast, qualitative technique that does not require the use of phase unwrapping or inversion algorithms for localizing stiff regions in an object. PMID:16342158
The Evolving Role of Diffusion Magnetic Resonance Imaging in Movement Disorders
Hess, Christopher W.; Ofori, Edward; Akbar, Umer; Okun, Michael S.; Vaillancourt, David E.
Significant advances have allowed diffusion MRI (dMRI) to evolve into a powerful tool in the field of movement disorders that can be used to study disease states and connectivity between brain regions. dMRI represents a promising potential biomarker for Parkinson's disease and other forms of parkinsonism, and may allow for the distinction of different forms of parkinsonism. Techniques such as tractography have contributed to our current thinking regarding the pathophysiology of dystonia and possible mechanisms of penetrance. dMRI measures could potentially assist in monitoring disease progression in Huntington's disease, and in uncovering the nature of the processes and structures involved the development of essential tremor. The ability to represent structural connectivity in vivo also makes dMRI an ideal adjunctive tool for the surgical treatment of movement disorders. We will review recent studies utilizing dMRI in movement disorders research and present the current state of the science as well as future directions. PMID:24046183
Magnetic resonance imaging of the pediatric brain
Salamon, G.; Raynaud, C.; Regis, J.; Rumeau, C.
The atlas presents sequences of MRI sections parallel to the orbito-meatal plane in children from birth through the age of sixteen years. Each child was studied horizontally and sagitally and three-dimensional brain images were reconstructed to facilitate accurate identification of sulci and gyri. The images show crucial aspects of brain development such as the constancy of the brain stem and primitive brain from birth onward; the development of the telencephalon, characterized by deepening of sulci and growth of the cerebral cortex surface; and the different stages of white matter myelinization.
Assessment of coronary artery stenosis by magnetic resonance imaging.
Pennell, D. J.; Bogren, H. G.; Keegan, J.; Firmin, D. N.; Underwood, S. R.
OBJECTIVE: The findings of magnetic resonance and x-ray angiography were compared for assessment of coronary artery stenosis in this validation study. BACKGROUND: Magnetic resonance angiography of the coronary arteries has recently been described, but there has been no comparison with x-ray angiography of localisation or assessment of important characteristics of coronary stenosis. METHODS: A breath hold, segmented k-space, 2D gradient echo imaging technique incorporating fat suppression was used in 39 patients (55 coronary stenoses) with known coronary artery disease. RESULTS: Overall, 47 stenoses (85%) were assessed by magnetic resonance (29 of 33 stenoses in the left anterior descending artery, one of one in the left main stem, 14 of 17 in the right coronary artery, and three of four in the left circumflex artery were detected). There was close agreement between magnetic resonance and x-ray angiography for the distance of the stenosis from the arterial origin (magnetic resonance mean (SD) 27 (16) mm versus x-ray angiography 27 (16) mm, P = NS, mean difference -0.2 mm). The distance to 39 stenoses (83%) agreed to within 5 mm, with increased scatter for more distal stenoses. The severity of magnetic resonance signal loss, assessed visually at the site of stenosis, varied significantly according to the percentage diameter stenosis (F = 30, P < 0.0001); stenosis severity with severe signal loss was 89 (7)%, with partial signal was 70 (16)%, and with irregular wall only 37 (11)%, with significant differences among the three groups (P < 0.001). A significant correlation was found between the proportional magnetic resonance signal loss at the stenosis and the percentage diameter stenosis severity (r = -0.67, P < 0.0001). The length of stenosis measured by magnetic resonance (6 (3) mm) was greater than by x-ray angiography (5 (2) mm, P < 0.006, mean difference +1.1 mm). Spearman's rank test showed that there was significant overestimation of stenosis length by magnetic resonance as stenosis severity increased (rs = 0.34, P < 0.02). CONCLUSIONS: Accurate localisation of coronary stenosis and a qualitative assessment of stenosis severity are possible by magnetic resonance, but stenosis length is overestimated as severity increases, probably because of disturbed patterns of flow with turbulence distal to severe stenoses. Reasonable results for the detection of coronary artery stenosis by magnetic resonance were achieved in this highly selected population, but further progress in imaging techniques is necessary before moving towards appreciable clinical application. Images PMID:8673749
Magnetic Resonance Imaging and Spectroscopy in Hepatic Encephalopathy
Chavarria, Laia; Cordoba, Juan
Hepatic encephalopathy is a brain alteration associated to liver failure that produces cognitive impairments at long term. Neuroimaging are non-invasive methods for the study of the brain by means of spectroscopy and imaging techniques. These technologies give huge information about cerebral metabolism and water distribution to explore brain pathways involved in the pathogenesis of hepatic encephalopathy. Furthermore, new magnetic resonance implementations such as voxel-based morphometry or resting-state functional magnetic resonance imaging allow studying brain atrophy and neuronal connectivity of the cerebral network involved in the neurocognitive impairments observed in the patients. The development of magnetic resonance technology will generate handy tools for the brain study of liver failure to elucidate the time-course of the pathology and thus to obtain an early diagnosis of cerebral complications.
Improvements in Magnetic Resonance Imaging Excitation Pulse Design
Goyal, Vivek K
Improvements in Magnetic Resonance Imaging Excitation Pulse Design by Adam Charles Zelinski magnetic spins are tilted by only a small amount, pulse transmission may be interpreted as depositing by . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Terry P. Orlando Chairman, Department Committee on Graduate Students #12;2 #12;Improvements in Magnetic
Contrast-enhanced magnetic resonance imaging of myocardium at risk
David S Fieno; Raymond J Kim; Enn-Ling Chen; Jon W Lomasney; Francis J Klocke; Robert M Judd
OBJECTIVESWe sought to determine the relationship of delayed hyperenhancement by contrast magnetic resonance imaging (MRI) to viable and nonviable myocardium within the region at risk throughout infarct healing.BACKGROUNDThe relationship of delayed MRI contrast enhancement patterns to injured but viable myocardium within the ischemic bed at risk has not been established.METHODSWe compared in vivo and ex vivo MRI contrast enhancement to
Facial Recognition From Volume-Rendered Magnetic Resonance Imaging Data
Fred W. Prior; Barry S. Brunsden; Charles Hildebolt; Tracy S. Nolan; Michael Pringle; S. Neil Vaishnavi; Linda J. Larson-Prior
Three-dimensional (3-D) reconstructions of computed tomography (CT) and magnetic resonance (MR) brain imaging studies are a routine component of both clinical practice and clinical and translational research. A side effect of such reconstructions is the creation of a potentially recognizable face. The Health Insurance Portability and Accountability Act of 1996 (HIPAA) Privacy Rule requires that individually identifiable health information may
Magnetic Resonance Imaging of Water Distribution in Welded Woods
Mojgan Vaziri; Greger Orädd; Owe Lindgren; Antonio Pizzi
This study was performed for a better understanding of water effect on welded wood and improving its water resistance. In this article, we have also attempted to demonstrate the feasibility of using Magnetic Resonance Imaging technology to study water movement in welded woods. Water distribution in welded woods of Scots pine (Pinus sylvestris) and beech (Fagus sylvatica) was investigated by
Assessment of the sinus lift operation by magnetic resonance imaging
Figen Cizmeci Senel; Serpil Duran; Onur Icten; Izlem Izbudak; Fulya Cizmeci
ObjectivesVertical bone loss in edentulous maxillary alveolar processes may necessitate a sinus lift before the placement of dental implants. We have measured and assessed maxillary sinuses meticulously before the operation and evaluated the postoperative results of the operation with magnetic resonance imaging (MRI).
Assessment of the sinus lift operation by magnetic resonance imaging
Figen Cizmeci Senel; Serpil Duran; Onur Icten; Izlem Izbudak; Fulya Cizmeci
Objectives: Vertical bone loss in edentulous maxillary alveolar processes may necessitate a sinus lift before the placement of dental implants. We have measured and assessed maxillary sinuses meticulously before the operation and evaluated the postoperative results of the operation with magnetic resonance imaging (MRI). Methods: Thirteen edentulous maxillary regions in eight patients were included in the study. The patients were
Magnetic resonance imaging of lumbar vertebral apophyseal ring fractures
Wilfred CG Peh; James F Griffith; Daniel KH Yip; John CY Leong
SUMMARY Posterior lumbar vertebral apophyseal ring fractures are described in three adolescents presenting with severe low back pain, spinal tenderness and lower limb neurological deficit. Magnetic resonance imaging showed severe L4\\/5 posterior disc protrusion in all three patients. The actual fracture fragment was visualized with difficulty on MRI alone. The diagnosis of apophyseal ring fracture was made by either radiography
Low Cost Magnetic Resonance Imaging-Compatible Stepper
Chesler, Naomi C.
collection of cardio- vascular MRI data during exercise. We developed a low-cost exercise deviceLow Cost Magnetic Resonance Imaging-Compatible Stepper Exercise Device for Use in Cardiac Stress during a car- diac stress test. Current approaches include either exercise or pharmacological stress
Three-Dimensional Magnetic Resonance Imaging of Velopharyngeal Structures
ERIC Educational Resources Information Center
Bae, Youkyung; Kuehn, David P.; Sutton, Bradley P.; Conway, Charles A.; Perry, Jamie L.
Purpose: To report the feasibility of using a 3-dimensional (3D) magnetic resonance imaging (MRI) protocol for examining velopharyngeal structures. Using collected 3D MRI data, the authors investigated the effect of sex on the midsagittal velopharyngeal structures and the levator veli palatini (levator) muscle configurations. Method: Ten Caucasian…
Tagged magnetic resonance imaging of the heart: a survey
Leon Axel; Albert Montillo; Daniel Kim
Magnetic resonance imaging (MRI) of the heart with magnetization tagging provides a potentially useful new way to assess car-diac mechanical function, through revealing the local motion of otherwise indistinguishable portions of the heart wall. While still an evolving area, tagged cardiac MRI is already able to provide novel quantitative information on cardiac function. Exploiting this potential requires developing tailored methods
Magnetic resonance imaging mapping of brain function. Human visual cortex
J. W. Belliveau; K. K. Kwong; D. N. Kennedy; J. R. Baker; C. E. Stern; R. Benson; D. A. Chesler; R. M. Weisskoff; M. S. Cohen; R. B. Tootell; P. T. Fox; T. J. Brady
Magnetic resonance imaging (MRI) studies of human brain activity are described. Task-induced changes in brain cognitive state were measured using high-speed MRI techniques sensitive to changes in cerebral blood volume (CBV), blood flow (CBF), and blood oxygenation. These techniques were used to generate the first functional MRI maps of human task activation, by using a visual stimulus paradigm. The methodology
Functional Connectivity Magnetic Resonance Imaging Classification of Autism
ERIC Educational Resources Information Center
Anderson, Jeffrey S.; Nielsen, Jared A.; Froehlich, Alyson L.; DuBray, Molly B.; Druzgal, T. Jason; Cariello, Annahir N.; Cooperrider, Jason R.; Zielinski, Brandon A.; Ravichandran, Caitlin; Fletcher, P. Thomas; Alexander, Andrew L.; Bigler, Erin D.; Lange, Nicholas; Lainhart, Janet E.
Group differences in resting state functional magnetic resonance imaging connectivity between individuals with autism and typically developing controls have been widely replicated for a small number of discrete brain regions, yet the whole-brain distribution of connectivity abnormalities in autism is not well characterized. It is also unclear…
Compact low field magnetic resonance imaging magnet: Design and optimization
M. Sciandrone; G. Placidi; L. Testa; A. Sotgiu
Magnetic resonance imaging (MRI) is performed with a very large instrument that allows the patient to be inserted into a region of uniform magnetic field. The field is generated either by an electromagnet (resistive or superconductive) or by a permanent magnet. Electromagnets are designed as air cored solenoids of cylindrical symmetry, with an inner bore of 80-100 cm in diameter.
Nuclear Magnetic Resonance Spectroscopy and Imaging in Animal Research
John C. Chatham; Stephen J. Blackband
Abstract Nuclear magnetic resonance (NMR) spectroscopy and imag- ing can be used to investigate, noninvasively, a wide range of biological processes in systems ,as diverse as protein solu- tions, single cells, isolated perfused organs, and tissues in vivo. It is also possible to combine ,different NMR tech- niques enabling metabolic, anatomical, and physiological information to be ,obtained in the same
Semi-Supervised Tumor Detection in Magnetic Resonance Spectroscopic Images
Hamprecht, Fred A.
for Scientific Computing (IWR), University of Heidelberg 3 Department of Radiology, German Cancer Research Center on metabolic processes and can thus be used for in vivo tumor diagnosis. However, each single spectrum has and prostate [9]. Magnetic resonance spectroscopic imaging (MRSI) allows to acquire such spectra on two
Breast cancer measurements with magnetic resonance imaging, ultrasonography, and mammography
Peter L. Davis; Melinda J. Staiger; Kathleen B. Harris; Marie A. Ganott; Jolita Klementaviciene; Kenneth S. McCarty; Hector Tobon
Summary Background: Accurate measurement of the size of breast cancers becomes more important as breast cancer therapy advances. This study reports the accuracy of magnetic resonance imaging (MRI), ultrasonography and mammography for measuring the largest breast cancer diameter in comparison to the pathology measurement.
Classification of magnetic resonance images by using genetic algorithms
Ziimray Dokur; Tamer Olmez; E. Yazgan
A neural network trained by genetic algorithms (GANN) is presented. Each neuron of the network forms a closed region in the input space. The closed regions which are formed by the neurons overlap each other, like STAR. Genetic algorithms are used to improve the classification performances of the magnetic resonance (MR) images with minimized number of neurons. GANN is examined
Accelerated Parallel Magnetic Resonance Imaging with Combined Gradient and Wavelet
Huang, Junzhou
Accelerated Parallel Magnetic Resonance Imaging with Combined Gradient and Wavelet Sparsity Chen time. In pMRI, multi-channel coils simultaneously receive a fraction of k-space data and the field of view (FOV) is then reconstructed with the coil profiles. The techniques for pMRI can be mainly divided
Insertable biplanar gradient coils for magnetic resonance imaging
M. A. Martens; L. S. Petropoulos; R. W. Brown; J. H. Andrews; M. A. Morich; J. L. Patrick
Insertable planar gradient coils offer the potential for significant performance increases in magnetic resonance imaging through higher gradient strength and shorter rise times. Using variational methods to minimize inductance, and thereby to optimize switching speeds, we have analyzed and constructed a biplanar y-gradient coil for insertion into a solenoidal magnet system where z is the magnet axis. We have also
Design of Optimized Gradient Coils for Magnetic Resonance Imaging
Yoseph Shiferaw
A gradient coil system for use in magnetic resonance imaging was designed and built. The geometry of the coil system was determined by computer simulation. An optimized variation of Anderson coils was chosen as a suitable configuration. This gradient coil system will be used in a Varian magnet system with a gap width of 4.4 cm.
Design of gradient coils for magnetic resonance imaging
K. Adamiak; B. K. Rutt; W. J. Dabrowski
A numerical technique for designing gradient coils used in magnetic resonance imaging is presented. It is assumed that the coil consists of a finite number of polygonal turns, each carrying identical current. Coordinates of the vertices defining the turns are determined to minimize the mean-square deviation of the actual magnetic flux density from the ideal linear distribution. The zeroth-order Powell
Functional magnetic resonance imaging of real and sham acupuncture
Functional magnetic resonance imaging (fMRI) is an ideal method to noninvasively explore the whole brain for cortical activation related to acupuncture. The results from this study demonstrate that fMRI can identify specific cortical regions associated with acupuncture stimulation. The choice of acupuncture stimulation using visual or auditory points simplifies the interpretation of the results because the anatomic correlates are well
Bioengineering 278: Magnetic Resonance Imaging Laboratory Winter 2012
California at San Diego, University of
water or fat, but not both. The goal of this lab is to plot the 2D response of the pulse in z-f (space-frequency of this transformed pulse is the frequency response at position z. Repeat for z=-10:(20/256):10 cm DisplayBioengineering 278: Magnetic Resonance Imaging Laboratory Winter 2012 Lab 4 1. The Spatial
The Future of Real-time Cardiac Magnetic Resonance Imaging
Southern California, University of
The Future of Real-time Cardiac Magnetic Resonance Imaging Krishna S. Nayak, PhD* and Bob S. Hu, MD:4551 Current Science Inc. ISSN 1523-3782 Copyright © 2005 by Current Science Inc. Introduction Cardiac function physiology and pathophysiology such as respiration and car- diac dysrhythmia disturbs this periodicity
GEOMETRIC COMPUTATION OF HUMAN GYRIFICATION INDEXES FROM MAGNETIC RESONANCE IMAGES By Shu Su Tonya;Geometric Computation of Gyrification Indexes Chiu-Yen Kao 1 Geometric Computation of Human Gyrification Computation of Gyrification Indexes Chiu-Yen Kao 2 Abstract Human Brains are highly convoluted surfaces
Blood Flow Magnetic Resonance Imaging of Retinal Degeneration
Duong, Timothy Q.
Blood Flow Magnetic Resonance Imaging of Retinal Degeneration Yingxia Li,1 Haiying Cheng,1 Qiang. Duong1,2,3,4,5,6,7 PURPOSE. This study aims to investigate quantitative basal blood flow as well as hypercapnia- and hyperoxia-induced blood flow changes in the retinas of the Royal College of Surgeons (RCS
Magnetic Resonance Imaging of Short T 2 Components in Tissue
P. D. Gatehouse; G. M. Bydder
The most widely used clinical magnetic resonance imaging techniques for the diagnosis of parenchymal disease employ heavily T2-weighted sequences to detect an increase or decrease in the signal from long T2 components in tissue. Tissues also contain short T2 components that are not detected or only poorly detected with conventional sequences. These components are the majority species in tendons, ligaments,
Mediterranean Diet and Magnetic Resonance ImagingAssessed Cerebrovascular Disease
Mediterranean Diet and Magnetic Resonance ImagingAssessed Cerebrovascular Disease Nikolaos of the previously reported relationship between Mediterranean-type diet (MeDi) and Alzheimer's disease (AD). We;We previously reported that higher adherence to a Mediterranean-type diet (MeDi) is associated
A humidifier for olfaction studies during functional magnetic resonance imaging
M. Corcoran; H. Zee; C. Sotak; Y. Mendelson
Functional magnetic resonance imaging has been used to study the transmission of olfactory sensations in the nervous system. Researchers hypothesize that olfactory sensation depends on the humidity of the air containing the odorant. We were asked to create this device for a biomedical design course offered at Worcester Polytechnic Institute. Our purpose was to create a device for researchers who
Serial magnetic resonance imaging in children with postinfectious encephalitis
Seiji Kimura; Atsuo Nezu; Noriyuki Ohtsuki; Takuya Kobayashi; Hitoshi Osaka; Saori Uehara
We analyzed follow-up magnetic resonance images (MRI) in eight children with clinical postinfectious encephalitis (PIE), and discussed their pathogeneses. Three categories of MRI findings were apparent: (1) multifocal lesions in the white matter with\\/without basal ganglia involvement consistent with acute disseminated encephalomyelitis (ADEM) (three patients); (2) single or multifocal lesions localized only in the gray matter (two patients); and (3)
Magnetic resonance imaging of traumatic knee articular cartilage injuries
Kevin P. Speer; Charles E. Spritzer; J. Leonard Goldner; William E. Garrett
The purpose of this study was to assess the sensitivity of magnetic resonance imaging in determining the pres ence of articular cartilage injuries of the knee with arthroscopy as the standard for comparison. Forty-nine articular cartilage lesions were documented in 28 knees (27 patients) by arthroscopy. There were 22 men and 5 women with an average age of 29 years.
Mathematical challenges in magnetic resonance imaging (MRI)
Fessler, Jeffrey A.
of RF pulses / gradient waveforms (many possibilities!) · coil design · contrast agents · reconstruction, big, small bone signal...) #12;3 Overview Two inverse problems in MRI · RF pulse design (spatially Lauterbur and Peter Mansfield (independently) add magnetic field gradients, making images · 1991. Nobel
Magnetic resonance imaging of traumatic brain injury: a pictorial review.
Aquino, Christopher; Woolen, Sean; Steenburg, Scott D
Traumatic brain injury (TBI) is a significant source of major morbidity and mortality in blunt trauma patients. Computed tomography (CT) is the primary imaging modality of choice for patients with potential brain injury in the acute setting, with magnetic resonance imaging (MRI) playing a role in evaluating equivocal CT findings and may help with determining long-term prognosis and recovery. MRI is being utilized more commonly in the acute and subacute setting of TBI; therefore, radiologists should be familiar with the MRI appearance of the various manifestations of TBI. Here, we review the imaging of common intracranial injuries with illustrative cases comparing CT and MRI. PMID:25027313
AnalyzeNNLS: Magnetic resonance multiexponential decay image analysis
NASA Astrophysics Data System (ADS)
Bjarnason, Thorarin A.; Mitchell, J. Ross
Exponential decays are fundamental to magnetic resonance imaging, yet adequately sampling and analyzing multiexponential decays is rarely attempted. The advantage of multiexponential analysis is the quantification of sub-voxel structure caused by water compartmentalization, with application as a non-invasive imaging biomarker for myelin. We have developed AnalyzeNNLS, software designed specifically for multiexponential decay image analysis that has a user-friendly graphical user interface and can analyze data from many MR manufacturers. AnalyzeNNLS is a simple, platform independent analysis tool that was created using the extensive mathematical and visualization libraries in Matlab, and released as open source code allowing scientists to evaluate, scrutinize, improve, and expand.
Ferromagnetic resonance imaging of Co films using magnetic resonance force microscopy
Suh, B.J.; Hammel, P.C.; Zhang, Z. [Condensed Matter and Thermal Physics, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Condensed Matter and Thermal Physics, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Midzor, M.M.; Roukes, M.L. [Condensed Matter Physics, California Institute of Technology, Pasadena, California 91125 (United States)] [Condensed Matter Physics, California Institute of Technology, Pasadena, California 91125 (United States); Childress, J.R. [University of Florida, Gainesville, Florida 32611 (United States)] [University of Florida, Gainesville, Florida 32611 (United States)
Lateral one-dimensional imaging of cobalt (Co) films by means of microscopic ferromagnetic resonance (FMR) detected using the magnetic resonance force microscope (MRFM) is demonstrated. A novel approach involving scanning a localized magnetic probe is shown to enable FMR imaging in spite of the broad resonance linewidth. We introduce a spatially selective local field by means of a small, magnetically polarized spherical crystallite of yttrium iron garnet (YIG). Using MRFM-detected FMR signals from a sample consisting of two Co films, we can resolve the {approximately}20 {mu}m lateral separation between the films. The results can be qualitatively understood by consideration of the calculated spatial profiles of the magnetic field generated by the YIG sphere. {copyright} {ital 1998 American Vacuum Society.}
Magnetic Resonance Imaging with Composite (Dual) Gradients
Parker, Dennis L.; Goodrich, K. Craig; Hadley, J. Rock; Kim, Seong-Eun; Moon, Sung M.; Chronik, Blaine A.; Fontius, Ulrich; Schmitt, Franz
The tradeoff between gradient performance factors, size of the imaging region, and physiological factors such as nerve stimulation typically leads to compromises in gradient design and ultimately suboptimal imaging performance. Local gradient systems can add some performance flexibility, but are cumbersome to set up and remove. In nearly all conventional MRI systems, the use of local gradients precludes the use of the more homogeneous whole body gradients. This paper presents the concept of dynamically selectable composite gradient systems where local gradients and whole body gradients can be selected independently and simultaneously. The relative performance of whole body, insert, and composite gradients is predicted for echoplanar (EPI), turbo spin echo (TSE), and steady state free precession (SSFP). A realization of the concept is presented. PMID:20160925
Magnetic Resonance Imaging of Pharmacological Systems
Hanbing Lu; Thomas J. Ross; Elliot A. Stein
\\u000a With the appropriate hardware, pulse sequences and analysis methods, modern MRI research is able to measure numerous neurobiologically\\u000a relevant parameters including functional activation (fMRI) using blood oxygen level dependent, diffusion tensor imaging –\\u000a either to measure integrity of white matter or to follow white matter fiber tracts, MR spectroscopy, changes in cerebral blood\\u000a flow, cerebral blood volume and oxygen metabolism
Magnetic resonance imaging using linear magneto-inductive waveguides
NASA Astrophysics Data System (ADS)
Syms, R. R. A.; Young, I. R.; Ahmad, M. M.; Rea, M.
Magneto-inductive waveguides are arrays of magnetically coupled, lumped element resonators, which support slow waves at radio frequency. Their use in internal magnetic resonance imaging (MRI), where they may provide an intrinsically safe method of signal detection and transmission, is described. A catheter-based receiver formed from a thin-film printed circuit mounted on a tubular scaffold using heat-shrink tubing is demonstrated, and its electrical response and imaging sensitivity are explained in terms of the excitation and propagation of magneto-inductive waves. The theoretical predictions are confirmed using the results of electrical measurement and 1H MRI at 1.5 T, and imaging is achieved over a total length greater than 1.5 m using a single receiver.
Nuclear magnetic resonance imaging with hyper-polarized noble gases
Schmidt, D.M.; George, J.S.; Penttila, S.I.; Caprihan, A.
This is the final report of a six-month, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The nuclei of noble gases can be hyper polarized through a laser-driven spin exchange to a degree many orders of magnitude larger than that attainable by thermal polarization without requiring a strong magnetic field. The increased polarization from the laser pumping enables a good nuclear magnetic resonance (NMR) signal from a gas. The main goal of this project was to demonstrate diffusion-weighted imaging of such hyper-polarized noble gas with magnetic resonance imaging (MRI). Possible applications include characterizing porosity of materials and dynamically imaging pressure distributions in biological or acoustical systems.
Para-Hydrogen-Enhanced Gas-Phase Magnetic Resonance Imaging
Bouchard, Louis-S.; Kovtunov, Kirill V.; Burt, Scott R.; Anwar,M. Sabieh; Koptyug, Igor V.; Sagdeev, Renad Z.; Pines, Alexander
Herein, we demonstrate magnetic resonance imaging (MRI) inthe gas phase using para-hydrogen (p-H2)-induced polarization. A reactantmixture of H2 enriched in the paraspin state and propylene gas is flowedthrough a reactor cell containing a heterogenized catalyst, Wilkinson'scatalyst immobilized on modified silica gel. The hydrogenation product,propane gas, is transferred to the NMR magnet and is spin-polarized as aresult of the ALTADENA (adiabatic longitudinal transport and dissociationengenders net alignment) effect. A polarization enhancement factor of 300relative to thermally polarized gas was observed in 1D1H NMR spectra.Enhancement was also evident in the magnetic resonance images. This isthe first demonstration of imaging a hyperpolarized gaseous productformed in a hydrogenation reaction catalyzed by a supported catalyst.This result may lead to several important applications, includingflow-through porous materials, gas-phase reaction kinetics and adsorptionstudies, and MRI in low fields, all using catalyst-free polarizedfluids.
The origins and future of nuclear magnetic resonance imaging
Wehrli, F.W. (Univ. of Pennsylvania Medical Center, Philadelphia, PA (United States))
What began as a curiosity of physics has become the preeminent method of diagnostic medical imaging and may displace x-ray-based techniques in the 21st century. During the past two decades nuclear magnetic resonance has revolutionized chemistry, biochemistry, biology and, more recently, diagnostic medicine. Nuclear magnetic resonance imaging, (MRI) as it is commonly called, is fundamentally different from x-ray-based techniques in terms of the principles of spatial encoding and mechanisms of signal and contrast generation involved. MRI has a far richer ultimate potential than any other imaging technique known today, and its technology and applications are still far from maturation, which may not occur until early in the 21st century. 23 refs., 6 figs.
Magnetic resonance imaging for image-guided implantology
NASA Astrophysics Data System (ADS)
Eggers, Georg; Kress, Bodo; Fiebach, Jochen; Rieker, Marcus; Spitzenberg, Doreen; Marmulla, Rüdiger; Dickhaus, Hartmut; Mühling, Joachim
Image guided implantology using navigation systems is more accurate than manual dental implant insertion. The underlying image data are usually derived from computer tomography. The suitability of MR imaging for dental implant planning is a marginal issue so far. MRI data from cadaver heads were acquired using various MRI sequences. The data were assessed for the quality of anatomical imaging, geometric accuracy and susceptibility to dental metal artefacts. For dental implant planning, 3D models of the jaws were created. A software system for segmentation of the mandible and maxilla MRI data was implemented using c++, mitk, and qt. With the VIBE_15 sequence, image data with high geometric accuracy were acquired. Dental metal artefacts were lower than in CT data of the same heads. The segmentation of the jaws was feasible, in contrast to the segmentation of the dentition, since there is a lack of contrast to the intraoral soft tissue structures. MRI is a suitable method for imaging of the region of mouth and jaws. The geometric accuracy is excellent and the susceptibility to artefacts is low. However, there are yet two limitations: Firstly, the imaging of the dentition needs further improvement to allow accurate segmentation of these regions. Secondly, the sequence used in this study takes several minutes and hence is susceptible to motion artefacts.
Partial volume segmentation of brain magnetic resonance images based on maximum a posteriori probability
resonance imaging, fuzzy C-mean algorithm, Markov random field, PV segmentation, intensity inhomogeneityPartial volume segmentation of brain magnetic resonance images based on maximum a posteriori, and image-intensity inhomogeneity render a challenging task for segmentation of brain magnetic resonance MR
[Magnetic resonance tomography and hybrid imaging in rheumatology].
Buchbender, C; Schneider, M; Ostendorf, B
In rheumatologic diseases magnet resonance imaging (MRI) is capable of depicting early inflammatory changes which are frequently missed by other imaging modalities. New MRI protocols and hardware, primarily whole-body MRI and low-field extremity MRI facilitate the use of MRI in rheumatology patients. The increasing number of functional MRI techniques provide additional molecular information on the tissue composition, e.g. cartilage quality. These molecular MRI techniques enable new ways for early disease detection and therapy monitoring. Hybrid imaging modalities, such as MRI-SPECT (single photon mmission tomography) and MRI-PET (positron emission tomography) provide a new level of molecular imaging in rheumatology by adding the advantages of the combined modalities. This article provides an up-to-date overview of new MRI techniques and innovative hybrid imaging modalities and summarizes the first available results of these procedures in rheumatologic applications. PMID:23446460
Magnetic resonance images of neuronal migration anomalies.
Jaw, T S; Sheu, R S; Liu, G C; Chou, M S
Neuronal migration anomalies are a spectrum of brain malformations caused by insults to migrating neuroblasts during the sixth week to fifth month of gestation. To study the characteristics of MRI findings in migration anomalies, MR images of 36 patients (28 children and 8 adults) with migration anomalies were evaluated. Five patients had lissencephaly, eight had pachygyria, twelve had schizencephaly, six had heterotopias of gray matter, three had hemimegalencephaly, and two had polymicrogyria. The frequency of migration anomalies was 0.51% of all cranial MRI studies and 1.21% of pediatric cranial MRI studies at our hospital. The major clinical presentations of these patients were seizure (64%), development delay (42%), motor deficits (42%) and mental retardation (25%). Twenty-five patients (69%) associated with other brain anomalies, including: other migration anomalies in 12 cases (33%), absence of the septum pellucidum in 10 cases (28%), Dandy-Walker malformation/variant in 5 cases, arachnoid cyst in 4 cases, agenesis of the corpus callosum in 3 cases, holoprosencephaly in 2 cases, mega cisterna magna in 1 case and cephalocele in 1 case. Some of them presented with multiple complicated anomalies. As MR imaging provides superb gray-white matter distinction, details of cortical anatomy and multiplanar capability, it can clearly delineate the detail morphologic changes of the brain caused by neuronal migration disorders as well as the associated anomalies. PMID:9780601
Medical Imaging Field of Magnetic Resonance Imaging: Identification of Specialties within the Field
ERIC Educational Resources Information Center
Grey, Michael L.
This study was conducted to determine if specialty areas are emerging in the magnetic resonance imaging (MRI) profession due to advancements made in the medical sciences, imaging technology, and clinical applications used in MRI that would require new developments in education/training programs and national registry examinations. In this…
Progress in Multimodality Imaging: Truly Simultaneous Ultrasound and Magnetic Resonance Imaging
Laura Curiel; Rajiv Chopra; Kullervo Hynynen
Multimodality medical imaging takes advantage of the strengths of different imaging modalities to provide a more complete picture of the anatomy under investigation. Many complementary modalities have been combined to form such systems and some are gaining use clinically. One combination that has not been developed, in large part due to technical difficulties, is a combined magnetic resonance (MR) and
Automatic contour propagation in cine cardiac magnetic resonance images.
Hautvast, Gilion; Lobregt, Steven; Breeuwer, Marcel; Gerritsen, Frans
We have developed a method for automatic contour propagation in cine cardiac magnetic resonance images. The method consists of a new active contour model that tries to maintain a constant contour environment by matching gray values in profiles perpendicular to the contour. Consequently, the contours should maintain a constant position with respect to neighboring anatomical structures, such that the resulting contours reflect the preferences of the user. This is particularly important in cine cardiac magnetic resonance images because local image features do not describe the desired contours near the papillary muscle. The accuracy of the propagation result is influenced by several parameters. Because the optimal setting of these parameters is application dependent, we describe how to use full factorial experiments to optimize the parameter setting. We have applied our method to cine cardiac magnetic resonance image sequences from the long axis two-chamber view, the long axis four-chamber view, and the short axis view. We performed our optimization procedure for each contour in each view. Next, we performed an extensive clinical validation of our method on 69 short axis data sets and 38 long axis data sets. In the optimal parameter setting, our propagation method proved to be fast, robust, and accurate. The resulting cardiac contours are positioned within the interobserver ranges of manual segmentation. Consequently, the resulting contours can be used to accurately determine physiological parameters such as stroke volume and ejection fraction. PMID:17117776
Regression Models for Identifying Noise Sources in Magnetic Resonance Images.
Zhu, Hongtu; Li, Yimei; Ibrahim, Joseph G; Shi, Xiaoyan; An, Hongyu; Chen, Yashen; Gao, Wei; Lin, Weili; Rowe, Daniel B; Peterson, Bradley S
Stochastic noise, susceptibility artifacts, magnetic field and radiofrequency inhomogeneities, and other noise components in magnetic resonance images (MRIs) can introduce serious bias into any measurements made with those images. We formally introduce three regression models including a Rician regression model and two associated normal models to characterize stochastic noise in various magnetic resonance imaging modalities, including diffusion-weighted imaging (DWI) and functional MRI (fMRI). Estimation algorithms are introduced to maximize the likelihood function of the three regression models. We also develop a diagnostic procedure for systematically exploring MR images to identify noise components other than simple stochastic noise, and to detect discrepancies between the fitted regression models and MRI data. The diagnostic procedure includes goodness-of-fit statistics, measures of influence, and tools for graphical display. The goodness-of-fit statistics can assess the key assumptions of the three regression models, whereas measures of influence can isolate outliers caused by certain noise components, including motion artifacts. The tools for graphical display permit graphical visualization of the values for the goodness-of-fit statistic and influence measures. Finally, we conduct simulation studies to evaluate performance of these methods, and we analyze a real dataset to illustrate how our diagnostic procedure localizes subtle image artifacts by detecting intravoxel variability that is not captured by the regression models. PMID:19890478
Resonant Mode Reduction in Radiofrequency Volume Coils for Ultrahigh Field Magnetic Resonance Imaging
Pang, Yong; Xie, Zhentian; Li, Ye; Xu, Duan; Vigneron, Daniel; Zhang, Xiaoliang
In a multimodal volume coil, only one mode can generate homogeneous Radiofrequency (RF) field for Magnetic Resonance Imaging. The existence of other modes may increase the volume coil design difficulties and potentially decreases coil performance. In this study, we introduce common-mode resonator technique to high and ultrahigh field volume coil designs to reduce the resonant mode while maintain the homogeneity of the RF field. To investigate the design method, the common-mode resonator was realized by using a microstrip line which was split along the central to become a pair of parallel transmission lines within which common-mode currents exist. Eight common-mode resonators were placed equidistantly along the circumference of a low loss dielectric cylinder to form a volume coil. Theoretical analysis and comparison between the 16-strut common-mode volume coil and a conventional 16-strut volume coil in terms of RF field homogeneity and efficiency was performed using Finite-Difference Time-Domain (FDTD) method at 298.2 MHz. MR imaging experiments were performed by using a prototype of the common-mode volume coil on a whole body 7 Tesla scanner. FDTD simulation results showed the reduced number of resonant modes of the common-mode volume coil over the conventional volume coil, while the RF field homogeneity of the two type volume coils was kept at the same level. MR imaging of a water phantom and a kiwi fruit showing the feasibility of the proposed method for simplifying the volume coil design is also presented. PMID:22081791
SNR analysis of 3D magnetic resonance tomosynthesis (MRT) imaging
NASA Astrophysics Data System (ADS)
Kim, Min-Oh; Kim, Dong-Hyun
In conventional 3D Fourier transform (3DFT) MR imaging, signal-to-noise ratio (SNR) is governed by the well-known relationship of being proportional to the voxel size and square root of the imaging time. Here, we introduce an alternative 3D imaging approach, termed MRT (Magnetic Resonance Tomosynthesis), which can generate a set of tomographic MR images similar to multiple 2D projection images in x-ray. A multiple-oblique-view (MOV) pulse sequence is designed to acquire the tomography-like images used in tomosynthesis process and an iterative back-projection (IBP) reconstruction method is used to reconstruct 3D images. SNR analysis is performed and shows that resolution and SNR tradeoff is not governed as with typical 3DFT MR imaging case. The proposed method provides a higher SNR than the conventional 3D imaging method with a partial loss of slice-direction resolution. It is expected that this method can be useful for extremely low SNR cases.
