NuclearMedicinePhysicsandInstrumentationMyUnderstandingofNM(Clinical)MedicineMedicalImagingandNuclearMedicineNuclearMedicineDiagnosisTherapyNMPhysicsNuclearPhysicsNuclearInstrumentTeacher：LuyiZhou(周绿漪)Dept.ofNuclearMedicineTel：85422330Topics.AtomandNucleus.ModesofRadioactiveDecay.DecayofRadioactivity.InteractionofParticleswithMatter.RadiationDetectors.InstrumentationforRadiationDetection.Camera.SPECT.PET.DevelopmentofNuclearMedicineInstruments.AtomandNucleus（I）AtomlAtomNucleusElectronBohrModelShellEnergyLevelBindingEnergyAtomicEmissionsCharacteristicXRayAugerEffectEnergyLevelandBindingEnergyAtomicEmissions:CharacteristicXRayAtomicEmissions:AugerEffect（II）Nucleus1.CompositionandNotationCompositionnucleon：protonandneutronlNotationExample:Shortened：Acceptable:X-AOr:I-131Mass numberElement symbolAtomic numberNumber of neutrons2.NuclidesandtheirclassificationNuclide:AnAtomwithgivenAandZ，exactarrangementofnucleoninthenucleus,andmeasurablelifetime.Isotope：Nuclideswiththesamenumberofprotons,butdifferentnumbersofneutrons.(Example:I-125,I-127,I-131areisotopesofI,andoneanother）Isomer:NuclideswithidenticalA,Z,andN,butdifferentenergystates.Nuclides:StablenuclidesandRadionuclidesRadionuclides:NaturalradionuclidesandArtificialradionuclides3.ForcesbetweennucleonsNucleonsaresubjecttoelectricalforcesandexchangeforcesElectricalforce：repulsive,longdistance,nonsaturable,weak(eV)Strongforce(exchangeforce)：attractive,shortdistance,saturable,strong(MeV)Whentheforcesarebalanced,thenucleusisstable,oritwilldecay.4、EnergystateofnucleusAnucleusmaybeinoneofthethreeenergystates:Groundstate：moststablestateExcitedstate：extremelyunstable，transientexistencebeforetransformingintootherstateMetastablestate：unstable,butwithrelativelylonglifetimebeforetransformingintoanotherstate.Alsocalledisomericstate.Isomer：Twonuclidesthatdifferfromoneanotherinthatoneisametastablestateoftheotherarecalledisomers（e.g.Tc-99andTc-99m）*Theenergylevelsarewelldefined5.Stableorunstable?lBalanceoftheforceslEnergystateIfUnstableRadioactivedecayRadioactivedisintegrationII.ModesofRadioactiveDecay（I）Terminologies(1)Radioactivedecay：Aprocessinwhichanunstablenucleustransformsintoamorestableonebyemittingparticlesand/orphotonsandreleasingnuclearenergy.Parent: the unstable radioactive nucleusDaughter: the more stable product nucleus (which may also be radioactive)Transition energy: energy releasedRadionuclide：radioactivenuclidewithasetofcharacteristicproperties:modeofradioactivedecayandtypeofemissions,thetransitionenergy,andtheaveragelifetime.Radioisotope：theradioactivemember(s)ofanisotopicfamily.（I）Terminologies(2)SpontaneityofradioactivedecayTheexactmomentatwhichagivennucleuswilldecaycannotbepredicted,norisitaffectedtoanysignificantextentbyeventsoccurringoutsidethenucleus(Eachnucleusdecaysindependently)（II）ModesofRadioactiveDecay1.decay(negatrondecay)：Aprocessinwhichaneutroninthenucleusistransformedintoaprotonandanelectron(particle,negatron).Standardnuclearnotationofdecay:X：parentY：daughterQ：transitionenergy,inMeV：neutrino.neutralparticle,nomass,rarelyinteractwithmatterDecayscheme：Diagrammaticdepictionofradioactivedecay.decaytotheright:atomicnumberincreases.v.v.verticaldistancebetweenthelinesisproportionaltothetransitionenergye.g.DecayofC-14ShareofQ：randomlybetween-andparticleenergydistribution(spectrum)May have any energy from 0 to QRarely carries away all QThe average energy is about 1/3 of Q The most possible energy is 1/3 of Q- Particle Kinetic Energy (MeV)RelativeNumberEmitted Particle Spctrum2.