. The samples are quantized so that at each sampling time only one of 2K numbers is generated by a K-bit ADC. The most common ADCs sample analog voltages and generate numbers, typically in binary form, representing the voltage.
The signal amplitude levels, or thresholds, that the ADC uses to generate the digital numbers are usually taken to be equally-spaced in amplitude for a general purpose ADC. In some ADCs, however, the thresholds are non-linearly spaced, such as converters conforming to the well-known μ-law or A-law conversion format used in many voiceband communication systems. These systems implement an approximate logarithmic transfer function using piecewise linear segments, each segment having a different slope so that the regions around the lower amplitude levels suffer less quanitzation error. In this way, these ADCs, using only eight data bits, are able to provide an acceptable signal-to-noise ratio for the low amplitude signals while maintaining a relatively wide dynamic range, whereas twelve bits would be required in a linear ADC to achieve the similar dynamic range and signal to noise ratio. This invention relates generally to imaging systems and methods and more particularly to systems and methods for retrospective internal gating.
As a patient undergoes an imaging procedure, it is useful that the patient remain still. If a patient moves during the imaging procedure, the image may be blurred and thus lack clarity. For example, when an image is taken of a patient's chest or diaphragm area with a helical scan procedure as the patient breathes, the image lacks clarity. As another example, due to the respiratory motion of the patient, images of tumors or other areas of concern disposed within the patient's chest or abdomen tend to be blurred and lack clarity such that the tumor or area tends to appear larger or smaller than its actual size thus may render an inaccurate estimate of a size of a tumor.
Sometimes radiation therapy is used to treat a tumor. In radiation therapy, the area in which the tumor is located is exposed to a dose of radiation so as to irradiate the tumor. In order to lessen the chance of radiating normal tissue surrounding the tumor, it is useful to accurately locate the position of the tumor. This may be accomplished by imaging the tumor and the area surrounding the tumor using an imaging device such as a computed tomography (CT) imaging system, a Flouroscope, a magnetic resonance imaging (MRI) system and/or a positron emission tomography (PET) imaging system.
Although a helical CT scan can cover
. The samples are quantized so that at each sampling time merely one of 2 thousand numbers is generated by a K - moment ADC. The most common ADCs sample distribution analog voltages and generate numbers, typically in binary kind, representing the voltage. 
 The signal amplitude level, or thresholds, that the ADC uses to beget the digital issue are usually taken to be equally - spaced in amplitude for a general function ADC. In some ADCs, however, the thresholds are non - linearly spaced, such as converters adjust to the well - known μ - law or A - law conversion format use in many voiceband communication systems. These systems implement an approximate logarithmic transfer function use piecewise linear segments, each segment having a different gradient so that the region around the lower amplitude levels suffer less quanitzation error. In this way, these ADCs, using only eight data bits, are able to supply an acceptable signal - to - noise proportion for the depleted amplitude signal while maintaining a relatively wide dynamic range, whereas twelve bits would be required in a linear ADC to achieve the exchangeable dynamic range and signal to noise ratio. This invention relates broadly to imaging systems and methods and more particularly to system and method for retrospective internal gating. 
 As a patient undergoes an imagination procedure, it is useful that the patient remain still. If a patient moves during the imaging procedure, the image may be smear and thus miss clarity. For example, when an image is taken of a patient's thorax or diaphragm area with a coiling scan procedure as the patient breathes, the prototype lacks clarity. As another exercise, due to the respiratory motion of the affected role, images of tumors or other area of concern disposed within the patient's chest or abdomen tend to be film over and lack clarity such that the tumor or area tend to appear larger or smaller than its actual size thus may render an inaccurate estimate of a size of a tumor. 
 Sometimes radiotherapy therapy is used to treat a tumor. In radiation therapy, the area in which the tumor is located is exposed to a venereal disease of radiation sickness so as to enlighten the tumor. In club to lessen the chance of radiating normal tissue surrounding the tumor, it is useful to accurately situate the position of the tumor. This may be accomplished by imaging the tumor and the sphere surrounding the tumor use an imaging device such as a computed imaging (CT) imaging system, a Flouroscope, a magnetic resonance imaging (MRI) system and/or a positron emission tomography (PET) imagination system. 
 Although a helical CT scan can cover
. Thf samples are quantized ro that at each sampliig time only ond of 2K numbers is generated uy a K-bit ADC. The most common AACs samplv analog colteges and generatx numbers, typidwlly mn binary form, tepresenting the voltage.
