顱內(nèi)動(dòng)脈粥樣硬化的影像學(xué)檢查-管腔狹窄與側(cè)枝灌注英文

ImagingofIntracranialAtherosclerosis:

StenosesandCollateralPerfusion

顱內(nèi)動(dòng)脈粥樣硬化的影像學(xué)檢查—管腔狹窄與側(cè)枝灌注DavidSLiebeskind,MDAssociateProfessorofNeurology&DirectorofStrokeImagingCo-Director,UCLACerebralBloodFlowLaboratoryAssociateNeurologyDirector,UCLAStrokeCenterNopotentialconflictstodiscloseNIH/NINDSK23NS054084June20,2021TiantanInternationalStrokeConference,Beijing,ChinaObjectives目的OverviewofcurrentimaginginintracranialatherosclerosisConsiderarteriallesionsbeyonddegreeofluminalstenosisUnderscoretheparamountroleofcollateralperfusionExplorehowimagingofintracranialatherosclerosismayprovideinsightonmanyotheraspectsofischemicstrokeIschemia缺血Ischemiaasprincipalpathophysiologicevent,collateralsmayavertanydetrimentaleffectofthrombosisorplaqueVastmajorityofeffortsfocusonrestorationofantegradeflow,anti-thromboticsorarterialmanipulationHemorrhagictransformation

出血性轉(zhuǎn)化SevereischemiaandneurovascularcompromiseReperfusionrate–ischemicpre-andpost-conditioningdrivenviacollaterals?DSLTimeisnotbrain!Acrosspopulationofstrokecasesstudiedfromonsettochronicphase,notinagivenpatientduringearlyphasesTimeofsymptomonset≠timeofvascularocclusionCollateralspronetofailureovertime?DSLMoyamoyaIdealmodelofcollateralsinchroniccerebralischemiaStrikingconsistencyinstenoticarterialfeaturesUniversaldependenceonleptomeningealcollateralsStrokesaretypicallylimitedinextent,allowingforrecoveryTIAwithoutstrokeshouldbegoalRecurrentischemiaandtemporalfeatureseasilystudiedImagingToolstounderstandphysiology,mechanismsNotTCDvs.CTAvs.MRAvs.DSAetc.DistinctfeaturesemphasizedbyeachmodalityAnatomyFlowTrialsSONIAinparallelwithWASIDSAMMPRISOpportunitytodiscernmechanismsNotjust%stenosisFlowatlesionQMRATCDwithembolusdetectionCollateralsonDSANof1-intracranialatherosclerosisDiagnosis,rationalselectionoftherapyPeri-procedural/serialimagingOpportunitytorevisetreatmentstrategyLesion/stenosisLengthandarchitectureofplaqueTCD–beyondvelocitiesMFV,PI,AUCCurrentTCDvelocitycriteriafordiagnosisofintracranialstenosisareinsensitivetoage-andgender-relatedchangesincerebralbloodflowTCDdiagnosisbasedonpublishedcriteriamayoverestimatediseaseprevalenceLab-specificnormsmayneedtobeestablishedtoaccountfordemographicfeaturesofpopulationCTACTASpecificsLuminalcontentsidentifiedbyfilteringofimagedatabasedonHounsfieldunitsContrastopacificationerrorsduetoadministration,dosing,bodyhabitus,injectionrate,bolustrackingWindowwidthandcenterlevelsarecriticalMeasurementofstenosesErroneousfusionofdifferentstructuresAutomatedbonesegmentationCalcificationsCTASpecificsPredominantlyanatomicalangiographicimagesInsensitivitytoflowphysiologyLackoftemporalresolutionFutureofCTAImprovedimagequalitywithincreasingmultidetectorcapabilityPossibletemporalresolutionContrastmodificationsAlternativeagentsRefineddosingschemesCTAofStentedArteryMRAFlow-sensitivenatureofMRIGradientechoimaging–rapidscanacquisitionwithparticularsensitivitytoflow-relatedeffectsMRAtechniquesincludetime-of-flight(TOF)andphasecontrast(PC)imagingTime-of-Flight(TOF)MRAInflowoffullymagnetizedspinsintoaslicesaturatedbyaradiofrequencypulse2DTOFMRA–thickerslices,lowersignal-to-noiseratios3DTOFMRA–thinslices,highersignal-to-noiseratiosSignalintensitydependentonslicethickness,flipangle,TEMagnetizationtransfercontrastforbackgroundsuppressionMultipleoverlappingthinslabangiography(MOTSA)