（ ，）decayWhen the daughter nucleus is in an excited state, it promptly decays to a more stable state by emission of a ray. The sequential decay process is (,) decay Decayschemeof133XeEnergySpectrumanditsApplicationComposed of a series of discrete lines The energy distribution is characteristic of the radionuclide.Quantity and space distribution of known radionuclide can be recorded by detecting rayRelativeNumberEmitted0.050.100.15rayenergy（MeV）1(0.080MeV)2(0.081MeV)3.IsometricTransitionandInternalConversionIsomerictransition(IT)ThedecayofthemetastableorisomericstatebytheemissionofarayInternalconversion(IC）Thenucleusdecaysbytransferringenergytoanorbitalelectron,whichisejectedinsteadoftherayConversion electron4.Electroncapture(EC)Aprocessinwhichanorbitalelectroniscapturedbythenucleusandcombineswithaprotontoformaneutron.ECisalsocalledinverse decay.(EC,)decay125Idecayscheme5.+decay(Positrondecay)Aprotoninthenucleusistransformedintoaneutronandapositivelychargedelectron(positron).Thepositronandaneutrinoareejectedfromthenucleus.p+n+e+energy15O的衰变AnnihilationofpositronAntiparticle(antimatter)ofanordinaryelectronAnnihilationreaction(Combineswithanelectron)MassconvertedintoenergyTwo0.511MeVannihilationphotonsOppositedirections(180Oapart).PET(PositronEmissionTomography)6.decayandNuclearFissiondecayThenucleusejectsanparticle,whichconsistsoftwoneutronsandtwoprotons.NuclearfissionThespontaneousfragmentationofaveryheavynucleusintotwolighternuclei.Thelighternucleussharethenuclearmassinabouta60:40ratio.Question：Isthereadecay?Why?7.Typeofdecaysaccordingtotheiremittedparticlesray：decayray：-decay,+decayray：（,）decay，（-,）decay，（+,）decay，IT，（EC，）Thoseemittingno,rays,butelectronsorXray：EC：CharacteristicXrayorAugerelectronsInternalconversion：Conversion electron, CharacteristicXrayorAugerelectronsIII.DecayofRadioactivity（I）Activityanditsunits1.Activity and its units, Specific activity,RadioactiveconcentrationActivity:Theactivityofaradioactivesampleistherateatwhichthenucleidisintegrate,ie.thenumberofdisintegrations/second(dps)ordpmUnitsS.I system: bequerel, Bq: 1 decay persecond=1BqTraditional：curie,Ci3.71010dps=1Ci Conversions1Ci=3.71010Bq1Bq0.2710-10Ci1mCi=10-3Ci=3.7107Bq1Ci=10-6Ci=10-3mCi=3.7104Bq;1KBq=103Bq;1MBq=106Bq;1GBq=109BqRelatedterminologiesSpecificactivityActivityperunitmassofaradioactivesource.e.g.0.5Ci/gRadioactiveconcentrationTheactivityperunitvolumeofsolventinwhichtheradionuclideisdissolved,e.g.37MBq/ml,1mCi/ml)（II）RuleofExponentialThe changeof the number of radioactivenucleiand activity against time follow the rule ofexponential.N=N0e-tA=A0e-te-t:decayfactorN：numberofradioactivenucleiattimetA：activityattimetN0：numberofradioactivenucleiattimet=0A0：activityattimet=0:decayconstantDecayplotLinear:anexponentiallydecreasingcurveSemilogarithmic:astraightlinewhoseslopeisdeterminedbydecayconstant.(=0.1/s)Time（S）Relative number or activity Time（S）DecayplotLinearSemilogRelative number or activity（III）DecayConstant,Half-LifeandEffectiveHalf-Life1.DecayconstantTheproportionalityconstantbetweentherateofradioactivenucleardecayandthenumberofradioactivenucleiremaining. A=N e.ge.g，assuming =0.02/s=2%/s,which means 2% of the assuming =0.02/s=2%/s,which means 2% of the radioactive nuclei decay in one second at any radioactive nuclei decay in one second at any moment, if N=10000moment, if N=10000，then A=0.02/s10000=200/s, then A=0.02/s10000=200/s, meaning 200 nuclei decayed in 1 second (on the meaning 200 nuclei decayed in 1 second (on the average). In the next second,?average). In the next second,?Decayconstant(cont)Each radionuclide has a characteristic valueIf a radionuclide has more than one mode of decay,(e.g 18F，97%+，3% EC），），with decay constant for each mode, 1、2、3n，then the total decay constant is the sum, =1+2+3n2.Half-lifeThetimeittakesfortheactivitytofallbyhalf.e.g.,99mTcT1/2=6.02h，=0.693/6.02=0.115/h3.Effectivehalf-lifeThetimeittakesfortheactivitytofallbyhalfbecauseofthecombinedprocessesofphysicaldecayandbiologicalclearancePhysicaldecay:,T1/2Biologicalclearance:b，Tbe=+bln2/Te=ln2/T1/2+ln2/TbEffectivehalf-lifeTe=T1/2Tb/(T1/2+Tb)Usually, T1/2 is known, Te can be measured, thus Tb determinedDetermine of exposureIV.InteractionofParticleswithMatter（I）InteractionsofChargedParticleswithMatter1.InteractionMechanisms:losingenergybyInteraction with orbital electron：Ionization,excitationInteractionwithnucleus:bremsstrahlung2.Specificionization()Totalnumberofionizations(ionpairs)perunitoftracklengthalongachargedparticletrackisrelatedtoparticlecharge(q),particlespeed(v)andmaterialdensitybyqve.g：particle（q，v）hasgreaterthanparticle,thushasgreaterionizationpower.3AbsorptionAfterlosingenergychargeparticlesareabsorbedbymatter.particle:AtomofHelium- particle and the like: free electron ororbitalelectron+particle:annihilation（II）InteractionofRaysandX-rayswithMatter*Particle?Wave?Photon?Ray?Ionizingradiation?1.Photoelectriceffect(photoelectricabsorption)A process in which an atom absorb the totalenergyofanincidentphotonThe photon disappearsThe energy is used to eject an orbital electron from the atom on a almost “inner first” baseLikelihood increases with increasing atomic number and decreasing photon energy ( Z3/E3)2.Comptoneffect(Comptonscattering)A collision between a photon and a outer shell orbital electron of an atom.transfers part of its energy to it, leaving the atom as the recoil electronThe photon is deflected through a scattering angle Aphoto-electroninteraction,notdependonthedensity,atomicnumberofthematerialMoreenergyislostwhenhighenergyphotonsarescattered.e.g.80keV:upto24%140keV:upto36%360keV:upto58%Theenergytransferredtotherecoilelectronrangesfrom0(0)uptothemaximum(180o,backscattering)Thelowertheenergy,thelessthechangeinenergyforagivenscatteringanglePhotonenergyandscatteringangleWaysofseparatingscatteredradiation(1)CollimatorWaysofseparatingscatteredradiation(2)Energy window3.ElectronPairProductionAninteractionwithanucleusinwhichthephotondisappears and its energy is used to create apositive-negativeelectronpair.Minimumphotonenergyis1.022MeV,whichistherestmassequivalentof2electrons.LikelihoodincreaseswithincreasingEandZ(NouseinNM)4.DepositionofPhotonEnergyinMatterV.RadiationDetectorsinNM（I）Mechanisms1.IonizationCollectingtheionpairsIonizationchambers,Geiger-MllerCounters2.scintillationdetectionofthefluorescentradiationManyapplicationsinNM3.Darkeningofphotographicfilm4.Changoftemperature5.Chemicalchange（II）Gas-filleddetectors1.Ionizationofgase.g.34eVperionpairinairVoltageCurrentVoltageresponsecurve2.VoltageresponsecurveA:recombinationB:saturationIonizationchamberC:proportionalGasamplificationProportionalcounterD:limitedproportionalE:Geiger-MllerAvalancheofsecondaryionizationsGeiger-MllercounterF:continuesdischarge3.Dosecalibrator1.Basicallyanionizationchamber:Displaythesampleactivitybymeasuringthetotalcurrentresultingfrommultipleevents.Currentisproportionaltosampleactivity,normalizedforvariousradionuclidetodisplayactivity.Canmeasure“hot”samples(1Ci)4.Othergas-filleddetectorslProportionalcounterParticleenergylG-McounterCountingrate(countperunittime)AreasurveymeterslPocketdosimeterRecordsthetotalchargecollectedoveraperiodoftime（III）ScintillationDetector1. Scintillation *The number of photons of light emitted (intensity), is proportional to the energy of the incoming radiation. scintillation detectors can be used to determine the energy.2. Basic Composition and PrincipleScintillator: converts radiation energy to photons of visible light Photomultiplier tube: converts photons to electrons and multiplies the number of electronsOutput: A electrical pulse whose height is proportional to the amount of radiation energy absorbed in the scintillator. 