Improved Guided Image Fusion for Magnetic Resonance and Computed Tomography Imaging
Jameel, Amina
Improved guided image fusion for magnetic resonance and computed tomography imaging is proposed. Existing guided filtering scheme uses Gaussian filter and two-level weight maps due to which the scheme has limited performance for images having noise. Different modifications in filter (based on linear minimum mean square error estimator) and weight maps (with different levels) are proposed to overcome these limitations. Simulation results based on visual and quantitative analysis show the significance of proposed scheme. PMID:24695586
Elastomeric actuator devices for magnetic resonance imaging
NASA Technical Reports Server (NTRS)
Dubowsky, Steven (Inventor); Hafez, Moustapha (Inventor); Jolesz, Ferenc A. (Inventor); Kacher, Daniel F. (Inventor); Lichter, Matthew (Inventor); Weiss, Peter (Inventor); Wingert, Andreas (Inventor)
The present invention is directed to devices and systems used in magnetic imaging environments that include an actuator device having an elastomeric dielectric film with at least two electrodes, and a frame attached to the actuator device. The frame can have a plurality of configurations including, such as, for example, at least two members that can be, but not limited to, curved beams, rods, plates, or parallel beams. These rigid members can be coupled to flexible members such as, for example, links wherein the frame provides an elastic restoring force. The frame preferably provides a linear actuation force characteristic over a displacement range. The linear actuation force characteristic is defined as .+-.20% and preferably 10% over a displacement range. The actuator further includes a passive element disposed between the flexible members to tune a stiffness characteristic of the actuator. The passive element can be a bi-stable element. The preferred embodiment actuator includes one or more layers of the elastomeric film integrated into the frame. The elastomeric film can be made of many elastomeric materials such as, for example, but not limited to, acrylic, silicone and latex.
Functionalized 129Xe contrast agents for magnetic resonance imaging
Taratula, Olena; Dmochowski, Ivan J.
The concept of 'xenon biosensor' for magnetic resonance imaging (MRI) was first proposed by a Berkeley team in 2001, with evidence that hyperpolarized 129Xe bound to a biotin-labeled cryptophane can detect streptavidin at much lower concentrations (nM-?M) than is typical for contrast-enhanced MRI experiments. 129Xe biosensors have undergone many recent developments to address challenges in molecular imaging. For example, cryptophanes have been synthesized that exhibit 10-fold higher xenon affinity with distinct 129Xe magnetic resonance spectra. Also relevant are dendrimeric cryptophane assemblies and inorganic zeolites that localize many 129Xe atoms to rare targets. Finally, this article considers biosensors that produce measurable changes in 129Xe chemical shift based upon the activity of oligonucleotides, proteins, or enzymes, and includes the first cell studies. PMID:19914122
Magnetic resonance imaging for the ophthalmologist: A primer
Simha, Arathi; Irodi, Aparna; David, Sarada
Magnetic resonance imaging (MRI) and computerized tomography (CT) have added a new dimension in the diagnosis and management of ocular and orbital diseases. Although CT is more widely used, MRI is the modality of choice in select conditions and can be complimentary to CT in certain situations. The diagnostic yield is best when the ophthalmologist and radiologist work together. Ophthalmologists should be able to interpret these complex imaging modalities as better clinical correlation is then possible. In this article, we attempt to describe the basic principles of MRI and its interpretation, avoiding confusing technical terms. PMID:22824600
Image contrast reversals in contact resonance atomic force microscopy
NASA Astrophysics Data System (ADS)
Ma, Chengfu; Chen, Yuhang; Wang, Tian
Multiple image contrast inversions are observed along with the increase of modulation frequency for contact resonance atomic force microscopy (CR-AFM) imaging of a highly oriented pyrolytic graphite (HOPG) specimen. Analysis of the contact vibrational spectra indicates that the inversions can be attributed to structure-induced variations of tip-sample contact mechanics. Contact stiffness and damping at HOPG step edges exhibit significant increases relative to those in the flat regions. For quantitative evaluation of mechanical properties in CR-AFM, coupling effects of the surface geometry must be considered.
The Australian magnetic resonance imaging-linac program.
Keall, Paul J; Barton, Michael; Crozier, Stuart
The Australian magnetic resonance imaging (MRI)-Linac program is a $16-million government-funded project to advance the science and clinical practice of exquisite real-time anatomical and physiological adaptive cancer therapy. The centerpiece of the program is a specifically designed 1-T open-bore MRI/6-MV linac system that is planned for delivery and completion of installation in 2014. Current scientific endeavors include engineering discovery in MRI component design, quantifying MRI and linac interactions, and developing image guidance and adaptation strategies. PMID:24931094
Hemodynamic Assessment of Carotid Stenosis by Functional Magnetic Resonance Imaging
Ulf Jensen; Kathrin Börsch; Robert Stingele; Olav Jansen; Karsten Alfke
Background: Functional magnetic resonance imaging (fMRI) is a method usually used to identify cortical representations of cerebral functions. Some studies and case reports suggest that stenoses of the brain-supplying arteries influence the BOLD (blood-oxygenation-level-dependent) signal. The objective of this study was to find out whether the BOLD signal differs in the ipsilateral hemisphere of patients with hemodynamically relevant and those
Phase and sensitivity of receiver coils in magnetic resonance imaging
McVeigh, E. R.; Bronskill, M. J.; Henkelman, R. M.
Receiver coil response is a major cause of nonuniformities in magnetic resonance images. The spatial dependence of the sensitivity and phase of single-saddle receiver coils has been investigated quantitatively by calculating the H1 field and comparing the results with measurements of a uniform phantom. Agreement between the measurements and calculations is excellent. A method is developed which corrects for both the nonuniform sensitivity and the phase shifts introduced by receiver coils. PMID:3796476
Electron Paramagnetic Resonance Imaging of Oxidative Stress in Renal Disease
Aki Hirayama; Sohji Nagase
The importance of analyzing the kinetics of reactive oxygen species or related substances in vivo is increasing. Electron paramagnetic resonance (EPR) is currently a powerful method for in vivo, non-invasive analysis of oxidative stress. We have applied EPR imaging for murine renal ischemia-reperfusion injury, as a model of acute renal damage, and NF-E2-related factor 2 (Nrf2)-deficient mice, a model for
Real-time functional magnetic resonance imaging: methods and applications
Nikolaus Weiskopf; Ranganatha Sitaram; Oliver Josephs; Ralf Veit; Frank Scharnowski; Rainer Goebele; Niels Birbaumer; Ralf Deichmann; Klaus Mathiakf
Functional magnetic resonance imaging (fMRI) has been limited by time-consuming data analysis and a low signal-to-noise ratio, impeding online analysis. Recent advances in acquisition techniques, computational power and algorithms increased the sensitivity and speed of fMRI significantly, making real-time analysis and display of fMRI data feasible. So far, most reports have focused on the technical aspects of real-time fMRI (rtfMRI).
Multifunctional magnetic nanoparticles for magnetic resonance imaging and cancer therapy
Murali M. Yallapu; Shadi F. Othman; Evan T. Curtis; Brij K. Gupta; Meena Jaggi; Subhash C. Chauhan
We have developed a multi-layer approach for the synthesis of water-dispersible superparamagnetic iron oxide nanoparticles for hyperthermia, magnetic resonance imaging (MRI) and drug delivery applications. In this approach, iron oxide core nanoparticles were obtained by precipitation of iron salts in the presence of ammonia and provided ?-cyclodextrin and pluronic polymer (F127) coatings. This formulation (F127250) was highly water dispersible which
Decoding brain states using functional magnetic resonance imaging
Dongha Lee; Changwon Jang; Hae-Jeong Park
Most leading research in basic and clinical neuroscience has been carried out by functional magnetic resonance imaging (fMRI),\\u000a which detects the blood oxygenation level dependent signals associated with neural activities. Among new fMRI applications,\\u000a brain decoding is an emerging research area, which infers mental states from fMRI signals. Brain decoding using fMRI includes\\u000a classification, identification, and reconstruction of brain states.
Magnetic Resonance Imaging of Benign Cardiac Masses: A Pictorial Essay
Ward, Thomas J.; Kadoch, Michael A.; Jacobi, Adam H.; Lopez, Pablo P.; Salvo, Javier Sanz; Cham, Matthew D.
The differential diagnosis for a cardiac mass includes primary and metastatic neoplasms. While primary cardiac tumors are rare, metastatic disease to the heart is a common finding in cancer patients. Several "tumor-like" processes can mimic a true cardiac neoplasm with accurate diagnosis critical at guiding appropriate management. We present a pictorial essay of the most common benign cardiac masses and "mass-like" lesions with an emphasis on magnetic resonance imaging features. PMID:24083071
Magnetic resonance imaging of the bone marrow in hematological malignancies
B. C. Vande Berg; F. E. Lecouvet; L. Michaux; A. Ferrant; B. Maldague; J. Malghem
. Despite its lack of specificity, magnetic resonance imaging (MRI) of the bone marrow has the potential to play a role in\\u000a the management of patients with primary neoplastic disorders of the hematopoietic system, including lymphomas, leukemias and\\u000a multiple myeloma. In addition to its use in the assessment of suspected spinal cord compression, bone marrow MRI could be\\u000a used as
Magnetic Resonance Imaging of Stroke in the Rat
CHOPP, Michael; LI, Lian; ZHANG, Li; ZHANG, Zheng-gang; LI, Qing-jiang; JIANG, Quan
Magnetic resonance imaging (MRI) is now a routine neuroimaging tool in the clinic. Throughout all phases of stroke from acute to chronic, MRI plays an important role to diagnose, evaluate and monitor the cerebral tissue undergoing stroke. This review provides a description of various MRI methods and an overview of selected MRI studies, with an embolic stroke model of rat, performed in the MRI laboratory of Department of Neurology, Henry Ford Hospital, Detroit, Michigan, US. PMID:24920874
Experiences with functional magnetic resonance imaging at 1 tesla
Functional magnetic resonance imaging (fMRI) has been performed on a standard 1 T system using a pulse sequence developed to utilize blood oxygen level dependent (BOLD) contrast and an oV-line analysis routine using correlation techniques. The sequence and the data analysis routine have been validated by reproducing the conventional hand movement paradigm studies reported by numerous other workers. Our work
Clinical Applications of Magnetic Resonance Imaging—Current Status
Cammoun, Driss; Davis, Kathleen A.; Hendee, William R.
Magnetic resonance imaging has far-reaching real and possible clinical applications. Its usefulness has been best explored and realized in the central nervous system, especially the posterior fossa and brain stem, where most abnormalities are better identified than with computed tomography. Its lack of ionizing radiation and extreme sensitivity to normal and abnormal patterns of myelination make magnetic resonance imaging advantageous for diagnosing many neonatal and pediatric abnormalities. New, reliable cardiac gating techniques open the way for promising studies of cardiac anatomy and function. The ability to image directly in three orthogonal planes gives us new insight into staging and follow-up of pelvic tumors and other pelvic abnormalities. Exquisite soft tissue contrast, far above that attainable by other imaging modalities, has made possible the early diagnosis of traumatic ligamentous knee injury, avascular necrosis of the hip and diagnosis, treatment planning and follow-up of musculoskeletal neoplasms. ImagesFigure 1.Figure 2.Figure 3.Figure 4.Figure 5.Figure 6.Figure 7.Figure 8.Figure 9. PMID:3911592
Simultaneous in vivo positron emission tomography and magnetic resonance imaging
Catana, Ciprian; Procissi, Daniel; Wu, Yibao; Judenhofer, Martin S.; Qi, Jinyi; Pichler, Bernd J.; Jacobs, Russell E.; Cherry, Simon R.
Positron emission tomography (PET) and magnetic resonance imaging (MRI) are widely used in vivo imaging technologies with both clinical and biomedical research applications. The strengths of MRI include high-resolution, high-contrast morphologic imaging of soft tissues; the ability to image physiologic parameters such as diffusion and changes in oxygenation level resulting from neuronal stimulation; and the measurement of metabolites using chemical shift imaging. PET images the distribution of biologically targeted radiotracers with high sensitivity, but images generally lack anatomic context and are of lower spatial resolution. Integration of these technologies permits the acquisition of temporally correlated data showing the distribution of PET radiotracers and MRI contrast agents or MR-detectable metabolites, with registration to the underlying anatomy. An MRI-compatible PET scanner has been built for biomedical research applications that allows data from both modalities to be acquired simultaneously. Experiments demonstrate no effect of the MRI system on the spatial resolution of the PET system and <10% reduction in the fraction of radioactive decay events detected by the PET scanner inside the MRI. The signal-to-noise ratio and uniformity of the MR images, with the exception of one particular pulse sequence, were little affected by the presence of the PET scanner. In vivo simultaneous PET and MRI studies were performed in mice. Proof-of-principle in vivo MR spectroscopy and functional MRI experiments were also demonstrated with the combined scanner. PMID:18319342
Chapter 24: Magnetic resonance imaging in experimental stroke
Duong, Timothy Q
Stroke is the third leading cause of death and the leading cause of long-term disability in the United States. Brain imaging data from experimental stroke models and stroke patients have shown that there is often a gradual progression of potentially reversible ischemic injury toward infarction. A central core with severely compromised cerebral blood flow (CBF) is surrounded by a rim of moderately ischemic tissue with diminished CBF and impaired electrical activity but preserved cellular metabolism, often referred to as the "ischemic penumbra." Re-establishing tissue perfusion and/or treating with neuroprotective drugs in a timely fashion are expected to salvage some ischemic tissues. Diffusion-weighted imaging (DWI) based on magnetic resonance imaging (MRI) in which contrast is based on water apparent diffusion coefficient (ADC) can detect ischemic injury within minutes after onsets, whereas computed tomography and other imaging modalities fail to detect stroke injury for at least a few hours. Along with quantitative perfusion imaging, the perfusion-diffusion mismatch which approximates the ischemic penumbra could be defined non-invasively. This chapter describes stroke modeling, perfusion, diffusion and some other MRI techniques commonly used to image acute stroke and, finally, image analysis pertaining to experimental stroke imaging. PMID:21279618
Respiratory Amplitude Guided 4-Dimensional Magnetic Resonance Imaging
Hu, Yanle, E-mail: firstname.lastname@example.com [Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri (United States)] [Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri (United States); Caruthers, Shelton D. [Department of Medicine, Washington University School of Medicine, St. Louis, Missouri (United States)] [Department of Medicine, Washington University School of Medicine, St. Louis, Missouri (United States); Low, Daniel A. [Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California (United States)] [Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California (United States); Parikh, Parag J.; Mutic, Sasa [Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri (United States)] [Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri (United States)
Purpose: To evaluate the feasibility of prospectively guiding 4-dimensional (4D) magnetic resonance imaging (MRI) image acquisition using triggers at preselected respiratory amplitudes to achieve T{sub 2} weighting for abdominal motion tracking. Methods and Materials: A respiratory amplitude-based triggering system was developed and integrated into a commercial turbo spin echo MRI sequence. Initial feasibility tests were performed on healthy human study participants. Four respiratory states, the middle and the end of inhalation and exhalation, were used to trigger 4D MRI image acquisition of the liver. To achieve T{sub 2} weighting, the echo time and repetition time were set to 75 milliseconds and 4108 milliseconds, respectively. Single-shot acquisition, together with parallel imaging and partial k-space imaging techniques, was used to improve image acquisition efficiency. 4D MRI image sets composed of axial or sagittal slices were acquired. Results: Respiratory data measured and logged by the MRI scanner showed that the triggers occurred at the appropriate respiratory levels. Liver motion could be easily observed on both 4D MRI image datasets by sensing either the change of liver in size and shape (axial) or diaphragm motion (sagittal). Both 4D MRI image datasets were T{sub 2}-weighted as expected. Conclusions: This study demonstrated the feasibility of achieving T{sub 2}-weighted 4D MRI images using amplitude-based respiratory triggers. With the aid of the respiratory amplitude-based triggering system, the proposed method is compatible with most MRI sequences and therefore has the potential to improve tumor-tissue contrast in abdominal tumor motion imaging.
Primary hepatocellular lesions: imaging findings on state-of-the-art magnetic resonance imaging, with pathologic correlation.
van den Bos, Indra C; Hussain, Shahid M; de Man, Robert A; Zondervan, Pieter E; Ijzermans, Jan N M; Krestin, Gabriel P
Magnetic resonance imaging is routinely used for the workup of patients with focal or diffuse liver disease, including primary hepatocellular lesions, storage diseases, metastatic liver disease, and diseases of the hepatobiliary tree. The most important magnetic resonance imaging sequences used for diagnostic imaging of the liver consist of T1-weighted sequences, T2-weighted sequences, and at least the arterial and delayed phases of dynamic gadolinium-enhanced imaging. This article provides an overview of magnetic resonance imaging of primary hepatocellular lesions and will describe the following: (1) the classification and etiology of primary hepatocellular lesions, including focal nodular hyperplasia, hepatocellular adenoma, and hepatocellular carcinoma; (2) the stepwise carcinogenesis of hepatocellular carcinoma in cirrhosis on magnetic resonance imaging; and (3) the typical imaging findings of primary hepatocellular lesions on magnetic resonance imaging, with differential diagnoses. PMID:18436110
A dual RF resonator system for high-field functional magnetic resonance imaging of small animals
R. Ludwig; G. Bodgdanov; J. King; A. Allard; C. F. Ferris
A new apparatus has been developed that integrates an animal restrainer arrangement for small animals with an actively tunable\\/detunable dual radio-frequency (RF) coil system for in vivo anatomical and functional magnetic resonance imaging of small animals at 4.7T. The radio-frequency coil features an eight-element microstrip line configuration that, in conjunction with a segmented outer copper shield, forms a transversal electromagnetic
Uniform Spinning Sampling Gradient Electron Paramagnetic Resonance Imaging
Johnson, David H.; Ahmad, Rizwan; Liu, Yangping; Chen, Zhiyu; Samouilov, Alexandre; Zweier, Jay L.
Purpose To improve the quality and speed of electron paramagnetic resonance imaging (EPRI) acquisition by combining a uniform sampling distribution with spinning gradient acquisition. Theory and Methods A uniform sampling distribution was derived for spinning gradient EPRI acquisition (Uniform Spinning Sampling, USS) and compared to the existing (Equilinear Spinning Sampling, ESS) acquisition strategy. Novel corrections were introduced to reduce artifacts in experimental data. Results Simulations demonstrated that USS puts an equal number of projections near each axis whereas ESS puts excessive projections at one axis, wasting acquisition time. Artifact corrections added to the magnetic gradient waveforms reduced noise and correlation between projections. USS images had higher SNR (85.9±0.8 vs. 56.2±0.8) and lower mean-squared error than ESS images. The quality of the USS images did not vary with the magnetic gradient orientation, in contrast to ESS images. The quality of rat heart images was improved using USS compared to that with ESS or traditional fast-scan acquisitions. Conclusion A novel EPRI acquisition which combines spinning gradient acquisition with a uniform sampling distribution was developed. This USS spinning gradient acquisition offers superior SNR and reduced artifacts compared to prior methods enabling potential improvements in speed and quality of EPR imaging in biological applications. PMID:23475830
Ferritin reporter used for gene expression imaging by magnetic resonance
Ono, Kenji; Fuma, Kazuya; Tabata, Kaori [Department of Brain Functions, Division of Stress Adaptation and Protection, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Aichi 464-8601 (Japan)] [Department of Brain Functions, Division of Stress Adaptation and Protection, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Aichi 464-8601 (Japan); Sawada, Makoto, E-mail: firstname.lastname@example.com [Department of Brain Functions, Division of Stress Adaptation and Protection, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Aichi 464-8601 (Japan)] [Department of Brain Functions, Division of Stress Adaptation and Protection, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Aichi 464-8601 (Japan)
Magnetic resonance imaging (MRI) is a minimally invasive way to provide high spatial resolution tomograms. However, MRI has been considered to be useless for gene expression imaging compared to optical imaging. In this study, we used a ferritin reporter, binding with biogenic iron, to make it a powerful tool for gene expression imaging in MRI studies. GL261 mouse glioma cells were over-expressed with dual-reporter ferritin-DsRed under {beta}-actin promoter, then gene expression was observed by optical imaging and MRI in a brain tumor model. GL261 cells expressing ferritin-DsRed fusion protein showed enhanced visualizing effect by reducing T2-weighted signal intensity for in vitro and in vivo MRI studies, as well as DsRed fluorescence for optical imaging. Furthermore, a higher contrast was achieved on T2-weighted images when permeating the plasma membrane of ferritin-DsRed-expressing GL261. Thus, a ferritin expression vector can be used as an MRI reporter to monitor in vivo gene expression.
Magnetic resonance microscopy of prostate tissue: How basic science can inform clinical imaging development
Bourne, Roger
This commentary outlines how magnetic resonance imaging (MRI) microscopy studies of prostate tissue samples and whole organs have shed light on a number of clinical imaging mysteries and may enable more effective development of new clinical imaging methods.
Quantitative analysis of brain magnetic resonance imaging for hepatic encephalopathy
NASA Astrophysics Data System (ADS)
Syh, Hon-Wei; Chu, Wei-Kom; Ong, Chin-Sing
High intensity lesions around ventricles have recently been observed in T1-weighted brain magnetic resonance images for patients suffering hepatic encephalopathy. The exact etiology that causes magnetic resonance imaging (MRI) gray scale changes has not been totally understood. The objective of our study was to investigate, through quantitative means, (1) the amount of changes to brain white matter due to the disease process, and (2) the extent and distribution of these high intensity lesions, since it is believed that the abnormality may not be entirely limited to the white matter only. Eleven patients with proven haptic encephalopathy and three normal persons without any evidence of liver abnormality constituted our current data base. Trans-axial, sagittal, and coronal brain MRI were obtained on a 1.5 Tesla scanner. All processing was carried out on a microcomputer-based image analysis system in an off-line manner. Histograms were decomposed into regular brain tissues and lesions. Gray scale ranges coded as lesion were then brought back to original images to identify distribution of abnormality. Our results indicated the disease process involved pallidus, mesencephalon, and subthalamic regions.
Magnetic resonance imaging of canine mast cell tumors.
Pokorny, Esteban; Hecht, Silke; Sura, Patricia A; LeBlanc, Amy K; Phillips, Jeffrey; Conklin, Gordon A; Haifley, Katherine A; Newkirk, Kim
Mast cell tumors (MCT) are the most common cutaneous tumors in dogs. Our purpose was to describe the magnetic resonance (MR) imaging characteristics of cutaneous MCT and to identify imaging characteristics that allow differentiation of metastatic from normal lymph nodes. Eight dogs with a total of nineMCT were imaged as were their presumed draining and associated contralateral lymph nodes. The signal intensity of tumors and lymph nodes was compared to adjacent musculature. On T2-W images, 7/9 MCT were hyperintense to muscle and 2/9 were isointense. On T1-W images, 8/9 MCT were isointense and 1/9 were mildly hypointense. All tumors were strongly contrast enhancing; 5/9 were homogeneous and 4/9 heterogeneous in their enhancement patterns. Six lymph node pairs were included in the evaluation (five sentinel lymph nodes with metastases, one without, and six contralateral lymph nodes). Metastatic lymph nodes were significantly larger than their contralateral lymph nodes (P = 0.039). All lymph nodes were isointense on T1-W images and hyperintense on T2-W images. 5/5 metastatic and 2/7 normal lymph nodes were heterogeneously T2-hyperintense. All lymph nodes were moderately to strongly contrast enhancing. 4/5 metastatic and 2/7 normal lymph nodes had heterogeneous enhancement patterns. While heterogeneity was more common in metastatic than in normal lymph nodes, this difference was not significant (P = 0.058 for T2-W images; P = 0.234 for postcontrast images). MR imaging may be useful in the presurgical evaluation and clinical staging of cutaneous MCT. PMID:22136427
Magnetic resonance imaging of the rhesus monkey brain: use for stereotactic neurosurgery
R. C. Saunders; T. G. Aigner; J. A. Frank
Standard stereotactic procedures rely upon external cranial landmarks and standardized atlases for localization of subcortical neural regions. Magnetic resonance imaging permits the visualization of the neural structure of the brain in vivo. A stereotactic instrument compatible with a magnetic resonance unit was constructed and together with magnetic resonance imaging a procedure was developed that overcomes the limitations and inaccuracies of
Advances in Surface Plasmon Resonance Imaging Enable Quantitative Tracking of Nanoscale Changes in Thickness and
Dutcher, John
Advances in Surface Plasmon Resonance Imaging Enable Quantitative Tracking of Nanoscale Changes: To date, detailed studies of the thickness of coatings using surface plasmon resonance have been limited a significant improvement to surface plasmon resonance imaging (SPRi) that allows this sensitive technique
Update of prostate magnetic resonance imaging at 3 T.
Kim, Chan Kyo; Park, Byung Kwan
More recently, 3-T magnetic resonance (MR) scanner become more clinically available, and clinical application of 3-T MR imaging (MRI) of the abdomen and pelvis is now feasible and being performed at many institutions. However, few prostrate 3-T MRI studies have been published. The increase in signal-to-noise ratio at 3 versus 1.5 T clearly improves spatiotemporal and spectral resolutions of the prostate. Thus, we asked whether 3-T MRI improves the localization and staging of prostate cancer versus 1.5-T MRI. To answer this question, this article reviews the current limitations of prostate 1.5-T MRI and addresses its pros and cons. Moreover, we present preliminary results of prostate 3-T MRI and introduce our experience for prostate 3-T MRI using a phased-array coil, with an emphasis on imaging sequences, for example, T2-weighted, dynamic contrast-enhanced, diffusion-weighted, and MR spectroscopic imaging. PMID:18379296
Applications of nuclear magnetic resonance imaging in process engineering
NASA Astrophysics Data System (ADS)
Gladden, Lynn F.; Alexander, Paul
During the past decade, the application of nuclear magnetic resonance (NMR) imaging techniques to problems of relevance to the process industries has been identified. The particular strengths of NMR techniques are their ability to distinguish between different chemical species and to yield information simultaneously on the structure, concentration distribution and flow processes occurring within a given process unit. In this paper, examples of specific applications in the areas of materials and food processing, transport in reactors and two-phase flow are discussed. One specific study, that of the internal structure of a packed column, is considered in detail. This example is reported to illustrate the extent of new, quantitative information of generic importance to many processing operations that can be obtained using NMR imaging in combination with image analysis.
The Spleen Revisited: An Overview on Magnetic Resonance Imaging
Palas, Joăo; Matos, António P.; Ramalho, Miguel
Despite being well visualized by different cross-sectional imaging techniques, the spleen is many times overlooked during the abdominal examination. The major reason is the low frequency of splenic abnormalities, the majority consisting of incidental findings. There has been a steady increase in the number of performed abdominal magnetic resonance imaging (MRI) studies; therefore, it is important to be familiar to the major MRI characteristics of disease processes involving the spleen, in order to interpret the findings correctly, reaching whenever possible the appropriate diagnosis. The spleen may be involved in several pathologic conditions like congenital diseases, trauma, inflammation, vascular disorders and hematologic disorders, benign and malignant tumors, and other disease processes that focally or diffusely affect the spleen. This paper presents a description and representative MRI images for many of these disorders. PMID:24377046
Nuclear magnetic resonance imaging of lipid in living plants.
Borisjuk, Ljudmilla; Rolletschek, Hardy; Neuberger, Thomas
This review highlights technological developments in magnetic resonance imaging (MRI), which are creating opportunities for the three dimensional visualization and quantification of lipids in plant materials. A major feature of MRI is that it is a non-invasive platform, and thus can be used for the analysis of living organisms. An overview of the theoretical aspects of MRI is provided, followed by a description of the various analytical modes available, and an explanation of how MRI can be applied to plant samples and what it can achieve. Various lipid maps and three dimensional models of seeds and fruits are included to demonstrate the potential of MRI and to exemplify recent cutting-edge advances in the field. The importance and prospects of the imaging of lipids in living plants, as well as the integration of lipid imaging with other emerging techniques, are outlined to provide impetus for future plant lipid research. PMID:23748080
Magnetic resonance imaging features of equine nigropallidal encephalomalacia.
Sanders, S G; Tucker, R L; Bagley, R S; Gavin, P R
Magnetic resonance imaging (MR) was used to make a diagnosis of equine nigropallidal encephalomalacia in a horse. Equine nigropallidal encephalomalacia is a neurodegenerative disease that has many characteristics with Parkinson-like diseases in humans. Historically, horses were euthanized based on clinical signs and exposure to the toxic weed, yellow star thistle (Centaurea solstitialis). Previously, the disease has only been confirmed on necropsy. MR imaging can provide accurate and sensitive visualization of typical lesions seen in the brain of horses affected with equine nigropallidal encephalomalacia. Lesions were seen on T1-weighted, T2-weighted and proton density images. There was no contrast enhancement following Gd-DTPA administration. Lesions seen on MR were confirmed at necropsy. Using MR to confirm a diagnosis of equine nigropallidal encephalomalacia will prevent unnecessary suffering of horses and expense to owners that would otherwise incur, while further diagnostics are performed. PMID:11499702
Novel technique in the segmentation of magnetic resonance image
NASA Astrophysics Data System (ADS)
Chan, Kwok-Leung
In this investigation, automatic image segmentation is carried out on magnetic resonance image (MRI). A novel technique based on the maximum minimum measure is devised. The measure is improved by combining the smoothing and counting processes, and then normalizing the number of maximum and minimum positions over the region of interest (ROI). Two parameters (MM_H and MM_V) are generated and used for the segmentation. The technique is tested on some brain MRIs of a human male from the Visible Human Project of the National Library of Medicine, National Institutes of Health, USA. Preliminary results indicate that the maximum minimum measure can provide effective parameters for human tissue characterization and image segmentation with an added advantage of faster computation.
Tracking immune cells in vivo using magnetic resonance imaging
Ahrens, Eric T.; Bulte, Jeff W. M.
The increasing complexity of in vivo imaging technologies, coupled with the development of cell therapies, has fuelled a revolution in immune cell tracking in vivo. Powerful magnetic resonance imaging (MRI) methods are now being developed that use iron oxide- and 19F-based probes. These MRI technologies can be used for image-guided immune cell delivery and for the visualization of immune cell homing and engraftment, inflammation, cell physiology and gene expression. MRI-based cell tracking is now also being applied to evaluate therapeutics that modulate endogenous immune cell recruitment and to monitor emerging cellular immunotherapies. These recent uses show that MRI has the potential to be developed in many applications to follow the fate of immune cells in vivo. PMID:24013185
The rotating biplanar linac-magnetic resonance imaging system.
Fallone, Biagio Gino
We have successfully built linac-magnetic resonance imaging (MR) systems based on a linac waveguide placed between open MR planes (perpendicular) or through the central opening of one of the planes (parallel) to improve dosimetric properties. It rotates on a gantry to irradiate at any angle. Irradiation during MR imaging and automatic 2-dimensional MR image-based target tracking and automatic beam steering to the moving target have been demonstrated with our systems. The functioning whole-body system (0.6-T MR and 6-MV linac) has been installed in an existing clinical vault without removing the walls or the ceiling and without the need of a helium exhaust vent. PMID:24931093
Magnetic Resonance Imaging Conditional Pacemakers: Rationale, Development and Future Directions
Cronin, Edmond M; Wilkoff, Bruce L
Pacemakers and other cardiac implantable electronic devices (CIEDs) have long been considered an absolute contraindication to magnetic resonance imaging (MRI), a crucial and growing imaging modality. In the last 20 years, protocols have been developed to allow MR scanning of CIED patients with a low complication rate. However, this practice has remained limited to a relatively small number of centers, and many pacemaker patients continue to be denied access to clinically indicated imaging. The introduction of MRI conditional pacemakers has provided a widely applicable and satisfactory solution to this problem. Here, the interactions of pacemakers with the MR environment, the results of MR scanning in patients with conventional CIEDs, the development and clinical experience with MRI conditional devices, and future directions are reviewed. PMID:23071382
Improved Cerebellar Tissue Classification on Magnetic Resonance Images of Brain
Datta, Sushmita; Tao, Guozhi; He, Renjie; Wolinsky, Jerry S.; Narayana, Ponnada A.
Purpose To develop and implement a method for improved cerebellar tissue classification on the magnetic resonance images of brain by automatically isolating the cerebellum prior to segmentation. Materials and Methods Dual fast spin echo (FSE) and fluid attenuation inversion recovery (FLAIR) images were acquired on eighteen normal volunteers on a 3 T Philips scanner. The cerebellum was isolated from rest of the brain by using a symmetric inverse consistent nonlinear registration of individual brain with the parcellated template. The cerebellum was then separated by masking the anatomical image with individual FLAIR images. Tissues in both the cerebellum and rest of the brain were separately classified using hidden Markov random field (HMRF), a parametric method, and then combined to obtain tissue classification of the whole brain. The proposed method for tissue classification on real magnetic resonance (MR) brain images was evaluated subjectively by two experts. The segmentation results on Brainweb images with varying noise and intensity nonuniformity levels were quantitatively compared with the ground truth by computing the Dice similarity indices. Results The proposed method has significantly improved the cerebellar tissue classification on all normal volunteers included in this study without compromising the classification in remaining part of the brain. The average similarity indices for gray matter (GM) and white matter (WM) in the cerebellum are 89.81 (± 2.34) and 93.04 (± 2.41), demonstrating excellent performance of the proposed methodology. Conclusion The proposed method significantly improved tissue classification in the cerebellum. The GM was overestimated when segmentation was performed on the whole brain as a single object. PMID:19388122
Biological effects of exposure to magnetic resonance imaging: an overview
Formica, Domenico; Silvestri, Sergio
The literature on biological effects of magnetic and electromagnetic fields commonly utilized in magnetic resonance imaging systems is surveyed here. After an introduction on the basic principles of magnetic resonance imaging and the electric and magnetic properties of biological tissues, the basic phenomena to understand the bio-effects are described in classical terms. Values of field strengths and frequencies commonly utilized in these diagnostic systems are reported in order to allow the integration of the specific literature on the bio-effects produced by magnetic resonance systems with the vast literature concerning the bio-effects produced by electromagnetic fields. This work gives an overview of the findings about the safety concerns of exposure to static magnetic fields, radio-frequency fields, and time varying magnetic field gradients, focusing primarily on the physics of the interactions between these electromagnetic fields and biological matter. The scientific literature is summarized, integrated, and critically analyzed with the help of authoritative reviews by recognized experts, international safety guidelines are also cited. PMID:15104797
Reconstruction of images from radiofrequency electron paramagnetic resonance spectra.
Smith, C M; Stevens, A D
This paper discusses methods for obtaining image reconstructions from electron paramagnetic resonance (EPR) spectra which constitute object projections. An automatic baselining technique is described which treats each spectrum consistently; rotating the non-horizontal baselines which are caused by stray magnetic effects onto the horizontal axis. The convolved backprojection method is described for both two- and three-dimensional reconstruction and the effect of cut-off frequency on the reconstruction is illustrated. A slower, indirect, iterative method, which does a non-linear fit to the projection data, is shown to give a far smoother reconstructed image when the method of maximum entropy is used to determine the value of the final residual sum of squares. Although this requires more computing time than the convolved backprojection method, it is more flexible and overcomes the problem of numerical instability encountered in deconvolution. Images from phantom samples in vitro are discussed. The spectral data for these have been accumulated quickly and have a low signal-to-noise ratio. The results show that as few as 16 spectra can still be processed to give an image. Artifacts in the image due to a small number of projections using the convolved backprojection reconstruction method can be removed by applying a threshold, i.e. only plotting contours higher than a given value. These artifacts are not present in an image which has been reconstructed by the maximum entropy technique. At present these techniques are being applied directly to in vivo studies. PMID:7874417
Magnetic resonance imaging features of cervical spinal cord meningiomas.
McDonnell, John J; Tidwell, Amy S; Faissler, Dominik; Keating, John
The records of four dogs with cervical spinal cord meningiomas were retrospectively reviewed. Signalment, history, laboratory findings, neurological examination, and histopathological findings were evaluated. Magnetic resonance imaging (MRI) was performed using a 1.0-T superconducting magnet and T2-weighted (W) and noncontrast and postcontrast T1-W spin echo pulse sequences. Meningiomas were located at the level of the second, third, and fifth cervical vertebrae and the C2-3 intervertebral space. All meningiomas appeared as focal masses that were hyperintense to the spinal cord on T2-W images and iso- to hypointense on the T1-W images. They could be identified as intradural and extramedullary in origin based on a broad-based dural margin seen on at least one of the imaging planes and a gradual expansion of the subarachnoid space cranial and caudal to the mass, best noted on the transverse and dorsal plane images. On dorsal plane T2-W images in three dogs, expansion of the subarachnoid space adjacent to the mass appeared similar to the myelographic "golf tee" sign. All meningiomas exhibited moderate, well-defined contrast enhancement with dural tails seen in three of the four dogs. One dog had extension into the intervertebral foramen along the nerve and ipsilateral atrophy of the muscles of the neck. By differentiating the meningiomas from intramedullary tumors and by clearly depicting the extent of the masses, MRI provided valuable information about treatment options and prognosis. PMID:16250392
Mascara--an unsuspected cause of magnetic resonance imaging artifact.
