the search for atraumatic evaluation of tissue during surgery has led to the development of optical coherence tomography ( oct ) . an  optical biopsy  is a non - invasive method of providing anatomical and potentially histological evaluation through imaging . optical coherence tomography is an fda - approved portable imaging system ( figs .  1 and 2 ) that provides real time histologic imaging . the system is analogous to ultrasound , however uses infrared light rather than acoustical waves and , unlike ultrasound , does not require direct contact with tissue or a transducing medium . the infra - red light is backscattered from the patient s tissue , collected by the probe s fiber , and , combined with a reference signal , produces a high spatial resolution image of the tissue microstructure . it acquires real - time images with 200    200  pixels , 15-m depth resolution in free space ( 11  m in tissue ) , and 25  m lateral resolution . given that oct is fiber - optic based , it allows for easy integration with endoscopes and catheters . note the flexible oct probe placed on the endopelvic fascia using the robotic articulating graspers niris computer - based system with a laparoscopic probe niris probe in vivo during animal robotic prostate surgery . note the flexible oct probe placed on the endopelvic fascia using the robotic articulating graspers optical coherence tomography was first applied in ophthalmology where it was used initially for transparent tissues of the eye . since then , oct has expanded its role to include macular disease , retinal pathology and corneal abnormalities [ 1 , 2 ] . once oct established itself in imaging delicate tissue , further expansion of its armamentarium to include solid organs was justified . through technological modifications ,  optical biopsies  of organs including gastrointestinal , cardiovascular , respiratory , skin , nervous system , and male and female reproductive organs have been performed [ 37 ] . the first application of optical coherence tomography in urology occurred in 1997 when in - vitro imaging of bladder , prostate , ureteral biopsies and neurovascular bundles were compared to h and e staining . as the first comparative study , high - resolution cross - sectional imaging obtained from oct correlated well with the histological architecture of all the tissues sampled . in this review , we highlight current and future applications of optical coherence tomography in the field of urology . through a comprehensive computer - based medline search , mesh terms including optical coherence tomography and/or laparoscopy , robotic , surgery , urology , bladder , prostate , cancer , and endoscopy were applied . all papers relevant to the use of optical coherence tomography in urological practice and published in english were included , such as case reports , and prospective , retrospective , and randomized studies . basic science and animal research the remaining journals focus primarily in oct s role in the imaging characteristics of the prostate or prostate cancer . there is currently a solitary paper evaluating the use of optical coherence tomography in robotic urological practice . urothelial malignancies are detected more commonly at a superficial stage and , although not aggressive , pose a significant challenge in monitoring due to high recurrence rates . early detection and treatment of non - muscle invasive bladder cancer is paramount for bladder preservation and longevity . however , diagnostic cystoscopy may overlook unapparent tumors , or falsely interpret malignant lesions as benign . secondly , cystoscopy does not provide information on submucosal architecture to determine depth of tumor penetration once a lesion is identified . an imaging modality that can provide near histopathological information can be an important diagnostic and prognostic tool for treating urothelial carcinoma . jessner et al .   compared in - vitro oct images to h and e analysis of human bladder tumor resection fragments . the tomography of muscle invasive urothelial carcinoma demonstrated architectural re - arrangement of the mucosal , submucosal , and muscularis boundaries in addition to individual muscle bundles . was able to address the in - vitro limitation of this study by imaging the urothelium in vivo . twenty - four patients that were visually suspected of having urothelial carcinoma were scanned using oct . tomography was able to detect 29 of the 36 suspect areas in addition to discriminating between lamina propria and muscularis propria invasion . overall , oct proved to be 100% sensitive and 89% specific with a negative predictive value of 100% . although preliminary , oct provides additional pathological information during diagnostic cystoscopy for the detection and staging of urothelial carcinoma . apart from malignancy , there are occasions where benign processes of the bladder are mistaken for malignancy . optical coherence tomography has demonstrated its ability to not only discern normal from malignant change , but also differentiate between proliferative and non - proliferative lesions of the bladder . a few examples of optical coherence tomography of the bladder demonstrating carcinoma in situ are seen in figs . no clear urothelial layer is identified and the combined urothelium and lamina propria are bright . b optical coherence tomography of the carcinoma in situ . preserved horizontal layering indicates no invasion into the muscularis propria a optical coherence tomography of the bladder urothelium demonstrating carcinoma in situ . no clear urothelial layer is identified and the combined urothelium and lamina propria are bright . b optical coherence tomography of the carcinoma in situ . preserved horizontal layering indicates no invasion into the muscularis propria