3.ScintillatorslPropertieslDensity and atomic numberlPhoto yield ( conversion efficiency)lScintillation decay timelNaI(Tl) ( Thallium-activated sodium iodide crystal)Usefulness Dense: =3.67g/cm3, Z=53 (iodine) Efficient: 30 eV per photon, or 13% conversion efficiency Adequate scintillation decay time: 230 nsecGood for penetrating radiations (X ray, ray)Disadvantages Fragile: sensitive to mechanical or thermal stress Hygroscopic: Hermetic sealing requiredOther scintillators BGO (Bi3Ge4O12) :for PET, =7.13g/cm3 , Scintillation decay time 300 nsec LiquidGasNaI(Tl)BGO4.PhotomultipliertubeslComposition: photocathode, dynodes, anodelFunction: converts photons to electrons and multiplies the number of electronslPropertieslAmplification factorlHigh voltage5.SpectrumTheIdealPulse-HeightSpectrumPhotopeakCompton region (plateau) Compton edgeCompton valley Multiple Compton scatteringlTheActualSpectrumlBroadened peaklRounded edgelBackscatter peaklOther componentslBroadened peak and Rounded edge, Why? 300 eV per photoelectron from photocathode-Poisson- or Gaussian- shaped photopeakEnergyResolutionThewidthofpeak(E)measuredacrossitspointsofofhalf-maximumamplitudeistheenergyresolution.Fullwidthathalfmaximum(FWHM)ofthephotopeakFWHM(%)=(E/E）*100%WhyFWHM?lResolutionv.senergylSpectrumv.sscintillatorsizeSpectrumv.sscatterE,morescatterE,easiertoseparatee.g.at90oscatteringanglePrimary，Scattered100keV,84keV500keV,253keV6.EnergyWindowApresetenergyrangeEnergy-Selective-counting,thusradionuclide-selective-countingDiscriminateagainstscatter,background,etc.outsidethedesiredenergyrange(Background?)7.LiquidScintillationCountersApplication：DetectinglowenergyraysFeaturesLiquid Scintillator(cocktail)Coincidence detection by two PMTs and coincidence circuitVI.InstrumentationforRadiationDetection（I）BasicCompositionandPrincipleAn instrument for radiation detection is oftencomposedof:1. Radiation detector: converts radiation energy to electrical signals by collecting ion pairs, scintillation photons, etc. Probe:Detectors are often assembled with primary electric circuit e.g. preamplifiers, to form a stand-alone component.2. Electronic instruments: amplifiers, pulse-height analyzers,scaler-timers, analog ratemeters.3. Ancillaries: sample servers, computers（II）ElectronicInstruments1.AmplifiersMatch（bypreamplifier）AmplificationShaping(Filtering:band-passfilter)2.Pulse-HeightAnalyzersFunction:Todeterminetheheightofpulse(1)Pulse-HeightDiscriminator(2)Single-ChannelAnalyzers(3)MultichannelAnalyzers(1).Pulse-HeightDiscriminatorComposition：OnevoltagecomparatorInput：PulsesofvariousheightOutput：PulsesofthesameamplitudeandshapeCondition：TheheightofainputpulseisabovethethresholdThreshold:apresettablevoltagelevelFunction：Totellifthepulse-height(thusenergy)isabovecertainvalue.(2).Single-ChannelAnalyzers(SCA)Composition：TwovoltagecomparatorsInput：PulsesofvariousheightOutput：PulsesofthesameamplitudeandshapeCondition：TheheightofainputpulseisbetweenthelowerthresholdandtheupperthresholdFunction：Totellifthepulse-height(thusenergy)iswithincertainrange.EnergyWindow(3).MultichannelAnalyzers(MCA)The core is an ADC: Analog- to-Digital Converter3.Scaler-TimerCountstheoutputpulsesfromPHAsinapresettime4.AnalogRatemetersDeterminestheaveragenumberofpulsesoccurringperunitoftime（III）Applications1.Configurations2.InVitroMeasurementlNaI(Tl) well counterScintillator shape High detection efficiency 100% Geometric efficiency Low background by lead shielding lLiquid scintillation counterlDose calibratorlCompare晶体光电倍增管样品井型闪烁探测器3.InvivoMeasurementlMeasuring rays from inside the bodylCollimatorsDesign: Cylindrical hole Expanding (conical) holeFunction: A passageway for rays from an area of interest lMultiprobesystemsLeadLeadDetectorUmbraPenumbraSingle-hole