Smith, F W; Crosher, G A
It is well recognised that metals, especially iron, will cause artifacts in magnetic resonance (MR) images. Hitherto it has not been recognised that some facial cosmetics contain magnetic materials, in sufficient quantities to cause artifacts. We report a case of a 25-year-old female who had MR images of her orbits made while wearing mascara eye makeup. The resultant images showed distortion of the signal over the anterior aspect of both eyes. Examination following the removal of the eye makeup resulted in the acquisition of normal images. The typical ingredients of mascara are natural and synthetic waxes, glycerine, water, kaolin, preservatives, polymer film formers and pigments. A wide range of pigments may be used, especially iron oxide, which is a constituent of both brown and blue mascara. In addition it is likely that a number of mascaras will be contaminated with heavy metals. As a result of this observation we now ensure that all patients who are undergoing MR imaging of the head, remove all facial cosmetics as well as any jewelry prior to imaging. PMID:4079676
Nuclear magnetic resonance proton imaging of bone pathology
Atlan, H.; Sigal, R.; Hadar, H.; Chisin, R.; Cohen, I.; Lanir, A.; Soudry, M.; Machtey, Y.; Schreiber, R.; Benmair, J.
Thirty-two patients with diversified pathology were examined with a supraconductive NMR imager using spin echo with different TR and TE to obtain T1 and T2 weighted images. They included 20 tumors (12 primary, eight metastasis), six osteomyelitis, three fractures, two osteonecrosis, and one diffuse metabolic (Gaucher) disease. In all cases except for the stress fractures, the bone pathology was clearly visualized in spite of the normal lack of signal from the compact cortical bone. Nuclear magnetic resonance (NMR) imaging proved to be at least as sensitive as radionuclide scintigraphy but much more accurate than all other imaging procedures including computed tomography (CT) and angiography to assess the extension of the lesions, especially in tumors extended to soft tissue. This is due both to easy acquisition of sagittal and coronal sections and to different patterns of pathologic modifications of T1 and T2 which are beginning to be defined. It is hoped that more experience in clinical use of these patterns will help to discriminate between tumor extension and soft-tissue edema. We conclude that while radionuclide scintigraphy will probably remain the most sensitive and easy to perform screening test for bone pathology, NMR imaging, among noninvasive diagnostic procedures, appears to be at least as specific as CT. In addition, where the extension of the lesions is concerned, NMR imaging is much more informative than CT. In pathology of the spine, the easy visualization of the spinal cord should decrease the need for myelography.
Magnetic resonance imaging and contrast enhancement. Scientific report
Swenberg, C.E.; Movius, E.G.
Chapters II through VI of this report discuss: Relaxation of Nuclear Spins; Echo Techniques; Basic Imaging Pulse Sequences; Partial Saturation Recovery; Inversion Recovery; Spin Echo; Effects of Pulse Sequence on Image Contrast; Contrast Agents; Theoretical Aspects; Pharmacokinetics and Toxicity; and Physiological Rationale for Agent Selection. One of the major goals in all medical imaging techniques is to maximize one's ability to visualize and differentiate adjacent tissue regions in the body on the basis of differences in anatomy, physiology, or various pathological processes. Magnetic resonance (MR) imaging offers distinct advantages over conventional x-ray imaging because of the possibility of selecting specific pulse sequences that can differentiate adjacent structures on the basis of differences in proton density, T/sub 1/ or T/sub 2/ relaxation rates, or flow. As a result of applying these various pulse sequences, numerous images have been obtained of the brain and other organs that demonstrate considerably more-detailed anatomical structure than had previously been available with computerized tomography, ultrasound, or nuclear medicine techniques. In some situations it is clearly superior, such as in the diagnosis of multiple sclerosis.
Innovative computing for diagnoses from medical, magnetic-resonance imaging
Diegert, C.
The author presents a final report on a Laboratory-Directed Research and Development (LDRD) project, Innovative Computing for Diagnoses from Medical, Magnetic-Resonance Imaging, performed during fiscal years 1992 and 1993. The project defined a role for high-performance computing in surgery: the supercomputer can automatically summarize the three-dimensional extents of lesions and other clinically-relevant structures, and can deliver these summaries to workstation-based, augmented-reality environments at the clinical site. The author developed methods and software to make these summaries from the digital data already acquired using clinical, magnetic-resonance machines. In joint work with Albuquerque`s Department of Veterans Affairs Hospital, the author applied this work, and obtained a basis for planning, for rehearsal, and for guidance during surgery.
Hyperpolarized Xenon-129 Magnetic Resonance Imaging of Functional Lung Microstructure
NASA Astrophysics Data System (ADS)
Dregely, Isabel
Hyperpolarized 129Xe (HXe) is a non-invasive contrast agent for lung magnetic resonance imaging (MRI), which upon inhalation follows the functional pathway of oxygen in the lung by dissolving into lung tissue structures and entering the blood stream. HXe MRI therefore provides unique opportunities for functional lung imaging of gas exchange which occurs from alveolar air spaces across the air-blood boundary into parenchymal tissue. However challenges in acquisition speed and signal-to-noise ratio have limited the development of a HXe imaging biomarker to diagnose lung disease. This thesis addresses these challenges by introducing parallel imaging to HXe MRI. Parallel imaging requires dedicated hardware. This work describes design, implementation, and characterization of a 32-channel phased-array chest receive coil with an integrated asymmetric birdcage transmit coil tuned to the HXe resonance on a 3 Tesla MRI system. Using the newly developed human chest coil, a functional HXe imaging method, multiple exchange time xenon magnetization transfer contrast (MXTC) is implemented. MXTC dynamically encodes HXe gas exchange into the image contrast. This permits two parameters to be derived regionally which are related to gas-exchange functionality by characterizing tissue-to-alveolar-volume ratio and alveolar wall thickness in the lung parenchyma. Initial results in healthy subjects demonstrate the sensitivity of MXTC by quantifying the subtle changes in lung microstructure in response to orientation and lung inflation. Our results in subjects with lung disease show that the MXTC-derived functional tissue density parameter exhibits excellent agreement with established imaging techniques. The newly developed dynamic parameter, which characterizes the alveolar wall, was elevated in subjects with lung disease, most likely indicating parenchymal inflammation. In light of these observations we believe that MXTC has potential as a biomarker for the regional quantification of 1) emphysematous tissue destruction in chronic obstructive pulmonary disease (using the tissue density parameter) and 2) parenchymal inflammation or thickening (using the wall thickness parameter). By simultaneously quantifying two lung function parameters, MXTC provides a more comprehensive picture of lung microstructure than existing lung imaging techniques and could become an important non-invasive and quantitative tool to characterize pulmonary disease.
Clinical Image Quality Assessment of Accelerated Magnetic Resonance Neuroimaging Using Compressed Sensing
Southern California, University of
Clinical Image Quality Assessment of Accelerated Magnetic Resonance Neuroimaging Using Compressed abnormality. Conclusion: Compressed sensing is able to moderately accelerate certain neu- roimaging sequences methods are capable of accelerating clinical magnetic resonance neuroimaging sequences. Methods: Two 2
A head holder for magnetic resonance imaging that allows the stereotaxic alignment of spontaneously occurring intracranial
A head holder for magnetic resonance imaging that allows the stereotaxic alignment of spontaneously neurosurgery in rodent models of human disease requires the alignment of central nervous system (CNS devised a method to correlate images of mouse brain tumors acquired by magnetic resonance imaging (MRI
Automatic Segmentation of Non-enhancing Brain Tumors in Magnetic Resonance Images
Hall, Lawrence O.
weighted images, T1, T2 and proton density PD. Fuzzy c-means FCM clustering is a widely used clusteringAutomatic Segmentation of Non-enhancing Brain Tumors in Magnetic Resonance Images Lynn M. Fletcher,hall,firstname.lastname@example.com, email@example.com. #12;2 Abstract Tumor segmentation from magnetic resonance MR images may aid in tumor
Inhomogeneity correction for magnetic resonance images with fuzzy C-mean algorithm
segmentation method. For example, the adaptive fuzzy c-mean (AFCM) image segmentation algorithm proposedInhomogeneity correction for magnetic resonance images with fuzzy C-mean algorithm Xiang Li of New York at Stony Brook, USA Abstract: Segmentation of magnetic resonance (MR) images plays
Ventilation and perfusion magnetic resonance imaging of the lung
Bauman, Grzegorz; Eichinger, Monika
Summary A close interaction between the respiratory pump, pulmonary parenchyma and blood circulation is essential for a normal lung function. Many pulmonary diseases present, especially in their initial phase, a variable regional impairment of ventilation and perfusion. In the last decades various techniques have been established to measure the lung function. Besides the global pulmonary function tests (PFTs) imaging techniques gained increasing importance to detect local variations in lung function, especially for ventilation and perfusion assessment. Imaging modalities allow for a deeper regional insight into pathophysiological processes and enable improved planning of invasive procedures. In contrast to computed tomography (CT) and the nuclear medicine techniques, magnetic resonance imaging (MRI), as a radiation free imaging modality gained increasing importance since the early 1990 for the assessment of pulmonary function. The major inherent problems of lung tissue, namely the low proton density and the pulmonary and cardiac motion, were overcome in the last years by a constant progress in MR technology. Some MR techniques are still under development, a process which is driven by scientific questions regarding the physiology and pathophysiology of pulmonary diseases, as well as by the need for fast and robust clinically applicable imaging techniques as safe therapy monitoring tools. MRI can be considered a promising ionizing-free alternative to techniques like CT or nuclear medicine techniques for the evaluation of lung function. The goal of this article is to provide an overview on selected MRI techniques for the assessment of pulmonary ventilation and perfusion. PMID:22802864
Prostate cancer magnetic resonance imaging (MRI): multidisciplinary standpoint
Li, Liang; Feng, Zhaoyan; Hu, Zhiquan; Wang, Guoping; Yuan, Xianglin; Wang, He; Hu, Daoyu
Prostate cancer is the most common cancer diagnosed in men and a leading cause of death. Accurate assessment is a prerequisite for optimal clinical management and therapy selection of prostate cancer. There are several parameters and nomograms to differentiate between patients with clinically insignificant disease and patients in need of treatment. Magnetic resonance imaging (MRI) is a technique which provides more detailed anatomical images due to high spatial resolution, superior contrast resolution, and multiplanar capability. State-of-the-art MRI techniques, such as diffusion weighted imaging (DWI), MR spectroscopic imaging (MRSI), dynamic contrast enhanced MRI (DCE-MRI), improve interpretation of prostate cancer imaging. In this article, we review the major role of MRI in the advanced management of prostate cancer to noninvasively improve tumor staging, biologic potential, treatment planning, therapy response, local recurrence, and to guide target biopsy for clinical suspected cancer with previous negative biopsy. Finally, future challenges and opportunities in prostate cancer management in the area of functional MRI are discussed as well. PMID:23630657
Measurement techniques for magnetic resonance imaging of fast relaxing nuclei.
Konstandin, Simon; Nagel, Armin M
In this review article, techniques for sodium ((23)Na) magnetic resonance imaging (MRI) are presented. These techniques can also be used to image other nuclei with short relaxation times (e.g., (39)K, (35)Cl, (17)O). Twisted projection imaging, density-adapted 3D projection reconstruction, and 3D cones are preferred because of uniform k-space sampling and ultra-short echo times. Sampling density weighted apodization can be applied if intrinsic filtering is desired. This approach leads to an increased signal-to-noise ratio compared to postfiltered acquisition in cases of short readout durations relative to T 2 (*) relaxation time. Different MR approaches for anisotropic resolution are presented, which are important for imaging of thin structures such as myocardium, cartilage, and skin. The third part of this review article describes different methods to put more weighting either on the intracellular or the extracellular sodium signal by means of contrast agents, relaxation-weighted imaging, or multiple-quantum filtering. PMID:23881004
Using surface plasmon resonance imaging to study bacterial biofilmsa
Abadian, Pegah N.; Tandogan, Nil; Jamieson, John J.; Goluch, Edgar D.
This paper describes the use of Surface Plasmon Resonance imaging (SPRi) as an emerging technique to study bacterial physiology in real-time without labels. The overwhelming majority of bacteria on earth exist in large multicellular communities known as biofilms. Biofilms are especially problematic because they facilitate the survival of pathogens, leading to chronic and recurring infections as well as costly industrial complications. Monitoring biofilm accumulation and removal is therefore critical in these and other applications. SPRi uniquely provides label-free, high-resolution images of biomass coverage on large channel surfaces up to 1?cm2 in real time, which allow quantitative assessment of biofilm dynamics. The rapid imaging capabilities of this technique are particularly relevant for multicellular bacterial studies, as these cells can swim several body lengths per second and divide multiple times per hour. We present here the first application of SPRi to image Escherichia coli and Pseudomonas aeruginosa cells moving, attaching, and forming biofilms across a large surface. This is also the first time that biofilm removal has been visualized with SPRi, which has important implications for monitoring the biofouling and regeneration of fluidic systems. Initial images of the removal process show that the biofilm releases from the surface as a wave along the direction of the fluid flow. PMID:24753735
Low-field magnetic resonance imaging of gases
Schmidt, D.M.; Espy, M.A.
This is the final report of a six-month, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The main goal of this project was to develop the capability to conduct low-field magnetic resonance imaging of hyper-polarized noble gas nuclei and of thermally polarized protons in water. The authors constructed a versatile low-field NMR system using a SQUID gradiometer detector inside a magnetically shielded room. This device has sufficient low-field sensitivity to detect the small signals associated with NMR at low magnetic fields.
Simulation of wave-function microscopy images of Stark resonances
NASA Astrophysics Data System (ADS)
Zhao, L. B.; Xiao, D. H.; Fabrikant, I. I.
Wave-function microscopy images for Stark resonance states of H atoms are simulated using the quantum-mechanical formalism developed previously. Spatial distributions of ejected electron current densities are compared with experiment, and a good agreement is shown. The nonzero values of minima in the experimentally observed electron current distributions are reproduced by convoluting the theoretical current distribution with an instrumental function representing uncertainties in the position. Our relative strengths of the ejected electron current densities differ from those calculated with the wave packet propagation technique. We show that for the full convergence of the calculation, the distance between the ionized atom and the detector should exceed 10 ? m .
Interpretation of the magnetic resonance imaging signal from a foam
McCarthy, M.J. (California Univ., Davis, CA (USA). Dept. of Food Science and Technology)
Foams are important in a variety of industries including food, petroleum and chemical processing. Recently several research groups have demonstrated the effectiveness of measuring vertical phase density in foams as a function of time by magnetic resonance imaging (MRI). The advantage of using MRI for studying the stability of such multiphase systems lies in the ability to uniquely determine the density as a function of position noninvasively. Data obtained from these experiments should prove to be a sensitive test of theoretical models of these systems. The objective of this communication is to describe difficulties associated with interpretation of the MRI signal from foams.
Use of magnetic resonance imaging to monitor iron overload.
Wood, John C
Treatment of iron overload requires robust estimates of total-body iron burden and its response to iron chelation therapy. Compliance with chelation therapy varies considerably among patients, and individual reporting is notoriously unreliable. Even with perfect compliance, intersubject variability in chelator effectiveness is extremely high, necessitating reliable iron estimates to guide dose titration. In addition, each chelator has a unique profile with respect to clearing iron stores from different organs. This article presents the tools available to clinicians to monitor their patients, focusing on noninvasive magnetic resonance imaging methods because they have become the de facto standard of care. PMID:25064711
Advanced Imaging of Athletes: Added Value of Coronary Computed Tomography and Cardiac Magnetic Resonance Imaging.
Martinez, Matthew W
Cardiac magnetic resonance imaging and cardiac computed tomographic angiography have become important parts of the armamentarium for noninvasive diagnosis of cardiovascular disease. Emerging technologies have produced faster imaging, lower radiation dose, improved spatial and temporal resolution, as well as a wealth of prognostic data to support usage. Investigating true pathologic disease as well as distinguishing normal from potentially dangerous is now increasingly more routine for the cardiologist in practice. This article investigates how advanced imaging technologies can assist the clinician when evaluating all athletes for pathologic disease that may put them at risk. PMID:26100420
Simultaneous Magnetic Resonance Imaging and Consolidation Measurement of Articular Cartilage
Wellard, Robert Mark; Ravasio, Jean-Philippe; Guesne, Samuel; Bell, Christopher; Oloyede, Adekunle; Tevelen, Greg; Pope, James M.; Momot, Konstantin I.
Magnetic resonance imaging (MRI) offers the opportunity to study biological tissues and processes in a non-disruptive manner. The technique shows promise for the study of the load-bearing performance (consolidation) of articular cartilage and changes in articular cartilage accompanying osteoarthritis. Consolidation of articular cartilage involves the recording of two transient characteristics: the change over time of strain and the hydrostatic excess pore pressure (HEPP). MRI study of cartilage consolidation under mechanical load is limited by difficulties in measuring the HEPP in the presence of the strong magnetic fields associated with the MRI technique. Here we describe the use of MRI to image and characterize bovine articular cartilage deforming under load in an MRI compatible consolidometer while monitoring pressure with a Fabry-Perot interferometer-based fiber-optic pressure transducer. PMID:24803188
Cardiovascular Magnetic Resonance Imaging of Myocardial Infarction, Viability, and Cardiomyopathies
West, Amy M.; Kramer, Christopher M.
Cardiovascular magnetic resonance provides the opportunity for a truly comprehensive evaluation of patients with a history of MI, with regards to characterizing the extent of disease, impact on LV function and degree of viable myocardium. The use of contrast-enhanced CMR for first-pass perfusion and late gadolinium enhancement is a powerful technique for delineating areas of myocardial ischemia and infarction. Using a combination of T2-weighted and contrast-enhanced CMR images, information about the acuity of an infarct can be obtained. There is an extensive amount of literature using contrast-enhanced CMR to predict myocardial functional recovery with revascularization in patients with ischemic cardiomyopathies. In addition, CMR imaging in patients with cardiomyopathies can distinguish between ischemic and non-ischemic etiologies, with the ability to further characterize the underlying pathology for non-ischemic cardiomyopathies. PMID:20197150
Direct Neural Imaging using Ultra-Low Field Magnetic Resonance
NASA Astrophysics Data System (ADS)
Maskaly, Karlene; Espy, Michelle; Flynn, Mark; Gomez, John; Kraus, Robert; Matlashov, Andrei; Mosher, John; Newman, Shaun; Owens, Tuba; Peters, Mark; Sandin, J.; Schultz, Larry; Urbaitis, Algis; Volegov, Petr; Zotev, Vadim
An enduring challenge in neuroscience is the accurate in vivo mapping of neural activity with high spatial and temporal resolution. A method being developed by our group tries to meet this challenge by using Ultra-Low Field (ULF) MRI. Other groups have attempted direct neural imaging (DNI) using high field MRI. However, the use of ULF presents two advantages. First, the susceptibility artifact at high fields, which masks the DNI signal, is negligible at low fields. Second, the reduced Larmor frequency at ULF may overlap with the frequency spectrum of the neural magnetic field, resonantly enhancing the MRI signal. In this presentation, I will first show our custom-built ULF MRI setups that have successfully produced ULF anatomical images. I will then highlight the numerous studies we have done to investigate the feasibility of DNI with these systems, including both experimental and theoretical studies.
Volume measurement of horizontal extraocular muscles with magnetic resonance imaging.
Nishida, Y; Aoki, Y; Hayashi, O; Murata, T; Nishida, E; Kani, K
The horizontal extraocular muscle volume of 11 normal adults and 3 ophthalmoplegic patients was measured with magnetic resonance imaging (MRI), using a 1.5 Tesla superconductive system which can provide T1 weighted images of 3 mm gapless slices of the orbit with the spin echo technique. The MRI film was projected and magnified on Kent paper with an overhead projector; muscle shapes were traced and cut from the paper. Muscle volume was defined as the total weight of the Kent paper shapes representing the muscles from all MRI slices. The average volumes of the medial and lateral rectus muscles (MRM, LRM) of the 11 subjects were 690 +/- 87 mm3 and 734 +/- 77 mm3. In two patients with peripheral nerve palsy, the small muscle volume was classified as atrophic; in the one patient with orbital myositis, the large muscle volume was classified as hypertrophic. This measurement technique is useful for evaluation of the extraocular muscles, especially in ophthalmoplegia. PMID:8988436
Applications of Manganese-Enhanced Magnetic Resonance Imaging in Neuroscience
NASA Astrophysics Data System (ADS)
McCreary, J. Keiko
Manganese-Enhanced Magnetic Resonance Imaging (MEMRI) has proven itself to be a beneficial technique in the field of Neuroscience. This thesis applies MEMRI to studies in neuroscience by first establishing the limitations concerning the use of MEMRI in live rats. Experiment 1 used an osmotic pump for manganese (Mn) delivery to the lateral ventricles for acquisition of anatomical images using MEMRI. From my knowledge, this was the first method demonstrating slow infusion of Mn to the lateral ventricles. In Experiment 2, MEMRI was used for volumetric analysis the whole brain and hippocampus of prenatally stressed rats. To my knowledge, this study was the first to investigate the effect of generational prenatal stress on the structure of a rat's brain using MEMRI and histology. Additionally, Experiment 2 investigated the use of a subcutaneous osmotic pump to deliver Mn for MEMRI. A summary on the use of MEMRI in Neuroscience concludes this thesis, with a discussion on the methods used and related technical considerations.
Diffusion weighted magnetic resonance imaging and its recent trend—a survey
Chilla, Geetha Soujanya; Tan, Cher Heng
Since its inception in 1985, diffusion weighted magnetic resonance imaging has been evolving and is becoming instrumental in diagnosis and investigation of tissue functions in various organs including brain, cartilage, and liver. Even though brain related pathology and/or investigation remains as the main application, diffusion weighted magnetic resonance imaging (DWI) is becoming a standard in oncology and in several other applications. This review article provides a brief introduction of diffusion weighted magnetic resonance imaging, challenges involved and recent advancements.
Magnetic Resonance Imaging of Human Tissue-Engineered Adipose Substitutes.
Proulx, Maryse; Aubin, Kim; Lagueux, Jean; Audet, Pierre; Auger, Michčle; Fortin, Marc-André; Fradette, Julie
Adipose tissue (AT) substitutes are being developed to answer the strong demand in reconstructive surgery. To facilitate the validation of their functional performance in vivo, and to avoid resorting to excessive number of animals, it is crucial at this stage to develop biomedical imaging methodologies, enabling the follow-up of reconstructed AT substitutes. Until now, biomedical imaging of AT substitutes has scarcely been reported in the literature. Therefore, the optimal parameters enabling good resolution, appropriate contrast, and graft delineation, as well as blood perfusion validation, must be studied and reported. In this study, human adipose substitutes produced from adipose-derived stem/stromal cells using the self-assembly approach of tissue engineering were implanted into athymic mice. The fate of the reconstructed AT substitutes implanted in vivo was successfully followed by magnetic resonance imaging (MRI), which is the imaging modality of choice for visualizing soft ATs. T1-weighted images allowed clear delineation of the grafts, followed by volume integration. The magnetic resonance (MR) signal of reconstructed AT was studied in vitro by proton nuclear magnetic resonance ((1)H-NMR). This confirmed the presence of a strong triglyceride peak of short longitudinal proton relaxation time (T1) values (200±53?ms) in reconstructed AT substitutes (total T1=813±76?ms), which establishes a clear signal difference between adjacent muscle, connective tissue, and native fat (total T1 ?300?ms). Graft volume retention was followed up to 6 weeks after implantation, revealing a gradual resorption rate averaging at 44% of initial substitute's volume. In addition, vascular perfusion measured by dynamic contrast-enhanced-MRI confirmed the graft's vascularization postimplantation (14 and 21 days after grafting). Histological analysis of the grafted tissues revealed the persistence of numerous adipocytes without evidence of cysts or tissue necrosis. This study describes the in vivo grafting of human adipose substitutes devoid of exogenous matrix components, and for the first time, the optimal parameters necessary to achieve efficient MRI visualization of grafted tissue-engineered adipose substitutes. PMID:25549069
Diagnostic Accuracy of Clinical Assessment, Magnetic Resonance Imaging, Magnetic Resonance Arthrography, and Intra-Articular Injection in Hip Arthroscopy Patients
J. W. Thomas Byrd; Kay S. Jones
Background: Hip arthroscopy has defined elusive causes of hip pain.Hypothesis\\/Purpose: It is postulated that the reliability of various investigative methods is inconsistent. The purpose of this study is to evaluate the diagnostic accuracy of these methods.Study Design: Retrospective review of prospectively collected data.Methods: Five parameters were assessed in 40 patients: clinical assessment, high-resolution magnetic resonance imaging, magnetic resonance imaging with
The physics of functional magnetic resonance imaging (fMRI)
NASA Astrophysics Data System (ADS)
Buxton, Richard B.
Functional magnetic resonance imaging (fMRI) is a methodology for detecting dynamic patterns of activity in the working human brain. Although the initial discoveries that led to fMRI are only about 20 years old, this new field has revolutionized the study of brain function. The ability to detect changes in brain activity has a biophysical basis in the magnetic properties of deoxyhemoglobin, and a physiological basis in the way blood flow increases more than oxygen metabolism when local neural activity increases. These effects translate to a subtle increase in the local magnetic resonance signal, the blood oxygenation level dependent (BOLD) effect, when neural activity increases. With current techniques, this pattern of activation can be measured with resolution approaching 1 mm3 spatially and 1 s temporally. This review focuses on the physical basis of the BOLD effect, the imaging methods used to measure it, the possible origins of the physiological effects that produce a mismatch of blood flow and oxygen metabolism during neural activation, and the mathematical models that have been developed to understand the measured signals. An overarching theme is the growing field of quantitative fMRI, in which other MRI methods are combined with BOLD methods and analyzed within a theoretical modeling framework to derive quantitative estimates of oxygen metabolism and other physiological variables. That goal is the current challenge for fMRI: to move fMRI from a mapping tool to a quantitative probe of brain physiology.
Radiation-induced optic neuropathy: A magnetic resonance imaging study
Guy, J.; Mancuso, A.; Beck, R.; Moster, M.L.; Sedwick, L.A.; Quisling, R.G.; Rhoton, A.L. Jr.; Protzko, E.E.; Schiffman, J. (Univ. of Florida, Gainesville (USA))
Optic neuropathy induced by radiation is an infrequent cause of delayed visual loss that may at times be difficult to differentiate from compression of the visual pathways by recurrent neoplasm. The authors describe six patients with this disorder who experienced loss of vision 6 to 36 months after neurological surgery and radiation therapy. Of the six patients in the series, two had a pituitary adenoma and one each had a metastatic melanoma, multiple myeloma, craniopharyngioma, and lymphoepithelioma. Visual acuity in the affected eyes ranged from 20/25 to no light perception. Magnetic resonance (MR) imaging showed sellar and parasellar recurrence of both pituitary adenomas, but the intrinsic lesions of the optic nerves and optic chiasm induced by radiation were enhanced after gadolinium-diethylenetriaminepenta-acetic acid (DTPA) administration and were clearly distinguishable from the suprasellar compression of tumor. Repeated MR imaging showed spontaneous resolution of gadolinium-DTPA enhancement of the optic nerve in a patient who was initially suspected of harboring recurrence of a metastatic malignant melanoma as the cause of visual loss. The authors found the presumptive diagnosis of radiation-induced optic neuropathy facilitated by MR imaging with gadolinium-DTPA. This neuro-imaging procedure may help avert exploratory surgery in some patients with recurrent neoplasm in whom the etiology of visual loss is uncertain.
Additional processing for phase unwrapping of magnetic resonance thermometry imaging
NASA Astrophysics Data System (ADS)
Suprijanto, S.; Vos, Frans M.; Vogel, M. W.; Vossepoel, Albert M.; Vrooman, Henri A.
Magnetic Resonance Thermometry imaging is a non-invasive method for temperature monitoring in hyperthermia treatment. The temperature can be determined from the phase shift in a gradient-echo sequence. Due to large temperature variations, the phase shift may exceed the (-? ,?) radians interval. The phase value beyond this interval will be wrapped. Unfortunately, the temperature is only proportional to the absolute phase change. Therefore, phase unwrapping (PU) is required to recover the absolute phase from the wrapped representation. While the phase may contain spurious discontinuities, the algorithm must distinguish them from true phase discontinuities. We propose additional processing to support PU in order to improve the algorithm for recovery of the best estimation of absolute phase. The Minimum Weight Discontinuity (MWD) algorithm was used for PU. The steps to be taken on additional processing consist of applying a Gaussian filter to the raw complex MRI images, deriving the weights of a quality map, and segmenting unreliable regions using the magnitude image. The raw wrapped phase images, acquired from a phantom and from a porcine liver (acquired under laser irradiation), were used to test the effect of additional processing. The effect was compared with the conventional approach (i.e. mere unwrapping with the MWD algorithm).
Multiparametric Magnetic Resonance Imaging Characteristics of Prostate Tuberculosis
Cheng, Yue; Huang, Lixiang; Zhang, Xiaodong; Ji, Qian
Objective To describe the multiparametric magnetic resonance imaging (MRI) appearance of prostate tuberculosis. Materials and Methods Six patients with prostate tuberculosis were analyzed retrospectively. The mean age of the patients was 60.5 years (range, 48-67 years). The mean prostate specific antigen concentration was 6.62 ng/mL (range, 0.54-14.57 ng/mL). All patients underwent a multiparametric MRI examination. Results The histopathological results were obtained from biopsies in four men and from transurethral resection of the prostate in two men after the MRI examination. Nodular (33%, 2/6 patients) and diffuse lesions (67%, 4/6 patients) were seen on MRI. The nodular lesions were featured by extremely low signal intensity (similar to that of muscle) on T2-weighted imaging (T2WI). The T2WI signal intensity of the diffuse lesions was low but higher than that of muscle, which showed high signal intensity on diffusion weighted imaging and low signal intensity on an apparent diffusion coefficient map. MR spectroscopic imaging of this type showed a normal-like spectrum. Abscesses were found in one patient with the nodular type and in one with the diffuse type. Conclusion The appearance of prostate tuberculosis on MRI can be separated into multiple nodular and diffuse types. Multiparametric MRI may offer useful information for diagnosing prostate tuberculosis. PMID:26175584
Active resonant subwavelength grating for scannerless range imaging sensors.
Kemme, Shanalyn A.; Nellums, Robert O.; Boye, Robert R.; Peters, David William
In this late-start LDRD, we will present a design for a wavelength-agile, high-speed modulator that enables a long-term vision for the THz Scannerless Range Imaging (SRI) sensor. It takes the place of the currently-utilized SRI micro-channel plate which is limited to photocathode sensitive wavelengths (primarily in the visible and near-IR regimes). Two of Sandia's successful technologies--subwavelength diffractive optics and THz sources and detectors--are poised to extend the capabilities of the SRI sensor. The goal is to drastically broaden the SRI's sensing waveband--all the way to the THz regime--so the sensor can see through image-obscuring, scattering environments like smoke and dust. Surface properties, such as reflectivity, emissivity, and scattering roughness, vary greatly with the illuminating wavelength. Thus, objects that are difficult to image at the SRI sensor's present near-IR wavelengths may be imaged more easily at the considerably longer THz wavelengths (0.1 to 1mm). The proposed component is an active Resonant Subwavelength Grating (RSG). Sandia invested considerable effort on a passive RSG two years ago, which resulted in a highly-efficient (reflectivity greater than gold), wavelength-specific reflector. For this late-start LDRD proposal, we will transform the passive RSG design into an active laser-line reflector.
Potential of magnetic resonance for imaging the fetal heart.
Wielandner, Alice; Mlczoch, Elisabeth; Prayer, Daniela; Berger-Kulemann, Vanessa
Significant congenital heart disease (sCHD) affects 3.6 per 1000 births, and is often associated with extracardiac and chromosomal anomalies. Although early mortality has been substantially reduced and the rate of long-term survival has improved, sCHD is, after preterm birth, the second most frequent cause of neonatal infant death. The prenatal detection of cardiac and vascular abnormalities enables optimal parental counselling and perinatal management. Echocardiography (ECG) is the first-line examination and gold standard by which cardiac malformations are defined. However, adequate examination by an experienced healthcare provider with modern technical imaging equipment is required. In addition, maternal factors and the gestational age may lower the image quality. Fetal magnetic resonance imaging (MRI) has been implemented over the last several years and is already used in the clinical routine as a second-line approach to assess fetal abnormalities. MRI of the fetal heart is still not routinely performed. Nevertheless, fetal cardiac MRI has the potential to complement ultrasound in detecting cardiovascular malformations and extracardiac lesions. The present work reviews the potential of MRI to delineate the anatomy and pathologies of the fetal heart. This work also deals with the limitations and continuing developments designed to overcome the current problems in cardiac imaging, including fast fetal heart rates, the lack of ECG-gating, and the presence of fetal movements. PMID:23742821
Magnetic resonance imaging of clays: swelling, sedimentation, dissolution
NASA Astrophysics Data System (ADS)
Dvinskikh, Sergey; Furo, Istvan
While most magnetic resonance imaging (MRI) applications concern medical research, there is a rapidly increasing number of MRI studies in the field of environmental science and technology. In this presentation, MRI will be introduced from the latter perspective. While many processes in these areas are similar to those addressed in medical applications of MRI, parameters and experimental implementations are often quite different and, in many respects, far more demanding. This hinders direct transfer of existing methods developed for biomedical research, especially when facing the challenging task of obtaining spatially resolved quantitative information. In MRI investigation of soils, clays, and rocks, mainly water signal is detected, similarly to MRI of biological and medical samples. However, a strong variation of water mobility and a wide spread of water spin relaxation properties in these materials make it difficult to use standard MRI approaches. Other significant limitations can be identified as following: T2 relaxation and probe dead time effects; molecular diffusion artifacts; varying dielectric losses and induced currents in conductive samples; limited dynamic range; blurring artifacts accompanying drive for increasing sensitivity and/or imaging speed. Despite these limitations, by combining MRI techniques developed for solid and liquid states and using independent information on relaxation properties of water, interacting with the material of interest, true images of distributions of both water, material and molecular properties in a wide range of concentrations can be obtained. Examples of MRI application will be given in the areas of soil and mineral research where understanding water transport and erosion processes is one of the key challenges. Efforts in developing and adapting MRI approaches to study these kinds of systems will be outlined as well. Extensive studies of clay/water interaction have been carried out in order to provide a quantitative measure of clay distribution in extended samples during different physical processes such as swelling, dissolution, and sedimentation on the time scale from minutes to years [1-3]. To characterize the state of colloids that form after/during clay swelling the water self-diffusion coefficient was measured on a spatially resolved manner. Both natural clays and purified and ion-exchanged montmorillonite clays were investigated. The primary variables were clay composition and water ionic strength. These results have a significant impact for engineering barriers for storage of spent nuclear fuel where clay erosion by low salinity water must be addressed. Presented methods were developed under the motivation of using bentonite clays as a buffer medium to build in-ground barriers for the encapsulation of radioactive waste. Nevertheless, the same approaches can be found suitable in other applications in soil and environmental science to study other types of materials as they swell, dissolve, erode, or sediment. Acknowledgements: This work has been supported by the Swedish Nuclear Fuel and Waste Management Co (SKB) and the Swedish Research Council VR. [1] N. Nestle, T. Baumann, R. Niessner, Magnetic resonance imaging in environmental science. Environ. Sci. Techn. 36 154A (2002). [2] S. V. Dvinskikh, K. Szutkowski, I. Furó. MRI profiles over a very wide concentration ranges: application to swelling of a bentonite clay. J. Magn. Reson. 198 146 (2009). [3] S. V. Dvinskikh, I. Furó. Magnetic resonance imaging and nuclear magnetic resonance investigations of bentonite systems. Technical Report, TR-09-27, SKB (2009), www.skb.se.
A comparison study of microarrays by fluorescence imaging and surface plasmon resonance imaging
NASA Astrophysics Data System (ADS)
Liu, Zhiyi; Zhang, Chongwen; Yang, Bin; Chong, Xinyuan; Liu, Le; Ma, Suihua; He, Yonghong; Zhang, Guang; Guo, Jihua
In the past decade the analysis of microarrays which are rich in biology information has generated considerable interest. One of the conventional techniques in this area is to detect the biomolecules labeled with fluorescence agents. In recent years, the surface plasmon resonance (SPR) imaging plays an important role in the detection of microarrays. The intensity of fluorescence signal acquired from fluorescence imaging is proportional to the amount of biomolecules, while the refractive index obtained from SPR imaging is relative to the concentration of sample, a comparison study of microarrays by these two detection techniques may be of great value. We develop a quasi-confocal parallel scan fluorescence imaging system which has only one moving part and can produce wide-field confocal images. The bacterial 16s rDNA universal primer labeled with CY5 fluorescence agents are used as probes and prepared as a microarray. The DNA-array is detected by both the quasi-confocal parallel scan fluorescence imaging system and the parallel scan spectral SPR imaging system. The results from these two imaging systems were compared and discussed in resolving power, homogeneity, etc. The refractive index information from the SPR imaging system and the fluorescence intensity information from the fluorescence imaging system are linked by bio-array concentration. The measured results can be inter-referred for bio-array studies.
[Three-dimensional mini-type permanent magnetic resonance imaging device and medical imaging of mice].