although there are various modes of treatment of prostate cancer , radical prostatectomy has been shown to improve survival beyond 15  years . despite its overall survival advantage , although anatomical nerve - sparing radical prostatectomy   has had a significant impact on postoperative potency , the overall outcomes do not meet both patient and surgeon expectations . during nerve - sparing radical prostatectomy , anatomical location of the neurovascular bundles there is currently no established visual modality available to conclusively identify the neurovascular bundles during radical prostatectomy . has shown that optical coherence tomography can provide real - time in - vitro imaging during prostate surgery . b surface tomography of the prostate showing a complex subcapsular venous network a surface tomography of the prostate demonstrating a dense fibromuscular stroma . b surface tomography of the prostate showing a complex subcapsular venous network there are currently four methods of performing radical prostatectomy  the perineal , retropubic , laparoscopic , and robot - assisted techniques . with the expanded role of oct , the potential use of in - vivo imaging of the neurovascular bundles during radical prostatectomy is now real . at our institution , the first fda - approved oct imaging system for non - ophthalmologic use , niris ( imalux , cleveland , oh , usa ) was used in vivo clinically . the niris system was applied to 24 patients that underwent either laparoscopic or robot - assisted radical prostatectomy . optical coherence tomography application during the procedure did not add to the operative time or morbidity to the patient . in an attempt to evaluate the feasibility of nerve - sparing prostatectomy , specimens were examined both in vivo and in vitro for the presence or absence of the neurovascular bundles . optical coherence tomography was performed during the radical prostatectomy in an attempt to preserve the nerves using real - time data acquisition . over 300 images using oct were accumulated including those of the endopelvic fascia , fat , lymphatics , prostatic capsule , and neurovascular bundles . in four patients who underwent a wide excision of the neurovascular bundle , bench examination of the specimen proved a 100% correlation between the oct image and the histological examination of the prostate . figures  5a and  5b demonstrate the characteristic images of the neurovascular bundles along the prostate . b cross - sectional tomography of a neurovascular bundle along the prostatic capsule a optical coherence tomography of the neurovascular bundle along the prostate . b cross - sectional tomography of a neurovascular bundle along the prostatic capsule more recently , fried et al . has used oct s properties to identify the cavernousal nerves via an open rodent model . six male sprague  dawley rats were anaesthetized and underwent open surgical exploration of the cavernous and ipsilateral major pelvic ganglion . following identification of the neurovascular structures , simultaneous cavernousal nerve stimulation and intracavernousal pressure monitoring was performed . a typical response achieved during 30  s of nerve stimulation resulted in a pressure increase from 10 to 80  mmhg . following stimulation , these animals were euthanized to evaluate the oct image in comparison to the histological appearance of the neurovascular bundle . examining the real - time optical coherence tomography during nerve - sparing radical prostatectomy will be the next logical step . by identifying the nerves prospectively with oct , perhaps an improved functional outcome can result . it has been well established that partial nephrectomy has equivalent oncological results to radical nephrectomy in select patients . the minimally invasive approach is technically demanding due to surgical resection and reconstruction of the kidney , usually within a limited time of warm ischemia . optical coherence tomography and its use in laparoscopic partial nephrectomy have been explored at our institution . images of the parenchyma and the capsule both on and adjacent to the renal mass were obtained . optical coherence tomography was able to detect structural abnormalities adjacent to and on the capsule of nine histologically confirmed renal cell carcinomas ( figs . b optical coherence tomography of renal parenchyma with a histological proven renal cell carcinoma a optical coherence tomography of normal renal parenchyma . a limitation of oct is its shallow depth of penetration and image acquisition . limited by its probe size and diameter , multiple data sites and angles further experience with oct in conjunction with histological analysis will also aid the operator in discerning from various structures which demonstrate overlapping imaging characteristics . for example , lymphatic tissue looks very similar tomographically to neural tissue ( fig .  7 ) . 7optical coherence tomography of lymphatic tissue which may be confused for a neurovascular bundle during prostatectomy optical coherence tomography of lymphatic tissue which may be confused for a neurovascular bundle during prostatectomy although relatively established in ophthalmology , its use in urology continues to evolve . with further technological advances in robotic surgery , a synergy between imaging and surgery will provide improved operative results and reduced patient morbidity .
optical coherence tomography is a new technology that provides an atraumatic  optical biopsy  providing both anatomical and possible histopathologic results . 
 it has only recently been incorporated into the urological field . 
 this paper highlights previous and prospective advances of optical coherence tomography in urology and its potential application in robotic urologic surgery .