Tc99在心血管影像中的应用

Tc99UsedInCardiacHeartImagingOutlineBackgroundofNuclearCardiologyElementsUsedinHeartImagingImagingTechniquesHeartImagesBackgroundofNuclearCardiologyNuclearcardiologyimagingprocedureshavevastlydevelopedoverthepast25yearswithadvantagesandtreatmentsofheartdisease.Myocardialperfusionimaging(MPI)offersahighdegreeofaccuracyinthedetection,diagnosis,andprognosisofcoronaryarterydisease.MPIisthemostcommonprocedureindeterminingheartdisease.InstrumentationofNuclearImagingUsesradiopharmaceuticalsthatlocalizetoatargetorgan.Inthecaseofcardiology,imagingagentsareusedthatwillflowtoandaccumulateinthemyocardiumoftheheart.Nuclearheartimagingisperformedwithanuclearcamera.TheheartimagingprocessisreferredtoasSinglePhotonEmissionComputerizedTomography(SPECT).Tc99isthemostcommonradionuclideusedtodayincardiacimaging.NuclearCardiologyCameraTheThalliusIon(201Tl)Thefirstuseofradiopharmaceuticalsincardiacheartimagingbeganin1975inwhichthethalliusionwasused.ProblemswithThalliumLimitedSensitivity/Accuracy80%ShorthalflifeDoesnotstayboundtotissueImagesmustbetakenquicklyduetoredistribution.Difficulttoconcentratetargetorgan.Technetium75%ofproceduresusestechnetium99indiagnosingcardiacdiseases.Half-lifeof6hours140KeVgammarayemissionHighenoughinenergytopenetratethebody’stissues,butlowenoughnottoharmthebody.Twotypesoftechnetiumtobediscussed1)Tc99TBI2)Tc99SestamibiTechnetium99TBI1stTechniciumcompoundintroducedtonuclearcardiacimagingStructuralNameHexakis-(t-butylisonitrile)-Technetium(I)SixCoordinateIsonitrileOctahedralgeometry+1oxidationstateStructureofTc99TBITcCCCCHCCNNNNNNCt-But-But-But-But-BuCH3CH3CH3+1ProblemswithTc99TBIHighactivityinotherpartsofthebody.RedistributionTc99Sestamibi(MIBI)DerivedfromTc99TBIComposedoffunctionalgroupsthatgiveclearancefromnon-targetorgansSixcoordinateOctahedralgeometryGreaterhydrophilicitythanTcTBIduetoitsmethoxygroups.LypophillicStructureofTc99SestamibiTcNNNNNNOOOOOOTc99MIBITechnique1)OneDayStressProtocol2)TwoDayStressProtocol3)DualIsotopeScanning4)Gating5)LVEF(LeftVentricleEjectionFraction)OneDayStressProtocolOnedayConsistsofarestexamfollowedbyastressexaminthesameday.InjectionofTcMIBIisperformedafteraresttestandafterastresstest.1stinjectionisalowdose2ndinjectionisahigherdose(3Xtherestinjection)ProblemsNotaccurateinsomeinstancesTwoDayStressProtocolTwoDayConductedonlyiftheonedaytestwasunsuccessful.Reststudynotnecessaryifstresstestwasnormal.ProblemsSameaswiththeonedayDualIsotopeScanningResttestwithThalliumstudyconductedondayoneThalliumredistributessoothertestingcanbeperformedStresstestwithTechnetiumstudyisconductedondaytwoDrawbacksDifferentresolutionmakesitdifficulttocompareheartimages.GatingMostpopularinnuclearheartimaging.ImprovesdiagnosticaccuracyofSPECTimaging.Sharper,clearerimagesthanothertechniques.Accessesregionalwallmotionandleftventricularejectionfraction.Providesinformationregardingmyocardialsystolicfunctionsandprognosis.Allowsanejectionfractiontobecalculated.LeftVentricleEjectionFractionsProvidesprognosticinformationfortheriskofheartdiseasesbyusingthegatedSPECT.Leftventricleiswheremostoftheheartfunctionismeasuredsinceitpumpsbloodthroughoutthebody.Measurestheamountofbloodthattheleftventriclepumpsoutperbeat.EFoflessthan40%areatriskofsomesortofcardiacevent.EFoflessthan30%areatriskforcardiacdeath.WhattheimagesmeanThickened,brighterimagesonSPECTscansindicatesviablehearttissue.Thinnerimageindicatesthatthereispossiblescarringorinfarctionoftheheart.NormalvsAbnormalHeartImageLeftImage-abnormalRightImage-normalPrognosisUsingTcHeartImagingPositiveMIBIscansarenearly100%accurate.NegativeMIBIscansarejustasaccurate.ConclusionTcMIBIisthebestradionuclearheartimagingagentusedtoday.Allowsmanyimagingtechniquestobeperformedthatarecriticalfordiagnosingheartdiseases.ReferencesJurisson,S.“CoordinationCompoundsinNuclearMedicine.”ChemicalReviews.1993,93,1137-1156.Holman,Sporn,Jones,etal.“MyocardialImagingwithTechnetium99CPI:InitialExperienceintheHuman”,TheJournalofNuclearMedicine.Angelberger,P.“Tc-99m(Tc-99m-TBI):optimizedsynthesis,radiochromatography,biodistribution,andpreliminarychemicalstudies.”“TechnetiumLabeledCardiacImaging.”“CardiacNuclearImaging.”