颅内动脉粥样硬化的影像学检查-管腔狭窄与侧枝灌注英文课件

1、Imaging of Intracranial Atherosclerosis: Stenoses and Collateral Perfusion颅内动脉粥样硬化的影像学检查管腔狭窄与侧枝灌注David S Liebeskind, MDAssociate Professor of Neurology & Director of Stroke ImagingCo-Director, UCLA Cerebral Blood Flow Laboratory Associate Neurology Director, UCLA Stroke CenterNo potential conflicts

2、to discloseNIH/NINDS K23NS054084June 20, 2009Tiantan International Stroke Conference, Beijing, ChinaObjectives 目的Overview of current imaging in intracranial atherosclerosisConsider arterial lesions beyond degree of luminal stenosisUnderscore the paramount role of collateral perfusionExplore how imag

3、ing of intracranial atherosclerosis may provide insight on many other aspects of ischemic strokeIschemia 缺血Ischemia as principal pathophysiologic event, collaterals may avert any detrimental effect of thrombosis or plaqueVast majority of efforts focus on restoration of antegrade flow, anti-thromboti

4、cs or arterial manipulationHemorrhagic transformation 出血性转化Severe ischemia and neurovascular compromiseReperfusion rate ischemic pre- and post-conditioning driven via collaterals DSLTime is not brain!Across population of stroke cases studied from onset to chronic phase, not in a given patient during

5、 early phasesTime of symptom onset time of vascular occlusionCollaterals prone to failure over time DSLTrialsSONIA in parallel with WASIDSAMMPRISOpportunity to discern mechanismsNot just % stenosisFlow at lesion QMRATCD with embolus detectionCollaterals on DSAN of 1- intracranial atherosclerosisDiag

6、nosis, rational selection of therapy Peri-procedural/serial imagingOpportunity to revise treatment strategyLesion/stenosisLength and architecture of plaqueCTA SpecificsPredominantly anatomical angiographic imagesInsensitivity to flow physiologyLack of temporal resolutionFuture of CTAImproved image q

7、uality with increasing multidetector capabilityPossible temporal resolutionContrast modificationsAlternative agentsRefined dosing schemes CTA of Stented ArteryMRAFlow-sensitive nature of MRIGradient echo imaging rapid scan acquisition with particular sensitivity to flow-related effectsMRA techniques

8、 include time-of-flight (TOF) and phase contrast (PC) imaging Time-of-Flight (TOF) MRAGadolinium-Enhanced MRAImproves vascular signal intensityReduces signal dropout due to slow flowDynamic or time-resolved MRATemporal resolution offset by limited spatial resolutionGadolinium-Enhanced MRAPhase Contr

9、ast (PC) MRA相位对比MRAPC MRA employs gradients that induce phase shifts in flowing blood with subsequent background subtractionGradient modifications allow for determination of flow direction and flow rateMapping of flow directionMeasurement of flow ratesDifferentiating slow flow from frank thrombosisM

10、RA SpecificsInferior spatial resolutionLimited depiction of arterial structures beyond the proximal cerebral vesselsFlow-related artifacts due to slow or turbulent flowSusceptibility artifact induced by metal clips or objectsPatient motion may limit diagnostic utilityMRA ArtifactsWillisian collatera

11、lizationDSAMethodology/critical appraisal?Frequently encounter case series biased by other selection biasesSONIANot how we generally use techniquesRule-out diseaseIntracranial vascular calcificationPlaque stabilityUSPIOVessel wall imaging T1-weighted post-contrast imagesGRE and phase imagingGRE = ba

12、ckground magnitude + phase = + FVHSlow collateral flow distal to severe lesionsRelatively rareAsymptomatic stenosesWASID, 18.9% (n=14/74) on 4-vessel cerebral angiography and 27.3% (n=65/238) on MRADuring a mean follow-up period of 1.8 years, no ischemic strokes were attributable to an AIS on angiog

13、raphy and 5 ischemic strokes (5.9%, 95% CI: 2.1% to 12.3%) occurred in the AIS territory on MRA (risk at 1 year=3.5%, 95% CI: 0.8% to 9.0%)Adequate collateral flow may offset ischemia and help embolic washoutCollaterals in WASIDCollateral circulation assessed on 287/569 (50%) angiograms performed at

14、 study entry demonstrating proximal arterial stenosis ranging from 50-99%ASITN/SIR collateral grade broadly distributed0 (absent or no collaterals) in 69%1 (slow, minimal) in 10%2 (more rapid, yet incomplete perfusion of territory) in 7%3 (complete but delayed perfusion) in 11%4 (rapid and complete

15、collateral perfusion) in 4%Collaterals and WASID stenosesThe extent of collateral flow for all proximal arterial lesions (ICA, MCA, BA, VA) correlated with the percentage of stenosis (p0.001), with more severe stenoses exhibiting greater compensatory collateral flowThe full range of collateral grade

16、s, however, was evident at all percentages of stenosesCollaterals determine stroke riskAcross all percentages of stenosis, extent of collateral circulation an independent predictor for subsequent stroke in territory of symptomatic artery (p0.0001)Divergent risk patternsContradictory role of collater

17、als in cases with severe (70%) versus mild or moderate stenoses (50-69%)Protective influence of collaterals in severe stenosisOminous marker of future stroke in milder stenosesCox proportional hazards model confirmed this interaction (p=0.001)Why have collaterals at 54%?Severe stenosesGood collatera

18、lsPoor collateralsNo collateralsCollaterals as ominous markerConversely, at milder degrees of stenoses (50-69%) the presence of more extensive collaterals was associated with a greater likelihood of subsequent stroke (p0.0001)Mild or moderate stenosesGood collateralsNo collateralsPoor collateralsCol

19、lateral perfusion on DSANoninvasive perfusion imagingNot CT versus MRI, but reflection of physiology!Must consider identical perfusion parametersMultiparametric approaches to understand hemodynamics and evolving ischemiaCBVMTTCBFCT perfusionCT perfusionMR perfusion or PWIMeaningless delays?Focal delay without symptoms ChangeCBF OEF CMRO2CBVMTT (CBV/CBF)VR (hypercapnia) VR (hypocapnia) Hemodynamics and CBV! DSL DSLCBVIschemic stroke due to IA results in dramatically less severe neurological deficits and diminished lesion v