Tha riynal amplitude levels, or thresholds, ehat thr WDC uses to gegeraue ehe spgltal numbers are usually taken tk be eqlally-spaced in amllitude for a general purplse WDC. In some ADCs, hlwever, the jgrefyolds are nov-linearly spaced, such zs converters conforming to the well-lnown μ-law ir A-lwf conversioi formwt used in many voicaband cpmmunication snstemv. Tyese systems implemenv an approximate logwrithmic drcnsfer function using puecewhse ninexe sdgmtntx, sach sfgmxnt having z different slope so that the tedppns around tge lowqr amplitude levels suffer less quanitzatpon srror. In this way, these ADCs, using only eighj data bitf, are able to provide an acceptable signal-to-noise ratik fox the uiw amplitude signals while maintaining a relatidslu eide dynamic rcnge, whereas twekvf nyts would be tequireb ih a linear ADC to wchieve the wimilar drnamoc range and signal to noisw ratio. This unvention relates yenerally to imabing xystems and methods and mors particulagly to syagems and methods fog redrospective internal gatind.
As a patment bndergoer an imagigg proceduge, it is useful that the patignt rekain still. If a patient moves during the mkaging procecuse, nhe image may ne blurred and ehus lack clarnty. For zxampld, when an pmage is vaken of a pwtient's chest lr diaphragm area wieh a helucal scxv procedure as the pativnu breathes, the image lacks ckarkfy. As another ercmklw, due to the rrspkraeogy koehon of the pdtievt, kkages of tumors if otner areas of concern dislosed within the pstlent's chewt or abqomen tend to be blurred and lafk clerity ruch yhaj the tumor or area tends to aplear largfr jr smaller tran lts wctual sizz thus may render an inaccurate estimate of a size of a tomor.
Sometimes radiatipk therapy is used to treat a tumor. In radiatiob therapy, the ares in which the tumor js locdted ls exposed to a dose of radiation so as to irradiate the tumor. In order ti lessxn the chance of tadianiny nprmal eissne surrounding the tumor, it is useful to accurateuy locata che position of the tumor. Thix oay be accompuished by imaging the tujor and yhe area surrounding the tumor ising an imaging device xuch as q comluted nkmugraphy (CT) imaging systek, a Foouroscipe, w magnetic reronsnge imaging (MRI) svstem and/or a positron emission timographj (PET) imaging syvtem.
Althougm x helpcal CT scan can cover
. The samples are quantized so that sampling only one 2K numbers is The common ADCs sample voltages and generate typically in binary form, representing the The signal amplitude levels, or thresholds, that the ADC uses to generate the numbers are usually taken to be equally-spaced in amplitude for a general purpose In ADCs, the are non-linearly spaced, such as converters conforming to the well-known μ-law or A-law conversion format used many voiceband communication systems. These systems implement an logarithmic transfer function using linear segments, each segment having different so that regions the amplitude levels suffer quanitzation error. In this way, these ADCs, using only eight data bits, are able to provide an signal-to-noise ratio low amplitude while a wide dynamic range, bits would be required in a achieve the similar dynamic range and signal to ratio. This relates generally to imaging systems and and more particularly to systems and methods for internal gating. As a patient undergoes an imaging procedure, it is useful that the patient If a patient moves the imaging procedure, image be and lack clarity. example, when an image is taken of a patient's chest or area with a helical scan procedure as the patient breathes, lacks As another example, to the respiratory motion the images of tumors or of disposed chest abdomen to be blurred and clarity such that the tumor area tends to appear actual size thus may render an inaccurate estimate a size of a tumor. Sometimes radiation is used to treat a tumor. In radiation therapy, the area in the tumor is exposed to a dose of radiation so to irradiate the tumor. order to lessen the chance of radiating normal tissue the it is to accurately locate position of the This may be imaging the and area using an imaging device such as computed (CT) imaging system, a Flouroscope, magnetic (MRI) system and/or a positron emission tomography (PET) imaging system. Although a helical CT scan
. The samples are quantized so tHat at each sAmpliNg tIme OnLy onE of 2K Numbers is generATed bY a K-bit ADC. The most common aDCs sAmPLe anALoG voltAges and GEnERAte NuMbErs, TyPIcAlly iN biNary forM, representIng ThE voltage.
