教学茨甲状腺

THYROIDANDPARATHYROIDSCINTIGRAPHYScottBritz-Cunningham,MD,PhDEVALUATIONOFTHESOLITARYTHYROIDNODULESolitaryNodule:DifferentialDiagnosisAdenomaFocalhyperplasiaCarcinomaFocalthyroiditisHemorrhageCystLymphomaMetastaticcarcinomafromanextrathyroidalprimaryBenigntumor(e.g.,hemangioma)SignsFavoringaBenignLesionSizestableoveryearsVeryrapidappearance(hours/days)ExcessordeficiencyofcirculatingthyroidhormonesRubbery/grittythyroidgland(suggestsautoimmunethyroiditis)MultiplenodulesSignsFavoringMalignancyIncreaseinsizewhilepatientisonsuppressivedosesofthyroidhormoneLocalpainDysphagia,hoarsenessHemoptysisFixationtotracheaorstrapmusclesCervicallymphadenopathy(usu.Ipsilateralanteriorcervicalnodes)Veryyoung(prepubescent)orveryold(>60years)ThyroidCarcinomaPapillary60-70%ofcasesmetastasizestolymphnodesFollicular20-25%ofcasesMorelikelytometastasizeviahematogenousrouteMedullary:5-10%ofcasesAnaplastic:10%ofcasesLaboratoryStudiesSerumthyroidfunctiontests:Hotnodules:80%areeuthyroid(usu.needtobeover2.5cmtobethyrotoxic)Carcinoma:usuallyeuthyroidSerumthyroglobulin:notspecificenoughfordiagnosticscreeningusefulasfollowupafterthyroidectomyMedullarycarcinoma:IncreasedserumcalcitoninIncreasedserumCEAUltrasoundCandetectnodulesdownto2mmCannotdifferentiatebenignfrommalignantnodulesUses:DistinguishingtruesolitarynodulesfrommultinodulargoiterConfirmingnoduleswhicharedifficulttopalpateGuidingFNAEvaluationofcystsImagingAgents123Iodine:BestimagingpropertiesHalf-life:13hrsEnergy:159keV(decaysbyelectroncapture)131Iodine:Usedforwhole-bodyscansandablationtherapyHalf-life:8daysEnergy:majorphotopeakat364keV(minorat80,284,607and723)ImagingAgents99mTc-Pertechnetate:Takenuplikeiodide,butnotorganifiedUptakerespondstoTSH,likeiodideWashesoutquicklyBackgroundishigherthanforiodideAdequatefordiagnosticscreeningofnodulesTypesofNodulesFunctioning(“hot”):10%ofallpalpablenodulesNon-functioning(“cold”):NosignificantuptakeThisisadefaultdiagnosis,ifyouareindoubt(hotnodulediagnosiswillterminatefurtherworkup)IndeterminateEvaluationofNodules5-15%ofclinicallydetectablesolitaryhypofunctioning(“cold”)noduleswillturnouttobemalignantAdominantcoldnoduleinamultinodulargoitershouldbeworkedupasasolitarynodule99mTc-Pertechnetate:nodulesusuallybehavethesameaswithiodide,butnotalwaysWHOLE-BODY

RADIOIODIDESCANSTumorsNotImageablewithRadioiodideAnaplasticthyroidcarcinomaHurthle-celltumorMedullarycarcinomaAlternativeimagingagents:FDGDMSA(dimercaptosuccinicacid)MIBG(metaiodobenzylguanidine)OctreotideMonoclonalantibodiesWhole-BodyRadioiodineScanNeedveryhighTSHleveltovisualizemetastasesreliablyWithdrawalfromSynthroid(T4)for4-6weeksbinantTSHAnyresidualthyroidtissuewilltakeuptracerbetterthancarcinomaImageafter2-3daystoreducebackgroundWhole-BodyRadioiodineScan:PhysiologicUptakeLiver:diffusepatternismetabolic;focalpatternismetastaticSalivaryglandsStomachIntestineUrinarybladderNasopharynxSweatglands/sweatGallbladderThymusWhole-BodyRadioiodineScans:FalsePositivesBronchiectasisBronchogeniccarcinomaRenalcystOvariancystMeckel’sdiverticulumStrumaovariiUrinarycontaminationZenker’sdiverticulumRadioiodideAblationTherapyPerformpreliminaryimagingwith2mCi(dosesabove5mCican“stun”lesions)Ifmetastasesareseen,giveafulltherapeuticdose(100-200mCi)Re-image1weekaftertherapyIfadditionallesionsappear,performafollow-upscanafter6-12monthsNote:ablationtherapycanonlybeeffectiveifthelesiontakesuptracerontheinitialimagingscanMETABOLIC

THYROIDDISEASESCausesofIncreasedUptakeGraves’diseaseAdenomas(functioning/hotnodules)LithiumtherapyReboundafterdiscontinuingthionamidesMultinodular(toxic)goiterHashimoto’sdisease(earlyphase)SimplegoiterReboundaftersubacutethyroiditisCausesofDecreasedUptakeExogenoushormoneHighdietaryiodineRadiographiccontrastmedium(maytake4-6weekstoclear)PropylthiouraciltreatmentSurgicalorradioiodineablationtherapyHashimoto’sdiseaseSubacutethyroiditisPostpartumthyroiditisStrumaovariiHyperthyroidism:DifferentialDiagnosisGraves’disease:mostcommonunderage40Toxicmultinodulargoiter/thyroidadenomaPituitarydysfunctionofadenoma(increasedTSH)Choriocarcinoma/hydatidiformmole(TSH-likesecretion)EctopicthyroidThyroiditisExogenousthyroidhormoneMultinodularGoiterEnlargedthyroidglandMultiplecold,warmandhotareasbilaterallySmallcoldfociarenotsuspicious,butdominantcoldnodulesshouldbetreatedlikesolitarycoldnodulesGraves’DiseaseEnlargedthyroidConvexbordersMayhaveaprominentpyramidallobeUptakeishomogeneousandincreasedrelativetobackground24-hruptake:typically40-70%Hashimoto’sThyroiditisScanappearancecanbevariable:Earlyphase:uptakemaybeuniformlyincreased(resemblingGraves’disease)Latephase:coarse,bilateralpatchydistributionSubacuteThyroiditisSerumT4ishigh,TSHislowThyroiduptakeislow(thyroidglandmaynotbevisualizedonscan)PARATHYROIDSCANSPrimaryHyperparathyroidismSingleormultipleadenoma:80-85%Hyperplasia:12-15%Carcinoma:1-3%ParathyroidScanTechniqueSubtractionmethod:201Thallium/9