症状性大脑中动脉粥样硬化斑块分布及形态学特征的高分辨率磁共振成像研究

Distribution and morphological characteristics of symptomatic atherosclerotic plaques in the middle cerebral artery using high-resolution magnetic resonance imaging

采用高分辨率磁共振(HR-MRI)血管壁成像技术观察症状性大脑中动脉(MCA)粥样硬化斑块的分布和形态学特征,初步探讨与急性脑梗死相关的高危斑块的HR-MRI特征.方法对2014年1月至2016年1月在扬州大学附属医院收集的57例症状性MCA粥样硬化患者进行弥散加权成像(DWI)、三维时间飞跃法头颅磁共振血管成像(3D TOF-MRA)及MCA HR-MRI检查.根据DWI检查结果将患者分为短暂性脑缺血发作(TIA)组(27例)和急性脑梗死组(30例),统计MCA管腔最狭窄层面斑块在4个90°扇形区域的分布情况,定量测量血管最狭窄处(MLN)的管腔面积(LAMLN)、血管面积(VAMLN)和参考血管的管腔面积(LAreference)、血管面积(VAreference),再以此计算出血管最狭窄处管壁面积(WAMLN)、斑块面积、斑块负荷百分比、狭窄率、重构指数,将各组数据进行对比.结果对57例患者MCA粥样硬化斑块进行定位及形态学分析发现,症状性MCA粥样硬化斑块位于腹侧壁19例(33.3%)、上侧壁15例(26.3%)、背侧壁10例(17.5%)、下侧壁13例(22.8%).TIA组和急性脑梗死组位于腹侧壁、上侧壁、背侧壁、下侧壁分别为6例(22.2%)、5例(18.5%)、7例(25.9%)、9例(33.3%)和13例(43.3%)、10例(33.3%)、3例(10.0%)、4例(13.3%),两组之间各侧壁分布的差异无统计学意义(均P>0.05).TIA组和急性脑梗死组的VAreference、LAreference、VAMLN、重构指数分别为(19.89± 1.34)mm^2、(15.19±2.04)mm^2、(20.78±1.78)mm^2、1.09±0.11和(19.70±1.34)mm^2、(14.60±2.33)mm^2、(21.53±2.34)mm^2、1.10±0.11,两组之间差异无统计学意义(均P>0.05).两组的重构方式均以正性重构为主,共44例(77.2%).TIA组和急性脑梗死组的WAMLN、斑块面积、狭窄率、斑块负荷百分比分别为(8.85±1.92)mm^2、(4.00±3.00)mm^2、20.92%±9.18%、19.05%±14.93%和(11.10±1.88)mm^2、(6.00± 2.25)mm^2、28.56%±8.67%、27.30%±7.69%,两组之间差异有统计学意义(t=-4.466,t=-2.865,t=-3.231, t=-2.580,均P<0.01). TIA组斑块表面不光整8例(29.6%),急性脑梗死组斑块表面不光整19例(63.3%),两组之间差异有统计学意义(χ^2=6.475,P<0.05).TIA组和急性脑梗死组的LAMLN分别为(11.93±1.59)mm^2和(10.43±2.08)mm^2,两组之间差异有统计学意义(t=3.033,P<0.01).结论急性脑梗死组的MCA粥样硬化斑块负荷更大,最大狭窄处管壁更厚,表面不光整更多,提示其具有高危斑块的特征性.

Objective To observe distribution and morphological characteristics of symptomatic atherosclerotic plaques in the middle cerebral artery (MCA) using high-resolution magnetic resonance imaging (HR-MRI), and to investigate HR-MRI characteristics of atherosclerotic plaques in the MCA in patients with acute cerebral infarction. Methods A total of 57 symptomatic patients with MCA atherosclerotic plaques recruited in the Affiliated Hospital of Yangzhou University from January 2014 to January 2016 were imaged with diffusion weighted imaging (DWI), three dimensional time of flight magnetic resonance angiography (3D TOF-MRA) and HR-MRI scanning for plaque on a 3.0 T MRI scanner. According to the results of DWI examination, the 57 patients were divided into transient ischemic attack (TIA) group (27 cases) and acute cerebral infarction group (30 cases). 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, lumen area (LAMLN), vessel area (VAMLN) at maximal lumen narrow (MLN) and LAreference, VAreference were measured, then wall area (WA), plaque area (PA), percentage of plaque burden, rate of lumen stenosis and remodeling index (RI) were calculated. The data of each group were compared and analyzed. Results The location and morphological analysis of the 57 patients with symptomatic MCA atherosclerotic plaques revealed that plaques were located in the ventral wall in 19 cases (33.3%), the upper wall in 15 cases (26.3%), the dorsal wall in 10 cases (17.5%), and the lower wall in 13 cases (22.8%). For the location variations in ventral wall, upper wall, dorsal wall and lower wall, the TIA group was shown as six cases (22.2%), five cases (18.5%), seven cases (25.9%) and nine cases (33.3%), and the acute cerebral infarction group was shown as 13 cases (43.3%), 10 cases (33.3%), three cases (10.0%) and four cases (13.3%), respectively. There was no statistically significant difference in the distribution of each side wall between the two groups (P>0.05). VAreference, LAreference, VAMLN and RI of the TIA group and the acute cerebral infarction group were (19.89 ± 1.34) mm^2,(15.19 ± 2.04) mm^2,(20.78 ± 1.78) mm^2, 1.09 ± 0.11 and (19.70 ± 1.34) mm^2,(14.60 ± 2.33) mm^2,(21.53 ± 2.34) mm^2, 1.10 ± 0.11, respectively. There was no statistically significant difference between the two groups (P>0.05). The remodeling patterns of both groups were mainly positive remodeling, with a total of 44 cases (77.2%). In the TIA group and the acute cerebral infarction group, the WAMLN, PA, stenosis rate and plaque load percentages were (8.85±1.92) mm2,(4.00±3.00) mm^2, 20.92%± 9.18%, 19.05%± 14.93% and (11.10 ± 1.88) mm2,(6.00 ± 2.25) mm^2, 28.56%± 8.67%, 27.30%± 7.69%, respectively. The differences between the two groups were statistically significant (t=-4.466, t=-2.865, t=-3.231, t=-2.580, P<0.01). There were eight patients (29.6%) with unsmooth plaque surface in the TIA group and 19 patients (63.3%) in the acute cerebral infarction group. The differences between the two groups were statistically significant (χ^2=6.475, P<0.05). LAMLN in the TIA group and the acute cerebral infarction group was (11.93±1.59) mm^2 and (10.43±2.08) mm^2 respectively, and the difference between the two groups was statistically significant (t=3.033, P<0.01). Conclusions Symptomatic atherosclerotic plaques in MCA in the acute cerebral infarction group have higher plaque load, thicker vascular wall at the maximum stenosis and more unsmooth plaque surface. This indicates the characteristics of high-risk plaques to a certain extent.