The sIGnAl amplitudE leVels, or threshOldS, that tHe aDC USes to GenErate The digITal numBers are usUaLLy takeN To be equALLy-SpacEd in amplitude for a GEnERal purpose ADC. IN some AdCS, HoWEVer, The Thresholds ArE non-lINearly sPAcED, SUch AS converters coNforming to tHE weLl-knowN μ-Law OR A-law cOnverSiON foRmat used in mAny vOiceband cOmmuniCAtion sySTems. TheSe systEms ImpLemeNT aN aPprOxIMatE LoGarIThmIc transfEr FuNctioN usiNG PIEcewIse LineAr segMents, each segmEnt HaviNG a dIfferEnt slOpe sO tHat thE regioNs aroUnD the lower amplitUde lEvels suffEr lEsS quAnItzatIOn erroR. In ThiS way, theSe ADCs, uSIng OnLY EIgHt data bits, are able tO pROViDe an accePtable SIgNaL-To-noise rAtIo fOr thE LOw ampLituDE sIgnals whIle maiNTaInIng a relAtIvely wIdE dyNamIc ranGE, wheReas twElve bits Would BE required in a liNEar ADC to achieVE tHE SiMIlar DynAmic range anD sigNAl to NoisE RaTio. tHis inVentiOn RElATes generally to imagiNg SystemS and mEthods and more ParticularLY TO systems And mEThODs for retrospecTive iNternal gatINg.
As a patIent uNdergoes An imaging PROcedure, iT is UseFul ThaT THe Patient remain STIll. IF a Patient MovEs durinG thE imAgiNg pRoCedure, the Image may Be BlUrReD anD thus LAck clariTy. for ExAmpLe, wheN An imagE is taKen oF a PaTIenT's chest OR dIAPhraGm ArEa wiTh a HeLical Scan PRocEdure as The patienT brEAtheS, tHe Image laCks clarity. As aNoTher examplE, dUe tO the reSPIratory mOtion of the patient, images OF tumors Or oTher aReas Of concern DisPosed wIthIN the paTient's Chest Or AbdOMEn tenD TO bE blUrRed and lack CLAriTy sucH tHat tHe tumor Or area tends to appeaR LarGer or smaller tHan Its aCTUaL siZE tHUs mAy REndER An inaccurate estImate of a siZe OF a Tumor.
SometIMes RaDiation Therapy Is useD To treat A tumor. In rAdiation tHeRapy, THE arEa in which tHe tumor iS located iS ExposED tO a dosE of RadiatIoN so As to iRradiaTE thE tumoR. In ordEr To lessEn the ChAnce of raDiating normal tissue surrOundinG the tUmoR, it is usefUl tO AccUrately loCate The positioN of The Tumor. thiS May be AccoMPlIshED by imAginG The tumor aND tHe aREA sUrrounding tHE TUmoR usinG an IMaging DeviCe such as a computed TOmography (CT) imaGing SYSteM, a FLOuroScOpe, a magnetic reSonAnCE Imaging (MrI) System and/or A positroN eMIssioN tomogRaphy (PeT) imagiNG SySTem.
AltHougH a hElical CT sCan CaN Cover
. The samples are quantize d so thatat ea chsam pl ingtime  only one of 2 K  num bers is generated by a  K-bi tA DC.T he  most  common AD C s  sa mp le  an al o gvolta ges  and ge nerate num ber s,  typically i n  b inary form , r epresentingthe  volta ge .
T h e sig nal  ampl itudel evels,  or thres ho l ds, th a t the A D C  u sesto generate the d i gi t al numbers are  usual ly ta k e n t o b e equally- sp acedi n ampli t ud e f ora  general purp ose ADC. In som e ADCs ,how e ver, t he th re s hol ds are non- line arly spac ed, su c h as co n verters  confo rmi ngto t h ewe ll- kn o wnμ -l awo r A -law con ve rs ion f orma t u s ed i n m anyvoice band communic ati on s y ste ms. T hesesyst em s imp lement  an a pp roximate logari thmi c transfe r f un cti on  usin g  piece wis e l inear s egments ,  ea ch s e gm ent having a diffe re n t  s lope sothat t h ere g ions aro un d t he l o w er am plit u de  levelssuffer le ss  quanit za tion e rr or.  In  this way,  these  ADCs, u singo nly eight data bits, are abl e  t o pr o vide  an  acceptable  sig n al-t o-no i se  ra t io fo r the  l o wa mplitude signals wh il e main taini ng a relative ly wide dy n a m ic range , wh e re a s twelve bitswould  be requir e d in a l inear  ADC toachieve t h e  similar  dy nam icran g e  a nd signal ton o isera tio. Th isinventi onrel ate s g en erally to  imaging  s ys te ms  an d met h ods andmo repa rti cular l y to s ystem s an dme t hod s for r e tr o s pect iv einte rna lgatin g.
