Morphological Characteristics Of Atherosclerotic Stenosis Of Middle Cerebral Arteries On3.0T High Resolution Magnetic Resonance Imaging

Objective Our aim was to quantitatively assess remodeling pattern, eccentric patternand plaque distribution of symptomatic atherosclerotic middle cerebral artery (MCA)stenosis with3.0T high-resolution magnetic resonance imaging (HRMRI).Methods Eighty-seven consecutive patients with symptomatic atheroscleroticstenoses at M1segment of MCA on digital subtraction angiography (DSA)(50%～99%) were enrolled from November2009to May2011. HRMRI was performed onthe target segment by using a3.0T MR scanner. The vessel area (VA), luminal area(LA), maximal wall thickness (Max WT) and minimal wall thickness (Min WT) atthe maximal lumen narrowing (MLN) sites, and VA and LA at reference sites weremeasured. Reference VA and LA was measured according to the following criterion:①reference VA was the means of the proximal and distal VA; reference LA was themeans of the proximal and distal LA.②the reference site was defined using the MCAsegment of normal appearance proximal to the stenotic segment, if the proximalreference site was not available, the neighboring distal site was used instead, then thereference VA and LA was the VA and LA at reference sits selected. Wall area (WA)was estimated by VA—LA. Plaque area (PA) was calculated by WA at MLNsite—reference WA. Percent plaque burden was calculated as (PA/VA at MLNsite)×100%. The following variables were estimated⑴Remodeling pattern:remodeling index (RI) was the ratio of VA at MLN site to reference VA. Accordingthe above criterion of reference VA and LA, the RI was calculated and classifiedrespectively.①Remodeling index≥1.0was defined as positive remodeling (PR) andremodeling index＜1.0as negative remodeling (NR);②RI≤0.95was defined asNR) RI≥1.05as PR and0.95＞RI＜1.05as intermediate remodeling (IR). Wallcharacteristics were compared between the NR and PR group.⑵Eccentric pattern: eccentric index (EI) was calculated as (Max WT-Min WT)/Max WT at MLN sites. EI≥1.0was defined as eccentric lesion and EI＜1.0as concentric lesion. Wallcharacteristics were compared between the eccentric lesions and concentric lesions.⑶Plaque distribution at MLN site was classified based on the involvement of thesuperior, inferior, dorsal, or ventral MCA wall.Results⑴Remodeling pattern.①According to the first criterion,44patients wereincluded in the final analysis. NR was found in19(43.2%) lesions and PR in25(56.8%) lesions. At MLN sites, lesions with NR, compared with lesions with PR, hada less VA, WA and percent plaque burden (p＜0.0001). At the same time, lesionswith NR had a significantly lower EI than did lesions with PR (0.5vs.0.6, p=0.023).②According to the second criterion, seventy patients were included in the finalanalysis, and NR was found in29(41.4%) patients, IR in6(8.6%) patients, and PR in35(50.0%) patients. At MLN sites, compared with lesions with PR, lesions with NRhad a less VA, WA, percent plaque burden(P﹤0.001).⑵78patients were includedin the final analysis. Eccentric lesion was found in55(70.5%) lesions and concentriclesion in23(29.5%) lesions. Eccentric lesion had a larger Max WT and less Min WT(p＜0.0001), compared with concentric lesion.⑶Of the78patients included inthe final analysis, plaques were located at the superior wall in16(20.5%) patients, thedorsal wall in7(9.0%) patients, inferior wall in29(37.2%) patients, and the ventralwall in26(33.3%) patients. In total, the plaque involved the superior and dorsal wallin29.5%patients, and inferior and ventral wall in70.5%patients.Conclusions HRMRI can help assess remodeling pattern, eccentric pattern, andplaque location of MCA stenosis.