Hou, Shulian; Xie, Huantong; Hou, Xiaowen; Zhao, Qiang; Wang, Guangxin; Chen, Wei; Zhang, Lianyuan; Men, Xiuli; Kong, Xiaoyan; Gong, Fengling
We developed a three-dimensional mini-type permanent magnetic resonance imaging (MRI) device in our lab. The purposes of this study were (1) for further development of MRI technologies, (2) for support of broadening practices of animal test modeling in medical research, and (3) for training more specialists from colleges or universities in the field of MRI. This paper describes the research and development at our lab(s), especially stressing on the design of the main magnet, the gradient coil and the radio frequency coil. In addition, the specific methodologies used in our lab(s) and the related data are emphasized. The 3D MRI technologies have met the needs of using small animals, super thin sections of live animal body and high imaging resolutions. MRI images of mice head and abdominal have been obtained successfully by using the imager that we developed. The imaging results and analyses have also been discussed. PMID:23488133
Methodological challenges and solutions in auditory functional magnetic resonance imaging
Peelle, Jonathan E.
Functional magnetic resonance imaging (fMRI) studies involve substantial acoustic noise. This review covers the difficulties posed by such noise for auditory neuroscience, as well as a number of possible solutions that have emerged. Acoustic noise can affect the processing of auditory stimuli by making them inaudible or unintelligible, and can result in reduced sensitivity to auditory activation in auditory cortex. Equally importantly, acoustic noise may also lead to increased listening effort, meaning that even when auditory stimuli are perceived, neural processing may differ from when the same stimuli are presented in quiet. These and other challenges have motivated a number of approaches for collecting auditory fMRI data. Although using a continuous echoplanar imaging (EPI) sequence provides high quality imaging data, these data may also be contaminated by background acoustic noise. Traditional sparse imaging has the advantage of avoiding acoustic noise during stimulus presentation, but at a cost of reduced temporal resolution. Recently, three classes of techniques have been developed to circumvent these limitations. The first is Interleaved Silent Steady State (ISSS) imaging, a variation of sparse imaging that involves collecting multiple volumes following a silent period while maintaining steady-state longitudinal magnetization. The second involves active noise control to limit the impact of acoustic scanner noise. Finally, novel MRI sequences that reduce the amount of acoustic noise produced during fMRI make the use of continuous scanning a more practical option. Together these advances provide unprecedented opportunities for researchers to collect high-quality data of hemodynamic responses to auditory stimuli using fMRI. PMID:25191218
Dedicated Magnetic Resonance Imaging in the Radiotherapy Clinic
Karlsson, Mikael [Radiation Physics Section, Department of Radiation Sciences, Umea University, 90187 Umea (Sweden)], E-mail: email@example.com; Karlsson, Magnus G. [Department of Radiation Physics, Umea University Hospital, 90185 Umea (Sweden); Nyholm, Tufve [Radiation Physics Section, Department of Radiation Sciences, Umea University, 90187 Umea (Sweden); Department of Radiation Physics, Umea University Hospital, 90185 Umea (Sweden); Amies, Christopher [Siemens Medical Systems, Oncology Care Systems Group, Concord, California (United States); Zackrisson, Bjoern [Section of Oncology, Department of Radiation Sciences, Umea University, 90187 Umea (Sweden)
Purpose: To introduce a novel technology arrangement in an integrated environment and outline the logistics model needed to incorporate dedicated magnetic resonance (MR) imaging in the radiotherapy workflow. An initial attempt was made to analyze the value and feasibility of MR-only imaging compared to computed tomography (CT) imaging, testing the assumption that MR is a better choice for target and healthy tissue delineation in radiotherapy. Methods and Materials: A 1.5-T MR unit with a 70-cm-bore size was installed close to a linear accelerator, and a special trolley was developed for transporting patients who were fixated in advance between the MR unit and the accelerator. New MR-based workflow procedures were developed and evaluated. Results: MR-only treatment planning has been facilitated, thus avoiding all registration errors between CT and MR scans, but several new aspects of MR imaging must be considered. Electron density information must be obtained by other methods. Generation of digitally reconstructed radiographs (DRR) for x-ray setup verification is not straight forward, and reliable corrections of geometrical distortions must be applied. The feasibility of MR imaging virtual simulation has been demonstrated, but a key challenge to overcome is correct determination of the skeleton, which is often needed for the traditional approach of beam modeling. The trolley solution allows for a highly precise setup for soft tissue tumors without the invasive handling of radiopaque markers. Conclusions: The new logistics model with an integrated MR unit is efficient and will allow for improved tumor definition and geometrical precision without a significant loss of dosimetric accuracy. The most significant development needed is improved bone imaging.
Grid Computing Application for Brain Magnetic Resonance Image Processing
NASA Astrophysics Data System (ADS)
Valdivia, F.; Crépeault, B.; Duchesne, S.
This work emphasizes the use of grid computing and web technology for automatic post-processing of brain magnetic resonance images (MRI) in the context of neuropsychiatric (Alzheimer's disease) research. Post-acquisition image processing is achieved through the interconnection of several individual processes into pipelines. Each process has input and output data ports, options and execution parameters, and performs single tasks such as: a) extracting individual image attributes (e.g. dimensions, orientation, center of mass), b) performing image transformations (e.g. scaling, rotation, skewing, intensity standardization, linear and non-linear registration), c) performing image statistical analyses, and d) producing the necessary quality control images and/or files for user review. The pipelines are built to perform specific sequences of tasks on the alphanumeric data and MRIs contained in our database. The web application is coded in PHP and allows the creation of scripts to create, store and execute pipelines and their instances either on our local cluster or on high-performance computing platforms. To run an instance on an external cluster, the web application opens a communication tunnel through which it copies the necessary files, submits the execution commands and collects the results. We present result on system tests for the processing of a set of 821 brain MRIs from the Alzheimer's Disease Neuroimaging Initiative study via a nonlinear registration pipeline composed of 10 processes. Our results show successful execution on both local and external clusters, and a 4-fold increase in performance if using the external cluster. However, the latter's performance does not scale linearly as queue waiting times and execution overhead increase with the number of tasks to be executed.
Towards simultaneous single emission microscopy and magnetic resonance imaging
NASA Astrophysics Data System (ADS)
Cai, Liang
In recent years, the combined nuclear imaging and magnetic resonance imaging (MRI) has drawn extensive research effort. They can provide simultaneously acquired anatomical and functional information inside the human/small animal body in vivo. In this dissertation, the development of an ultrahigh resolution MR-compatible SPECT (Single Photon Emission Computed Tomography) system that can be operated inside a pre-existing clinical MR scanner for simultaneous dual-modality imaging of small animals will be discussed. This system is constructed with 40 small pixel CdTe detector modules assembled in a fully stationary ring SPECT geometry. Series of experiments have demonstrated that this system is capable of providing an imaging resolution of <500?m, when operated inside MR scanners. The ultrahigh resolution MR-compatible SPECT system is built around a small pixel CdTe detector module that we recently developed. Each module consists of CdTe detectors having an overall size of 2.2 cm x 1.1 cm, divided into 64 x 32 pixels of 350 mum in size. A novel hybrid pixel-waveform (HPWF) readout system is also designed to alleviate several challenges for using small-pixel CdTe detectors in ultrahigh-resolution SPECT imaging applications. The HPWF system utilizes a modified version of a 2048-channel 2-D CMOS ASIC to readout the anode pixel, and a digitizing circuitry to sample the signal waveform induced on the cathode. The cathode waveform acquired with the HPWF circuitry offers excellent spatial resolution, energy resolution and depth of interaction (DOI) information, even with the presence of excessive charge-sharing/charge-loss between the small anode pixels. The HPWF CdTe detector is designed and constructed with a minimum amount of ferromagnetic materials, to ensure the MR-compatibility. To achieve sub-500?m imaging resolution, two special designed SPECT apertures have been constructed with different pinhole sizes of 300?m and 500?m respectively. It has 40 pinhole inserts that are made of cast platinum (90%)-iridium (10%) alloy, which provides the maximum stopping power and are compatible with MR scanners. The SPECT system is installed on a non-metal gantry constructed with 3-D printing using nylon powder material. This compact system can work as a "low-cost" desktop ultrahigh resolution SPECT system. It can also be directly operated inside an MR scanner. Accurate system geometrical calibration and corresponding image reconstruction methods for the MRC-SPECT system is developed. In order to account for the magnetic field induced distortion in the SPECT image, a comprehensive charge collection model inside strong magnetic field is adopted to produce high resolution SPECT image inside MR scanner.
4D MR imaging of respiratory organ motion using an intersection profile method
NASA Astrophysics Data System (ADS)
Masuda, Yoshitada; Haneishi, Hideaki
We propose an intersection profile method for reconstructing a 4D-MRI of respiratory organ motion from time sequential images of 2D-MRI. In the proposed method, first, time sequential MR images in many coronal planes set to widely cover the lung region are acquired as the data slices. Second, the time sequential MR images in a proper sagittal plane are acquired as the navigator slice. 4D-MRI is reconstructed by extracting and combining a proper respiratory pattern from each data slice which is most similar to an adequately selected respiratory pattern in the navigator slice on the intersection between the navigation slice and each data slice. Successful visualization of the respiratory organ motion is demonstrated and the validation of reconstruction is also presented. Such a 4D-MRI has a great potential for many medical applications. In this paper, we further propose to construct a diaphragmatic function map from a 4D-MRI reconstructed by the intersection profile method to evaluate diaphragmatic motion quantitatively. Experimental results using three healthy volunteers and three patients are shown.
Monitoring water accumulation in a glacier using magnetic resonance imaging
NASA Astrophysics Data System (ADS)
Legchenko, A.; Vincent, C.; Baltassat, J. M.; Girard, J. F.; Thibert, E.; Gagliardini, O.; Descloitres, M.; Gilbert, A.; Garambois, S.; Chevalier, A.; Guyard, H.
Tęte Rousse is a small polythermal glacier located in the Mont Blanc area (French Alps) at an altitude of 3100 to 3300 m. In 1892, an outburst flood from this glacier released about 200 000 m3 of water mixed with ice, causing much damage. A new accumulation of melt water in the glacier was not excluded. The uncertainty related to such glacier conditions initiated an extensive geophysical study for evaluating the hazard. Using three-dimensional surface nuclear magnetic resonance imaging (3-D-SNMR), we showed that the temperate part of the Tęte Rousse glacier contains two separate water-filled caverns (central and upper caverns). In 2009, the central cavern contained about 55 000 m3 of water. Since 2010, the cavern is drained every year. We monitored the changes caused by this pumping in the water distribution within the glacier body. Twice a year, we carried out magnetic resonance imaging of the entire glacier and estimated the volume of water accumulated in the central cavern. Our results show changes in cavern geometry and recharge rate: in two years, the central cavern lost about 73% of its initial volume, but 65% was lost in one year after the first pumping. We also observed that, after being drained, the cavern was recharged at an average rate of 20 to 25 m3 d-1 during the winter months and 120 to 180 m3 d-1 in summer. These observations illustrate how ice, water and air may refill englacial volume being emptied by artificial draining. Comparison of the 3-D-SNMR results with those obtained by drilling and pumping showed a very good correspondence, confirming the high reliability of 3-D-SNMR imaging.
Advanced theory of driven birdcage resonator with losses for biomedical magnetic resonance imaging and spectroscopy.
Novikov, Alexander
A complete time-dependent physics theory of symmetric unperturbed driven hybrid birdcage resonator was developed for general application. In particular, the theory can be applied for radiofrequency (RF) coil engineering, computer simulations of coil-sample interaction, etc. Explicit time dependence is evaluated for different forms of driving voltage. The major steps of the solution development are shown and appropriate explanations are given. Green's functions and spectral density formula were developed for any form of periodic driving voltage. The concept of distributed power losses based on transmission line theory is developed for evaluation of local losses of a coil. Three major types of power losses are estimated as equivalent series resistances in the circuit of the birdcage resonator. Values of generated resistances in legs and end-rings are estimated. An application of the theory is shown for many practical cases. Experimental curve of B(1) field polarization dependence is measured for eight-sections birdcage coil. It was shown that the steady-state driven resonance frequencies do not depend on damping factor unlike the free oscillation (transient) frequencies. An equivalent active resistance is generated due to interaction of RF electromagnetic field with a sample. Resistance of the conductor (enhanced by skin effect), Eddy currents and dielectric losses are the major types of losses which contribute to the values of generated resistances. A biomedical sample for magnetic resonance imaging and spectroscopy is the source of the both Eddy current and dielectric losses of a coil. As demonstrated by the theory, Eddy current loss is the major effect of coil shielding. PMID:20869184
A prototype manipulator for magnetic resonance-guided interventions inside standard cylindrical magnetic resonance imaging scanners.
Tsekos, Nikolaos V; Ozcan, Alpay; Christoforou, Eftychios
The aim of this work is to develop a remotely controlled manipulator to perform minimally invasive diagnostic and therapeutic interventions in the abdominal and thoracic cavities, with real-time magnetic resonance imaging (MRI) guidance inside clinical cylindrical MR scanners. The manipulator is composed of a three degree of freedom Cartesian motion system, which resides outside the gantry of the scanner, and serves as the holder and global positioner of a three degree of freedom arm which extends inside the gantry of the scanner At its distal end, the arm's end-effector can carry an interventional tool such as a biopsy needle, which can be advanced to a desired depth by means of a seventh degree of freedom. These seven degrees of freedom, provided by the entire assembly, offer extended manipulability to the device and a wide envelope of operation to the user, who can select a trajectory suitable for the procedure. The device is constructed of nonmagnetic and nonconductive fiberglass, and carbon fiber composite materials, to minimize artifacts and distortion on the MR images as well as eliminate effects on its operation from the high magnetic field and the fast switching magnetic field gradients used in MR imaging. A user interface was developed for man-in-the-loop control of the device using real-time MR images. The user interface fuses all sensor signals (MR and manipulator information) in a visualization, planning, and control command environment. Path planning is performed with graphical tools for setting the trajectory of insertion of the interventional tool using multislice and/or three dimensional MR images which are refreshed in real time. The device control is performed with an embedded computer which runs real-time control software. The manipulator compatibility with the MR environment and image-guided operation was tested on a 1.5 T MR scanner. PMID:16438235
Magnetic resonance velocimetry: applications of magnetic resonance imaging in the measurement of fluid motion
NASA Astrophysics Data System (ADS)
Elkins, Christopher J.; Alley, Marcus T.
Magnetic resonance velocimetry (MRV) is a non-invasive technique capable of measuring the three-component mean velocity field in complex three-dimensional geometries with either steady or periodic boundary conditions. The technique is based on the phenomenon of nuclear magnetic resonance (NMR) and works in conventional magnetic resonance imaging (MRI) magnets used for clinical imaging. Velocities can be measured along single lines, in planes, or in full 3D volumes with sub-millimeter resolution. No optical access or flow markers are required so measurements can be obtained in clear or opaque MR compatible flow models and fluids. Because of its versatility and the widespread availability of MRI scanners, MRV is seeing increasing application in both biological and engineering flows. MRV measurements typically image the hydrogen protons in liquid flows due to the relatively high intrinsic signal-to-noise ratio (SNR). Nonetheless, lower SNR applications such as fluorine gas flows are beginning to appear in the literature. MRV can be used in laminar and turbulent flows, single and multiphase flows, and even non-isothermal flows. In addition to measuring mean velocity, MRI techniques can measure turbulent velocities, diffusion coefficients and tensors, and temperature. This review surveys recent developments in MRI measurement techniques primarily in turbulent liquid and gas flows. A general description of MRV provides background for a discussion of its accuracy and limitations. Techniques for decreasing scan time such as parallel imaging and partial k-space sampling are discussed. MRV applications are reviewed in the areas of physiology, biology, and engineering. Included are measurements of arterial blood flow and gas flow in human lungs. Featured engineering applications include the scanning of turbulent flows in complex geometries for CFD validation, the rapid iterative design of complex internal flow passages, velocity and phase composition measurements in multiphase flows, and the scanning of flows through porous media. Temperature measurements using MR thermometry are discussed. Finally, post-processing methods are covered to demonstrate the utility of MRV data for calculating relative pressure fields and wall shear stresses.
Bacteria tracking by in vivo magnetic resonance imaging
Background Different non-invasive real-time imaging techniques have been developed over the last decades to study bacterial pathogenic mechanisms in mouse models by following infections over a time course. In vivo investigations of bacterial infections previously relied mostly on bioluminescence imaging (BLI), which is able to localize metabolically active bacteria, but provides no data on the status of the involved organs in the infected host organism. In this study we established an in vivo imaging platform by magnetic resonance imaging (MRI) for tracking bacteria in mouse models of infection to study infection biology of clinically relevant bacteria. Results We have developed a method to label Gram-positive and Gram-negative bacteria with iron oxide nano particles and detected and pursued these with MRI. The key step for successful labeling was to manipulate the bacterial surface charge by producing electro-competent cells enabling charge interactions between the iron particles and the cell wall. Different particle sizes and coatings were tested for their ability to attach to the cell wall and possible labeling mechanisms were elaborated by comparing Gram-positive and -negative bacterial characteristics. With 5-nm citrate-coated particles an iron load of 0.015 ± 0.002 pg Fe/bacterial cell was achieved for Staphylococcus aureus. In both a subcutaneous and a systemic infection model induced by iron-labeled S. aureus bacteria, high resolution MR images allowed for bacterial tracking and provided information on the morphology of organs and the inflammatory response. Conclusion Labeled with iron oxide particles, in vivo detection of small S. aureus colonies in infection models is feasible by MRI and provides a versatile tool to follow bacterial infections in vivo. The established cell labeling strategy can easily be transferred to other bacterial species and thus provides a conceptual advance in the field of molecular MRI. PMID:23714179
Simulation and experimental validation of resonant electric markers used for medical device tracking in magnetic resonance imaging
Johannes Krug; Karl Will; Georg Rose
Magnetic resonance imaging (MRI), which was traditionally used for patient diagnosis, has gained in importance in minimally invasive interventions in the recent past. Hence, there is an increasing demand for medical devices compatible with the MR environment. One of the challenges is to visualize the medical devices, e.g. catheters, within the MR image. Several methods exist to cope with this
Nanoparticle Pharmacokinetic Profiling in vivo using Magnetic Resonance Imaging
Neubauer, Anne M.; Sim, Hoon; Winter, Patrick M.; Caruthers, Shelton D.; Williams, Todd A.; Robertson, J. David; Sept, David; Lanza, Gregory M.; Wickline, Samuel A.
Contrast agents targeted to molecular markers of disease are currently being developed with the goal of identifying disease early and evaluating treatment effectiveness using non-invasive imaging modalities such as MRI. Pharmacokinetic profiling of the binding of targeted contrast agents, while theoretically possible with MRI, has thus far only been demonstrated with more sensitive imaging techniques. Paramagnetic liquid perfluorocarbon nanoparticles were formulated to target ?v?3-integrins associated with early atherosclerosis in cholesterol-fed rabbits in order to produce a measurable signal increase on magnetic resonance images after binding. In this work, we combine quantitative information of the in vivo binding of this agent over time obtained via MRI with blood sampling to derive pharmacokinetic parameters using simultaneous and individual fitting of the data to a three compartment model. A doubling of tissue exposure (or area under the curve) is obtained with targeted as compared to control nanoparticles, and key parameter differences are discovered that may aid in development of models for targeted drug delivery. PMID:19025903
Magnetic resonance imaging of inflammatory arthropathies of peripheral joints.
Forney, Michael C; Winalski, Carl S; Schils, Jean P
As the treatment of inflammatory arthropathies has advanced with new therapies that can slow or even halt the development of disabling disease, early and accurate diagnosis has become imperative. Magnetic resonance (MR) imaging has proved to be very sensitive in the detection of erosions, but more importantly, it can demonstrate pre-erosive changes. Detection of synovitis and edema-like bone marrow lesions for initial diagnosis and as an indicator of disease progression can provide crucial information leading to therapeutic interventions before permanent joint damage occurs. Understanding the characteristic intra-articular and extra-articular MR imaging findings of the inflammatory arthritides allows the radiologist to provide appropriate consultations in the care of these patients. The MR appearances of both intra-articular and extra-articular findings of inflammatory arthritis are presented. Despite the advances in imaging, however, many of the MR findings remain nonspecific, and radiologists must avoid overdiagnosis by synthesizing all of the clinical information available into their interpretations. PMID:22648080
Confocal UV and resonance Raman microscopic imaging of pharmaceutical products.
Vogt, Frederick G; Strohmeier, Mark
Chemical imaging using confocal Raman microscopy is a useful analytical tool in drug development because of its ability to spatially image active ingredients and excipients in dosage forms and relate their distribution to product performance. While Raman spectra are highly specific for individual components of a formulation, most Raman microscopic mapping experiments require extensive experimental time. Laser wavelengths in the near-infrared range are used to suppress fluorescence but reduce sensitivity because of the inverse quadratic dependence of Raman scattering on laser wavelength. Compact, simple ultraviolet (UV) laser designs now allow for confocal UV Raman microscopy to be performed using a versatile instrument also capable of conventional Raman microscopy and epifluorescence imaging analyses. This study presents the results of UV Raman microscopy analyses using 266 nm laser irradiation of four pharmaceutical compositions of interest, including two types of tablets containing low doses of active ingredients (in the 0.2% w/w range), an amorphous dispersion containing 1% w/w of a small molecule drug, and an enteric coated layered peptide formulation. Resonance Raman enhancements are observed for four of the active ingredients studied in these formulations. The spectroscopic properties of the materials used in this study are also assessed by diffuse reflectance UV-visible spectroscopy, fluorescence spectroscopy, and conventional bulk Fourier transform Raman spectroscopy using 1064 nm laser irradiation. Confocal UV Raman microscopy was found to offer good sensitivity and allowed for rapid microscopic mapping of drugs and excipients at low concentrations in pharmaceutical formulations. PMID:24050305
Magnetic resonance imaging findings in horses with septic arthritis.
Easley, Jeremiah T; Brokken, Matthew T; Zubrod, Chad J; Morton, Alison J; Garrett, Katherine S; Holmes, Shannon P
Fourteen horses with septic arthritis underwent high-field (1.5 T) magnetic resonance imaging (MRI). Septic arthritis was diagnosed based on results from historical and clinical findings, synovial fluid analyses and culture, and radiographic, ultrasonographic, arthroscopic, and histopathologic findings. MR findings included diffuse hyperintensity within bone and extracapsular tissue on fat-suppressed images in 14/14 horses (100%), joint effusion, synovial proliferation, and capsular thickening in 13/14 horses (93%), bone sclerosis in 11/14 horses (79%), and evidence of cartilage and subchondral bone damage in 8/14 horses (57%). Intravenous gadolinium was administered to five of the 14 horses and fibrin deposition was noted in all horses. Other findings after gadolinium administration included synovial enhancement in 4/5 (80%) horses, and bone enhancement in 1/5 (20%) horses. The MR findings of septic arthritis in horses were consistent with those reported in people. MRI may allow earlier and more accurate diagnosis of septic arthritis in horses as compared with other imaging modalities, especially when the clinical diagnosis is challenging. It also provides additional information not afforded by other methods that may influence and enhance treatment. PMID:21447039
Proton magnetic resonance imaging with para-hydrogen induced polarization.
Dechent, Jan F; Buljubasich, Lisandro; Schreiber, Laura M; Spiess, Hans W; Münnemann, Kerstin
A major challenge in imaging is the detection of small amounts of molecules of interest. In the case of magnetic resonance imaging (MRI) their signals are typically concealed by the large background signal of e.g. the body. This problem can be tackled by hyperpolarization which increases the NMR signals up to several orders of magnitude. However, this strategy is limited for (1)H, the most widely used nucleus in NMR and MRI, because the enormous number of protons in the body screens the small amount of hyperpolarized ones. Here, we describe a method giving rise to high (1)H MRI contrast for hyperpolarized molecules against a large background signal. The contrast is based on the J-coupling induced rephasing of the NMR signal of molecules hyperpolarized via PHIP and it can easily be implemented in common pulse sequences. We discuss several scenarios with different or equal dephasing times T(2)* for the hyperpolarized and thermally polarized compounds and verify our approach by experiments. This method may open up unprecedented opportunities to use the standard MRI nucleus (1)H for e.g. metabolic imaging in the future. PMID:22240943
Towards Real-Time Intravascular Endoscopic Magnetic Resonance Imaging
Sathyanarayana, Shashank; Schär, Michael; Kraitchman, Dara L.; Bottomley, Paul A.
Fast, minimally invasive, high-resolution intravascular imaging is essential for identifying vascular pathological features and for developing novel diagnostic tools and treatments. Intravascular magnetic resonance imaging (MRI) with active internal probes offers high sensitivity to pathological features without ionizing radiation or the limited luminal views of conventional X-rays, but has been unable to provide a high-speed, high-resolution, endoscopic view. Herein, real-time MRI endoscopy is introduced for performing MRI from a viewpoint intrinsically locked to a miniature active, internal transmitter–receiver in a clinical 3.0-TMRI scanner. Real-time MRI endoscopy at up to 2 frames/s depicts vascular wall morphological features, atherosclerosis, and calcification at 80 to 300 ?m resolution during probe advancement through diseased human iliac artery specimens and atherosclerotic rabbit aortas in vivo. MRI endoscopy offers the potential for fast, minimally invasive, transluminal, high-resolution imaging of vascular disease on a common clinical platform suitable for evaluating and targeting atherosclerosis in both experimental and clinical settings. PMID:21071004
Imaging Atherosclerosis with Hybrid Positron Emission Tomography/Magnetic Resonance Imaging
Kjćr, Andreas
Noninvasive imaging of atherosclerosis could potentially move patient management towards individualized triage, treatment, and followup. The newly introduced combined positron emission tomography (PET) and magnetic resonance imaging (MRI) system could emerge as a key player in this context. Both PET and MRI have previously been used for imaging plaque morphology and function: however, the combination of the two methods may offer new synergistic opportunities. Here, we will give a short summary of current relevant clinical applications of PET and MRI in the setting of atherosclerosis. Additionally, our initial experiences with simultaneous PET/MRI for atherosclerosis imaging are presented. Finally, future potential vascular applications exploiting the unique combination of PET and MRI will be discussed. PMID:25695091
Penumbral imaging by using perfusion computed tomography and perfusion-weighted magnetic resonance imaging: current concepts.
Sasaki, Makoto; Kudo, Kohsuke; Christensen, Soren; Yamashita, Fumio; Goodwin, Jonathan; Higuchi, Satomi; Ogawa, Akira
Perfusion computed tomography and perfusion-weighted magnetic resonance imaging are used to evaluate the extent of the area with ischemic penumbra; however, different parameters, algorithms, and software packages show significant discrepancies in the size of perfusion abnormalities, which should be minimized. Recently, cross-validation studies were performed using digital phantoms and have elucidated the precision and reliability of various penumbral imaging techniques. These research initiatives can promote further multicenter trials on recanalization therapies by providing accurate inclusion/exclusion criteria for appropriate patient selection. PMID:23153549
Distribution of topical medication in the human vagina as imaged by magnetic resonance imaging
Kurt Barnhart; E. Scott Pretorius; Alan Stolpen; Daniel Malamud
Objective: To assess the use of magnetic resonance imaging (MRI) to determine the varying distribution of a vaginally placed gel over time and with different levels of patient activity.Design: Prospectives interventional trial.Setting: University medical center.Patient(s): One nulliparous volunteer with normal menstrual cycles and no gynecologic disease who underwent seven MRI scans of the pelvis.Intervention(s): Five mL of a commercially available
New magnetic resonance imaging and computed tomography techniques for imaging of acute stroke
Amie W. Hsia; David C. Tong
With continued advances in acute stroke therapy, the ability to accurately assess the physiologic status of ischemic brain\\u000a tissue and related vascular lesions has become increasingly important. In this review, evidence regarding the use of new magnetic\\u000a resonance imaging and computed tomography techniques to guide thrombolytic therapy, diagnose stroke subtype, and detect acute\\u000a hemorrhage are discussed in order to provide
Functional imaging as an indicator of diagnostic information in cardiac magnetic-resonance images
NASA Astrophysics Data System (ADS)
Klingler, Joseph W.; Andrews, Lee T.; Begeman, Michael S.; Zeiss, Jacob; Leighton, Richard F.
Magnetic Resonance (MR) images of the human heart provide three dimensional geometric information about the location of cardiac structures throughout the cardiac cycle. Analysis of this four dimensional data set allows detection of abnormal cardiac function related to the presence of coronary artery disease. To assist in this analysis, quantitative measurements of cardiac performance are made from the MR data including ejection fractions, regional wall motion and myocardial wall thickening. Analysis of cardiac performance provided by quantitative analysis of MR data can be aided by computer graphics presentation techniques. Two and three dimensional functional images are computed to indicate regions of abnormality based on the previous methods. The two dimensional images are created using color graphics overlays on the original MR image to represent performance. Polygon surface modeling techniques are used to represent data which is three dimensional, such as blood pool volumes. The surface of these images are color encoded by regional ejection fraction, wall motion or wall thickening. A functional image sequence is constructed at each phase of the cardiac cycle and displayed as a movie loop for review by the physician. Selection of a region on the functional image allows visual interpretation of the original MR images, graphical plots of cardiac function and tabular results. Color encoding is based on absolute measurements and comparison to standard normal templates of cardiac performance.
Mechanical effects of leg position on vertebral structures examined by magnetic resonance imaging
Yoshihiro Hirabayashi; Takashi Igarashi; Hideo Suzuki; Hirokazu Fukuda; Kazuhiko Saitoh; Norimasa Seo
Background and Objectives: Leg manipulation has been postulated to affect spinal curvature and position of the cauda equina within the dural sac. However, no evidence of such mechanical effects has been shown in living subjects. We used magnetic resonance imaging to evaluate the mechanical effects of leg position on these 2 parameters. Methods: Sagittal and axial magnetic resonance images of
We report a novel method to identify brain regions generically activated by periodic experimental design in functional magnetic resonance imaging data. This involves: 1) registering each of N individual functional magnetic resonance imaging datasets in a standard space; 2) computing the median standardised power of response to the experimental design; 3) testing median standardised power at each voxel against its
Angulo-spectral surface plasmon resonance imaging of nanofabricated grating surfaces
Boyer, Edmond
Angulo-spectral surface plasmon resonance imaging of nanofabricated grating surfaces Mohamed, 2010 We present a surface plasmon resonance imaging (SPRI) setup, based on the Kretschmann Optical Society of America OCIS codes: 240.6680, 220.4241. A surface plasmon wave (SPW) is a boundary
In vivo Magnetic Resonance Imaging of Tumor Protease Activity
Haris, Mohammad; Singh, Anup; Mohammed, Imran; Ittyerah, Ranjit; Nath, Kavindra; Nanga, Ravi Prakash Reddy; Debrosse, Catherine; Kogan, Feliks; Cai, Kejia; Poptani, Harish; Reddy, Damodar; Hariharan, Hari; Reddy, Ravinder
Increased expression of cathepsins has diagnostic as well as prognostic value in several types of cancer. Here, we demonstrate a novel magnetic resonance imaging (MRI) method, which uses poly-L-glutamate (PLG) as an MRI probe to map cathepsin expression in vivo, in a rat brain tumor model. This noninvasive, high-resolution and non-radioactive method exploits the differences in the CEST signals of PLG in the native form and cathepsin mediated cleaved form. The method was validated in phantoms with known physiological concentrations, in tumor cells and in an animal model of brain tumor along with immunohistochemical analysis. Potential applications in tumor diagnosis and evaluation of therapeutic response are outlined. PMID:25124082
Multimodality magnetic resonance imaging in hepatic encephalopathy: An update
Zhang, Xiao-Dong; Zhang, Long-Jiang; Wu, Sheng-Yong; Lu, Guang-Ming
Hepatic encephalopathy (HE) is a neuropsychiatric complication of cirrhosis or acute liver failure. Currently, HE is regarded as a continuous cognitive impairment ranging from the mildest stage, minimal HE to overt HE. Hyperammonaemia and neuroinflammation are two main underlying factors which contribute to the neurological alterations in HE. Both structural and functional impairments are found in the white mater and grey mater involved in HE. Although the investigations into HE pathophysiological mechanism are enormous, the exact pathophysiological causes underlying HE remain controversial. Multimodality magnetic resonance imaging (MRI) plays an important role in helping to understand the pathological process of HE. This paper reviews the up-to-date multimodality MRI methods and predominant findings in HE patients with a highlight of the increasingly important role of blood oxygen level dependent functional MRI. PMID:25170210
Recycling of 3He from lung magnetic resonance imaging.
Salhi, Z; Grossmann, T; Gueldner, M; Heil, W; Karpuk, S; Otten, E W; Rudersdorf, D; Surkau, R; Wolf, U
We have developed the means to recycle (3) He exhaled by patients after imaging the lungs using magnetic resonance of hyperpolarized (3) He. The exhaled gas is collected in a helium leak proof bag and further compressed into a steel bottle. The collected gas contains about 1-2% of (3) He, depending on the amount administered and the number of breaths collected to wash out the (3) He gas from the lungs. (3) He is separated from the exhaled air using zeolite molecular sieve adsorbent at 77 K followed by a cold head at 8 K. Residual gaseous impurities are finally absorbed by a commercial nonevaporative getter. The recycled (3) He gas features high purity, which is required for repolarization by metastability exchange optical pumping. At present, we achieve a collection efficiency of 80-84% for exhaled gas from healthy volunteers and cryogenic separation efficiency of 95%. PMID:22135249
Nonlinear split-ring metamaterial slabs for magnetic resonance imaging
NASA Astrophysics Data System (ADS)
Lopez, Marcos A.; Freire, Manuel J.; Algarin, Jose M.; Behr, Volker C.; Jakob, Peter M.; Marqués, Ricardo
This work analyzes the ability of split-ring metamaterial slabs with zero/high permeability to reject/confine the radiofrequency magnetic field in magnetic resonance imaging systems. Split-ring slabs are designed and fabricated to work in a 1.5 T system. Nonlinear elements consisting of pairs of crossed diodes are inserted in the split-rings, so that the slab permeability can be switched between a value close to unity when interacting with the strong field of the transmitting coil, and zero or high values when interacting with the weak field produced by protons in tissue. Experiments are shown where these slabs locally increase the signal-to-noise-ratio.
Grey matter abnormalities in trichotillomania: morphometric magnetic resonance imaging study
Chamberlain, Samuel R.; Menzies, Lara A.; Fineberg, Naomi A.; del Campo, Natalia; Suckling, John; Craig, Kevin; Müller, Ulrich; Robbins, Trevor W.; Bullmore, Edward T.; Sahakian, Barbara J.
Background Trichotillomania (repetitive hair-pulling) is an Axis I psychiatric disorder whose neurobiological basis is incompletely understood. Whole-brain trichotillomania neuroimaging studies are lacking. Aims To investigate grey and white matter abnormalities over the whole brain in patients with trichotillomania. Method Eighteen patients with DSM–IV trichotillomania and 19 healthy controls undertook structural magnetic resonance imaging after providing written informed consent. Differences in grey and white matter were investigated using computational morphometry. Results Patients with trichotillomania showed increased grey matter densities in the left striatum, left amygdalo-hippocampal formation, and multiple (including cingulate, supplementary motor, and frontal) cortical regions bilaterally. Conclusions Trichotillomania was associated with structural grey matter changes in neural circuitry implicated in habit learning, cognition and affect regulation. These findings inform animal models of the disorder and highlight key regions of interest for future translational research. PMID:18757980
Assessment of gray matter heterotopia by magnetic resonance imaging
Donkol, Ragab H; Moghazy, Khaled M; Abolenin, Alaeddin
AIM: To evaluate magnetic resonance imaging (MRI) features of different types of gray matter heterotopia. METHODS: Between June 2005 and December 2009, the medical records and MRI studies of patients with gray matter heterotopia were reviewed. The MRI morphologic findings of heterotopia were recorded along with the presence and type of associated cranial malformations. Available clinical and electrophysiological data were also recorded. RESULTS: 20 patients were included in the study. Their ages ranged from 9 mo to 39 years with a mean age of 15 years. All patients suffered from epileptic seizures. According to the location of heterotopia, patients were classified into three groups: subependymal (12), subcortical (5) and band (3) heterotopia. CONCLUSION: MRI was useful in diagnosing and differentiating between various types of gray matter heterotopia. The severity of clinical manifestations of heterotopia was related to the location and pattern of heterotopia. Determination of heterotopia type and its extent is useful for management planning and predicting prognosis. PMID:22468189
Combining functional magnetic resonance imaging with transcranial electrical stimulation
Saiote, Catarina; Turi, Zsolt; Paulus, Walter; Antal, Andrea
Transcranial electrical stimulation (tES) is a neuromodulatory method with promising potential for basic research and as a therapeutic tool. The most explored type of tES is transcranial direct current stimulation (tDCS), but also transcranial alternating current stimulation (tACS) and transcranial random noise stimulation (tRNS) have been shown to affect cortical excitability, behavioral performance and brain activity. Although providing indirect measure of brain activity, functional magnetic resonance imaging (fMRI) can tell us more about the global effects of stimulation in the whole brain and what is more, on how it modulates functional interactions between brain regions, complementing what is known from electrophysiological methods such as measurement of motor evoked potentials. With this review, we aim to present the studies that have combined these techniques, the current approaches and discuss the results obtained so far. PMID:23935578
Utility of Magnetic Resonance Imaging in Cardiac Venous Anatomic Variants
Eckart, Robert E. [Brooke Army Medical Center, 3851 Roger Brooke Drive, Fort Sam Houston, Texas 78234-6200, Cardiology Service (United States)], E-mail: email@example.com; Leitch, W. Shad [Brooke Army Medical Center, 3851 Roger Brooke Drive, Fort Sam Houston, Texas 78234-6200, Internal Medicine (United States); Shry, Eric A. [Brooke Army Medical Center, 3851 Roger Brooke Drive, Fort Sam Houston, Texas 78234-6200, Cardiology Service (United States); Krasuski, Richard A. [Wilford Hall Air Force Medical Center, Texas, Cardiology Service (United States); Lane, Michael J. [Brooke Army Medical Center, 3851 Roger Brooke Drive, Fort Sam Houston, Texas 78234-6200, Department of Radiology (United States); Leclerc, Kenneth M. [Brooke Army Medical Center, 3851 Roger Brooke Drive, Fort Sam Houston, Texas78234-6200, Cardiology Service (United States)
The incidence of persistent left superior venacava (PLSVC) is approximately 0.5% in the general population; however,the coexistent absence of the right SVC has a reported incidence in tertiary centers of 0.1%. The vast majority of reports are limited to pediatric cardiology. Likewise, sinus of Valsalva aneurysm is a rare congenital anomaly, with a reported incidence of 0.1-3.5% of all congenital heart defects. We present a 71-year-old patient undergoing preoperative evaluation for incidental finding of aortic root aneurysm,and found to have all three in coexistence. Suggestive findings were demonstrated on cardiac catheterization and definitive diagnosis was made by magnetic resonance imaging. The use of MRI for the diagnosis of asymptomatic adult congenital heart disease will be reviewed.