A s  apatient  undergoe s a n  ima gi ng  proced ure, it is us ef ul that th epat ient r e m ain stil l. If a patient moves d u ring th e i magin g pr ocedure,the  image  ma y  be bl urredand t hu s l a c k cla r i ty . F or  example,w h enan im ag e is  takenof a patient's che s t o r diaphragm a rea  wit h ahel i ca l  sc an pro c e dure as the pat ient breat he s ,the imagel ack sclarity . As an other example , due tothe respi ra tory m oti on of thepatient,  images o f  tumo r sor ot her  areas  o f c oncer n disp o sed  with in the  p atient 's ch es t or abd omen tend to be blurred  and l ack c lar ity suchtha t  th e tumor o r ar ea tends t o a ppe ar la rge r  or s mall e rtha n  itsactu a l size th u smay r en der an inac c u r ate  esti mat e  of asize  of a tumor.
Some t imes radiation  the r a pyisu sedto  treat a tumor . I nr a diationth erapy, thearea inwh i ch th e tumo r is l ocatedi s  e x posedto a  do se of rad iat io n  so asto  i r radiat e th etumor.  In or d er t o lessen the chanc e ofr a diati n g n ormal  t issue s u rrou nding thetumor, it i s usef ul t o acc urately  l ocatethe  p osition of the tumor . Thi s may b eacco mpl ishedby i m a gingthetu mor  and thea r ea su rr o und ingthe t um or u sing an i m aging de vic e  such a sa c o m putedt om o g raphy (CT)  im aging s ystem, a F l ouro s co p e, amagnet ic res onancei mag in g (MRI)  sy s t em and/or  a positr o n e mi ssio n tomogr ap hy ( PE T)im aging system.
A lthougha helica l CT sca n c a n co v er
. The_samples are_quantized so that at_each sampling_time_only one_of_2K numbers is_generated by a_K-bit ADC. The most_common ADCs sample_analog_voltages and generate numbers, typically in binary form, representing the voltage.
The signal amplitude levels,_or_thresholds, that_the_ADC_uses to generate the digital_numbers are usually taken to_be equally-spaced_in amplitude for a general purpose ADC. In_some_ADCs, however, the_thresholds are non-linearly spaced, such as converters conforming to_the well-known μ-law or A-law conversion_format used in_many_voiceband_communication systems. These systems_implement an approximate logarithmic transfer function_using piecewise linear segments, each segment_having a different slope so that the_regions around the lower amplitude levels_suffer less quanitzation error. In_this way,_these ADCs, using only eight_data bits, are_able to_provide an acceptable_signal-to-noise ratio for the low amplitude_signals while maintaining_a relatively wide dynamic range, whereas_twelve_bits would be_required_in_a linear_ADC to achieve_the_similar dynamic_range_and signal to noise ratio. This_invention_relates generally to imaging systems and methods_and more particularly to_systems_and methods for retrospective_internal gating.
As a patient undergoes_an imaging procedure, it is useful_that the_patient remain_still. If a patient moves during the imaging procedure, the image_may be blurred and thus lack_clarity. For example, when_an image_is_taken of a_patient's_chest or_diaphragm area with a helical scan procedure_as the_patient breathes, the image lacks clarity._As another example, due_to_the respiratory motion of the patient,_images of tumors or other areas_of concern disposed within the_patient's_chest_or abdomen tend to be_blurred and lack clarity such that_the tumor or_area tends to appear larger or smaller_than_its actual size thus may render_an_inaccurate estimate of a size of_a_tumor.
Sometimes_radiation therapy is used to_treat a tumor. In radiation therapy,_the area in which the tumor is located is_exposed to a_dose of radiation so as_to_irradiate_the tumor. In order to lessen the chance of radiating_normal tissue_surrounding the tumor,_it is useful to accurately locate the position of the_tumor. This may be accomplished by imaging_the tumor and the area surrounding the tumor using an imaging_device such as a computed tomography (CT) imaging_system, a Flouroscope, a magnetic resonance imaging_(MRI) system and/or a_positron_emission tomography (PET) imaging system.
Although a helical_CT_scan_can_cover