腦腫瘤MR診斷.ppt

BrainTumor-SystematicApproachbyRobinSmithuisandWalterMontanera河南省人民醫(yī)院放射科高明譯講,IntroductionIncidenceofCNStumorsAgedistributionTumorspreadIntra-versusExtraaxialMidlinecrossingMultifocaldiseaseCorticalbasedtumorsCTandMRCharacteristics,Fat-Calcification-CystHighonT1LowonT2DiffusionweightedimagingPerfusionImagingEnhancementDifferentialdiagnosisforspecific,anatomicareaSkullbaseSella/suprasellarCerebello-pontineanglePinealregionIntraventricular4thventricleTumorMimics,Schwannomalocatedinthecerebellopontineangle(CPA)withtypicalsignsofanextraaxialtumor,Meningiomawithabroadduralbaseandaduraltail，hyperostosisintheadjacentbone，enhanceshomogeneously，noblood-brain-barrier,Melanomametastasiswithgraymatterontheanteromedialsideofthelesion(redarrow)，intra-axial.,Ependymomawithextensiontothecerebellopontineangle(bluearrow)andintotheforamenmagnum(redarrow)ortothecisternamagna,Toassesstheextentofatumor.Anextra-axialtumorintheregionoftheleftcavernoussinuswithhomogeneousenhancementandabroadduraltail.Thisistypicalforameningioma.,Actualextentofthistumorisgreaterthanexpected.Thetumorissituatedinthepterygopalatinefossaandextendsintotheorbit.Italsospreadsanteriorlyintothemiddlecranialfossa.,Considerationfortheeffectonthesurroundingstructures.Primarybraintumorsarederivedfrombraincellsandoftenhavelessmasseffectfortheirsizethanyouwouldexpect,duetotheirinfiltrativegrowth.Thereisnoenhancementsothiswouldprobablybealow-gradeastrocytoma,TheabilityoftumorstocrossthemidlineGlioblastomamultiforme(GBM)frequentlycrossesthemidlinebyinfiltratingthewhitemattertractsofthecorpuscallosum.RadiationnecrosiscanlooklikerecurrentGBMandcansometimescrossthemidline.Meningiomaisanextra-axialtumorandcanspreadalongthemeningestothecontralateralside.Lymphomaisusuallylocatednearthemidline.Epidermoidcystscancrossthemidlineviathesubarachnoidspace.MScanalsopresentasamasslesioninthecorpuscallosum.,Left:MetastasesRight:MultiplemeningiomasandaschwannomainapatientwithNeurofibromatosisII,Multifocaldisease:MetastaticdiseaselymphomasMulticentricGlioblastomamultiforme(GBM)GliomatosiscerebriSeedingmetastases:Medulloblastomas,Ependymomas,GBMsandoligodendrogliomasPhacomatoses:NeurofibromatosisI:opticgliomasandastrocytomasNeurofibromatosisII:meningiomas,ependymomas,choroidplexuspapillomasTuberousSclerosis:subependymaltubers,intraventriculargiantcellastrocytomas,ependymomasvonHippelLindau:hemangioblastomasNon-tumorousdiseaseslikesmallvesseldisease,infections(septicemboli,abscesses)ordemyelinatingdiseaseslikeMS,CorticalbasedtumorsMostintra-axialtumorsarelocatedinthewhitematter.Sometumors,however,spreadtoorarelocatedinthegraymatter.Thesecorticalbasedtumorsincludesoligodendroglioma,gangliogliomaandDysembryoplasticNeuroepithialTumor(DNET).Thedifferentialdiagnosisincludesnon-tumorouslesionslikecerebritis,herpessimplexencephalitis,infarctionandpost-ictalchanges.,A45-year-oldfemalewithastableseizuredisorderfor15years.Thisisaganglioglioma.ThedifferentialdiagnosisincludesDNETandpilocyticastrocytoma.,A10-year-oldmalewithsecondaryepilepsy.ThisisaDysembryoplasticNeuroepithialTumor(DNET).,52-year-oldfemalewhocomplainedofheadacheandneckpainforoneyearwitharecentonsetoftonic-clonicseizures.Thisisaninfiltratingtumorwhichextendsallthewaytothecortex,withlimitedmasseffectonsurroundingstructuresandcalcifications.Themostlikelydiagnosisisoligodendroglioma.,Fat-Calcification-CystAruptureddermoidcystwiththeclassicalfindings.Chemicalshiftartefactindicatesthepresenceoffat,seenonlyinthefrequencyencodingdirection.Fatwithinatumorisseeninlipomas,dermoidcystsandteratomas.Sometumorslikelymphoma,colloidcystandPNET-MB(medulloblastoma)canhaveahighdensityonCT.,Acalcifiedmassinthesuprasellarregion,causingobstructivehydrocephalus.ThislocationandthecalcificationaretypicalforaCraniopharyngioma.Apineocytomaitselfdoesnotcalcify,butinsteaditexplodesthecalcificationsofthepinealgland.,Thecalcificationandtheextensionofthetumortothecortexareverytypicalforanoligodendroglioma.Anastrocytomashouldbeinthedifferential.,Apatientwithprogressivevisualloss.OnthecoronalandsagittalT1WIthereisalargemasscenteredaroundthesellawithabroadduralbase.Thereisextensionintothesella.Thisisacalcifiedmeningioma.,ManycysticlesionscansimulateaCNStumor.Theseincludeepidermoid,dermoid,arachnoid,neuroentericandneuroglialcysts,enlargedperivascularspacesofVirchowRobin.Inordertodeterminewhetheralesionisacystorcysticmass，lookforthefollowingcharacteristics:MorphologyFluid/fluidlevelContentusuallyisointensetoCSFonT1,T2andFLAIRDWI:restricteddiffusionAnarachnoidcystisisointensetoCSFonallsequences.Tumornecrosismaysometimeslooklikeacyst,butitisnevercompletelyisointensetoCSF.,CysticversusSolid,Ontheleftacraniopharyngiomawithanenhancingrimsurroundingthecysticcomponent.InthemiddleaneuroentericcystwiththecontentsofwhichhavethesamesignalintensityasCSF.Ontherightaglioblastomamultiforme(GBM)withacentralcysticcomponent.TheenhancementinGBMisusuallymoreirregular.,MosttumorshavealoworintermediatesignalintensityonT1WI.Exceptionstothisrulecanindicateaspecifictypeoftumor.CalcificationsaremostlydarkonT1WI,butdependingonthematrixofthecalcificationstheycansometimesbebrightonT1.EspeciallyongradientechoimagesslowflowcanbeseenasbrightsignalonT1WIandshouldnotbeconfusedwithenhancement.Ifyouonlydoanenhancedscan,rememberthathighsignalisnotalwaysenhancement.,HighonT1,SometumorswithhighsignalintensitiesonT1WI.Onthefarleftimagesofapatientwhopresentedwithapoplexy.Thehighsignalisduetohemorrhageinapituitarymacroadenoma.Thepatientinthemiddlehasaglioblastomamultiforme,whichcausedahemorrhageinthespleniumofthecorpuscallosum.Ontherightisapatientwithametastasisofamelanoma.Thehighsignalintensityisduetothemelanincontent.,MosttumorswillbebrightonT2WIduetoahighwatercontent.Whentumorshavealowwatercontenttheyareverydenseandhypercellularandthecellshaveahighnuclear-cytoplasmasmicratio.ThesetumorswillbedarkonT2WI.TheclassicexamplesareCNSlymphomaandPNET(alsohyperdenseonCT).CalcificationsaremostlydarkonT2WI.Paramagneticeffectscauseasignaldropandareseenintumorsthatcontainhemosiderin.ProteinaceousmaterialcanbedarkonT2dependingonthecontentoftheproteinitself.Aclassicexampleofthisisthecolloidcyst.FlowvoidsarealsodarkonT2andindicatethepresenceofvesselsorflowwithinalesion.Thisisseenintumorsthatcontainalotofvesselslikehemangioblastomas,butalsoinnon-tumorouslesionslikevascularmalformations.,LowonT2,Melanomawithmelanin.GBMsometimeswithahighnuclear-cytoplasmicratio.MostGBMsarehyperintenseonT2WI.PNETtypicallyhasahighnuclear-cytoplasmicratio，whichmostlylocatedintheregionofthe4thventricle,anotherlesscommonlocationisintheregionofthepinealgland.Mucinousmetastasesoftenwithcalcifications.Meningiomas：iso-SI.HighSIonT2WIiftheycontainalotofwater.LowSIonT2WIiftheyareverydenseandhypercellularorwhentheycontaincalcifications.,HighintensityonDWIindicatesrestrictionoftheabilityofwaterprotonstodiffuseextracellularly.Restricteddiffusionisseeninabscesses,epidermoidcystsandacuteinfarction(duetocytotoxicedema).Incerebralabscessesthediffusionisprobablyrestrictedduetotheviscosityofpus,resultinginahighsignalonDWI.Inmosttumorsthereisnorestricteddiffusion-eveninnecroticorcysticcomponents.Thisresultsinanormal,lowsignalonDWI.,Diffusionweightedimaging,PerfusionimagingcanplayanimportantroleindeterminingthemalignancygradeofaCNStumor.Perfusiondependsonthevascularityofatumorandisnotdependentonthebreakdownoftheblood-brainbarrier.Theamountofperfusionshowsabettercorrelationwiththegradeofmalignancyofatumorthantheamountofcontrastenhancement.,PerfusionImaging,BloodbrainbarrierThebrainhasauniquetriplelayeredblood-brainbarrier(BBB)withtightendothelialjunctionsinordertomaintainaconsistentinternalmilieu.Contrastwillnotleakintothebrainunlessthisbarrierisdamaged.EnhancementisseenwhenaCNStumordestroystheBBB.Extra-axialtumorssuchasmeningiomasandschwannomasarenotderivedfrombraincellsanddonothaveaBBB.Thereforetheywillenhance.Thereisalsonoblood-brainbarrierinthepituitary,pinealandchoroidplexusregions.Somenon-tumorallesionsenhancebecausetheycanalsobreakdowntheBBBandmaysimulateabraintumor.Theselesionsincludelikeinfections,demyelinatingdiseases(MS)andinfarctions.,Enhancement,Contrastenhancementcannotvisualizethefullextentofatumorincasesofinfiltratingtumors,likegliomas.Thereasonforthisisthattumorcellsblendwiththenormalbrainparenchymawherethebloodbrainbarrierisstillintact.TumorcellscanbefoundbeyondtheenhancingmarginsofthetumorandbeyondanyMRsignalalteration-evenbeyondtheareaofedema.,OntheT2WIthereisalesioninthelefttemporallobe,foundincidentally.TherewasnoenhancementandtheDWIwasnormal.Duringfollow-uptherewasaslightincreaseinsize.Thiswasdiagnosedasalow-gradeastrocytoma.Itisnotpossibletoresectsuchalesion,sincetheinfiltratingtumorscellsarewithinthenormal-appearingbraintissue.,Ingliomas-likeastrocytomas,oligodendrogliomasandglioblastomamultiforme-enhancementusuallyindicatesahigherdegreeofmalignancy.Thereforewhenduringthefollowupofalow-gradegliomathetumorstartstoenhance,itisasignofmalignanttransformation.Gangliogliomasandpilocyticastrocytomasaretheexceptionstothisrule:theyarelow-gradetumors,buttheyenhancevividly.Asdiscussedabove,itrecentlyhasbeenshownthattumorangiogenesisasshownbyperfusionMRcorrelatesbetterwithtumorgradethanenhancementaftertheadministrationofintravenouscontrast.,Low-gradetumorswithenhancementaGanglioglioma(left)andapilocyticastrocytoma(right),Theamountofenhancementdependsontheamountofcontrastthatisdeliveredtotheinterstitium.Ingeneral,thelongerwewait,thebettertheinterstitialenhancementwillbe.Theoptimaltimingisabout30minutesanditisbettertogivecontrastatthestartoftheexaminationandtodotheenhancedT1WIattheend.,Left:SchwannomaextendingintothemiddlecranialfossawithhomogeneousenhancemantRight:Primarylymphomaknownforitsvividenhancement,Noenhancementisseenin:LowgradeastrocytomasCysticnon-tumorallesions:DermoidcystEpidermoidcystArachnoidcyst,Anintra-axialtumorinanadultcenteredinthetemporallobeandinvolvesthecortex.Massiveinfiltrativegrowthinvolvingalargepartoftherightcerebralhemisphere,withminimalmasseffect&noenhancement.Thesearetypicalforalow-gradeastrocytoma.,Homogeneousenhancementcanbeseenin:MetastasesLymphomaGerminomaandotherpinealglandtumorsPituitarymacroadenomaPilocyticastrocytomaandhemangioblastoma(onlythesolidcomponent)GangliogliomaMeningiomaandSchwannoma,Patchyenhancementcanbeseenin:MetastasesOligodendrogliomaGlioblastomamultiformeRadiationnecrosis,Aglioblastomamultiforme(GBM).Theenhancementindicatesthatthisisahigh-gradetumor,butonlypartsofitenhancewithacysticcomponentwithringenhancement.ThetumorcellsprobablyextendbeyondtheareaofedemaasseenontheFLAIRimage,becausegliomasgrowinfiltrativelyintonormalbrain-initiallywithoutanyMRchanges.,Alargetumorislocatedintherighthemispherewithlimitedmass-effect,indicateingthatthereismarkedinfiltrativegrowth.HeterogeneityonbothT2WIandFLAIR.Thereispatchyenhancement.AllthesefindingsaretypicalforaGBM.Virtuallynoothertumorbehavesinthisway.,Threedifferentringenhancinglesions,ConspicuityoftumorswithcontrastThecaseontheleftdemonstratesthevalueofGadoliniumintheconspicuityoftumors.ThisisapatientwithNeurofibromatosisII.Aftertheadministrationofcontrastthetwomeningiomasandtheschwannomaareeasilyseen.,Leptomeningealmetastasesareusuallynotseenwithouttheadministrationofintravenouscontrast.Thecaseonthetopdemonstratestheabnormalenhancementalongthebrainstem,alongthefoliaofthecerebellum(yellowarrow)andalongthefifthintracranialnerve(bluearrow)inapatientwithLeptomeningealmetastases.,SkullbaseCommonskullbasetumorseitherarisefromextracranialstructureslikethesinuses(sinonasalcarcinoma),orfromtheskullbaseitself(chordoma,chondrosarcoma,fibrousdysplasia).Chordomaisusuallylocatedinthemidline,whilechondrasarcomausuallyarisesoffthemidline.,Differentialdiagnosisforspecificanatomicarea,Amidlinetumorarisingfromtheclivus.Thisisthetypicalpresentationofachordoma.Thedifferentialdiagnosiswouldincludeametastasisandachondrosarcoma.,Anotherskullbasetumorlocatedoffmidline.Thisisatypicalpresentationforachondrosarcoma.Thedifferentialdiagnosiswouldincludeametastasisandaparaganglioma.Chondrosarcomascanbelocatedinthemidlineandchordomasaresometimeslocatedoffmidlinebutthosecasesareexceptional.,AnexampleofaSkullBaseParaganglioma.,A58-year-oldmalewithagradualonsetofrightfacialpainandnumbnessandarecentonsetofdoublevision.Thereisanenhancingmassanteriortotheskullbaseandalsointheregionoftherightcavernoussinus.Inthebonewindowsettingthereissclerosisoftheskullbase,particularlyintheregionoftheclivus.ContinuewiththeMRimages.,Themoststrikingfindingistheblackclivusduetothesclerosis.AnormalclivusisbrightonT1WIasaresultofthefattybonemarrow.Thereisanenhancingmassanteriortotheclivus.Onthecoronalimagesweseetheenhancementextendingthroughtheforamenovaletotherightofthecavernoussinus.ThediagnosisisaNasopharyngealsquamouscellcarcinomawithintracranialextension.,Sella/suprasellar：InthisregionitisimportanttokeepthepossibilityofanAneurysminthedifferentialdiagnosis.,Imagesofamassinthesuprasellarcistern.OntheNECTwecanseethatitcontainscalcium.OntheT1WIthereisahyperintenseareathatshowsnoenhancement(i.e.cystic).Thereareothercomponentsthatshowenhancement.Withahydrocephalus.ThesefindingsareveryspecificforaCraniopharyngeoma.,OntheleftNECTandenhancedCT-imagesofa33-year-oldfemalewithsevereheadache(worseinthea.m.),reductioninvisualacuityandvisualfieldsandpapilledema.ContinuewiththeMRimages.,Noticethenormalinferiorlydisplacedpituitarygland.Thismeansitisnotamacroadenoma.ThediagnosisisagainaCraniopharyngioma.Thedifferentialdiagnosiswouldincludeanastrocytomaandameningioma.,Cerebello-pontineangle,A52-year-oldmalewithhearinglossontheright.Theimagesshowanunusualcysticmasswithenhancingseptations.Thereisalsosomeenhancementwithintheinternalacousticcanal.Basedontheimagesthemostlikelydiagnosiswouldbeacysticschwannoma,butthisha