Primate comparative neuroscience using magnetic resonance imaging: promises and challenges
Mars, Rogier B.; Neubert, Franz-Xaver; Verhagen, Lennart; Sallet, Jérôme; Miller, Karla L.; Dunbar, Robin I. M.; Barton, Robert A.
Primate comparative anatomy is an established field that has made rich and substantial contributions to neuroscience. However, the labor-intensive techniques employed mean that most comparisons are often based on a small number of species, which limits the conclusions that can be drawn. In this review we explore how new developments in magnetic resonance imaging have the potential to apply comparative neuroscience to a much wider range of species, allowing it to realize an even greater potential. We discuss (1) new advances in the types of data that can be acquired, (2) novel methods for extracting meaningful measures from such data that can be compared between species, and (3) methods to analyse these measures within a phylogenetic framework. Together these developments will allow researchers to characterize the relationship between different brains, the ecological niche they occupy, and the behavior they produce in more detail than ever before. PMID:25339857
Magnetic resonance imaging diagnosis of brain tumors in dogs.
Bentley, R Timothy
A great deal of information is now available regarding the range of magnetic resonance imaging (MRI) features of many primary and secondary brain tumors from dogs. In this review, these canine neoplasms are grouped into meningeal masses, ventricular masses, intra-axial enhancing lesions, intra-axial mildly to non-enhancing lesions, and multifocal lesions. For each of these patterns, the major and sporadic neoplastic differential diagnoses are provided, and guidance on how to rank differential diagnoses for each individual patient is presented. The implication of MRI features such as contrast-enhancement, signal intensities and location is discussed. However, the information garnered from MRI must be correlated with all available clinical information and with epidemiological data before creating a differential diagnosis. PMID:25792181
Methodology to study polymers interaction by surface plasmon resonance imaging?
Vollmer, N.; Trombini, F.; Hely, M.; Bellon, S.; Mercier, K.; Cazeneuve, C.
The surface plasmon resonance (SPR) technique has been primarily used in the field of biology, in particular for the study of antibody-antigen interactions. Recently, polymers were introduced to form inclusion complexes. We describe here, a methodology based on surface plasmon resonance imaging to study water-resistant and reversible inclusion complexes using systems which are compatible with a cosmetic use. The purpose of this study is to follow in real time the interaction between two polymers. To carry out this study: • A biochip based on a covalent binding of one "host polymer" on a gold-activated surface was developed. • The binding of the host polymer to a guest polymer was monitored. • The presence of interactions between the ?-cyclodextrins groups of the host polymer and the adamantyl functional groups of the guest polymer and the possibility of dissociating the complex were established. This technique allowed carrying out parallel assays for optimizing the amount of complexes formed, the host polymer being spotted at five concentrations. It was then possible to study the influence of the concentration in host system for two concentrations of the guest polymer. The concentration in the host polymer yielding the highest immobilization of the guest system was further determined.
Exploiting image registration for automated resonance assignment in NMR.
Strickland, Madeleine; Stephens, Thomas; Liu, Jian; Tjandra, Nico
Analysis of protein NMR data involves the assignment of resonance peaks in a number of multidimensional data sets. To establish resonance assignment a three-dimensional search is used to match a pair of common variables, such as chemical shifts of the same spin system, in different NMR spectra. We show that by displaying the variables to be compared in two-dimensional plots the process can be simplified. Moreover, by utilizing a fast Fourier transform cross-correlation algorithm, more common to the field of image registration or pattern matching, we can automate this process. Here, we use sequential NMR backbone assignment as an example to show that the combination of correlation plots and segmented pattern matching establishes fast backbone assignment in fifteen proteins of varying sizes. For example, the 265-residue RalBP1 protein was 95.4 % correctly assigned in 10 s. The same concept can be applied to any multidimensional NMR data set where analysis comprises the comparison of two variables. This modular and robust approach offers high efficiency with excellent computational scalability and could be easily incorporated into existing assignment software. PMID:25828257
Electron beam imaging and spectroscopy of plasmonic nanoantenna resonances
NASA Astrophysics Data System (ADS)
Vesseur, E. J. R.
Nanoantennas are metal structures that provide strong optical coupling between a nanoscale volume and the far field. This coupling is mediated by surface plasmons, oscillations of the free electrons in the metal. Increasing the control over the resonant plasmonic field distribution opens up a wide range of applications of nanoantennas operating both in receiving and transmitting mode. This thesis presents how the dispersion and confinement of surface plasmons in nanoantennas are resolved and further engineered. Fabrication of nanostructures is done using focused ion beam milling (FIB) in metallic surfaces. We demonstrate that patterning in single-crystal substrates allows us to precisely control the geometry in which plasmons are confined. The nanoscale properties of the resonant plasmonic fields are resolved using a new technique developed in this thesis: angle- and polarization controlled cathodoluminescence (CL) imaging spectroscopy. The use of a tightly focused electron beam allows us to probe the optical antenna properties with deep subwavelength resolution. We show using this technique that nanoantennas consisting of 500-1200 nm long polycrystalline Au nanowires support standing plasmon waves. We directly observe the plasmon wavelengths which we use to derive the dispersion relation of guided nanowire plasmons. A 590-nm-long ridge-shaped nanoantenna was fabricated using FIB milling on a single-crystal Au substrate, demonstrating a level of control over the fabrication impossible with polycrystalline metals. CL experiments show that the ridge supports multiple-order resonances. The confinement of surface plasmons to the ridge is confirmed by boundary-element-method (BEM) calculations. The resonant modes in plasmonic whispering gallery cavities consisting of a FIB-fabricated circular groove are resolved. We find an excellent agreement between boundary element method calculations and the measured CL emission from the ring-shaped cavities. The calculations show that the ring supports resonances with increasing azimuthal or radial order. The smallest cavity fits only one wavelength in its circumference. We theoretically show that in these cavities, spontaneous emission can be enhanced over a broad spectral band due to the small modal volume of the plasmon resonances. A Purcell factor >2000 was found. We further study the mode symmetries and coupling of the ring resonances using far-field excitation, fluorescence, angle-resolved cathodoluminescence and photoelectron emission microscopy. We demonstrate spectral reshaping of emitters, mode-specific angular emission patterns, and a mode-selective excitation by incoming light, and we directly resolve the modal fields at high resolution. In the next chapter, we present metal-insulator-metal plasmon waveguides in which we engineer the dispersion to reach a refractive index of zero. Using spatially- and angle-resolved CL we directly observe the spatial mode profiles and determine the dispersion relation of plasmon modes. At the cutoff frequency, the emission pattern corresponds to that of a line dipole antenna demonstrating the entire waveguide is in phase (n=0). A strongly enhanced density of optical states is directly observed at cutoff from the enhanced CL intensity. Finally, we present 5 possible applications: a localized surface plasmon sensor, a plasmon ring laser, template stripping technique, an in-situ monitor of ionoluminescence and cathodoluminescence in a FIB system and a single-photon source.
Nanostructured surfaces for surface plasmon resonance spectroscopy and imaging
NASA Astrophysics Data System (ADS)
Petefish, Joseph W.
Surface plasmon resonance (SPR) has achieved widespread recognition as a sensitive, label-free, and versatile optical method for monitoring changes in refractive index at a metal-dielectric interface. Refractive index deviations of 10-6 RIU are resolvable using SPR, and the method can be used in real-time or ex-situ. Instruments based on carboxymethyl dextran coated SPR chips have achieved commercial success in biological detection, while SPR sensors can also be found in other fields as varied as food safety and gas sensing. Chapter 1 provides a physical background of SPR sensing. A brief history of the technology is presented, and publication data are included that demonstrate the large and growing interest in surface plasmons. Numerous applications of SPR sensors are listed to illustrate the broad appeal of the method. Surface plasmons (SPs) and surface plasmon polaritions (SPPs) are formally defined, and important parameters governing their spatial behavior are derived from Maxwell's equations and appropriate boundary conditions. Physical requirements for exciting SPs with incident light are discussed, and SPR imaging is used to illustrate the operating principle of SPR-based detection. Angle-tunable surface enhanced infrared absorption (SEIRA) of polymer vibrational modes via grating-coupled SPR is demonstrated in Chapter 2. Over 10-fold enhancement of C-H stretching modes was found relative to the absorbance of the same film in the absence of plasmon excitation. Modeling results are used to support and explain experimental observations. Improvements to the grating coupler SEIRA platform in Chapter 2 are explored in Chapters 3 and 4. Chapter 3 displays data for two sets of multipitch gratings: one set with broadly distributed resonances with the potential for multiband IR enhancement and the other with finely spaced, overlapping resonances to form a broadband IR enhancement device. Diffraction gratings having multiple periods were fabricated using a Lloyd's mirror interferometer to perform multiple exposures at multiple angles before developing. Precise control of the resonance position is shown by locating three SPR dips at predetermined wavenumbers of 5000, 4000, and 3000 cm-1, respectively. A set of three gratings, each having four closely spaced resonances is employed to show how the sensor response could be broadened. The work in Chapter 3 shows potential for simultaneous enhancement of multiple vibrational modes; the multiband approach might find application for modes at disparate locations within the IR spectrum, while the broadband approach may allow concurrent probing of broad single modes or clusters of narrow modes within a particular neighborhood of the spectrum. Chapter 4 uses the rigorous coupled-wave analysis (RCWA) method to numerically explore another facet of the nanostructure-based tunability of grating-baed SPR sensing. The work in this chapter illustrates how infrared signal enhancement could be tailored by through adjustment of the grating amplitude. Modeled infrared reflection absorption (IRRAS) spectra and electric field distributions were generated for several nanostructured grating configurations. It was found that there exists a critical amplitude value for a given grating pitch where the plasmon response achieves a maximum. Amplitudes greater than this critical value produce a broader and attenuated plasmon peak, while smaller amplitudes produce a plasmon resonance that is not as intense. Field simulations show how amplitudes nearer the critical amplitude resulted in large increases in the electric field within an analyte film atop the sensor surface, and the relative strength of the increased field is predictable based on the appearance of the IRRAS spectra. It is believed that these larger fields are the cause of observed enhanced absorption. Published reports pertaining to interactions of SPs with molecular resonance and to diffraction-based tracking of plasmons without a spectrometer are included in the Appendix to this thesis. In the first of the two reports, it is shown that plasmons
PTFOS: Flexible and Absorbable Intracranial Electrodes for Magnetic Resonance Imaging
Bonmassar, Giorgio; Fujimoto, Kyoko; Golby, Alexandra J.
Intracranial electrocortical recording and stimulation can provide unique knowledge about functional brain anatomy in patients undergoing brain surgery. This approach is commonly used in the treatment of medically refractory epilepsy. However, it can be very difficult to integrate the results of cortical recordings with other brain mapping modalities, particularly functional magnetic resonance imaging (fMRI). The ability to integrate imaging and electrophysiological information with simultaneous subdural electrocortical recording/stimulation and fMRI could offer significant insight for cognitive and systems neuroscience as well as for clinical neurology, particularly for patients with epilepsy or functional disorders. However, standard subdural electrodes cause significant artifact in MRI images, and concerns about risks such as cortical heating have generally precluded obtaining MRI in patients with implanted electrodes. We propose an electrode set based on polymer thick film organic substrate (PTFOS), an organic absorbable, flexible and stretchable electrode grid for intracranial use. These new types of MRI transparent intracranial electrodes are based on nano-particle ink technology that builds on our earlier development of an EEG/fMRI electrode set for scalp recording. The development of MRI-compatible recording/stimulation electrodes with a very thin profile could allow functional mapping at the individual subject level of the underlying feedback and feed forward networks. The thin flexible substrate would allow the electrodes to optimally contact the convoluted brain surface. Performance properties of the PTFOS were assessed by MRI measurements, finite difference time domain (FDTD) simulations, micro-volt recording, and injecting currents using standard electrocortical stimulation in phantoms. In contrast to the large artifacts exhibited with standard electrode sets, the PTFOS exhibited no artifact due to the reduced amount of metal and conductivity of the electrode/trace ink and had similar electrical properties to a standard subdural electrode set. The enhanced image quality could enable routine MRI exams of patients with intracranial electrode implantation and could also lead to chronic implantation solutions. PMID:22984396
A method for correlating in vivo prostate magnetic resonance imaging and histopathology using individualized magnetic resonance -based molds
NASA Astrophysics Data System (ADS)
Shah, Vijay; Pohida, Thomas; Turkbey, Baris; Mani, Haresh; Merino, Maria; Pinto, Peter A.; Choyke, Peter; Bernardo, Marcelino
A method for the design and rapid manufacture of a patient specific tissue slicing device based on in vivo images in order to facilitate the process of correlating the images with histopathology is presented. The method is applied to radical prostatectomy specimens where the customized mold is designed using magnetic resonance (MR) images of each patient obtained prior to surgery. In this case, the mold holds the prostate in place while a knife with a single blade or multiple blades is inserted in slots which are positioned to obtain tissue blocks corresponding to the slices in the MR images. The resulting histological specimens demonstrate good anatomical correlation with the MR images.
Gray Matter Alterations in Early Aging: A Diffusion Magnetic Resonance Imaging Study
Rathi, Y.; Pasternak, O.; Savadjiev, P.; Michailovich, O.; Bouix, S.; Kubicki, M.; Westin, C.-F.; Makris, N.; Shenton, M.E.
Many studies have observed altered neurofunctional and structural organization in the aging brain. These observations from functional neuroimaging studies show a shift in brain activity from the posterior to the anterior regions with aging (PASA model), as well as a decrease in cortical thickness, which is more pronounced in the frontal lobe followed by the parietal, occipital, and temporal lobes (retrogenesis model). However, very little work has been done using diffusion MRI (dMRI) with respect to examining the structural tissue alterations underlying these neurofunctional changes in the gray matter. Thus, for the first time, we propose to examine gray matter changes using diffusion MRI in the context of aging. In this work, we propose a novel dMRI based measure of gray matter "heterogeneity" that elucidates these functional and structural models (PASA and retrogenesis) of aging from the viewpoint of diffusion MRI. In a cohort of 85 subjects (all males, ages 15–55 years), we show very high correlation between age and "heterogeneity" (a measure of structural layout of tissue in a region-of-interest) in specific brain regions. We examine gray matter alterations by grouping brain regions into anatomical lobes as well as functional zones. Our findings from dMRI data connects the functional and structural domains and confirms the "retrogenesis" hypothesis of gray matter alterations while lending support to the neurofunctional PASA model of aging in addition to showing the preservation of paralimbic areas during healthy aging. PMID:24382651
Comparison of computed tomography and magnetic resonance imaging for the evaluation of canine intranasal neoplasia
Drees, R.; Forrest, L. J.; Chappell, R.
Objectives Canine intranasal neoplasia is commonly evaluated using computed tomography to indicate the diagnosis, to determine disease extent, to guide histological sampling location and to plan treatment. With the expanding use of magnetic resonance imaging in veterinary medicine, this modality has been recently applied for the same purpose. The aim of this study was to compare the features of canine intranasal neoplasia using computed tomography and magnetic resonance imaging. Methods Twenty-one dogs with confirmed intranasal neoplasia underwent both computed tomography and magnetic resonance imaging. The images were reviewed retrospectively for the bony and soft tissue features of intranasal neoplasia. Results Overall computed tomography and magnetic resonance imaging performed very similarly. However, lysis of bones bordering the nasal cavity and mucosal thickening was found on computed tomography images more often than on magnetic resonance images. Small amounts of fluid in the nasal cavity were more often seen on magnetic resonance images. However, fluid in the frontal sinuses was seen equally well with both modalities. Clinical Significance We conclude that computed tomography is satisfactory for evaluation of canine intranasal neoplasia, and no clinically relevant benefit is gained using magnetic resonance imaging for intranasal neoplasia without extent into the cranial cavity. PMID:19508490
Clinical positron emission tomography/magnetic resonance imaging applications.
von Schulthess, Gustav K; Kuhn, Felix Pierre; Kaufmann, Philipp; Veit-Haibach, Patrick
Although clinical positron emission tomography (PET)/computed tomography (CT) applications were obvious and have completely replaced PET in oncology, clinical applications of PET/magnetic resonance (MR) are currently not clearly defined. This is due to the lack of clinical data, which is mainly because PET/MR technology is not clinically mature at this point. Open issues are technical and concern ease of obtaining PET attenuation correction maps, dealing with, for example, MR surface coil metal in the PET field-of-view and appropriate workflows leading to a cost-effective examination. All issues can be circumvented by using a shuttle-connected PET/CT-MR system, but the penalty is that simultaneous PET and MR imaging are not possible and potential motion between examinations may occur. Clinically, some systems installed worldwide start to have a reasonable bulk of clinical data. Preliminary results suggest that in oncology, PET/MR may have advantages over PET/CT in head and neck imaging. In liver imaging, more PET-positive lesions are seen on MR than on CT, but that does not mean that PET/MR is superior to PET/CT. Possibly in some settings where a contrast-enhanced PET/CT is needed to be diagnostic, PET/MR can be done without contrast media. Although PET/CT has virtually no role in brain imaging, this may be an important domain for PET/MR, particularly in dementia imaging. The role of PET/MR in the heart is as yet undefined, and much research will have to be done to elucidate this role. At this point, it is also not clear where the simultaneity afforded by a fully integrated PET/MR is really needed. Sequential data acquisition even on separate systems and consecutive software image fusion may well be appropriate. With the increasing installed base of systems, clinical data will be forthcoming and define more clearly where there is clinical value in PET/MR at an affordable price. PMID:23178084
Magnetic Resonance Imaging and Magnetic Resonance Spectroscopy Characterize a Rodent Model of Covert Stroke
NASA Astrophysics Data System (ADS)
Herrera, Sheryl Lyn
Covert stroke (CS) comprises lesions in the brain often associated by risk factors such as a diet high in fat, salt, cholesterol and sugar (HFSCS). Developing a rodent model for CS incorporating these characteristics is useful for developing and testing interventions. The purpose of this thesis was to determine if magnetic resonance (MR) can detect brain abnormalities to confirm this model will have the desired anatomical effects. Ex vivo MR showed brain abnormalities for rats with the induced lesions and fed the HFSCS diet. Spectra acquired on the fixed livers had an average percent area under the fat peak relative to the water peak of (20+/-4)% for HFSCS and (2+/-2)% for control. In vivo MR images had significant differences between surgeries to induce the lesions (p=0.04). These results show that applying MR identified abnormalities in the rat model and therefore is important in the development of this CS rodent model.
Functional investigations of exercising muscle: a noninvasive magnetic resonance spectroscopy-magnetic resonance imaging approach.
Bendahan, D; Giannesini, B; Cozzone, P J
Muscle fatigue, which is defined as the decline in muscle performance during exercise, may occur at different sites along the pathway from the central nervous system through to the intramuscular contractile machinery. Historically, both impairment of neuromuscular transmission and peripheral alterations within the muscle have been proposed as causative factors of fatigue development. However, according to more recent studies, muscle energetics play a key role in this process. Intramyoplasmic accumulation of inorganic phosphate (P(i)) and limitation in ATP availability have been frequently evoked as the main mechanisms leading to fatigue. Although attractive, these hypotheses have been elaborated on the basis of experimental results obtained in vitro, and their physiological relevance has never been clearly demonstrated in vivo. In that context, noninvasive methods such as 31-phosphorus magnetic resonance spectroscopy and surface electromyography have been employed to understand both metabolic and electrical aspects of muscle fatigue under physiological conditions. Mapping of muscles activated during exercise is another interesting issue which can be addressed using magnetic resonance imaging (MRI). Exercise-induced T2 changes have been used in order to locate activated muscles and also as a quantitative index of exercise intensity. The main results related to both issues, i.e. the metabolic and electrical aspects of fatigue and the MRI functional investigation of exercising muscle, are discussed in the present review. PMID:15112049
Brain Magnetic Resonance Imaging and Magnetic Resonance Spectroscopy Findings of Children with Kernicterus
Sar?, Sahabettin; Yavuz, Alpaslan; Batur, Aabdussamet; Bora, Ayd?n; Caksen, Huseyin
Summary Background The term kernicterus, or bilirubin encephalopathy, is used to describe pathological bilirubin staining of the basal ganglia, brain stem, and cerebellum, and is associated with hyperbilirubinemia. Kernicterus generally occurs in untreated hyperbilirubinemia or cases where treatment is delayed. Magnetic resonance imaging (MRI)-based studies have shown characteristic findings in kernicterus. The objective of our study was to describe the role of 1H magnetic resonance spectroscopy (MRS) in demonstrating these metabolic changes and to review conventional MRI findings of kernicterus. Material/Methods Forty-eight pediatric cases with kernicterus were included in this study. MRI and MRS examinations were performed on variable dates (10–29 days after birth). NAA, Cr, Cho, NAA/Cr, NAA/Cho, and Cho/Cr values were evaluated visually and by computer analysis. Results There was no statistically significant difference between the NAA and Cho levels in the acute kernicterus patients and the control group (healthy patients), whereas both were significantly elevated in the chronic kernicterus patients. Both the mean NAA/Cr and Cho/Cr ratio values were significantly higher in the acute and chronic cases compared to the control group. The NAA/Cho ratio value was statistically lower in the acute cases than in the control group while it was similar in the chronic cases. Conclusions Conventional MR imaging and 1H-MRS are important complementary tools in the diagnostics of neonatal bilirubin encephalopathy. This study provided important information for applying these MR modalities in the evaluation of neonates with bilirubin encephalopathy. PMID:25745520
Advances in Magnetic Resonance Imaging of the Skull Base
Kirsch, Claudia F.E.
Introduction?Over the past 20 years, magnetic resonance imaging (MRI) has advanced due to new techniques involving increased magnetic field strength and developments in coils and pulse sequences. These advances allow increased opportunity to delineate the complex skull base anatomy and may guide the diagnosis and treatment of the myriad of pathologies that can affect the skull base. Objectives?The objective of this article is to provide a brief background of the development of MRI and illustrate advances in skull base imaging, including techniques that allow improved conspicuity, characterization, and correlative physiologic assessment of skull base pathologies. Data Synthesis?Specific radiographic illustrations of increased skull base conspicuity including the lower cranial nerves, vessels, foramina, cerebrospinal fluid (CSF) leaks, and effacement of endolymph are provided. In addition, MRIs demonstrating characterization of skull base lesions, such as recurrent cholesteatoma versus granulation tissue or abscess versus tumor, are also provided as well as correlative clinical findings in CSF flow studies in a patient pre- and post-suboccipital decompression for a Chiari I malformation. Conclusions?This article illustrates MRI radiographic advances over the past 20 years, which have improved clinicians' ability to diagnose, define, and hopefully improve the treatment and outcomes of patients with underlying skull base pathologies. PMID:25992137
A localized surface plasmon resonance imaging instrument for multiplexed biosensing.
Ruemmele, Julia A; Hall, W Paige; Ruvuna, Laura K; Van Duyne, Richard P
Localized surface plasmon resonance (LSPR) spectroscopy has been widely used for label-free, highly sensitive measurements of interactions at a surface. LSPR imaging (LSPRi) has the full advantages of LSPR but enables high-throughput, multiplexed measurements by simultaneously probing multiple individually addressable sensors on a single sample surface. Each spatially distinct sensor can be tailored to provide data regarding different surface functionalities or reaction environments. Previously, LSPRi has focused on single-particle sensing where the size scale is very small. Here, we create defined macroscale arrays of nanoparticles that are compatible with common patterning methods such as dip-pen nanolithography and multichannel microfluidic delivery devices. With this new LSPR sensing format, we report the first demonstration of multiplexed LSPR imaging and show that the increased throughput of our instrument enables the collection of a complete Langmuir binding curve on a single sensor surface. In addition, the multiplexed LSPR sensor is highly selective, as demonstrated by the hybridization of single-stranded DNA to complementary sequences immobilized on the sensor surface. The LSPR arrays described in this work exhibit uniform sensitivity and tailorable optical properties, making them an ideal platform for high-throughput, label-free analysis of a variety of molecular binding interactions. PMID:23560643
Nuclear magnetic resonance imaging of experimentally induced liver disease. [Rats
Stark, D.D.; Bass, N.M.; Moss, A.A.; Bacon, B.R.; McKerrow, J.H.; Cann, C.E.; Brito, A.; Goldberg, H.I.
Experimental animal models of hepatitis, fatty liver, and hepatic iron overload were evaluated using a 3.5-kGauss nuclear magnetic resonance (NMR) imaging system. Increases in image intensity measurements and in T/sub 2/ relaxation times equalled the sensitivity of histologic findings for the detection of early stages of hepatitis. A significant shift in T/sub 1/ relaxation times characterized the early stages of hepatic necrosis. Liver triglyceride content correlated significantly with increases in NMR intensity measurements (p<0.01); however, changes in liver water content had a much greater influence on intensity, T/sub 1/, and T/sub 2/. Thus, it may be possible to distinguish hepatitis from benign fatty liver. Liver iron content correlated with decreases in NMR intensity measurements (p<0.001), and iron levels as low as 1.2 mg/g were detected. NMR may more specifically identify hepatocellular iron overload than do other techniques that do not distinguish hepatocellular from reticuloendothelial iron.
Unconventional gradient coil designs in magnetic resonance imaging.
Zhu, Minhua; Xia, Ling; Liu, Feng
In magnetic resonance imaging (MRI), the gradient coils are used to encode the spatial positions of protons by varying the magnetic field linearly across the imaging subject. With the latest development of MRI technique and new clinical and research applications, the gradient coil system requires increasingly innovative designs. In this paper, four unconventional gradient coil designs are reviewed: (1) local gradient coils; (2) new coil configurations with reduced peripheral nerve stimulation (PNS); (3) dedicated structures designed for hybrid systems (combining MRI with other medical devices); and (4) the full 3D coil designs. For the first type, the development of local gradient coils (mainly head coils) is discussed chronologically and divided into three stages: the "golden" stage in the 1990s, the "wane" stage in the 2000s, and the "revival" stage in the 2010s. For the second type, various designs for the reduction of PNS problems have been described, including local and whole-body gradient coil systems. For the third design, a dedicated gradient coil design for multi-modality combination is illustrated with an MRI-LINAC system. Finally, gradient systems with non-layered coil structure are described in the fourth design type. We hope that this review on unconventional gradient coil designs will be useful for the new development of MRI technology and emerging medical applications. PMID:25955713
Accurate Measurement of Magnetic Resonance Imaging Gradient Characteristics
Liu, Hui; Matson, Gerald B.
Recently, gradient performance and fidelity has become of increasing interest, as the fidelity of the magnetic resonance (MR) image is somewhat dependent on the fidelity of the gradient system. In particular, for high fidelity non-Cartesian imaging, due to non-fidelity of the gradient system, it becomes necessary to know the actual k-space trajectory as opposed to the requested trajectory. In this work we show that, by considering the gradient system as a linear time-invariant system, the gradient impulse response function (GIRF) can be reliably measured to a relatively high degree of accuracy with a simple setup, using a small phantom and a series of simple experiments. It is shown experimentally that the resulting GIRF is able to predict actual gradient performance with a high degree of accuracy. The method captures not only the frequency response but also gradient timing errors and artifacts due to mechanical vibrations of the gradient system. Some discussion is provided comparing the method presented here with other analogous methods, along with limitations of these methods. PMID:25343017
Radio-frequency energy quantification in magnetic resonance imaging
NASA Astrophysics Data System (ADS)
Alon, Leeor
Mapping of radio frequency (RF) energy deposition has been challenging for 50+ years, especially, when scanning patients in the magnetic resonance imaging (MRI) environment. As result, electromagnetic simulation software is often used for estimating the specific absorption rate (SAR), the rate of RF energy deposition in tissue. The thesis work presents challenges associated with aligning information provided by electromagnetic simulation and MRI experiments. As result of the limitations of simulations, experimental methods for the quantification of SAR were established. A system for quantification of the total RF energy deposition was developed for parallel transmit MRI (a system that uses multiple antennas to excite and image the body). The system is capable of monitoring and predicting channel-by-channel RF energy deposition, whole body SAR and capable of tracking potential hardware failures that occur in the transmit chain and may cause the deposition of excessive energy into patients. Similarly, we demonstrated that local RF power deposition can be mapped and predicted for parallel transmit systems based on a series of MRI temperature mapping acquisitions. Resulting from the work, we developed tools for optimal reconstruction temperature maps from MRI acquisitions. The tools developed for temperature mapping paved the way for utilizing MRI as a diagnostic tool for evaluation of RF/microwave emitting device safety. Quantification of the RF energy was demonstrated for both MRI compatible and non-MRI-compatible devices (such as cell phones), while having the advantage of being noninvasive, of providing millimeter resolution and high accuracy.
Stable cerasomes for simultaneous drug delivery and magnetic resonance imaging
Cao, Zhong; Zhu, Wenjian; Wang, Wei; Zhang, Chunyang; Xu, Ming; Liu, Jie; Feng, Shi-Ting; Jiang, Qing; Xie, Xiaoyan
Magnetic liposomes have been frequently used as nanocarriers for targeted drug delivery and magnetic resonance imaging in recent years. Despite great potentials, their morphological/structural instability in the physiological environment still remains an intractable challenge for clinical applications. In this study, stable hybrid liposomal cerasomes (ie, liposomes partially coated with silica) which can co-encapsulate Fe3O4 nanoparticles and the anticancer drug paclitaxel were developed using thin film hydration method. Compared with the drug loaded liposomes, the paclitaxel-loaded magnetic cerasomes (PLMCs) exhibited much higher storage stability and better sustained release behavior. Cellular uptake study showed that the utilization of an external magnetic field significantly facilitated the internalization of PLMCs into cancer cells, resulting in potentiated drug efficacy of killing tumor cells. The T2 relaxivity (r2) of our PLMCs was much higher than that of free Fe3O4 nanoparticles, suggesting increased sensitivity in T2-weighted imaging. Given its excellent biocompatibility also shown in the study, such dual functional PLMC is potentially a promising nanosystem for effective cancer diagnosis and therapy. PMID:25395848
Magnetic resonance imaging of white matter diseases of prematurity.
Rutherford, Mary A; Supramaniam, Veena; Ederies, Ashraf; Chew, Andrew; Bassi, Laura; Groppo, Michela; Anjari, Mustafa; Counsell, Serena; Ramenghi, Luca A
Periventricular leucomalacia (PVL) and parenchymal venous infarction complicating germinal matrix/intraventricular haemorrhage have long been recognised as the two significant white matter diseases responsible for the majority of cases of cerebral palsy in survivors of preterm birth. However, more recent studies using magnetic resonance imaging to assess the preterm brain have documented two new appearances, adding to the spectrum of white matter disease of prematurity: punctate white matter lesions, and diffuse excessive high signal intensity (DEHSI). These appear to be more common than PVL but less significant in terms of their impact on individual neurodevelopment. They may, however, be associated with later cognitive and behavioural disorders known to be common following preterm birth. It remains unclear whether PVL, punctate lesions, and DEHSI represent a continuum of disorders occurring as a result of a similar injurious process to the developing white matter. This review discusses the role of MR imaging in investigating these three disorders in terms of aetiology, pathology, and outcome. PMID:20422407
Superresolution parallel magnetic resonance imaging: Application to functional and spectroscopic imaging
Otazo, Ricardo; Lin, Fa-Hsuan; Wiggins, Graham; Jordan, Ramiro; Sodickson, Daniel; Posse, Stefan
Standard parallel magnetic resonance imaging (MRI) techniques suffer from residual aliasing artifacts when the coil sensitivities vary within the image voxel. In this work, a parallel MRI approach known as Superresolution SENSE (SURE-SENSE) is presented in which acceleration is performed by acquiring only the central region of k-space instead of increasing the sampling distance over the complete k-space matrix and reconstruction is explicitly based on intra-voxel coil sensitivity variation. In SURE-SENSE, parallel MRI reconstruction is formulated as a superresolution imaging problem where a collection of low resolution images acquired with multiple receiver coils are combined into a single image with higher spatial resolution using coil sensitivities acquired with high spatial resolution. The effective acceleration of conventional gradient encoding is given by the gain in spatial resolution, which is dictated by the degree of variation of the different coil sensitivity profiles within the low resolution image voxel. Since SURE-SENSE is an ill-posed inverse problem, Tikhonov regularization is employed to control noise amplification. Unlike standard SENSE, for which acceleration is constrained to the phase-encoding dimension/s, SURE-SENSE allows acceleration along all encoding directions — for example, two-dimensional acceleration of a 2D echo-planar acquisition. SURE-SENSE is particularly suitable for low spatial resolution imaging modalities such as spectroscopic imaging and functional imaging with high temporal resolution. Application to echo-planar functional and spectroscopic imaging in human brain is presented using two-dimensional acceleration with a 32-channel receiver coil. PMID:19341804
Graph-partitioned spatial priors for functional magnetic resonance images.
Harrison, L M; Penny, W; Flandin, G; Ruff, C C; Weiskopf, N; Friston, K J
Spatial models of functional magnetic resonance imaging (fMRI) data allow one to estimate the spatial smoothness of general linear model (GLM) parameters and eschew pre-process smoothing of data entailed by conventional mass-univariate analyses. Recently diffusion-based spatial priors [Harrison, L.M., Penny, W., Daunizeau, J., and Friston, K.J. (2008). Diffusion-based spatial priors for functional magnetic resonance images. NeuroImage.] were proposed, which provide a way to formulate an adaptive spatial basis, where the diffusion kernel of a weighted graph-Laplacian (WGL) is used as the prior covariance matrix over GLM parameters. An advantage of these is that they can be used to relax the assumption of isotropy and stationarity implicit in smoothing data with a fixed Gaussian kernel. The limitation of diffusion-based models is purely computational, due to the large number of voxels in a brain volume. One solution is to partition a brain volume into slices, using a spatial model for each slice. This reduces computational burden by approximating the full WGL with a block diagonal form, where each block can be analysed separately. While fMRI data are collected in slices, the functional structures exhibiting spatial coherence and continuity are generally three-dimensional, calling for a more informed partition. We address this using the graph-Laplacian to divide a brain volume into sub-graphs, whose shape can be arbitrary. Their shape depends crucially on edge weights of the graph, which can be based on the Euclidean distance between voxels (isotropic) or on GLM parameters (anisotropic) encoding functional responses. The result is an approximation the full WGL that retains its 3D form and also has potential for parallelism. We applied the method to high-resolution (1 mm(3)) fMRI data and compared models where a volume was divided into either slices or graph-partitions. Models were optimized using Expectation-Maximization and the approximate log-evidence computed to compare these different ways to partition a spatial prior. The high-resolution fMRI data presented here had greatest evidence for the graph partitioned anisotropic model, which was best able to preserve fine functional detail. PMID:18790064
Magnetic Resonance Imaging Characteristics of Ovarian Clear Cell Carcinoma
Wang, Wei; Ding, Jianhui; Zhu, Xiaoli; Li, Yuan; Gu, Yajia; Peng, Weijun
Purpose To probe the magnetic resonance imaging (MRI) features of ovarian clear cell carcinoma (OCCC). Methods This study retrospectively collected MRI data for 21 pathology-confirmed OCCCs from 19 female patients. The MRI findings were analyzed to determine the tumor size, shape/edge, shape and number of protrusions within the cyst, cystic or necrotic components, signal intensity (SI) and enhancement features. Results The age of the 19 patients ranged from 28 to 63 years (mean age: 53 years). Unilateral tumors were found in 17 patients (17/19, 89%); the average size of all tumors was 10.8 cm. The tumors on MRI were classified into two categories: (a) "cystic adnexal mass with solid protrusions" in 12 (57%) and (b) "solid adnexal mass with cystic areas or necrosis" in 9 (43%). For group a, high to very high SI was observed for most tumors (10/12, 83%) on T1-weighted images (T1WIs), and very high SI was observed on T2-weighted images (T2WIs) for all 12 tumors. Most solid protrusions were irregular and few in number and exhibited heterogeneous intermediate SI on T1WIs and T2WIs and prolonged enhanced SI in the contrast study. All 9 OCCCs in group b were predominantly solid masses with unequally sized necrotic or cystic areas in which some cysts were located at the periphery of the tumor (4/9, 44%). The solid components in all 9 tumors showed iso- or slightly high SI on T1WIs, heterogeneous iso-high SI on T2WIs and heterogeneous prolonged enhancement. According to FIGO classification, 14 tumors (14/19, 74%) were stages I-II, and 5 (5/19, 26%) were stages III-IV. Conclusions On MRI, OCCCs present as large unilateral multilocular or unilocular cystic masses with irregular intermediate SI solid protrusions or predominantly solid masses with cysts or necrosis at an early FIGO stage. PMID:26161555
Magnetic Resonance Imaging Features of Adenosis in the Breast
Gity, Masoumeh; Arabkheradmand, Ali; Shakiba, Madjid; Khademi, Yassaman; Bijan, Bijan; Sadaghiani, Mohammad Salehi; Jalali, Amir Hossein
Purpose Adenosis lesions of the breast, including sclerosing adenosis and adenosis tumors, are a group of benign proliferative disorders that may mimic the features of malignancy on imaging. In this study, we aim to describe the features of breast adenosis lesions with suspicious or borderline findings on dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Methods In our database, we identified 49 pathologically proven breast adenosis lesions for which the final assessment of the breast MRI report was classified as either category 4 (n=45) or category 5 (n=4), according to the Breast Imaging Reporting and Data System (BI-RADS) published by the American College of Radiology (ACR). The lesions had a final diagnosis of either pure adenosis (n=33, 67.3%) or mixed adenosis associated with other benign pathologies (n=16, 32.7%). Results Of the 49 adenosis lesions detected on DCE-MRI, 32 (65.3%) appeared as enhancing masses, 16 (32.7%) as nonmass enhancements, and one (2.1%) as a tiny enhancing focus. Analysis of the enhancing masses based on the ACR BI-RADS lexicon revealed that among the mass descriptors, the most common features were irregular shape in 12 (37.5%), noncircumscribed margin in 20 (62.5%), heterogeneous internal pattern in 16 (50.0%), rapid initial enhancement in 32 (100.0%), and wash-out delayed en-hancement pattern in 21 (65.6%). Of the 16 nonmass enhancing lesions, the most common descriptors included focal distribution in seven (43.8%), segmental distribution in six (37.5%), clumped internal pattern in nine (56.3%), rapid initial enhancement in 16 (100.0%), and wash-out delayed enhancement pattern in eight (50.0%). Conclusion Adenosis lesions of the breast may appear suspicious on breast MRI. Awareness of these suspi-cious-appearing features would be helpful in obviating unnecessary breast biopsies. PMID:26155296
Echo-Planar Magnetic Resonance Imaging Studies of Frontal Cortex Activation During Word Generation in Humans
Gregory McCarthy; Andrew M. Blamire; Douglas L. Rothman; Rolf Gruetter; Robert G. Shulman
Nine subjects were studied by high-speed magnetic resonance imaging while performing language-based tasks. Subjects were asked either to repeat or to generate verbs associated with nouns read by an experimenter while magnetic resonance images were obtained of the left inferior frontal lobe. The echo-planar imaging sequence was used with a gradient echo time of 70 ms to give an apparent
Cardiac Magnetic Resonance Imaging for the Investigation of Cardiovascular Disorders. Part 1: Current Applications
Goenka, Ajit H.
