Application Of High - Resolution Magnetic Resonance Angiography In Intracranial Atherosclerotic Plaques

Part I Middle cerebral artery atherosclerotic plaques distribution and morphological characteristics in symptomatic patients by high-resolution Magnetic Resonance ImagingPurposeTo investigate middle cerebral artery (MCA) atherosclerotic plaques distribution characteristics and morphological characteristics in symptomatic patients by high-resolution MRI,try to explore the high risk features of MCA plaque in acute stroke.MethodsWe collected 57 patients with middle cerebral artery infarction,in which thirty patients with actue ischemic strokes and twenty-seven ones with transient ischemic attacks.The MRJ program included diffusion weighted imaging (DWI),MR angiography (MRA),and MCA high-resolution MRJ examinations.The distribution of the narrowest lumen plaque was evaluated by cross-section division into four equal arcs (superior, inferior, ventral, dorsal arcs).For quantitative analysis> we measured maximal lumen narrowing(MLN),lumen area(LAMLN),vessel area(VAMLN) and LAreference,VAreference,then calculated wall area(WA),plaque area(PA),remodeling ratio(RI),plaque burden.lumen stenosis.Each parameter was compared by analysis.ResultsOverall,plaques were more frequently located at the ventral (33.3%) and superior (26.3%),The plaques have no distribution discrepancy between two groups(.P>0.05).There are 27 irregularity of plaque surface were observed,the concentrations of Hs-CRP are in the range of normal values,and there is no significant difference between two groups(P>0.05).More positive remodeling were observed than negative remodeling.The VAMLN,WAMLN,PA,lumen stenosis and plaque burden in actue ischemic stroke group are bigger than TIA group and more irregularity of plaque surface were observed,while LAMLN is samller.We used receiver operating characteristic curve (ROC curve) carries on the analysis to the above mentioned indices, atherosclerotic plaques are found for the percentage of capacity, stenosis rate, PA, WAMLN, LAMLN on acute ischemic stroke have diagnostic capabilities, which WAMLN the diagnostic ability of best curve area (area under the curve (AUC) is 0.817 (95% confidence interval (CI) in [0.703,0.931]), optimal cutoff value is 9.50mm2 and corresponding sensitivity and specificity respectively for 86.7% and 63.0%.ConclusionsHigh-resolution MRI is able to detect MCA atherosclerotic plaques distributi on characteristics and morphological characteristics in symptomatic patients.We found that plaque size of patients with actue ischemic stroke is bigger than TI A,and lumen area of maximal lumen narrowing is smaller,which shows the cha racteristics of high risk plaque,to a certain extent.The diagnostic capability of WAMLN is best,and the optimal cutoff value is 9.50mm2Part II The relationship of intracranial atherosclerotic plaque enhancement and time on 3D high-resolution MR.PurposeTo characterize the enhancement of intacranial atherosclerotic plaque by using three-dimensional (3D) high-resolution MR1.We try to the correlation between the enhancement of palque and time elapsing.MethodsThe 61 patients included in the study were divided into three group accroding to the elapsed time between symptoms appear and MRI examination,these are acute phase (4 weeks from acute stroke), subacute phase (4-12 weeks), and chronic phase (>12 weeks).The MRI program included diffusion weighted imaging (DWI),MR angiography (MRA),and 3D-SPACE MRI examinations,then characterize the enhancement of intacranial atherosclerotic plaque.ResultsAcute group had obvious enhancement, enhanced rate is the larggest; subacute group to mild enhancement; chronic group has not been strengthened, enhancement ratio is the smallest. In acute and subacute groups, acute group and chronic group, subacute group and chronic group enhancement degree and enhanced rates were significantly different(P<0.05).The time of onset to HRMRI examination showed a significant negative correlation with the enhancement rate(r=-0.580, P<0.05).ConclusionsThe enhancement degree and enhanced rate of the atherosclerotic plaque decreased with time telapsing, may provide evidence for vulnerability of plaque in some degree and guide the secondary prevention of ischemic stroke.