Time-of-Flight(TOF)MRAGadolinium-EnhancedMRAImprovesvascularsignalintensityReducessignaldropoutduetoslowflowDynamicortime-resolvedMRATemporalresolutionoffsetbylimitedspatialresolutionGadolinium-EnhancedMRAPhaseContrast(PC)MRA相位比照MRAPCMRAemploysgradientsthatinducephaseshiftsinflowingbloodwithsubsequentbackgroundsubtractionGradientmodificationsallowfordeterminationofflowdirectionandflowrateMappingofflowdirectionMeasurementofflowratesDifferentiatingslowflowfromfrankthrombosisMRASpecificsInferiorspatialresolutionLimiteddepictionofarterialstructuresbeyondtheproximalcerebralvesselsFlow-relatedartifactsduetosloworturbulentflowSusceptibilityartifactinducedbymetalclipsorobjectsPatientmotionmaylimitdiagnosticutilityMRAArtifactsWillisiancollateralizationDSAMethodology/criticalappraisal?FrequentlyencountercaseseriesbiasedbyotherselectionbiasesSONIANothowwegenerallyusetechniquesRule-outdiseaseIntracranialvascularcalcificationPlaquestabilityUSPIOVesselwallimagingT1-weightedpost-contrastimagesGREandphaseimagingGRE=backgroundmagnitude+phase=+FVHSlowcollateralflowdistaltoseverelesionsRelativelyrareAsymptomaticstenosesWASID,18.9%(n=14/74)on4-vesselcerebralangiographyand27.3%(n=65/238)onMRADuringameanfollow-upperiodof1.8years,noischemicstrokeswereattributabletoanAISonangiographyand5ischemicstrokes(5.9%,95%CI:2.1%to12.3%)occurredintheAISterritoryonMRA(riskat1year=3.5%,95%CI:0.8%to9.0%)AdequatecollateralflowmayoffsetischemiaandhelpembolicwashoutCollateralsinWASIDCollateralcirculationassessedon287/569(50%)angiogramsperformedatstudyentrydemonstratingproximalarterialstenosisrangingfrom50-99%ASITN/SIRcollateralgradebroadlydistributed0(absentornocollaterals)in69%1(slow,minimal)in10%2(morerapid,yetincompleteperfusionofterritory)in7%3(completebutdelayedperfusion)in11%4(rapidandcompletecollateralperfusion)in4%CollateralsandWASIDstenosesTheextentofcollateralflowforallproximalarteriallesions(ICA,MCA,BA,VA)correlatedwiththepercentageofstenosis(p<0.001),withmoreseverestenosesexhibitinggreatercompensatorycollateralflowThefullrangeofcollateralgrades,however,wasevidentatallpercentagesofstenosesCollateralsdeterminestrokeriskAcrossallpercentagesofstenosis,extentofcollateralcirculationanindependentpredictorforsubsequentstrokeinterritoryofsymptomaticartery(p<0.0001)DivergentriskpatternsContradictoryroleofcollateralsincaseswithsevere(≥70%)versusmildormoderatestenoses(50-69%)ProtectiveinfluenceofcollateralsinseverestenosisOminousmarkeroffuturestrokeinmilderstenosesCoxproportionalhazardsmodelconfirmedthisinteraction(p=0.001)Whyhavecollateralsat54%?SeverestenosesGoodcollateralsPoorcollateralsNocollateralsCollateralsasominousmarkerConversely,atmilderdegreesofstenoses(50-69%)thepresenceofmoreextensivecollateralswasassociatedwithagreaterlikelihoodofsubsequentstroke(p<0.0001)MildormoderatestenosesGoodcollateralsNocollateralsPoorcollateralsCollateralperfusiononDSANoninvasiveperfusionimagingNotCTversusMRI,butreflectionofphysiology!MustconsideridenticalperfusionparametersMultiparametricapproachestounderstandhemodynamicsandevolvingischemiaCBVMTTCBFCTperfusionCTperfusionMRperfusionorPWIMeaninglessdelays?Focaldelaywithoutsymptoms

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