Cardiac magnetic resonance imaging is a robust noninvasive technique for investigating cardiovascular disorders. The evolution of cardiac magnetic resonance and its widening span of diagnostic and prognostic applications have generated excitement as well as uncertainty regarding its potential clinical use and its role vis-ŕ-vis conventional imaging techniques. The purpose of this evidence-based review is to discuss some of these issues by highlighting the current (Part 1) and emerging (Part 2) applications of cardiac magnetic resonance. Familiarity with the versatility and usefulness of cardiac magnetic resonance will facilitate its wider clinical acceptance for improving the management of cardiovascular disorders. PMID:24512394
Functional connectivity magnetic resonance imaging classification of autism.
Anderson, Jeffrey S; Nielsen, Jared A; Froehlich, Alyson L; DuBray, Molly B; Druzgal, T Jason; Cariello, Annahir N; Cooperrider, Jason R; Zielinski, Brandon A; Ravichandran, Caitlin; Fletcher, P Thomas; Alexander, Andrew L; Bigler, Erin D; Lange, Nicholas; Lainhart, Janet E
Group differences in resting state functional magnetic resonance imaging connectivity between individuals with autism and typically developing controls have been widely replicated for a small number of discrete brain regions, yet the whole-brain distribution of connectivity abnormalities in autism is not well characterized. It is also unclear whether functional connectivity is sufficiently robust to be used as a diagnostic or prognostic metric in individual patients with autism. We obtained pairwise functional connectivity measurements from a lattice of 7266 regions of interest covering the entire grey matter (26.4 million connections) in a well-characterized set of 40 male adolescents and young adults with autism and 40 age-, sex- and IQ-matched typically developing subjects. A single resting state blood oxygen level-dependent scan of 8 min was used for the classification in each subject. A leave-one-out classifier successfully distinguished autism from control subjects with 83% sensitivity and 75% specificity for a total accuracy of 79% (P = 1.1 × 10(-7)). In subjects <20 years of age, the classifier performed at 89% accuracy (P = 5.4 × 10(-7)). In a replication dataset consisting of 21 individuals from six families with both affected and unaffected siblings, the classifier performed at 71% accuracy (91% accuracy for subjects <20 years of age). Classification scores in subjects with autism were significantly correlated with the Social Responsiveness Scale (P = 0.05), verbal IQ (P = 0.02) and the Autism Diagnostic Observation Schedule-Generic's combined social and communication subscores (P = 0.05). An analysis of informative connections demonstrated that region of interest pairs with strongest correlation values were most abnormal in autism. Negatively correlated region of interest pairs showed higher correlation in autism (less anticorrelation), possibly representing weaker inhibitory connections, particularly for long connections (Euclidean distance >10 cm). Brain regions showing greatest differences included regions of the default mode network, superior parietal lobule, fusiform gyrus and anterior insula. Overall, classification accuracy was better for younger subjects, with differences between autism and control subjects diminishing after 19 years of age. Classification scores of unaffected siblings of individuals with autism were more similar to those of the control subjects than to those of the subjects with autism. These findings indicate feasibility of a functional connectivity magnetic resonance imaging diagnostic assay for autism. PMID:22006979
Extragastrointestinal stromal tumors: Computed tomography and magnetic resonance imaging findings
Extragastrointestinal stromal tumors (EGISTs) are rare mesenchymal tumors that originate outside the gastrointestinal tract. The aim of the present study was to investigate the computed tomography (CT) and magnetic resonance imaging (MRI) features of EGISTs and analyze the correlations between radiological findings and pathological features. CT and MRI images of 24 patients with EGISTs were reviewed retrospectively. Patient demographics and tumor characteristics, including localization, size, contours, borders, cystic-necrotic components, calcification, hemorrhage, tumor vessels, attenuation and intensity, degree and pattern of enhancement, ascites, tumor invasion, lymphadenopathy and distant metastasis were recorded. Statistical analyses to compare the radiological characteristics of low- and high-grade EGISTs were performed with ?2 or Fisher's exact tests. The mean patient age at the time of presentation was 53 years. A total of 24 EGISTs were detected, originating in the omentum (n=4), mesentery (n=19) and retroperitoneum (n=1), respectively. The EGISTs displayed a predominantly spindle cell subtype (87.5%; 21/24). The majority of the EGISTs appeared as large (>10 cm; 70.8%; 17/24), round or oval (66.7%; 16/24), cystic-solid (87.5%; 21/24) and ill-defined (66.7%; 16/24) soft-tissue masses. The EGISTs were hypodense (69.6%; 16/23) or isodense (30.4%; 7/23) on CT images, hypointense (50%; 3/6), isointense (33.3%; 2/6) or hyperintense (16.7%; 1/6) on T1-weighted imaging (T1WI), and hyperintense on T2WI (100%; 6/6) and diffusion-WI (DWI; 100%; 6/6). A total of 54.2% (13/24) of the EGISTs displayed tumor vessels. Overall, 95.8% (23/24) of the masses showed marked enhancement and 87.5% (21/24) demonstrated heterogeneous enhancement. Calcification, hemorrhage, ascites and lymphadenopathy were rare characteristics in the EGISTs. Distant metastases were present in 10 patients (41.7%). The size, borders, tumor vessels and distant metastasis correlated with high-grade EGISTs [>5 mitoses/50 high-power fields (HPFs)] (P<0.05). The results of the present study indicated that clinical and radiological features, including advanced age, a large tumor size, cystic-necrotic components, rare lymphadenopathy, a heterogeneous enhancement pattern and hepatic metastasis may aid in the diagnosis of EGISTs. Radiological characteristics, such as a large size (>10 cm), ill-defined borders, tumor vessels and distant metastasis, can provide useful information in identifying the malignant behavior of EGISTs. PMID:25435959
Hemophilic arthropathy. A scoring system for magnetic resonance imaging.
Soler, R; López-Fernández, F; Rodríguez, E; Marini, M
The aim of this study was to define a system for scoring hemophilic arthropathy (HA) based on MR findings, providing for objective evaluation of the degree of joint involvement and evolution after on-demand administration of FVIII substitutional therapy or prophylactic treatment. A total of 133 MR examinations (89 basal and 44 during follow-up) were performed in 25 patients. Patients were divided in two groups depending on the therapy received and the length of time that the disease had been evolving at the start of the study. Group I was composed of 10 patients with secondary prophylaxis and group II was composed by 15 treated on demand. T1-weighted and T2*-weighted images performed on a 0.5-T unit were prospectively evaluated. The joint involvement was established on a scale of 0 (no abnormalities), I (minimal amount of hemosiderin), II (large amount of hemosiderin and isolated cartilaginous erosion), III (cartilage destruction, bone erosions, and subchondral cysts) to IV (large internal joint derangement, secondary osteoarthritis and/or ankylosis). At basal MR examination, patients of group I showed no abnormalities ( n=28, 75.6%), grade I ( n=3), and grade II ( n=6) of HA. Patients of group II corresponded to MR grades III ( n=21) and IV ( n=11) of HA. The MR follow-up showed improvement in three joints of group I and worsening in 5 joints in group I and 2 joints in group II. Early signs of HA were detected in 10 joints with MR imaging but were underestimated on plain radiographs. Advanced degrees of HA were classified as severe under both imaging techniques. Magnetic resonance is the preferred imaging technique to assess HA. The earliest signs of joint damage, detected by MR, are overlooked by plain radiography. The MR scoring system can be used for evaluating HA. Follow-up MR should be performed to evaluate regression or worsening of the abnormalities, primarily in the case of patients with prophylaxis who usually suffer normal or early joint involvement not detected by other means. PMID:11960235
Layer-by-layer capsules for magnetic resonance imaging and drug delivery
Hua Ai
Layer-by-layer (LbL) self-assembled polyelectrolyte capsules have demonstrated their unique advantages and capability in drug delivery applications. These ordered micro\\/nano-structures are also promising candidates as imaging contrast agents for diagnostic and theranostic applications. Magnetic resonance imaging (MRI), one of the most powerful clinical imaging modalities, is moving forward to the molecular imaging field and requires the availability of advanced imaging probes.
Feasibility of resonant metalens for the subwavelength imaging using a single sensor in the far field.
Li, Lianlin; Li, Fang; Cui, Tie Jun
This paper investigates the feasibility of the resonant metalens for the imaging beyond the diffraction limit using a single sensor in the far-field. It is shown that the resonant metalens can be related to the super-resonance phenomenon. We demonstrate that the super-resonance supports the enhancement of the information capacity of an imaging system, which is responsible for the subwavelength imaging of the probed objects by using a single sensor in combination with a broadband illumination. Such imaging concept has its unique advantage of producing real-time data when an object is illuminated by broadband waves, without the harsh requirements such as near-field scanning, mechanical scanning, or antenna arrays. The proposed method is expected to find its applications in nanolithography, detection, sensing, and subwavelength imaging in the near future. PMID:25089486
Characterization of reversible myocardial dysfunction by magnetic resonance imaging.
Fedele, F; Scopinaro, F; Montesano, T; Di Cesare, E; Di Renzi, P; Vitarelli, A; Dagianti, A
Some recent cardiovascular applications of nuclear magnetic resonance imaging (MRI) are discussed, on the basis of both literature and personal data. Management of coronary patients has become directed to strategies aiming at salvaging the ischemic myocardium, and MRI can play an important role in providing the necessary data leading to an appropriate assessment. Due to its capability in showing morphofunctional information on wall thickness and thickening, cine-MRI technique can be used to detect myocardial ischemia and infarction, since it allows the acquisition of 16 or more frames of the cardiac cycle which can be displayed in a cine loop format. In an Italian Cooperative Study the role of MRI in discriminating stunned from necrotic areas has been investigated. Comparison of fractional area change by echo versus cine-MR turned out to be almost completely overlapping, but cine-MRI allowed a more accurate measurement of systolic wall thickening due to better visualization of endo- and epicardial borders (more sensitive marker of kinetic damage than wall motion). Other studies have also been performed in order to determine the capability of contrast agents of allowing differentiation between reperfused reversible and irreversible myocardial injury and allowing distinction between reperfused and occlusive myocardial infarction. In a recent study we investigated the MRI possibility of identifying viable myocardium in severely chronic systolic dysfunctioning areas by comparing, in corresponding left ventricular segments, regional perfusion and metabolism at IPPA scintigraphy and regional signal intensity at MR images obtained before and after paramagnetic contrast media administration. The potential role of MRI was shown in the identification of viable myocardium with the use of contrast medium, that is of crucial importance in this respect. PMID:7959535
Nuclear magnetic resonance imaging and spectroscopy of human brain function.
Shulman, R G; Blamire, A M; Rothman, D L; McCarthy, G
The techniques of in vivo magnetic resonance (MR) imaging and spectroscopy have been established over the past two decades. Recent applications of these methods to study human brain function have become a rapidly growing area of research. The development of methods using standard MR contrast agents within the cerebral vasculature has allowed measurements of regional cerebral blood volume (rCBV), which are activity dependent. Subsequent investigations linked the MR relaxation properties of brain tissue to blood oxygenation levels which are also modulated by consumption and blood flow (rCBF). These methods have allowed mapping of brain activity in human visual and motor cortex as well as in areas of the frontal lobe involved in language. The methods have high enough spatial and temporal sensitivity to be used in individual subjects. MR spectroscopy of proton and carbon-13 nuclei has been used to measure rates of glucose transport and metabolism in the human brain. The steady-state measurements of brain glucose concentrations can be used to monitor the glycolytic flux, whereas subsequent glucose metabolism--i.e., the flux into the cerebral glutamate pool--can be used to measure tricarboxylic acid cycle flux. Under visual stimulation the concentration of lactate in the visual cortex has been shown to increase by MR spectroscopy. This increase is compatible with an increase of anaerobic glycolysis under these conditions as earlier proposed from positron emission tomography studies. It is shown how MR spectroscopy can extend this understanding of brain metabolism. Images Fig. 1 Fig. 2 Fig. 3 PMID:8475050
Myelin Imaging Compound (MIC)-enhanced Magnetic Resonance Imaging of Myelination
Frullano, Luca; Zhu, Junqing; Wang, Changning; Wu, Chunying; Miller, Robert H.; Wang, Yanming
The vertebrate nervous system is characterized by myelination, a fundamental biological process that protects the axons and facilitates electric pulse transduction. Damage to myelin is considered a major effect of autoimmune diseases such as multiple sclerosis (MS). Currently, therapeutic interventions are focused on protecting myelin integrity and promoting myelin repair. These efforts need to be accompanied by an effective imaging tool that correlates the disease progression with the extent of myelination. To date, magnetic resonance imaging (MRI) is the primary imaging technique to detect brain lesions in MS. However, conventional MRI cannot differentiate demyelinated lesions from other inflammatory lesions, and therefore cannot predict disease progression in MS. To address this problem, we have prepared a Gd-based contrast agent, termed MIC (Myelin Imaging Compound), which binds to myelin with high specificity. In this work, we demonstrate that MIC exhibits a high kinetic stability towards transmetallation with promising relaxometric properties. MIC was used for in vivo imaging of myelination following intracerebroventricular infusion in the rat brain. MIC was found to distribute preferentially in highly myelinated regions and was able to detect regions of focally induced demyelination. PMID:22098543
Delayed enhancement of peripheral zone of neurofibromas at magnetic resonance imaging
Y. Kurosaki; K. Kuramoto; Y. Itai
It is well known that bizonal histologic appearance characteristic of neurofibromas are reflected on magnetic resonance (MR) images. We report a case in which a delayed enhanced MR image showed that the entire mass enhanced homogeneously resulting in loss of zonal distinction on early enhanced MR image
Kinetics of the migration of lipids in composite chocolate measured by magnetic resonance imaging
Marc E Miquel; Sophie Carli; Patrick J Couzens; Hans-J Wille; Laurance D Hall
Migration of hazelnut oil into chocolate was followed non-invasively by magnetic resonance imaging, using a spin echo pulse sequence to acquire images with a 5 ms echo time and a 2000 ms repetition time. A calibration curve was used to correlate the image intensity with the concentration of hazelnut oil. Two different degrees of chocolate temper, at three different storage
Magnetic resonance imaging of structure and coarsening in three-dimensional foams
Burkhard Armin Prause
The rate of growth of individual bubbles in three-dimensional liquid foams (and crystallites in polycrystalline metals) is a major unsolved problem in material science. We have used Magnetic Resonance Imaging (MRI) to observe non-destructively the structure of disordered liquid foams. Volumetric imaging of coarsening foams required a robust imaging method with sufficient spatial and temporal resolution to resolve the small
Magnetic Resonance Imaging and Endometriosis: Deeply Infiltrating Endometriosis Does Not Originate from the Rectovaginal Septum
Charles Chapron; Etienne Liaras; Patricia Fayet; Christine Hoeffel; Arnaud Fauconnier; Marco Vieira; Habib Barakat; Bertrand Dousset; Paul Legmann; André Bonnin; Jean-Bernard Dubuisson
The goal of this study was to describe the magnetic resonance (MR) imaging signs of deeply infiltrating endometriosis (DIE) lesions and above all to find out if MR imaging can pinpoint the location of these lesions. We made a retrospective study of 8 patients presenting with histologically proven DIE lesions. The MR imaging results were compared with intraoperative findings. Nodules
Ultra-wideband antennas for combined magnetic resonance imaging and UWB radar applications
U. Schwarz; F. Thiel; F. Seifert; R. Stephan; M. Hein
Magnetic resonance imaging (MRI) is one of the most highly appreciated medical diagnostic techniques worldwide. Recent developments aim at adding the capability of creating focused images of moving objects. Among the potential navigator techniques required for such an improved MRI is ultra-wideband (UWB) radar. We have studied the performance of UWB antennas for biomedical imaging inside the 3-Tesla MRI system
A method for foetal heart rate monitoring during magnetic resonance imaging using Doppler ultrasound
Simon A Shakespeare; Rachel J Moore; John A Crowe; Penny A Gowland; Barrie R Hayes-Gill
A means of monitoring foetal heart rate (FHR) during magnetic resonance imaging (MRI) is presented. Foetal heart rate was measured using a modified standard Doppler ultrasound based monitor. The transducer and lead from the monitor required alteration to reduce interference and distortion in the MR images to acceptable levels. These changes enabled high quality images to be produced with insignificant
MAGNETIC RESONANCE - ELECTRICAL IMPEDANCE TOMOGRAPHY (MR-EIT): A new technique for high resolution conductivity imaging
B. Murat EYUBOGLU; Ozlem Birgul; Y. Ziya Ider
In this study, a new imaging modality for high resolution conductivity imaging is proposed. Both, the surface potentials and the magnetic fields produced by the probing current are measured. Surface potentials are measured by using conventional electrical impedance tomography techniques and high resolution magnetic field measurements are performed by using magnetic resonance imaging techniques. The conductivity distribution is reconstructed iteratively,
Model-based 3-D segmentation of multiple sclerosis lesions in magnetic resonance brain images
Micheline Kamber; Rajjan Shinghal; D. L. Collins; Gordon S. Francis; Alan C. Evans
Human investigators instinctively segment medical images into their anatomical components, drawing upon prior knowledge of anatomy to overcome image artifacts, noise, and lack of tissue contrast. The authors describe: 1) the development and use of a brain tissue probability model for the segmentation of multiple sclerosis (MS) lesions in magnetic resonance (MR) brain images, and 2) an empirical comparison of
A multimodal magnetic resonance imaging nanoplatform for cancer theranostics.
Benyettou, Farah; Lalatonne, Yoann; Chebbi, Imčne; Di Benedetto, Mélanie; Serfaty, Jean-Michel; Lecouvey, Marc; Motte, Laurence
We describe an innovative multimodal system, which combines magnetic targeting of therapeutic agents with both magnetic resonance and fluorescence imaging into one system. This new magnetic nanoplatform consists of superparamagnetic ?Fe(2)O(3) nanoparticles, used clinically as an MRI contrast agent, conjugated to therapeutic molecules of the hydroxylmethylene bisphosphonate family (HMBPs): alendronate with an amine function as the terminal group. In vitro tests with breast cancer cells show that the ?Fe(2)O(3)@alendronate hybrid nanomaterial reduces cell viability and acts as a drug delivery system. We also investigated the anti-tumoural properties in vivo in nude mice xenografted with MDA-MB-231 tumours. We show that the presence of both ?Fe(2)O(3)@alendronate and a magnetic field significantly reduced the development of tumours. The amine functionalities can be used as precursor groups for the covalent coupling of peptides or monoclonal antibodies for specific biological targeting. The feasibility of this process was demonstrated by coupling rhodamine B, a fluorescence marker, to the ?Fe(2)O(3)@alendronate nanohybrid. The system showed fluorescent properties and high affinity for cells. Flow cytometry and fluorescence microscopy were used to study the kinetics of ?Fe(2)O(3)@alendronate uptake by cells. The magnetic and fluorescent nanoparticles are potential candidates for smart drug-delivery systems. Also, the superparamagnetic behaviour of such nanoparticles may be exploited as MRI contrast agents to improve therapeutic diagnostics. PMID:21409252
Is Knee Magnetic Resonance Imaging Overutilized in Current Practice?
Song, Young Dong; Jain, Nimesh Prakash; Kim, Seok Jin; Kwon, Sae Kwang; Chang, Moon Jong; Chang, Chong Bum
Purpose To determine what proportion of patients visiting a tertiary knee clinic had pre-obtained knee magnetic resonance imaging (MRI) and to assess the impact of pre-obtained knee MRI on the selection of treatment plans. Materials and Methods Six hundred and eighty patients were enrolled from patients who visited our knee clinic during a 6-month period. The proportion of patients with pre-obtained knee MRI was calculated, and associations of sociodemographic factors, disease category, and finally selected treatment options with knee MRI pre-obtainment were investigated. A utility assessment panel of five orthopaedic surgeons was formed and established utility assessment criteria. Two rounds of utility assessment (before and after MRI review) were performed. Results Of the 680 patients, 185 (27%) had pre-obtained knee MRI. In the first round of utility assessment, 39%, 18%, and 43% of the 185 knee MRIs were evaluated as useful, equivocal, and arguably useless, respectively, and almost identical results were obtained in the second round. The proportion of assessed 'useful MRI' was higher in sports related injury (84%) and other conditions (91%) than in degenerative joint disease (18%) and nonspecific knee pain (31%). Utility assessment results among panels varied little for practice patterns and education duration. Conclusions This study suggests clinicians should reconsider and counsel patients the expected utility of knee MRI acquisition. PMID:26060608
Voxelwise multivariate analysis of multimodality magnetic resonance imaging
Naylor, Melissa G.; Cardenas, Valerie A.; Tosun, Duygu; Schuff, Norbert; Weiner, Michael; Schwartzman, Armin
Most brain magnetic resonance imaging (MRI) studies concentrate on a single MRI contrast or modality, frequently structural MRI. By performing an integrated analysis of several modalities, such as structural, perfusion-weighted, and diffusion-weighted MRI, new insights may be attained to better understand the underlying processes of brain diseases. We compare two voxelwise approaches: (1) fitting multiple univariate models, one for each outcome and then adjusting for multiple comparisons among the outcomes and (2) fitting a multivariate model. In both cases, adjustment for multiple comparisons is performed over all voxels jointly to account for the search over the brain. The multivariate model is able to account for the multiple comparisons over outcomes without assuming independence because the covariance structure between modalities is estimated. Simulations show that the multivariate approach is more powerful when the outcomes are correlated and, even when the outcomes are independent, the multivariate approach is just as powerful or more powerful when at least two outcomes are dependent on predictors in the model. However, multiple univariate regressions with Bonferroni correction remains a desirable alternative in some circumstances. To illustrate the power of each approach, we analyze a case control study of Alzheimer's disease, in which data from three MRI modalities are available. PMID:23408378
Functional magnetic resonance imaging of autism spectrum disorders
Dichter, Gabriel S.
This review presents an overview of functional magnetic resonance imaging findings in autism spectrum disorders (ASDs), Although there is considerable heterogeneity with respect to results across studies, common themes have emerged, including: (i) hypoactivation in nodes of the "social brain" during social processing tasks, including regions within the prefrontal cortex, the posterior superior temporal sulcus, the amygdala, and the fusiform gyrus; (ii) aberrant frontostriatal activation during cognitive control tasks relevant to restricted and repetitive behaviors and interests, including regions within the dorsal prefrontal cortex and the basal ganglia; (iii) differential lateralization and activation of language processing and production regions during communication tasks; (iv) anomalous mesolimbic responses to social and nonsocial rewards; (v) task-based long-range functional hypoconnectivity and short-range hyper-connectivity; and (vi) decreased anterior-posterior functional connectivity during resting states. These findings provide mechanistic accounts of ASD pathophysiology and suggest directions for future research aimed at elucidating etiologic models and developing rationally derived and targeted treatments. PMID:23226956
Magnetic resonance imaging of solvent transport in polymer networks
Botto, R.E.; Cody, G.D.
The spectroscopic technique of magnetic resonance imaging (MRI) has recently provided a new window into transport of solvents in polymer networks. Diffusion of solvent as a rate-controlling phenomenon is paramount to understanding transport in many important industrial and biological processes, such as upgrading fossil fuels, film casting and coating, development of photoresists, design of drug-delivery systems, development of solvent resistant polymers, etc. By MRI mapping the migration of solvent molecules through various polymer specimens, researchers Robert Botto and George Cody of Argonne National Laboratory, with support from the Division of Chemical Sciences at DOE, were able to characterize and distinguish between different modes of transport behavior associated with fundamentally different types of polymer systems. The method was applied to rubbers, glassy polymers, and coals. In polymers shown to undergo a glass transition from a rigid to rubbery state, a sharply defined solvent front was observed that propagated through specimens in the manner of a constant velocity shock wave. This behavior was contrasted with a smooth solvent concentration gradient found in polymer systems where no glass transition was observed. The results of this analysis have formed the basis of a new model of anomalous transport in polymeric solids and are helping to ascertain fundamental information on the molecular architectures of these materials.
A review of magnetic resonance imaging compatible manipulators in surgery.
Elhawary, H; Zivanovic, A; Davies, B; Lampérth, M
Developments in magnetic resonance imaging (MRI), coupled with parallel progress in the field of computer-assisted surgery, mean that an ideal environment has been created for the development of MRI-compatible robotic systems and manipulators, capable of enhancing many types of surgical procedure. However, MRI does impose severe restrictions on mechatronic devices to be used in or around the scanners. In this article a review of the developments in the field of MRI-compatible surgical manipulators over the last decade is presented. The manipulators developed make use of different methods of actuation, but they can be reduced to four main groups: actuation transmitted through hydraulics, pneumatic actuators, ultrasonic motors based on the piezoceramic principle and remote manual actuation. Progress has been made concerning material selection, position sensing, and different actuation techniques, and design strategies have been implemented to overcome the multiple restrictions imposed by the MRI environment. Most systems lack the clinical validation needed to continue on to commercial products. PMID:16808074
Magnetic Resonance Imaging Traits in Siblings Discordant for Alzheimer Disease
Cuenco, Karen T.; Green, Robert C.; Zhang, J.; Lunetta, Kathryn; Erlich, Porat M.; Cupples, L. Adrienne; Farrer, Lindsay A.; DeCarli, Charles; Baldwin, C. T.; Auerbach, S.; Akomolafe, A.; Freedman, Lorin; Ofili, E.; Chui, H.; DeCarli, C.; Duara, R.; Foroud, T.; Farlow, M.; Friedland, R.; Go, R.; Kurz, A.; Obisesan, T.; Petrovitch, H.; White, L.; Relkin, N.; Sabbagh, M.; Sadovnick, D.; Tsolaki, M.
BACKGROUND Magnetic resonance imaging (MRI) can aid clinical assessment of brain changes potentially correlated with Alzheimer disease (AD). MRI traits may improve our ability to identify genes associated with AD-outcomes. We evaluated semi-quantitative MRI measures as endophenotypes for genetic studies by assessing their association with AD in families from the Multi-Institutional Research in Alzheimer Genetic Epidemiology (MIRAGE) Study. METHODS Discordant siblings from multiple ethnicities were ascertained through a single affected proband. Semi-quantitative MRI measures were obtained for each individual. The association between continuous/ordinal MRI traits and AD were analyzed using generalized estimating equations. Medical history and Apolipoprotein E (APOE)?4 status were evaluated as potential confounders. RESULTS Comparisons of 214 affected and 234 unaffected subjects from 229 sibships revealed that general cerebral atrophy, white matter hyperintensities (WMH), and mediotemporal atrophy differed significantly between groups (each at P < .0001) and varied by ethnicity. Age at MRI and duration of AD confounded all associations between AD and MRI traits. Among unaffected sibs, the presence of at least one APOE?4 allele and MRI infarction was associated with more WMH after adjusting for age at MRI. CONCLUSION The strong association between MRI traits and AD suggests that MRI traits may be informative endophenotypes for basic and clinical studies of AD. In particular, WMH may be a marker of vascular disease that contributes to AD pathogenesis. PMID:18808654
Effect of magnetic resonance imaging on lymphocyte subsets
Reese, A.C.; Reichard, S.M.; Dickinson, M.M.; Allison, J.D.; Figueroa-Ortiz, R.E. (Medical College of Georgia, Augusta, GA (United States))
Research reports in both the lay press and the scientific literature raise the question as to the role of long term exposure to low level electromagnetic fields (EMF) in inducing cancers. Although sutdies have shown that EMF may have some effects on cells in tissue culture, it has been very difficult to determine if there is an effect in vivo. Since currents induced in the body by environmental EMF are lower than naturally existing currents, e.g., heart and brain, the authors have studied the effect of the high EMF generated by magnetic resonance imaging (MRI). It is also important for physicians to know if this procedure may have some effect on their patients since the use of this technique is growing rapidly. Blood samples were drawn by veinipuncture immediately prior to and just after patients were subjected to MRI scans of either their brain or lumbar regions. Samples were analyzed in the flow cytometer for various leukocyte subpopulations. Concentrations of monocytes, granulocytes, total T cells and helper T cells (p < 0.03) and the helper T cell/suppressor T cell ratio (a measure of immune system reactivity) increased (p < 0.05). There is a tendency toward an increase in the number of B cells following MRI (p < 0.13). Additional studies will correlate changes in leukocyte subset distribution with levels of various neurohormones that influence immune function.
Mapping social target detection with functional magnetic resonance imaging.
Dichter, Gabriel S; Felder, Jennifer N; Bodfish, James W; Sikich, Linmarie; Belger, Aysenil
The neural correlates of cognitive control and social processing functions, as well as the characteristic patterns of anomalous brain activation patterns in psychiatric conditions associated with impairment in these functions, have been well characterized. However, these domains have primarily been examined in isolation. The present study used event-related functional magnetic resonance imaging to map brain areas recruited during a target-detection task designed to evaluate responses to both non-social (i.e. shape) and social (i.e. face) target stimuli. Both shape and face targets activated a similar brain network, including the postcentral gyrus, the anterior and posterior cingulate gyri and the right midfrontal gyrus, whereas face targets additionally activated the thalamus, fusiform and temporooccipital cortex, lingual gyrus and paracingulate gyrus. Comparison of activations to social and non-social target events revealed that a small portion of the dorsal anterior cingulate gyrus (Brodmann's area 32) and the supracalcarine cortex were preferentially activated to face targets. These findings indicate that non-social and social stimuli embedded within a cognitive control task activate overlapping and distinct brain regions. Clinical cognitive neuroscience research of disorders characterized by cognitive dysfunction and impaired social processing would benefit from the use of tasks that evaluate the combined effects of deficits in these two domains. PMID:19015088
Pointwise observations for rheological characterization using nuclear magnetic resonance imaging
Arola, D.F.; Powell, R.L. [Department of Chemical Engineering and Materials Science, University of California, One Shields Avenue, Davis, California 95616-5294 (United States)] [Department of Chemical Engineering and Materials Science, University of California, One Shields Avenue, Davis, California 95616-5294 (United States); Barrall, G.A. [Quantum Magnetics, 7740 Kenamar Court, San Diego, California 92121-2425 (United States)] [Quantum Magnetics, 7740 Kenamar Court, San Diego, California 92121-2425 (United States); McCarthy, M.J. [Department of Food Science and Technology, University of California, One Shields Avenue, Davis, California 95616-8598 (United States)] [Department of Food Science and Technology, University of California, One Shields Avenue, Davis, California 95616-8598 (United States)
This study focuses on development of a nuclear magnetic resonance (NMR) imaging based viscometric technique using pulsed gradient NMR for characterizing fluid materials under steady tube flow conditions. By simultaneously measuring velocity profiles and pressure gradients it is possible to characterize complex fluids locally. Shear viscosity{endash}shear rate data, ranging from one to over two decades of shear rate from one combined velocity profile/pressure drop per unit tube length measurement, are provided for five fluids that exhibit both Newtonian and shear thinning characteristics. The resolution of the velocity data controls the accuracy of the measured shear viscosity whereas the radial resolution prescribes the number of shear viscosity{endash}shear rate data points and the minimum shear rate. Velocity profile measurements with a velocity resolution of 1 mm/s and radial resolutions which provided from 22 to 110 spatially resolved velocity data points accurately characterized fluids for shear rates greater than 0.1 s{sup {minus}1}. Dynamic yield values measured from velocity data for a microfibrous cellulose solution were within 2{percent} of those measured with a conventional rheometer using the controlled shear rate method and a vane attachment. {copyright} {ital 1999 Society of Rheology.}
Nanoscale ?-nuclear magnetic resonance depth imaging of topological insulators.
Koumoulis, Dimitrios; Morris, Gerald D; He, Liang; Kou, Xufeng; King, Danny; Wang, Dong; Hossain, Masrur D; Wang, Kang L; Fiete, Gregory A; Kanatzidis, Mercouri G; Bouchard, Louis-S
Considerable evidence suggests that variations in the properties of topological insulators (TIs) at the nanoscale and at interfaces can strongly affect the physics of topological materials. Therefore, a detailed understanding of surface states and interface coupling is crucial to the search for and applications of new topological phases of matter. Currently, no methods can provide depth profiling near surfaces or at interfaces of topologically inequivalent materials. Such a method could advance the study of interactions. Herein, we present a noninvasive depth-profiling technique based on ?-detected NMR (?-NMR) spectroscopy of radioactive (8)Li(+) ions that can provide "one-dimensional imaging" in films of fixed thickness and generates nanoscale views of the electronic wavefunctions and magnetic order at topological surfaces and interfaces. By mapping the (8)Li nuclear resonance near the surface and 10-nm deep into the bulk of pure and Cr-doped bismuth antimony telluride films, we provide signatures related to the TI properties and their topological nontrivial characteristics that affect the electron-nuclear hyperfine field, the metallic shift, and magnetic order. These nanoscale variations in ?-NMR parameters reflect the unconventional properties of the topological materials under study, and understanding the role of heterogeneities is expected to lead to the discovery of novel phenomena involving quantum materials. PMID:26124141
Orthogonal resonators for pulse in vivo electron paramagnetic imaging at 250 MHz
Sundramoorthy, Subramanian V.; Epel, Boris; Halpern, Howard J.