collimator（IV）NuclearCountingStatisticsFluctuationofcounts:Cause：DecayisaspontaneousprocessDistribution： Gaussiandistribution(normaldistribution)whenN20Standard Deviation (SD) and Relative StandardDeviation(%SD)：forcountNSD=%SD=1/e.g.NSD%SD1001010%10,0001001%Conclusion:Largernumbersofcountshavesmallerpercentageuncertaintiesandarestatisticallymorereliablethansmallnumbersofcounts.Waystoreducetheeffectoffluctuation:Longermeasuringtime(notoftenpracticable,e.g.decay)HigherdetectingefficiencyAlargerdoseLowerbackgroundcountingrateDataprocess,e.g.SmoothingandfilteringofcurvesandimagesCurvesmoothRawdataOne3-pointsmoothFive3-pointsmoothTwenty3-pointsmoothVII.Cameras（I）CompositionandprincipleCrystalPositionandEnergyCircuitsCollimatorDotDisplayand/orComputerInterfaceZYXPMTs and theirPreamplifiersCamera1.BasicPrinciple(1)Collimator:Projectingspacedistributiontothecrystalplane(2)CrystalandPMTarray:energyconverters.(3)PositionandEnergycircuits:Calculatingthepositionofthescintillationandtheenergyabsorbed(4)DotDisplayand/orComputerInterface:Displayingaflashdotorsendingpositioncoordinatestocomputer2.CollimatorsCollimatorsTypesGeometric：Pinhole, Parallel hole, Diverging,ConvergingEnergy：Low energy, Medium energy, High energyResolution and Sensitivity Performance：All purpose, High resolution, High sensitivitye.g. LEAP (Low Energy All Purpose)3.CrystalandPMTarrayCircularorrectangularNaI(Tl)crystalThickercrystalmakeshigherdetectionsensitivityThinnercrystalmakesbetterspaceresolutionMorePMTsmakebetterspaceresolutionTheoutputofeachPMTsimultaneouslyfeedstoX,YandZchanneltoprocessRectangularPMTarrayfromGE4.PositionandEnergyCircuitslEnergy-independent positioning signal: Centroid of scintillationlEnergy-selective imaging: Multichannel AnalyzerXiYYiX0AxiandAyiaretheweightsoftheithPMT,Axi=kXi;Ayi=kYi.IiistheintensityofscintillationreceivedbyithPMTkisacommonproportionalfactorwhichisfinallycanceledoutinXandY5.ImageRecordinglOnesetof(X,Y,Z)signalisgeneratedforeachandeveryvalidevent.lOne flash dot is displayed for one valid eventlOr one set of (X, Y) value is converted to digitslRecordingmanyeventsmakesaimagelPolaroid camera or 35-mm cameralComputer display(II)ComputersinNM1. PrinciplereviewHardwaresTangible PartsCPUMemoryDiskSoftwaresContainingInstructionsDataOperating System SoftwaresApplication Softwares2. ComputerInterfaceComputers Communication Channel with Imaging DevicesGamma CameraSPECTPETOutput From ComputerAcquisition InstructionsDigital to Analog Conversion (DAC)Input From Imaging DeviceImagesAnalog to Digital Conversion (ADC)(T,Xd,Yd,R).(T,Xd,Yd)(T,3.ImageCreationFrameModeListModeRadio-pharmaceuticalsMatrixPixel (Picture Element)RadioactivityBrightness or Color versus RadioactivityFunctional ImageCellular Level Organ Function3.ImageCreation(cont)4.Image Storage and TransmissionImages Stored as Computer FilesPublic Format (JPEG, GIF)Inter (Only in Nuclear Medicine)DICOM Standard Format (All Medical Images)Manufacturers Proprietary FormatsImage Computer NetworksFTP ( Protocol)Web Based Upload/DownloadPACS (Picture Archiving and Communication System)BenefitsLong Term StorageTelemedicine(III)GammaCameraApplications1.MatrixSizeandImageModeLargermatrixcanbetterpreservetheimageresolution.Typical: 128128, 6464Pixel Size: 3mm, 6mmImagemodeisdeterminedbypixeldepthByte Mode: 1 byte/pixel Maximum counts/pixel=255 Word Mode: 1 word/pixel Maximum counts/pixel=655352.StaticAcquisitionPurposeDemonstrating the Size and Position of an OrganThe Distribution of Function within the organAcquisitionParameters128128, Word Mode, Counts/frame or Time/frameAlsocalledImage