A 250 MHz bimodal resonator with a 19 mm internal diameter for in vivo pulse electron paramagnetic resonance (EPR) imaging is presented. Two separate coaxial cylindrical resonators inserted one into another were used for excitation and detection. The Alderman-Grant excitation resonator (AGR) showed the highest efficiency among all the excitation resonators tested. The magnetic field of AGR is confined to the volume of the detection resonator, which results in highly efficient use of the radio frequency power. A slotted inner single loop single gap resonator (SLSG LGR), coaxial to the AGR, was used for signal detection. The resulting bimodal resonator (AG/LGR) has two mutually orthogonal magnetic field modes; one of them has the magnetic field in the axial direction. The resonator built in our laboratory achieved 40dB isolation over 20 MHz bandwidth with quality factors of detection and excitation resonators of 36 and 11 respectively. Considerable improvement of the B1 homogeneity and EPR image quality in comparison with reflection loop-gap resonator of similar size and volume was observed. PMID:24530507
Diffusion-weighted imaging of biliopancreatic disorders: Correlation with conventional magnetic resonance imaging
Lee, Nam Kyung; Kim, Suk; Kim, Gwang Ha; Kim, Dong Uk; Seo, Hyung Il; Kim, Tae Un; Kang, Dae Hwan; Jang, Ho Jin
Diffusion-weighted magnetic resonance imaging (DWI) is a well established method for the evaluation of intracranial diseases, such as acute stroke. DWI for extracranial application is more difficult due to physiological motion artifacts and the heterogeneous composition of the organs. However, thanks to the newer technical development of DWI, DWI has become increasingly used over the past few years in extracranial organs including the abdomen and pelvis. Most previous studies of DWI have been limited to the evaluation of diffuse parenchymal abnormalities and focal lesions in abdominal organs, whereas there are few studies about DWI for the evaluation of the biliopancreatic tract. Although further studies are needed to determine its performance in evaluating bile duct, gallbladder and pancreas diseases, DWI has potential in the assessment of the functional information on the biliopancreatic tract concerning the status of tissue cellularity, because increased cellularity is associated with impeded diffusion, as indicated by a reduction in the apparent diffusion coefficient. The detection of malignant lesions and their differentiation from benign tumor-like lesions in the biliopancreatic tract could be improved using DWI in conjunction with findings obtained with conventional magnetic resonance cholagiopancreatography. Additionally, DWI can be useful for the assessment of the biliopancreatic tract in patients with renal impairment because contrast-enhanced computed tomography or magnetic resonance scans should be avoided in these patients. PMID:22919242
Imaging of stroke: a comparison between X-ray fluorescence and magnetic resonance imaging methods
Zheng, Weili; Haacke, E. Mark; Webb, Samuel M.; Nichol, Helen
A dual imaging approach, combining magnetic resonance imaging to localize lesions and synchrotron rapid scanning X-ray fluorescence (XRF) mapping to localize and quantify calcium, iron and zinc was used to examine one case of recent stroke with hemorrhage and two cases of ischemia 3 and 7 years before death with the latter showing superficial necrosis. In hemorrhagic lesions, more Fe is found accompanied with less Zn. In chronic ischemic lesions, Fe, Zn and Ca are lower indicating that these elements are removed as the normal tissue dies and scar tissue forms. Both susceptibility and T2* maps were calculated to visualize iron in hemorrhages and validated by XRF Ca and Fe maps. The former was superior for imaging iron in hemorrhagic transformation and necrosis but did not capture ischemic lesions. In contrast, T2* could not differentiate Ca from Fe in necrotic tissue but did capture ischemic lesions, complementing the susceptibility mapping. The spatial localization, accurate quantitative data and elemental differentiation shown here could also be valuable for imaging other brain tissue damage with abnormal Ca and Fe content. PMID:22789844
Phase-based regional oxygen metabolism in magnetic resonance imaging at high field
Fan, Audrey Peiwen
Venous oxygen saturation (Yv) in cerebral veins and the cerebral metabolic rate of oxygen (CMRO?) are important indicators for brain function and disease. Phase-susceptibility measurements in magnetic resonance imaging ...
Multimodal neuroimaging with simultaneous electroencephalogram and high-field functional magnetic resonance imaging
Purdon, Patrick L. (Patrick Lee), 1974-
Simultaneous recording of electroencephalogram (EEG) and functional magnetic resonance imaging (tMRI) is an important emerging tool in functional neuroimaging with the potential to reveal new mechanisms for brain function ...
T2*-weighted magnetic resonance imaging used to detect coagulative necrosis in tissue
Van Hyfte, John Bruce
to prevent unnecessary collateral damage to surrounding healthy tissue. This research focuses on using T2*-weighted FLASH magnetic resonance imaging to detect irreversible changes in i . n vitro bovine liver tissue and tissuesimulating polyacrylamide gel...
Highly Parallel Magnetic Resonance Imaging with a Fourth Gradient Channel for Compensation of RF Phase Patterns
Bosshard, John 1983-
A fourth gradient channel was implemented to provide slice dependent RF coil phase compensation for arrays in dual-sided or "sandwich" configurations. The use of highly parallel arrays for single echo acquisition magnetic resonance imaging allows...
The appearance of levator ani muscle abnormalities in magnetic resonance images after vaginal delivery
John O. L DeLancey; Rohna Kearney; Queena Chou; Steven Speights; Shereen Binno
ObjectiveTo describe the appearance and occurrence of abnormalities in the levator ani muscle seen on magnetic resonance imaging (MRI) in nulliparous women and in women after their first vaginal birth.
Prefrontal Cortical Thickness in First-Episode Psychosis: A Magnetic Resonance Imaging Study
Prefrontal Cortical Thickness in First-Episode Psychosis: A Magnetic Resonance Imaging Study Laura patients (n 17), first-episode affective psychosis patients (n 17), and normal control subjects (n 17
Local-feature-based similarity measure for stochastic resonance in visual perception of spatially structured images.
Delahaies, Agnčs; Rousseau, David; Fasquel, Jean-Baptiste; Chapeau-Blondeau, François
For images, stochastic resonance or useful-noise effects have previously been assessed with low-level pixel-based information measures. Such measures are not sensitive to coherent spatial structures usually existing in images. As a result, we show that such measures are not sufficient to properly account for stochastic resonance occurring in visual perception. We introduce higher-level similarity measures, inspired from visual perception, and based on local feature descriptors of scale invariant feature transform (SIFT) type. We demonstrate that such SIFT-based measures allow for an assessment of stochastic resonance that matches the visual perception of images with spatial structures. Constructive action of noise is registered in this way with both additive noise and multiplicative speckle noise. Speckle noise, with its grainy appearance, is particularly prone to introducing spurious spatial structures in images, and the stochastic resonance visually perceived and quantitatively assessed with SIFT-based measures is specially examined in this context. PMID:22751385
Highly Parallel Magnetic Resonance Imaging with a Fourth Gradient Channel for Compensation of RF Phase Patterns
Bosshard, John 1983-
A fourth gradient channel was implemented to provide slice dependent RF coil phase compensation for arrays in dual-sided or "sandwich" configurations. The use of highly parallel arrays for single echo acquisition magnetic resonance imaging allows...
Brain functional magnetic resonance imaging response to glucose and fructose infusions in humans
Technology Transfer Automated Retrieval System (TEKTRAN)
Objective: In animals, intracerebroventricular glucose and fructose have opposing effects on appetite and weight regulation. In humans, functional brain magnetic resonance imaging (fMRI) studies during carbohydrate ingestion suggest that glucose may regulate HT signaling but are potentially confoun...
One-pot synthesis of magnetic nanoclusters enabling atherosclerosis-targeted magnetic resonance imaging
Kukreja, Aastha; Lim, Eun-Kyung; Kang, Byunghoon; Choi, Yuna; Lee, Taeksu; Suh, Jin-Suck; Huh, Yong-Min; Haam, Seungjoo
In this study, dextran-encrusted magnetic nanoclusters (DMNCs) were synthesized using a one-pot solution phase method for detection of atherosclerosis by magnetic resonance imaging. Pyrenyl dextran was used as a surfactant because of its electron-stabilizing effect and its amphiphilic nature, rendering the DMNCs stable and water-dispersible. The DMNCs were 65.6±4.3 nm, had a narrow size distribution, and were superparamagnetic with a high magnetization value of 60.1 emu/g. Further, they showed biocompatibility and high cellular uptake efficiency, as indicated by a strong interaction between dextran and macrophages. In vivo magnetic resonance imaging demonstrated the ability of DMNCs to act as an efficient magnetic resonance imaging contrast agent capable of targeted detection of atherosclerosis. In view of these findings, it is concluded that DMNCs can be used as magnetic resonance imaging contrast agents to detect inflammatory disease. PMID:24904209
Surface-based analysis methods for high-resolution functional magnetic resonance imaging
Texas at Austin, University of
hemodynamic correlates using functional magnetic resonance imaging (fMRI) with blood oxygen-level dependent-surface algorithms to create a smooth sur- face representation at the gray-white interface and pial membrane
An iterative technique for refinement of selective excitations for magnetic resonance imaging
Lebsack, Eliot Todd
Selective RF pulses are needed or many application in magnetic resonance imaging (MRI). The desired excitation profile is omen used as the spectrum of the applied RF pulse; the modulation waveform of the RF pulse which approximately excites...
Eight-Channel Head Array and Control System for Parallel Transmit/Receive Magnetic Resonance Imaging
Moody, Katherine
Interest in magnetic resonance imaging (MRI) at high fields strengths (3 Tesla and above) is driven by the associated improvements in signal-to-noise ratio and spectral resolution. In practice, however, technical challenges prevent these benefits...
Surface Plasmon Resonance Imaging Using a High Numerical Aperture Microscope Objective
Zare, Richard N.
Surface Plasmon Resonance Imaging Using a High Numerical Aperture Microscope Objective Bo Huang-5080 We designed, constructed, and tested a surface plasmon resonance (SPR) microscope using a high numerical aperture objective from a commercially available inverted optical microscope. Such a configuration
In Situ Surface Plasmon Resonance Imaging Detection of DNA Hybridization to Oligonucleotide
In Situ Surface Plasmon Resonance Imaging Detection of DNA Hybridization to Oligonucleotide Arrays, and these arrays have been used in DNA hybridization experiments with in situ surface plasmon resonance (SPR on Gold Surfaces Andrew J. Thiel, Anthony G. Frutos, Claire E. Jordan, Robert M. Corn, and Lloyd M. Smith
Near field imaging of surface plasmon resonances of noble metal nanospheres
Near field imaging of surface plasmon resonances of noble metal nanospheres M. Shopa, A. Derkachova light intensities spectra for gold 75 nm radius nanosphere, with surface plasmon dipole resonance characteristics of surface plasmons and their manifestation in scattering properties of metal particles. J
Classification of brain compartments and head injury lesions by neural networks applied to magnetic resonance images
Kischell, Eric Robert
' (Member) A. D. Patton ( ead of epartment) August 1993 Major Subject: Electrical Engineering ABSTRACT Classification of Brain Compartments and Head Injury Lesions by Neural Networks Applied to Magnetic Resonance Images. (August 1993) Eric Robert... Kischell, B. S. , Northeastern University Chair of Advisory Committee: Dr. Nasser Kehtarnavaz An automatic neural network-based approach was ap- plied to segment brain compartments and closed-head-injury lesions in magnetic resonance (MR) images Two...
Application of nuclear magnetic resonance imaging and spectroscopy to fluids in porous media
Mandava, Shanthi Sree
Watson (Chair of Committee) Raymond W. Flumerfelt (Member) James F. Haw (Member) Raymond W. Fl merfelt (Head of Department) May 1991 ABSTRACT Application of Nuclear Magnetic Resonance Imaging and Spectroscopy to Fluids in Porous Media. (May 1991...-echo sequence. This part of the work was preliminary research done for a better understanding of fluid diffusion and coefficients. Magnetic Resonance Imaging (MRI) of a series of two phase immiscible displacements was conducted to monitor the flow processes...
Stepping stone sampling for retrieving artifact-free electroencephalogram during functional magnetic resonance imaging
Kimitaka Anami; Takeyuki Mori; Fumiko Tanaka; Yusuke Kawagoe; Jun Okamoto; Masaru Yarita; Takashi Ohnishi; Masato Yumoto; Hiroshi Matsuda; Osamu Saitoh
Ballistocardiogram and imaging artifacts cause major interference with simultaneous electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) recording. In particular, the large amplitude of the imaging artifact precludes easy retrieval of EEG signals during fMRI scanning. Recording with 20,000-Hz digitization rate combined with 3000-Hz low-pass filter revealed the real waveform of the imaging artifact, in which it was elucidated that
The use of a permanent magnetic resonance imaging system for radiotherapy treatment planning of bone metastases
Takashi Mizowaki; Norio Araki; Yasushi Nagata; Yoshiharu Negoro; Tetsuya Aoki; Masahiro Hiraoka
Purpose: To evaluate the usefulness of magnetic resonance (MR) imaging–based radiotherapy treatment planning (RTTP) for bone metastases in clinical applications.Methods and Materials: MR imaging–based RTTP was carried out for 28 patients with bone metastases using a permanent magnetic MR unit. Twenty-three patients received MR imaging–assisted X-ray simulation, and five underwent MR simulation. In MR imaging–assisted X-ray simulation, the radiation fields
Magnetic resonance imaging seems safe in patients with intracoronary stents.
Schroeder, A P; Houlind, K; Pedersen, E M; Thuesen, L; Nielsen, T T; Egeblad, H
We elucidated whether exposure to cardiac magnetic resonance imaging (MRI) of patients with implanted intracoronary stents is associated with increased risk of stent-thrombosis, stent-restenosis, or other cardiovascular complications. Forty-seven patients admitted with acute myocardial infarction (AMI) were studied. Twenty-three were included in a serial cardiac MRI study, using 1.5-T scanners with standard gradient systems. The remaining patients were control subjects who were matched for age and gender with the MRI group. All patient had intracoronary stents implanted in connection with primary angioplastic treatment (PTCA) of AMI (n = 21), secondary PTCA procedures due to recurrent angina (n = 22), or both (n = 4). In the MRI group (n = 23, aged 58 +/- 10 yr), MRI was carried out one to five times in each patient a median of 166 days (range, 1-501) after stent implantation. The control group comprised 24 patients, ages 59 +/- 11 yr. The incidences of stent-thrombosis, stent-restenosis, and other cardiovascular complications did not differ statistically significantly between the two groups. In the MRI group, stent-related thrombosis (n = 1) or restenosis (n = 7) was observed in eight cases a median of 102 days (range, 7-547) after MR examination and a median of 318 days (range, 138-713) after stent implantation, compared with nine cases in the control group (thrombosis, n = 1; restenosis, n = 8) observed a median of 147 days (range, 1-267) after stent implantation. No acute thromboembolic or other complication occurred in immediate connection with MRI. The follow-up time was 21.3 +/- 4.5 months. This small study shows no evidence of an MRI-related risk of stent-restenosis or other cardiovascular complications, not even if cardiac MRI is performed early after stent implantation. PMID:11545106
Magnetic resonance imaging detected prostate evasive anterior tumours: Further insights
Edwan, Ghazi Al; Ghai, Sangeet; Margel, David; Kulkarni, Girish; Hamilton, Rob; Toi, Ants; Haidar, Masoom A.; Finelli, Antonio; Fleshner, Neil E.
Introduction: Clinical confusion continues to exist regarding the underestimation of cancers among patients on active surveillance and among men with repeated negative prostate biopsies despite worrisome prostate-specific antigen (PSA) levels. We have previously described our initial experience with magnetic resonance imaging (MRI)-based detection of tumours in the anterior prostate gland. In this report, we update and expand our experience with these tumours in terms of multiparametric-MRI findings, staging, and grading. Furthermore, we report early treatment outcomes with these unique cancers. Methods: We reviewed our prostate MRI dataset of 1117 cases from January 2006 until December 2012 and identified 189 patients who fulfilled criteria for prostate evasive anterior tumors (PEATS). Descriptive analyses were performed on multiple covariates. Kaplan-Meier actuarial technique was used to plot the treatment-related outcomes from PEATS tumours. Results: Among the 189 patients who had MRI-detectable anterior tumours, 148 had biopsy proven disease in the anterior zone. Among these tumours, the average PSA was 18.3 ng/mL and most cancers were Gleason 7. In total, 68 patients chose surgical therapy. Among these men, most of their cancers had extra prostatic extension and 46% had positive surgical margins. Interestingly, upgrading of tumours that were biopsy Gleason 6 in the anterior zone was common, with 59% exhibiting upgrading to Gleason 7 or higher. Biochemical-free survival among men who elected surgery was not ideal, with 20% failing by 20 months. Conclusion: PEATS tumours are found late and are disproportionally high grade tumours. Careful consideration to MRI testing should be given to men at risk for PEATS. PMID:26029293
Compact low field magnetic resonance imaging magnet: Design and optimization
NASA Astrophysics Data System (ADS)
Sciandrone, M.; Placidi, G.; Testa, L.; Sotgiu, A.
Magnetic resonance imaging (MRI) is performed with a very large instrument that allows the patient to be inserted into a region of uniform magnetic field. The field is generated either by an electromagnet (resistive or superconductive) or by a permanent magnet. Electromagnets are designed as air cored solenoids of cylindrical symmetry, with an inner bore of 80-100 cm in diameter. In clinical analysis of peripheral regions of the body (legs, arms, foot, knee, etc.) it would be better to adopt much less expensive magnets leaving the most expensive instruments to applications that require the insertion of the patient in the magnet (head, thorax, abdomen, etc.). These "dedicated" apparati could be smaller and based on resistive magnets that are manufactured and operated at very low cost, particularly if they utilize an iron yoke to reduce power requirements. In order to obtain good field uniformity without the use of a set of shimming coils, we propose both particular construction of a dedicated magnet, using four independently controlled pairs of coils, and an optimization-based strategy for computing, a posteriori, the optimal current values. The optimization phase could be viewed as a low-cost shimming procedure for obtaining the desired magnetic field configuration. Some experimental measurements, confirming the effectiveness of the proposed approach (construction and optimization), have also been reported. In particular, it has been shown that the adoption of the proposed optimization based strategy has allowed the achievement of good uniformity of the magnetic field in about one fourth of the magnet length and about one half of its bore. On the basis of the good experimental results, the dedicated magnet can be used for MRI of peripheral regions of the body and for animal experimentation at very low cost.
Properties of a novel magnetized alginate for magnetic resonance imaging.
Shen, Feng; Poncet-Legrand, Celine; Somers, Sat; Slade, Andrea; Yip, Christopher; Duft, Andy M; Winnik, Françoise M; Chang, Patricia L
Implanting recombinant cells encapsulated in alginate microcapsules to secrete therapeutic proteins has been proven clinically effective in treating several murine models of human diseases. However, once implanted, these microcapsules cannot be assessed without invasive surgery. We now report the preparation and characterization of a novel ferrofluid to render these microcapsules visible with magnetic resonance imaging (MRI). The ferrofluid was prepared as a colloidal iron oxide stabilized in water by alginate. The presence of iron particles in the ferrofluid was verified with chemical titration, dynamic light scattering, and magnetization measurement. The microcapsules fabricated with various concentrations of the ferrofluid in the core, or on the surface of alginate microcapsules, or both, all produced microcapsules with smooth surfaces as shown with light and scanning electron microscopy. However, at the nanoscale level, as revealed with atomic force microscopy, the ferrofluid-fabricated microcapsules demonstrated increased granularity, particularly when the ferrofluid was used to laminate the surface. From the force spectroscopy measurements, these modified microcapsules showed increasing surface rigidity in the following order: traditional alginate < ferrofluid in the core < ferrofluid on the surface. Although the mechanical stability of low-concentration ferrofluid (0.1%) microcapsules was reduced, increasing concentrations, up to 20%, were able to improve stability. When these ferrofluid microcapsules were examined with MRI, their T(2) relaxation time was reduced, thereby producing increased contrast readily detectable with MRI, whereas the traditional alginate microcapsules showed no difference when compared with water. In conclusion, such ferrofluid-enhanced alginate is suitable for fabricating microcapsules that offer the potential for in vivo tracking of implanted microcapsules without invasive surgery. PMID:12783484
Complications of three deep sedation methods for magnetic resonance imaging
Tith, Solina; Lalwani, Kirk; Fu, Rongwei
Background: Propofol and pentobarbital are commonly used to sedate children undergoing magnetic resonance imaging (MRI). Aim/Objective: To compare the safety of three types of sedation: intravenous propofol (PROP), mixed pentobarbital/propofol (PENT), and mixed pentobarbital group requiring supplemental sedation (PENT SUPP) regimens in pediatric patients following deep sedation (DS) for noncardiac MRI. Materials and Methods: We conducted a case-control study matching 619 cases with complications with 619 controls using data from our institution's sedation database for children deeply sedated for noncardiac MRI. Cases were defined as patients with any complication and we characterized complications from cases, and used a conditional logistic regression model to assess the association between three DS methods and occurrence of complications after adjusting for confounding variables. Results: We found that complications occurred in association with 794 (10.1%) of the 7,839 DSs performed for MRI between 1998 and 2008. Of the 794 cases, 619 cases met inclusion criteria for the study. Among the 619 cases that met inclusion criteria, 24 (0.3% of 7,839 DSs total) were associated with major complications. Type of sedation was significantly associated with the occurrence of complications, and the PENT group was associated with decreased odds of complications when compared to the PROP regimen (OR 0.68; 95% CI 0.46, 0.98; P=0.040) and compared to the PENT SUPP group (OR 0.60; 95% CI 0.31, 0.89; P<0.0001). Conclusions: DS with a pentobarbital technique was associated with decreased odds for complications when compared to a propofol-based technique or a pentobarbital technique requiring supplemental sedation. PMID:22557739
Brain Characterization Using Normalized Quantitative Magnetic Resonance Imaging
Warntjes, Jan B. M.; Engström, Maria; Tisell, Anders; Lundberg, Peter
Objectives To present a method for generating reference maps of typical brain characteristics of groups of subjects using a novel combination of rapid quantitative Magnetic Resonance Imaging (qMRI) and brain normalization. The reference maps can be used to detect significant tissue differences in patients, both locally and globally. Materials and Methods A rapid qMRI method was used to obtain the longitudinal relaxation rate (R1), the transverse relaxation rate (R2) and the proton density (PD). These three tissue properties were measured in the brains of 32 healthy subjects and in one patient diagnosed with Multiple Sclerosis (MS). The maps were normalized to a standard brain template using a linear affine registration. The differences of the mean value ofR1, R2 and PD of 31 healthy subjects in comparison to the oldest healthy subject and in comparison to an MS patient were calculated. Larger anatomical structures were characterized using a standard atlas. The vector sum of the normalized differences was used to show significant tissue differences. Results The coefficient of variation of the reference maps was high at the edges of the brain and the ventricles, moderate in the cortical grey matter and low in white matter and the deep grey matter structures. The elderly subject mainly showed significantly lower R1 and R2 and higher PD values along all sulci. The MS patient showed significantly lower R1 and R2 and higher PD values at the edges of the ventricular system as well as throughout the periventricular white matter, at the internal and external capsules and at each of the MS lesions. Conclusion Brain normalization of rapid qMRI is a promising new method to generate reference maps of typical brain characteristics and to automatically detect deviating tissue properties in the brain. PMID:23940653
Magnetic resonance imaging of human extraocular muscles in convergence.
Demer, Joseph L; Kono, Reika; Wright, Weldon
Extraocular muscle (EOM) paths during asymmetrical convergence were evaluated by tri-planar, contrast-enhanced magnetic resonance imaging of the orbits of eight young adults during binocular fixation of a target aligned to one eye at 800 and 15 cm distance. Cross sections and paths of EOMs were determined from area centroids. In convergence, the aligned eye rotated and translated negligibly, while its inferior oblique (IO) muscle exhibited significant contractile thickening. There were no significant contractile changes in the cross sections of aligned eye rectus or superior oblique (SO) muscles in convergence. The converging eye rotated nasally 22.4 degrees but translated negligibly. The converging eye medial (MR) and lateral rectus (LR) muscles exhibited large contractile cross-section changes, and the IO showed significant contractile thickening, while the vertical rectus muscles and the SO did not. Anterior paths of three aligned eye rectus EOMs could be determined in convergence and shifted consistent with a 1.9 degrees extorsion of the rectus pulley array. Such extorsional reconfiguration of the rectus pulleys would move the pulleys in coordination with globe extorsion and avoid imparting torsional action to these EOMs. Extorsional rectus pulley shift in convergence is inconsistent with the reconfiguration predicted to explain the temporal tilting of Listing's planes, instead suggesting that this temporal tilting is due to variations in oblique EOM innervation. Absence of globe translation in convergence argues against overall EOM co-contraction. The reconfiguration of EOM geometry in convergence has important implications for single-unit studies of neural control. PMID:12686579
Brain magnetic resonance imaging in patients with Cowden syndrome.
Lok, Catherine; Viseux, Valérie; Avril, Marie Françoise; Richard, Marie Aleth; Gondry-Jouet, Catherine; Deramond, Hervé; Desfossez-Tribout, Caroline; Courtade, Sandrine; Delaunay, Michčle; Piette, Fréderic; Legars, Daniel; Dreno, Brigitte; Saďag, Philippe; Longy, Michel; Lorette, Gérard; Laroche, Liliane; Caux, Fréderic
Cowden syndrome (CS) is a rare autosomal dominant genodermatosis, characterized by multiple hamartomas, particularly of the skin, associated with high frequencies of breast, thyroid, and genitourinary malignancies. Although Lhermitte-Duclos disease (LDD) or dysplastic gangliocytoma of the cerebellum, a slowly progressive unilateral tumor, is a major criterion of CS, its frequency in patients with CS is unknown. Other cerebral abnormalities, especially meningioma and vascular malformations, have also been described, albeit rarely, in these patients. The aim of the current study was to use cerebral magnetic resonance imaging (MRI) to evaluate LDD frequency and to investigate other brain abnormalities in CS patients recruited by dermatologists. A multicenter study was conducted in 8 hospital dermatology departments between January 2000 and December 2003. Twenty patients with CS were included; specific cerebral MRI abnormalities were found in 35% (7/20) of them. Cerebral MRI revealed LDD in 3 patients, a meningioma in 1, and numerous vascular malformations in 6 patients. Five patients had venous angiomas (3 associated with LDD) and 2 patients had cavernous angiomas (1 associated with LDD and a venous angioma). The discovery of asymptomatic LDD in 3 patients and a cavernous angioma in another prompted us to perform neurologic examinations regularly and MRI to estimate the size and the extension of the tumor, and to assess the need for surgery. CS similarities with Bannayan-Riley-Ruvalcaba (BRR) are discussed because some patients could also have the BRR phenotype (for example, genital lentigines, macrocephaly, multiple lipomas) and because BRR seems to have more central nervous system vascular anomalies. Because CS signs can involve numerous systems, all physicians who might encounter this disease should be aware of its neurologic manifestations. Our findings confirm the contribution of brain MRI to detecting asymptomatic LDD, vascular malformations, and meningiomas in patients with CS. PMID:15758842
Intervertebral disc magnetic resonance image: correlation with gross morphology and biochemical composition
Bishop, Paul B
The magnetic resonance image, gross morphology, and biochemical composition of the intervertebral disc nucleus pulposus (NP), anulus fibrosus (AF) and cartilaginous endplates (CEP) from two groups of three human lumbar spines were compared. Group I consisted of all healthy discs from young donors (Grade I) and group II was comprised of discs that had undergone degeneration and age-related changes (average Grade 4). The gross morphological changes in the individual disc tissues associated with ageing/degeneration were consistent with specific changes in the characteristics of the magnetic resonance image. In particular, the mid-nuclear band of decreased magnetic resonance signal intensity seen in Grade 4 discs was associated with the appearance of clefts and fissures as well as a region of mucinous infiltration. The results of the biochemical analysis suggest that the changes in signal intensity are not due merely to changes in water content, but are also associated with changes in proteoglycan content. The changes associated with ageing/degeneration in the magnetic resonance image of the disc were related to a decrease in the proteoglycan content of the AF and NP. The water content of the NP also decreased. There was no clear association between the biochemical composition of the CEP and the magnetic resonance image. These results demonstrate that magnetic resonance imaging is an effective technique for evaluating subtle morphological changes in the intervertebral disc tissues and may be a sensitive indicator of the proteoglycan content of the AF and NP. ImagesFigure 1Figure 2
Dipole and quadrupole surface plasmon resonances contributions in formation of near-field images of a gold nanosphere
Dipole and quadrupole surface plasmon resonances contributions in formation of near-field images surface proximity are studied. The multipolar plasmon size characteristic: plasmon resonance frequencies-field imaging, multipolar surface plasmon resonances, Mie theory, optical properties of noble metal nanospheres
Detection of Light Images by Simple Tissues as Visualized by Photosensitized Magnetic Resonance Imaging
Tempel-Brami, Catherine; Pinkas, Iddo; Scherz, Avigdor; Salomon, Yoram
In this study, we show how light can be absorbed by the body of a living rat due to an injected pigment circulating in the blood stream. This process is then physiologically translated in the tissue into a chemical signature that can be perceived as an image by magnetic resonance imaging (MRI). We previously reported that illumination of an injected photosynthetic bacteriochlorophyll-derived pigment leads to a generation of reactive oxygen species, upon oxygen consumption in the blood stream. Consequently, paramagnetic deoxyhemoglobin accumulating in the illuminated area induces changes in image contrast, detectable by a Blood Oxygen Level Dependent (BOLD)-MRI protocol, termed photosensitized (ps)MRI. Here, we show that laser beam pulses synchronously trigger BOLD-contrast transients in the tissue, allowing representation of the luminous spatiotemporal profile, as a contrast map, on the MR monitor. Regions with enhanced BOLD-contrast (7-61 fold) were deduced as illuminated, and were found to overlap with the anatomical location of the incident light. Thus, we conclude that luminous information can be captured and translated by typical oxygen exchange processes in the blood of ordinary tissues, and made visible by psMRI (Fig. 1). This process represents a new channel for communicating environmental light into the body in certain analogy to light absorption by visual pigments in the retina where image perception takes place in the central nervous system. Potential applications of this finding may include: non-invasive intra-operative light guidance and follow-up of photodynamic interventions, determination of light diffusion in opaque tissues for optical imaging and possible assistance to the blind. PMID:18030327
Ultrafast magnetic resonance imaging improves the staging of pancreatic tumors.
Trede, M; Rumstadt, B; Wendl, K; Gaa, J; Tesdal, K; Lehmann, K J; Meier-Willersen, H J; Pescatore, P; Schmoll, J
OBJECTIVE: This prospective study was undertaken to evaluate the accuracy of a noninvasive "all-in-one" staging method in predicting surgical resectability in patients with pancreatic or periampullary tumors. SUMMARY BACKGROUND DATA: Despite progress in imaging techniques, accurate staging and correct prediction of resectability remains one of the chief problems in the management of pancreatic tumors. Staging algorithms designed to separate operable from inoperable patients to save the latter an unnecessary laparotomy are becoming increasingly complex, expensive, time-consuming, invasive, and not without risks for the patient. METHODS: Between August 1996 and February 1997, 58 consecutive patients referred for operation of a pancreatic or periampullary tumor were examined clinically and by 5 staging methods: 1) percutaneous ultrasonography (US); 2) ultrafast magnetic resonance imaging (UMRI); 3) dual-phase helical computed tomography (CT); 4) selective visceral angiography; and 5) endoscopic cholangiopancreatography (ERCP). The assessment of resectability by each procedure was verified by surgical exploration and histologic examination. RESULTS: The study comprised 40 male and 18 female patients with a median age of 63 years. Thirty-five lesions were located in the pancreatic head (60%), 11 in the body (19%), and 1 in the tail of the gland (2%); there were 9 tumors of the ampulla (16%) and 2 of the distal common duct (3%). All five staging methods were completed in 36 patients. For reasons ranging from metallic implants to contrast medium allergy or because investigations already had been performed elsewhere, US was completed in 57 (98%), UMRI in 54 (93%), CT in 49 (84%), angiography in 48 (83%), and ERCP in 49 (84%) of these 58 patients. Signs of unresectability found were vascular involvement in 22 (38%), extrapancreatic tumor spread in 16 (26%), liver metastases in 10 (17%), lymph node involvement in 6 (10%), and peritoneal nodules in only 2 patients (3%). These findings were collated with those of surgical exploration in 47 patients (81 %) and percutaneous biopsy in 5 (9%); such invasive verification was deemed unnecessary and therefore unethical in 6 clearly inoperable patients (10%). In assessing the four main signs of unresectability (extrapancreatic tumor spread, liver metastases, lymph node involvement, and vascular invasion), the overall accuracy of UMRI was 95.7%, 93.5%, 80.4%, as compared to 85.1%, 87.2%, 76.6% for US and 74.4%, 87.2%, 69.2% for CT. In assessing vascular invasion, the sensitivity, specificity, and overall accuracy of angiography were 42.9%, 100%, and 68.8%, respectively. There were 3 complications (12.5%) after 24 resections, 5 in 17 palliative procedures, and none after 6 explorations only. The hospital stay was 14 days after resection, 13 after palliative bypass, and 6 after exploration alone. There was no operative or hospital mortality in these 58 cases. CONCLUSIONS: Although it is by no means 100% accurate, UMRI is equal or even superior to all other staging methods. It probably will replace most of these, because it provides an "all-in-one" investigation avoiding endoscopy, vascular cannulation, allergic reactions, and x-radiation. But because even UMRI is not perfect, the final verdict on resectability of a tumor still will depend on surgical exploration in some cases. Images Figure 2. Figure 4. Figure 5. Figure 6. Figure 7. Figure 8. Figure 9. Figure 10. Figure 11. PMID:9351708
Microwave Dielectric Contrast Imaging in a Magnetic Resonant Environment and the Effect of using Magnetic Resonant Spatial Information in Image Reconstruction
Epstein, Neil R.; Golnabi, Amir H.; Meaney, Paul M.; Paulsen, Keith D.
Microwave Tomography (MT) can determine the permittivity and conductivity of a volume of interest; it has been shown that a contrast exists between these electrical properties in healthy and malignant tissues, and MT can be used to discern the dielectric contrast image of these tissues by recovering their electrical property values. Simulation and phantom experiments of objects with known spatial locations have shown that using boundary information derived from internal structures in the imaged volume greatly increases the accuracy of the recovered property values. In practice this spatial information, which will be used for reconstructing the tissue's electrical property images, must be determined with high enough resolution to segment boundary regions and internal structures of interest. This experiment investigates the use of Magnetic Resonant Imaging (MRI) in obtaining the desired spatial information used in mesh generation for image reconstruction and provides microwave image results comparing electrical properties recovered with and without this prior spatial information. PMID:22255643
Imaging instantaneous electron flow with ultrafast resonant x-ray scattering
Popova-Gorelova, Daria
We propose a novel way to image dynamical properties of nonstationary electron systems using ultrafast resonant x-ray scattering. Employing a rigorous theoretical analysis within the framework of quantum electrodynamics, we demonstrate that a single scattering pattern from a nonstationary electron system encodes the instantaneous interatomic electron current in addition to the structural information usually obtained by resonant x-ray scattering from stationary systems. Thus, inelastic contributions that are indistinguishable from elastic processes induced by a broadband probe pulse, instead of being a concern, serve as an advantage for time-resolved resonant x-ray scattering. Thereby, we propose an approach combining elastic and inelastic resonant x-ray scattering for imaging dynamics of nonstationary electron systems in both real space and real time. In order to illustrate its power, we show how it can be applied to image the electron hole current in an ionized diatomic molecule.
Imaging instantaneous electron flow with ultrafast resonant x-ray scattering
NASA Astrophysics Data System (ADS)
Popova-Gorelova, Daria; Santra, Robin
We propose a way to image dynamical properties of nonstationary electron systems using ultrafast resonant x-ray scattering. Employing a rigorous theoretical analysis within the framework of quantum electrodynamics, we demonstrate that a single scattering pattern from a nonstationary electron system encodes the instantaneous interatomic electron current in addition to the structural information usually obtained by resonant x-ray scattering from stationary systems. Thus, inelastic contributions that are indistinguishable from elastic processes induced by a broadband probe pulse, instead of being a concern, serve as an advantage for time-resolved resonant x-ray scattering. Thereby, we propose an approach combining elastic and inelastic resonant x-ray scattering for imaging dynamics of nonstationary electron systems in both real space and real time. In order to illustrate its power, we show how it can be applied to image the electron-hole current in an ionized diatomic molecule.
Far-field subwavelength imaging with near-field resonant metalens scanning at microwave frequencies
Wang, Ren; Wang, Bing-Zhong; Gong, Zhi-Shuang; Ding, Xiao
A method for far-field subwavelength imaging at microwave frequencies using near-field resonant metalens scanning is proposed. The resonant metalens is composed of switchable split-ring resonators (SRRs). The on-SRR has a strong magnetic coupling ability and can convert evanescent waves into propagating waves using the localized resonant modes. In contrast, the off-SRR cannot achieve an effective conversion. By changing the switch status of each cell, we can obtain position information regarding the subwavelength source targets from the far field. Because the spatial response and Green's function do not need to be measured and evaluated and only a narrow frequency band is required for the entire imaging process, this method is convenient and adaptable to various environment. This method can be used for many applications, such as subwavelength imaging, detection, and electromagnetic monitoring, in both free space and complex environments. PMID:26053074
Far-field subwavelength imaging with near-field resonant metalens scanning at microwave frequencies.
Wang, Ren; Wang, Bing-Zhong; Gong, Zhi-Shuang; Ding, Xiao
A method for far-field subwavelength imaging at microwave frequencies using near-field resonant metalens scanning is proposed. The resonant metalens is composed of switchable split-ring resonators (SRRs). The on-SRR has a strong magnetic coupling ability and can convert evanescent waves into propagating waves using the localized resonant modes. In contrast, the off-SRR cannot achieve an effective conversion. By changing the switch status of each cell, we can obtain position information regarding the subwavelength source targets from the far field. Because the spatial response and Green's function do not need to be measured and evaluated and only a narrow frequency band is required for the entire imaging process, this method is convenient and adaptable to various environment. This method can be used for many applications, such as subwavelength imaging, detection, and electromagnetic monitoring, in both free space and complex environments. PMID:26053074
Dynamic friction-force microscopy using fractional-resonance excitation: Image contrast of graphite surface defects
NASA Astrophysics Data System (ADS)
Mertens, F.; Göddenhenrich, T.; Lushta, V.; Schirmeisen, A.
Dynamic friction-force microscopy with fractional-resonance excitation is used to analyze defect structures on graphite. The sample is modulated laterally at one third of the resonance of the cantilever in contact with the surface. Nonlinear tip-sample interactions then lead to cantilever oscillations at resonance, the amplitude of which is recorded as the dynamic friction signal during scanning. We show that this method is extremely sensitive to subtle surface defects, allowing direct imaging of grain boundaries. In order to understand the image contrast mechanism, we compare the dynamic friction signal to simulations for different surface defects. Further, the complete resonance behavior of the cantilever is analyzed using a fast band excitation scheme. We find that the surface elasticity plays an important role for the image contrast formation.
Surface Plasmon Resonance of Nanoparticles and Applications in Imaging
Habib Ammari; Youjun Deng; Pierre Millien
In this paper we provide a mathematical framework for localized plasmon resonance of nanoparticles. Using layer potential techniques associated with the full Maxwell equations, we derive small-volume expansions for the electromagnetic fields, which are uniformly valid with respect to the nanoparticle's bulk electron relaxation rate. Then, we discuss the scattering and absorption enhancements by plasmon resonant nanoparticles. We study both the cases of a single and multiple nanoparticles. We present numerical simulations of the localized surface plasmonic resonances associated to multiple particles in terms of their separation distance.
Fast Magnetic Resonance Imaging via Adaptive Broadband Encoding of the MR Signal Content
Dimitris Mitsouras; Frank J. Rybicki; Alan Edelman; Gary P. Zientara
Our goal is to increase the time-efficiency of contin- uous data acquisition in Magnetic Resonance Imaging. In order to realize this increase in efficiency, we follow the proposition of extending the applicability of the physics that MR imaging is based on. That is, the MR signal may be partially encoded at the excitation step. In so doing, we create a
Burkhard A. Prause
Abstract by Burkhard A. Prause The rate of growth of individual bubbles in three-dimensional liquid foams (and crystallites in polycrystalline metals) is a major unsolved problem in mate- rial science. We have used Magnetic Resonance Imaging (MRI) to observe non- destructively thestructure ofdisordered liquid foams. Volumetricimaging ofcoars- ening foams required a robust imaging method with sucient spatial and temporal resolution
Nuclear magnetic resonance imaging. (Latest citations from the US Patent database). Published Search
Not Available
The bibliography contains citations of selected patents concerning imaging systems and components used in nuclear magnetic resonance (NMR) devices. Data acquisition methods and applications in fluid flow are presented. Magnet systems used in the imaging process are briefly cited. (Contains a minimum of 159 citations and includes a subject term index and title list.)
Functional Imaging of Plants: A Nuclear Magnetic Resonance Study of a Cucumber Plant
Tom Scheenen; Anneriet Heemskerk; Andrie de Jager; Frank Vergeldt; Henk Van As
Functional magnetic resonance imaging was used to study transients of biophysical parameters in a cucumber plant in response to environmental changes. Detailed flow imaging experiments showed the location of xylem and phloem in the stem and the response of the following flow characteristics to the imposed environmental changes: the total amount of water, the amount of stationary and flowing water,
3D kinematics of the tarsal joints from magnetic resonance images
Bruce E. Hirsch; Jayaram K. Udupa; Enyi Okereke; Howard J. Hillstrom; Sorin Siegler; Stacie I. Ringleb; Carl W. Imhauser
We have developed a method for analyzing motion at skeletal joints based on the 3D reconstruction of magnetic resonance (MR) image data. Since the information about each voxel in MR images includes its location in the scanner, it follows that information is available for each organ whose 3D surface is computed from a series of MR slices. In addition, there
A novel, cylindrical, transverse gradient coil design for magnetic resonance imaging of large samples
S. Di Luzio; G. Placidi; S. Di Giuseppe; M. Alecci; A. Sotgiu
Magnetic resonance imaging (MRI) requires the use of three sets of coils to produce magnetic field gradients, one for each axis, to encode three-dimensional information. The magnetic field generated by gradient coils has to change as linearly as possible with distance so as to avoid heavy distortion of the resulting image of the sample. The reduction of the dimensions of
A Functional Magnetic Resonance Imaging Study of Tic Suppression in Tourette Syndrome
Bradley S. Peterson; Pawel Skudlarski; Adam W. Anderson; Heping Zhang; J. Chris Gatenby; Cheryl M. Lacadie; James F. Leckman; John C. Gore
Background: The inability to inhibit unwanted behav- iors and impulses produces functional debility in a broad range of neuropsychiatric disorders. A potentially im- portant model of impulse control is volitional tic sup- pression in Tourette syndrome. Methods: Tic suppression was studied in 22 adult subjects with Tourette syndrome by using functional magnetic resonance imaging. Images acquired during periods of voluntary
Dynamic magnetic resonance imaging of human brain activity during primary sensory stimulation
Kenneth K. Kwong; J. W. Belliveau; D. A. Chesler; I. E. Goldberg; R. M. Weisskoff; B. P. Poncelet; D. N. Kennedy; B. E. Hoppel; M. S. Cohen; Robert Turner
Neuronal activity causes local changes in cerebral blood flow, blood volume, and blood oxygenation. Magnetic resonance imaging (MRI) techniques sensitive to changes in cerebral blood flow and blood oxygenation were developed by high-speed echo planar imaging. These techniques were used to obtain completely noninvasive tomographic maps of human brain activity, by using visual and motor stimulus paradigms. Changes in blood
Oxygenation-sensitive contrast in magnetic resonance image of rodent brain at high magnetic fields
S. Ogawa; T. M. Lee; A. S. Nayak; P. Glynn
At high magnetic fields (7 and 8.4 T), water proton magnetic resonance images of brains of live mice and rats under pentobarbital anesthetization have been measured by a gradient echo pulse sequence with a spatial resolution of 65 x 65-microns pixel size and 700-microns slice thickness. The contrast in these images depicts anatomical details of the brain by numerous dark
Long time echo STIR sequence magnetic resonance imaging of optic nerves in optic neuritis
A. Tartaro; M. Onofrj; C. Delli Pizzi; L. Bonomo; A. Thomas; T. Fulgente; D. Gambi
Magnetic resonance images of optic nerves were obtained in 20 patients with acute optic neuritis (ON), and assessed by means of clinical, visual field and visual evoked potential evaluations; the imaging was repeated 1 year later. The results of the conventional Short Tau Inversion Recovery (STIR) sequence obtained using short time echo (STE-STIR: 22 msec) were compared with those of
Magnetic resonance imaging for the in vivo determination of body composition in animal science
U. Baulain
Magnetic resonance imaging (MRI) is a diagnostic tool, originally developed for human medicine. It generates cross-sectional images of nearly all parts of the body with a high contrast between soft tissues. In animal science it has been utilized predominantly as an in vivo technique for the determination of body composition. The process of scanning live animals and especially the choice
The Ill-Posed Problem and Regularization in Parallel Magnetic Resonance Imaging
XiaoFang Liu; WenLong Xu; XiuZi Ye
From a linear algebra point of view, the article has studied the ill-posed problems in parallel magnetic resonance imaging (MRI), and posed its influences on the final reconstructed image. Consequently, the article proposed the regularization methods in parallel MRI, and also by g-factor the article has compared the regularized parallel MRI with the conventional reconstruction. In the result, the article
High incidence and spontaneous resolution of mastoid effusion after craniotomy on early postoperative magnetic resonance images
T. Watanabe; N. Saito; N. Sato; A. Takahashi; H. Fujimaki; M. Tosaka; T. Sasaki
Mastoid effusion is a poorly understood complication after craniotomy. The incidence and severity of postoperative mastoid effusion were retrospectively examined on postoperative magnetic resonance (MR) images to assess any association with craniotomy procedures, time course, and neuro-otological complications. We evaluated the early postoperative MR images (within 4 days of craniotomy) and medical records of 74 patients who underwent 77 operations for
Magnetic resonance imaging of perfusion diffusion mismatch in rodent and non-human
Duong, Timothy Q.
with energy failure and breakdown of membrane potential in animal models.1012 The reduction in cerebral blood coefficient, Cerebral blood flow, Diffusion-weighted imaging, Perfusion-weighted imaging, Experimental stroke model, Rodents, Oxygen challenge, Predictive mode, Rats, Hyperperfusion, Functional magnetic resonance
Recent advances of in vivo magnetic resonance imaging with laser-polarized noble gases
R. C. Welsh; T. E. Chupp; K. P. Coulter; M. S. Rosen; S. D. Swanson
The field of polarization-based magnetic resonance imaging has expanded rapidly in the past few years. Realization of this new modality of medical imaging is dependent upon the production of large quantities of noble gas. Additionally the noble gas must be delivered to the subject in controlled and efficient manner. The process of delivery must also preserve a large fraction of
Elucidating Structure and Function In Vivo With Hybrid Fluorescence and Magnetic Resonance Imaging
Mark Niedre; Vasilis Ntziachristos
While the mathematics, physics, and technology behind magnetic resonance (MR) and fluorescence image formation are distinctively different, the two modalities have significant complementary features to impart strong preclinical and clinical application synergies. Traditionally, hybrid MR and fluorescence imaging implied the use of a system where optical and MR signals can be concurrently acquired. In this case, the common geometry allows
Blood-flow magnetic resonance imaging of the retina Yingxia Li,a,1
Duong, Timothy Q.
Blood-flow magnetic resonance imaging of the retina Yingxia Li,a,1 Haiying Cheng,a,1 and Timothy Q 1 November 2007 This study describes a novel MRI application to image basal blood flow, physiologically induced blood-flow changes, and the effects of isoflurane concentration on blood flow
Effect of 1. 5 tesla nuclear magnetic resonance imaging scanner on implanted permanent pacemakers
David L. Hayes; David R. Holmes Jr.; Joel E. Gray
Patients with a permanent pacemaker are currently restricted from diagnostic nuclear magnetic resonance (NMR) imaging because of potential adverse effects on the pacemaker by the magnet. Previous work has shown that NMR imaging will result in asynchronous pacing of the pulse generator within a given distance of the magnet. The radiofrequency signal generated by the system may also result in
Focus on Diffusion MR Investigations of Musculoskeletal Tissue to Improve Osteoporosis Diagnosis: A Brief Practical Review
Capuani, Silvia; Manenti, Guglielmo; Tarantino, Umberto
Nowadays, a huge number of papers have documented the ability of diffusion magnetic resonance imaging (D-MRI) to highlight normal and pathological conditions in a variety of cerebral, abdominal, and cardiovascular applications. To date, however, the role of D-MRI to investigate musculoskeletal tissue, specifically the cancellous bone, has not been extensively explored. In order to determine potentially useful applications of diffusion techniques in musculoskeletal investigation, D-MRI applications to detect osteoporosis disease were reviewed and further explained. PMID:25861652
Magnetic resonance imaging of the presumed normal canine adrenal glands.
Llabres-Diaz, Francisco J; Dennis, Ruth
Forty-three dogs without evidence of endocrine disease that underwent spinal or abdominal magnetic resonance imaging (MRI) for clinical reasons were studied. Because the procedures were not optimized for inclusion of the adrenal glands, they were not always visible in all planes. Eighty-five of the 86 adrenal glands were seen and only the left gland in a 6-month-old Irish wolfhound could not be found. The right adrenal gland lay cranial to the left in all of the animals in which both glands were seen. The best landmarks for localization of the glands were vascular; both adrenal glands were always cranial to the ipsilateral renal vessels and in the region of the celiac and cranial mesenteric arteries. Various measurements were made on all the available scan planes. In some dogs the whole adrenal gland was difficult to visualize clearly, and this hindered the measuring process, especially when the right adrenal gland was in close contact with the caudal vena cava. The adrenal glands were mainly linear in shape but also had a variable degree of modification of their poles, especially the cranial pole of the right adrenal gland, which tended to be consistently wider and to present different shapes (rounded, arrowhead, inverted P, hook-shaped, triangular, or dome-shaped). Two main patterns of signal intensity were seen on fast spin echo (FSE) sequences (T2-weighted, T1-weighted, and T1-weighted after administration of a paramagnetic contrast medium): homogeneous and hypointense to surroundings or a corticomedullary type pattern with a hyperintense central area surrounded by a hypointense rim of tissue. The outline of the left adrenal gland was always very clear. The clarity of outline of the right adrenal gland was more variable, especially if it was in contact with the liver or the caudal vena cava. It was felt that the amount of retroperitoneal fat was not as important as stated in the human literature for visualization of the adrenal glands and that with an appropriate selection of scan planes and pulse sequences good assessment of the adrenal glands can be performed with MRI in canine patients. PMID:12620044
Graph-partitioned spatial priors for functional magnetic resonance images
Harrison, LM; Penny, W; Flandin, G; Ruff, CC; Weiskopf, N; Friston, KJ
Spatial models of functional magnetic resonance imaging (fMRI) data allow one to estimate the spatial smoothness of general linear model (GLM) parameters and eschew pre-process smoothing of data entailed by conventional mass-univariate analyses. Recently diffusion-based spatial priors (Harrison et al., 2008) were proposed, which provide a way to formulate an adaptive spatial basis, where the diffusion kernel of a weighted graph-Laplacian (WGL) is used as the prior covariance matrix over GLM parameters. An advantage of these is that they can be used to relax the assumption of isotropy and stationarity implicit in smoothing data with a fixed Gaussian kernel. The limitation of diffusion-based models is purely computational, due to the large number of voxels in a brain volume. One solution is to partition a brain volume into slices, using a spatial model for each slice. This reduces computational burden by approximating the full WGL with a block diagonal form, where each block can be analysed separately. While fMRI data are collected in slices, the functional structures exhibiting spatial coherence and continuity are generally three-dimensional, calling for a more informed partition. We address this using the graph-Laplacian to divide a brain volume into sub-graphs, whose shape can be arbitrary. Their shape depends crucially on edge weights of the graph, which can be based on the Euclidean distance between voxels (isotropic) or on GLM parameters (anisotropic) encoding functional responses. The result is an approximation the full WGL that retains its 3D form and also has potential for parallelism. We applied the method to high-resolution (1mm3) fMRI data and compared models where a volume was divided into either slices or graph-partitions. Models were optimized using Expectation-Maximization and the approximate log-evidence computed to compare these different ways to partition a spatial prior. The real high-resolution fMRI data presented here had greatest evidence for the graph partitioned anisotropic model, which was best able to preserve fine functional detail. PMID:18790064
Magnetic Resonance Imaging–guided Volumetric Ablation of Symptomatic Leiomyomata: Correlation of Imaging with Histology
Venkatesan, Aradhana M.; Partanen, Ari; Pulanic, Tajana Klepac; Dreher, Matthew R.; Fischer, John; Zurawin, Robert K.; Muthupillai, Raja; Sokka, Sham; Nieminen, Heikki J.; Sinaii, Ninet; Merino, Maria; Wood, Bradford J.; Stratton, Pamela
Purpose To describe the preliminary safety and accuracy of a magnetic resonance (MR) imaging– guided high-intensity–focused ultrasound (HIFU) system employing new technical developments, including ablation control via volumetric thermal feedback, for the treatment of uterine leiomyomata with histopathologic correlation. Materials and Methods In this phase I clinical trial, 11 women underwent MR-guided HIFU ablation (Sonalleve 1.5T; Philips Medical Systems, Vantaa, Finland), followed by hysterectomy within 30 days. Adverse events, imaging findings, and pathologic confirmation of ablation were assessed. The relationship between MR imaging findings, thermal dose estimates, and pathology and HIFU spatial accuracy were assessed using Bland-Altman analyses and intraclass correlations. Results There were 12 leiomyomata treated. No serious adverse events were observed. Two subjects decided against having hysterectomy and withdrew from the study before surgery. Of 11 women, 9 underwent hysterectomy; all leiomyomata demonstrated treatment in the expected location. A mean ablation volume of 6.92 cm3 ± 10.7 was observed at histopathologic examination. No significant differences between MR imaging nonperfused volumes, thermal dose estimates, and histopathology ablation volumes were observed (P > .05). Mean misregistration values perpendicular to the ultrasound beam axis were 0.8 mm ± 1.2 in feet-head direction and 0.1 mm ± 1.0 in and left-right direction and ?0.7 mm ± 3.1 along the axis. Conclusions Safe, accurate ablation of uterine leiomyomata was achieved with an MR-guided HIFU system with novel treatment monitoring capabilities, including ablation control via volumetric thermal feedback. PMID:22626269
Magnetic resonance imaging of amyloid plaques in transgenic mouse models of Alzheimer's disease
Chamberlain, Ryan; Wengenack, Thomas M.; Poduslo, Joseph F.; Garwood, Michael; Jack, Clifford R.
A major objective in the treatment of Alzheimer's disease is amyloid plaque reduction. Transgenic mouse models of Alzheimer's disease provide a controlled and consistent environment for studying amyloid plaque deposition in Alzheimer's disease. Magnetic resonance imaging is an attractive tool for longitudinal studies because it offers non-invasive monitoring of amyloid plaques. Recent studies have demonstrated the ability of magnetic resonance imaging to detect individual plaques in living mice. This review discusses the mouse models, MR pulse sequences, and parameters that have been used to image plaques and how they can be optimized for future studies. PMID:21499442
Magnetic resonance imaging of severely disturbed children--a preliminary study.
Hendren, R L; Hodde-Vargas, J E; Vargas, L A; Orrison, W W; Dell, L
This study investigates the relationship between brain pathology and psychiatric disturbance in 37 psychiatric inpatients between 5 and 14 years of age referred for magnetic resonance imaging (MRI). Of 37 images, 13 were categorized as abnormal by neuroradiologists who were blind to the diagnoses of subjects. Three of six children with schizophrenia-related diagnoses had abnormal scans. In contrast, only one of 15 children with a primary disruptive behavior disorder diagnosis had an abnormal magnetic resonance image. A greater proportion of children with schizophrenia spectrum diagnoses had greater left than right frontal horns of the lateral ventricles than children with other diagnoses. PMID:2055885
A novel radio frequency coil for veterinary magnetic resonance imaging system
NASA Astrophysics Data System (ADS)
Meng, Bin; Huang, Kai-Wen; Wang, Wei-Min
In this article, a novel designed radio frequency (RF) coil is designed and built for the imaging of puppies in a V-shape permanent magnetic resonance imaging (MRI) system. Two sets of Helmholtz coil pairs with a V-shape structure are used to improve the holding of an animal in the coil. The homogeneity and the sensitivity of the RF field in the coil are analysed by theoretical calculation. The size and the shape of the new coil are optimized and validated by simulation through using the finite element method (FEM). Good magnetic resonance (MR) images are achieved on a shepherd dog.
Assessment of coronary artery stenosis by magnetic resonance imaging
D. J. Pennell; H. G. Bogren; J. Keegan; D. N. Firmin; S. R. Underwood
OBJECTIVE: The findings of magnetic resonance and x-ray angiography were compared for assessment of coronary artery stenosis in this validation study. BACKGROUND: Magnetic resonance angiography of the coronary arteries has recently been described, but there has been no comparison with x-ray angiography of localisation or assessment of important characteristics of coronary stenosis. METHODS: A breath hold, segmented k-space, 2D gradient
Nanoscale confined mode ferromagnetic resonance imaging of an individual Ni81Fe19 disk using magnetic resonance force microscopy (invited)
NASA Astrophysics Data System (ADS)
Lee, Inhee; Obukhov, Yuri; Hauser, A. J.; Yang, F. Y.; Pelekhov, Denis V.; Hammel, P. Chris
We demonstrate and characterize the localized Ferromagnetic Resonance (FMR) modes created in an individual micron-sized Ni81Fe19 disk by means of a strong inhomogeneous probe field applied anti-parallel to the saturated magnetization of the sample. Our variational calculation accurately predicts the frequencies of the localized modes in FMR spectra, and characterizes the sizes and all related internal magnetic fields of the Bessel function modes in a simple model analogous to particle wavefunctions in a quantum well. The localized modes enable FMR imaging of the nonuniform demagnetizing field inside a Py disk demonstrating a novel magnetic resonance imaging technique able to map internal fields in ferromagnets with spectroscopic accuracy.
Imaging of Nitroxides at 250 MHz using Rapid-Scan Electron Paramagnetic Resonance
Biller, Joshua R.; Tseitlin, Mark; Quine, Richard W.; Rinard, George A.; Weismiller, Hilary A.; Elajaili, Hanan; Rosen, Gerald M.; Kao, Joseph P. Y.; Eaton, Sandra S.; Eaton, Gareth R.
Projections for 2D spectral-spatial images were obtained by continuous wave and rapid-scan electron paramagnetic resonance using a bimodal cross-loop resonator at 251 MHz. The phantom consisted of three 4 mm tubes containing different 15N,2H-substituted nitroxides. Rapid-scan and continuous wave images were obtained with 5 min total acquisition times. For comparison, images also were obtained with 29 s acquisition time for rapid scan and 15 min for continuous wave. Relative to continuous wave projections obtained for the same data acquisition time, rapid-scan projections had significantly less low-frequency noise and substantially higher signal-to-noise at higher gradients. Because of the improved image quality for the same data acquisition time, linewidths could be determined more accurately from the rapid-scan images than from the continuous wave images. PMID:24650729
Schistosomal myelopathy in childhood: findings of magnetic resonance imaging in 26 patients.
Henriques-Souza, Adélia Maria de Miranda; Valença, Marcelo Moraes
We describe magnetic resonance image findings of 26 children (16 boys; average age, 9.4 years) with schistosomal myelopathy. All children lived in Pernambuco State, Brazil, an area of endemic mansoni schistosomiasis. Imaging abnormalities were identified in 92.3% of the children. The most frequent findings included: (1) enlargement of the spinal cord at the thoracic level, usually below T(8), in 23/24 (96%) patients; (2) hypointense signals in T(1)-weighted imaging; (3) hyperintense signals in T(2) imaging; and (4) heterogeneous enhancement with gadolinium. Although enlargement was evident at the thoracic level, abnormal signals frequently extended to the lower cervical level, or inferiorly to the lumbar and sacral cord. Magnetic resonance imaging of the spinal cord can play a strong role in the investigation of children with schistosomal myelopathy. Although imaging abnormalities are not specific, their presence strengthens presumptive diagnoses, to expedite treatment and avoid invasive procedures. PMID:22114998
Wavelet smoothing of functional magnetic resonance images: A ...
surements and hence have high resolution and low noise, fMRI images, which are not fused, are typically of low ... maximum magnitude is assigned 255 grey levels. ... image pixels have more power than tests on the magnitude alone.
Bioengineering/Radiology 278: Magnetic Resonance Imaging Laboratory Winter 2012
California at San Diego, University of
imaging Motion artifact 4 RF pulses Design and test an RF pulse Spatial-Spectral Pulses 5 Echo Planar Imaging Echo Planar Imaging 6 Echo formation Spin echoes Gradient echoes Generate an interferogram Frequency dependence of balanced SSFP 7 Multidimensional pulses 2D pulse coding 2D pulses 8 RF Coils (b) RF
A brief review of parallel magnetic resonance imaging
Robin M. Heidemann; Özkan Özsarlak; Paul M. Parizel; Johan Michiels; Berthold Kiefer; Vladimir Jellus; Mathias Müller; Felix Breuer; Martin Blaimer; Mark A. Griswold; Peter M. Jakob
Since the 1980s, the implementation of fast imaging methods and dedicated hardware for MRI scanners has reduced the image acquisition time from nearly an hour down to several seconds and has therefore enabled a widespread use of MRI in clinical diagnosis. Since this development, the greatest incremental gain in imaging speed has been provided by the development of parallel MRI
Magnetic Resonance Imaging of Temperature Changes During Interstitial Microwave Heating: A Phantom Study
I. A. Vitkina; J. A. Moriarty; R. D. Peters; Michael C Kolios; A. S. Gladman; J. C. Chen; R. S. Hinks; J. W. Hunt; B. C. Wilson; A. C. Easty; M. J. Bronskill; W. Kucharczyk; M. D. Sherar; R. M. Henkelman
Changes in magnetic resonance (MR) signals during interstitial microwave heating are reported, and correlated with simultaneously acquired temperature readings from three fiber-optic probes implanted in a polyacrylamide gel phantom. The heating by a MR-compatible microwave antenna did not interfere with simultaneous MR image data acquisition. MR phase-difference images were obtained using a fast two-dimensional-gradient echo sequence. From these images the
Reconstruction of Cardiac Ventricular Geometry and Fiber Orientation Using Magnetic Resonance Imaging
D. F. Scollan; A. Holmes; J. Zhang; R. L. Winslow
An imaging method for the rapid reconstruction of fiber orientation throughout the cardiac ventricles is described. In this method, gradient-recalled acquisition in the steady-state (GRASS) imaging is used to measure ventricular geometry in formaldehyde-fixed hearts at high spatial resolution. Diffusion-tensor magnetic resonance imaging (DTMRI) is then used to estimate fiber orientation as the principle eigenvector of the diffusion tensor measured
Dynamic Mapping of the Human Visual Cortex by High-Speed Magnetic Resonance Imaging
Andrew M. Blamire; Seiji Ogawa; Kamil Ugurbil; Douglas Rothman; Gregory McCarthy; Jutta M. Ellermann; Fahmeed Hyder; Zachary Rattner; Robert G. Schulman
We report the use of high-speed magnetic resonance imaging to follow the changes in image intensity in the human visual cortex during stimulation by a flashing checkerboard stimulus. Measurements were made in a 2.1-T, 1-m-diameter magnet, part of a Bruker Biospec spectrometer that we had programmed to do echo-planar imaging. A 15-cm-diameter surface coil was used to transmit and receive
Intraventricular mass lesions at magnetic resonance imaging: iconographic essay - part 2*
de Castro, Felipe Damásio; Reis, Fabiano; Guerra, José Guilherme Giocondo
The present essay is illustrated with magnetic resonance images obtained at the authors' institution over the past 15 years and discusses the main imaging findings of intraventricular tumor-like lesions (colloid cyst, oligodendroglioma, astroblastoma, lipoma, cavernoma) and of inflammatory/infectious lesions (neurocysticercosis and an atypical presentation of neurohistoplasmosis). Such lesions represent a subgroup of intracranial lesions with unique characteristics and some imaging patterns that may facilitate the differential diagnosis. PMID:25741092
Characterization of tumor microvascular structure and permeability: comparison between magnetic resonance imaging and intravital confocal imaging
NASA Astrophysics Data System (ADS)
Reitan, Nina Kristine; Thuen, Marte; Goa, Pa?L. Erik; de Lange Davies, Catharina
Solid tumors are characterized by abnormal blood vessel organization, structure, and function. These abnormalities give rise to enhanced vascular permeability and may predict therapeutic responses. The permeability and architecture of the microvasculature in human osteosarcoma tumors growing in dorsal window chambers in athymic mice were measured by confocal laser scanning microscopy (CLSM) and dynamic contrast enhanced magnetic resonance imaging (DCE-MRI). Dextran (40 kDa) and Gadomer were used as molecular tracers for CLSM and DCE-MRI, respectively. A significant correlation was found between permeability indicators. The extravasation rate Ki as measured by CLSM correlated positively with DCE-MRI parameters, such as the volume transfer constant Ktrans and the initial slope of the contrast agent concentration-time curve. This demonstrates that these two techniques give complementary information. Extravasation was further related to microvascular structure and was found to correlate with the fractal dimension and vascular density. The structural parameter values that were obtained from CLSM images were higher for abnormal tumor vasculature than for normal vessels.
Acoustic subwavelength imaging of subsurface objects with acoustic resonant metalens
Cheng, Ying; Liu, XiaoJun, E-mail: firstname.lastname@example.com [Key Laboratory of Modern Acoustics, Nanjing University, Nanjing 210093 (China) [Key Laboratory of Modern Acoustics, Nanjing University, Nanjing 210093 (China); State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190 (China); Zhou, Chen; Wei, Qi; Wu, DaJian [Key Laboratory of Modern Acoustics, Nanjing University, Nanjing 210093 (China)] [Key Laboratory of Modern Acoustics, Nanjing University, Nanjing 210093 (China)
Early research into acoustic metamaterials has shown the possibility of achieving subwavelength near-field acoustic imaging. However, a major restriction of acoustic metamaterials is that the imaging objects must be placed in close vicinity of the devices. Here, we present an approach for acoustic imaging of subsurface objects far below the diffraction limit. An acoustic metalens made of holey-structured metamaterials is used to magnify evanescent waves, which can rebuild an image at the central plane. Without changing the physical structure of the metalens, our proposed approach can image objects located at certain distances from the input surface, which provides subsurface signatures of the objects with subwavelength spatial resolution.
Dual-Enzyme-Loaded Multifunctional Hybrid Nanogel System for Pathological Responsive Ultrasound Imaging and T2-Weighted Magnetic Resonance Imaging.
Wang, Xia; Niu, Dechao; Li, Pei; Wu, Qing; Bo, Xiaowan; Liu, Boji; Bao, Song; Su, Teng; Xu, Huixiong; Wang, Qigang
A dual-enzyme-loaded multifunctional hybrid nanogel probe (SPIO@GCS/acryl/biotin-CAT/SOD-gel, or SGC) has been developed for dual-modality pathological responsive ultrasound (US) imaging and enhanced T2-weighted magnetic resonance (MR) imaging. This probe is composed of functionalized superparamagnetic iron oxide particles, a dual enzyme species (catalase and superoxide dismutase), and a polysaccharide cationic polymer glycol chitosan gel. The dual-modality US/MR imaging capabilities of the hybrid nanogel for responsive US imaging and enhanced T2-weighted MR imaging have been evaluated both in vitro and in vivo. These results show that the hybrid nanogel SGC can exhibit efficient dual-enzyme biocatalysis with pathological species for responsive US imaging. SGC also demonstrates increased accumulation in acidic environments for enhanced T2-weighted MR imaging. Further research on these nanogel systems may lead to the development of more efficient US/MR contrast agents. PMID:26035730
Magnetic resonance imaging susceptibility artifact due to pigmented intraorbital silicone prosthesis.
Dees, D Dustin; Knollinger, Amy M; Simmons, Jeffery P; Seshadri, Ravi; MacLaren, Nicole E
Magnetic resonance imaging (MRI) findings of two cases with intracranial disease and pigmented intraorbital prosthetics are presented. A brown prosthetic (Case 1) caused a significant magnetic susceptibility artifact, which necessitated removal to properly image the brain. The artifact observed on MRI images is likely due to ferromagnetic pigments used for coloring. A black prosthetic (Case 2) caused no imaging artifact. The carbon-based pigments used to color the black prosthetic implant do not appear to cause imaging artifact. The pigments currently used to color the brown pigmented orbital prostheses cause significant magnetic susceptibility artifact and may require removal to evaluate the brain and surrounding structures completely. PMID:22243647
Design for the optimal arrangement of magnetic resonance images on PACS monitors
NASA Astrophysics Data System (ADS)
Strickland, Nicola H.; Allison, David J.; Deshaies, Marc J.
A default display protocol (DDP) has been designed for reading magnetic resonance (MR) images on PACS workstations. This MR DDP is very flexible allowing any MR series from the current or previous studies to be simultaneously viewed and juxtaposed for direct comparison. There is a choice of image display format, selected by the radiologist from an icon bar, comprising four linked image series stacks, two linked image series tile clusters and linked tile mode. The selection and resultant monitor display arrangement is made by dragging and dropping token images into the chosen display format icon. The radiologist selects the best reversibly locked together so they can be scrolled in synchrony.
Making sense of real-time functional magnetic resonance imaging (rtfMRI) and rtfMRI neurofeedback.
Brühl, Annette B
This review explains the mechanism of functional magnetic resonance imaging in general and specifically introduces real-time functional magnetic resonance imaging as a method for training self-regulation of brain activity. Using real-time functional magnetic resonance imaging neurofeedback, participants can acquire control over their own brain activity. In patients with neuropsychiatric disorders, this control can potentially have therapeutic implications. In this review, the technical requirements are presented and potential applications and limitations are discussed. PMID:25716778
Quantitative Determination of Lateral Mode Dispersion in Film Bulk Acoustic Resonators through Laser Acoustic Imaging
Ken Telschow; John D. Larson III
Film Bulk Acoustic Resonators are useful for many signal processing applications. Detailed knowledge of their operation properties are needed to optimize their design for specific applications. The finite size of these resonators precludes their use in single acoustic modes; rather, multiple wave modes, such as, lateral wave modes are always excited concurrently. In order to determine the contributions of these modes, we have been using a newly developed full-field laser acoustic imaging approach to directly measure their amplitude and phase throughout the resonator. This paper describes new results comparing modeling of both elastic and piezoelectric effects in the active material with imaging measurement of all excited modes. Fourier transformation of the acoustic amplitude and phase displacement images provides a quantitative determination of excited mode amplitude and wavenumber at any frequency. Images combined at several frequencies form a direct visualization of lateral mode excitation and dispersion for the device under test allowing mode identification and comparison with predicted operational properties. Discussion and analysis are presented for modes near the first longitudinal thickness resonance (~900 MHz) in an AlN thin film resonator. Plate wave modeling, taking account of material crystalline orientation, elastic and piezoelectric properties and overlayer metallic films, will be discussed in relation to direct image measurements.
Initial experience of 3 tesla endorectal coil magnetic resonance imaging and 1H-spectroscopic imaging of the prostate
J. J. Fütterer; Tom W. J. Scheenen; Henkjan J. Huisman; Dennis W. J. Klomp; Ferdi A. van Dorsten; J Alfred Witjes; Arend Heerschap; Jelle O. Barentsz
RATIONALE AND OBJECTIVES: We sought to explore the feasibility of magnetic resonance imaging (MRI) of the prostate at 3T, with the knowledge of potential drawbacks of MRI at high field strengths. MATERIAL AND METHOD: MRI, dynamic MRI, and 1H-MR spectroscopic imaging were performed in 10 patients with prostate cancer on 1.5T and 3T whole-body scanners. Comparable scan protocols were used,
Visualizing Implanted Tumors in Mice with Magnetic Resonance Imaging Using Magnetotactic Bacteria
Benoit, Michael R.; Mayer, Dirk; Barak, Yoram; Chen, Ian Y.; Hu, Wei; Cheng, Zhen; Wang, Shan X.; Spielman, Daniel M.; Gambhir, Sanjiv S.; Matin, A.
Purpose To determine if magnetotactic bacteria can target tumors in mice and provide positive contrast for visualization using magnetic resonance imaging. Experimental Design The ability of the magnetotactic bacterium, Magnetospirillum magneticum AMB-1 (referred to from here as AMB-1), to confer positive magnetic resonance imaging contrast was determined in vitro and in vivo. For the latter studies, AMB-1 were injected either i.t. or i.v. Bacterial growth conditions were manipulated to produce small (~25-nm diameter) magnetite particles, which were observed using transmission electron microscopy. Tumor targeting was confirmed using 64Cu-labeled bacteria and positron emission tomography and by determination of viable cell counts recovered from different organs and the tumor. Results We show that AMB-1 bacteria with small magnetite particles generate T1-weighted positive contrast, enhancing in vivo visualization by magnetic resonance imaging. Following i.v. injection of 64Cu-labeled AMB-1, positron emission tomography imaging revealed increasing colonization of tumors and decreasing infection of organs after 4 hours. Viable cell counts showed that, by day 6, the bacteria had colonized tumors but were cleared completely from other organs. Magnetic resonance imaging showed a 1.22-fold (P = 0.003) increased positive contrast in tumors on day 2 and a 1.39-fold increase (P = 0.0007) on day 6. Conclusion Magnetotactic bacteria can produce positive magnetic resonance imaging contrast and colonize mouse tumor xenografts, providing a potential tool for improved magnetic resonance imaging visualization in preclinical and translational studies to track cancer. PMID:19671860
Multimodal imaging of human cerebellum - merging X-ray phase microtomography, magnetic resonance microscopy and histology
Schulz, Georg; Waschkies, Conny; Pfeiffer, Franz; Zanette, Irene; Weitkamp, Timm; David, Christian; Müller, Bert
Imaging modalities including magnetic resonance imaging and X-ray computed tomography are established methods in daily clinical diagnosis of human brain. Clinical equipment does not provide sufficient spatial resolution to obtain morphological information on the cellular level, essential for applying minimally or non-invasive surgical interventions. Therefore, generic data with lateral sub-micrometer resolution have been generated from histological slices post mortem. Sub-cellular spatial resolution, lost in the third dimension as a result of sectioning, is obtained using magnetic resonance microscopy and micro computed tomography. We demonstrate that for human cerebellum grating-based X-ray phase tomography shows complementary contrast to magnetic resonance microscopy and histology. In this study, the contrast-to-noise values of magnetic resonance microscopy and phase tomography were comparable whereas the spatial resolution in phase tomography is an order of magnitude better. The registered data with their complementary information permit the distinct segmentation of tissues within the human cerebellum. PMID:23145319
Magnetic resonance imaging without field cycling at less than earth's magnetic field
NASA Astrophysics Data System (ADS)
Lee, Seong-Joo; Shim, Jeong Hyun; Kim, Kiwoong; Yu, Kwon Kyu; Hwang, Seong-min
A strong pre-polarization field, usually tenths of a milli-tesla in magnitude, is used to increase the signal-to-noise ratio in ordinary superconducting quantum interference device-based nuclear magnetic resonance/magnetic resonance imaging experiments. Here, we introduce an experimental approach using two techniques to remove the need for the pre-polarization field. A dynamic nuclear polarization (DNP) technique enables us to measure an enhanced resonance signal. In combination with a ? / 2 pulse to avoid the Bloch-Siegert effect in a micro-tesla field, we obtained an enhanced magnetic resonance image by using DNP technique with a 34.5 ?T static external magnetic field without field cycling. In this approach, the problems of eddy current and flux trapping in the superconducting pickup coil, both due to the strong pre-polarization field, become negligible.