sequenceCountmatters-50k500k2.DynamicAcquisitionPurposeAseriesofimagestotrackthechangeofradiopharmaceuticaldistributionAcquisitionParameters6464or128128,bytemodeorwordmodeNumberofgroups,Numberofframesinagroup,Time/frameinthegroups,Pausebetweengroups2.DynamicAcquisition(cont)DynamicImageDisplayMultipleframesCinematic3.WholeBodyScanMethodContinuous move of camera head or bed Step and shootAcquisition ParametersSpeed, Time, (Matrix size) 4.MultigatedAcquisitionMethodR wave of ECG is used as a triggerA cardiac cycle is divided into 16 to 24 frameThe corresponding frames are added to form one frame Cycle1Cycle21324561324561324564.MultigatedAcquisition(cont)AcquisitionParametersMatrixsizeandImagemodeFrames/Cycle,Totalcounts,time,ornumberofbeats5.ImageProcessinglDigital ImagelMatrix and pixellPixel and CountslRegion of Interest (ROI) AnalysislTotal Counts, Number of Pixel, Average CountslTime-Activity CurveslImage MathlImage FilteringSpatialDomainandFrequencyDomainThey are Equal and interchangeable via Fourier TransformationWhat should we look at in frequency domain?SpatialDomainFrequencyDomainFTSpatialdomainandfrequencydomain(cont)Spatial domain: Amplitude and positionFrequency domain: Amplitude and frequencyLarger size in spatial domain has lower frequency in frequency domain and V.VSpatialdomainandfrequencydomain(cont)Image filtering: Modification of amplitude in frequency domainBasic Types of Filter：Lowpass, Bandpass, HighpassCut-offfrequencyVIII.SPECT(Single-Photon Emission (Single-Photon Emission Computed Tomograph)Computed Tomograph)(I)BasicCompositionCamerawithimprovedperformance:uniformity,linearityRotatingGantryandLow-AttenuationbedComputerandSPECTsoftware(II)Principles1. Projection and TomographyProjection:ascount,proview180oor360oProjectionsReconstruction:Projection-TomographSectionProfileView(s)2. Reconstruction by BackprojectionlHow to dolProblemlStar artifactlCause of problemlBackprojection causes reciprocal filteringAA=1/fFrequency3.ReconstructionbyFilteredBackprojectionRampFilterAA=1/fFrequencyFrequencyA1/fxf=1AFrequencyRampFilter(A=f)4.WindowFilterPurpose:Reducenoise0.5100.51FrequencyAmplitudeA.RampFilter10.500.51FrequencyAmplitudeB.WindowedRamp4.WindowFilter(cont)Parameters:cut-offfrequencyandorder5.ReconstructionSteps6.AttenuationandScatterCorrectionBeforeAfter（III）ApplicationsPlanar (Projection) Tomograph1.Purpose：Bettercontrast（Resolution improvement is limited）2.AcquisitionandReconstructionParametersAcquisitionArcofAcquisition,MatrixSize,NumberofViews,TimeorCountperviewReconstructionWindowFilterType,Cut-offFrequency,Order3.ImageDisplayImageReformatting3DVolumeDisplay（IV）QualityControlofCameraandSPECT1.QualityAssuranceAlleffortsmadetoachieveideal,error-and-artifacts-freeoutcome2.QualityControlofNMInstrumentsPerformanceTestsTo verify the usefulnessCorrectionorCalibration To improve performance by modifying some quantities3. Performance CharacteristicsTypesIntrinsic Performance: Collimator offSystem (extrinsic) Performance: Collimator on Linearity, Uniformity, Spatial ResolutionTrueDistributionBarrelDistortionPincushionDistortionImageoffour-quadrantbarphantomGoodUniformityBadUniformity4.Corrections：UniformityCorrection，CenterofRotationCorrectionSinogramXProjectionAngleyx1/0.90.915.TotalPerformanceOptimization(BestCondition)Performance5.TotalPerformance(cont)ClinicalConditionPerformanceAnthropomorphicthoraxphantomCardiacinsert.PET(PositronEmissionTomograph)1.CoincidenceDetectionLOR: Line of ResponseMore Effective, Better Spatial ResolutionCoincidenceDetection2.ProjectionAcquisitionandImageReconstructionTrue coincidence events are recordedAngular projections formed by regrouping events Images are reconstructed by Filtered Backprojection, etc.DualHeadAcqRingDetectorAcqRegroupingProjectionbyRegroupingX.DevelopmentofNuclearMedicineInstrumentsThankYou！