MRI评估颈动脉粥样硬化斑块成分、类型及其与临床症状的相关性

To evaluate the composition and typing of carotid artery atherosclerotic plaque and the relationship between plaque morphology and clinical symptoms

目的：应用3.0 T MRI评估颈动脉粥样硬化斑块内成分，并据此对斑块进行分型；探讨斑块成分、类型与临床发生缺血性脑血管事件的相关性，评价应用高场强MR对斑块进行早期诊断的预警作用。方法对108例经超声检查发现颈动脉粥样硬化斑块的患者施行颈动脉斑块的MRI检查。颈动脉MR检查使用Philips或GE 3.0 T MR扫描仪，线圈选用颈动脉专用8通道表面线圈，扫描序列包括3D TOF、T1WI、T2WI、PDWI、MP-RAGE及CE-T1WI。FOV 14 cm，TOF及MP-RAGE序列扫描层厚2 mm，间隔-1 mm，余各序列扫描层厚2 mm，间隔0。对颈动脉分叉前后管腔的狭窄程度、斑块的成分（有无出血、钙化、疏松间质）、纤维帽的状况（厚、薄、破溃）等情况做出判断，依据颈动脉粥样硬化斑块MRI分型标准对每支血管的斑块进行分型。将入组血管按照颈动脉供血区相应脑缺血性症状的有无分为有症状组及无症状组两组，用独立t检验比较两组血管在狭窄程度上的差异；用卡方检验评估两组血管斑块内出现出血、钙化、疏松间质及纤维帽破溃的情况差异，判断斑块类型与临床症状的相关性；用Logistic回归分析狭窄程度、纤维帽破溃、斑块内出血、钙化及疏松间质对临床症状的影响度强弱。结果108例患者中，共发现有斑块血管198支：有症状组血管共计64支；无症状组血管共有134支，其中3支血管因MRI检查前已施行支架置入术不予入组，故无症状组血管共计131支。两组血管在管腔狭窄程度、纤维帽的完整性和斑块是否有出血方面均有统计学差异（P＜0.01或P＜0.05），而在斑块钙化、疏松间质的出现率上则无统计学差异（P＞0.05）。在有症状组血管中，斑块类型比较密集，Ⅵ型斑块所占比例最大（71.8%），而在无症状组，Ⅵ型与Ⅳ～Ⅴ型均较多（分别为44.7%和30.4%）；将两组中斑块类型粗略分为Ⅵ型与非Ⅵ型斑块，显示Ⅵ型斑块所占比例在有症状组更显著（P＜0.01）。在血管狭窄度、纤维帽破溃、斑块有出血、钙化及疏松间质这5个因素中，纤维帽是否有破溃与临床症状的关联程度最大，其次为管腔狭窄度的高低，而斑块内出血及疏松间质的有无对临床症状影响较弱，斑块内钙化则与临床症状的发生无关。结论有症状组与无症状组颈动脉斑块的MRI形态学特征具有明显差异；斑块内成分的差异与临床症状的出现有明显相关性，其与临床脑缺血性事件发生的相对危险度依次为：斑块破溃、管腔狭窄程度提升、斑块内存在疏松间质、斑块内有出血、斑块钙化；在斑块分型上，Ⅵ型代表了临床所谓的易损斑块，间接反映出斑块表面纤维帽破溃和斑块出血与临床症状关系密切。提示通过MRI检查分析斑块内成分来预测临床缺血性脑血管事件的发生是可行的，将能为临床采取相应治疗措施预防卒中发生提供可靠信息。

Objective To compare plaque morphology from patients with and without stroke symptoms, determine the relationship between carotid plaque morphology and stroke pathogenesis, and evaluate the warning function of high-field MR on early diagnosis of plaque. Methods Patients with carotid artery atherosclerotic plaque detected by B-mode ultrasonography were examined with MR imaging. Imaging was performed with a 3.0-T MR imager （Philips or GE） and a special 8-channel phased-array surface coil for carotid artery. The protocols include T1-, intermediate-, T2-, and post-contrast T1-weighted MR imaging, as well as three-dimensional time-of-flight （TOF） and MP-RAGE. All examinations were performed with a 14cm field of view, a matrix of 256 ＆#215; 256 pixels,a 2-mm section thickness, and two acquired signals. An intersection space of -1 mm was used for three-dimensional TOF angiography and MP-RAGE, whereas no intersection space was used for MR imaging. Gadopentetate Dimeglumine was the contrast agent with the dosage of 0.1 mmol/Kg（0.2 ml/Kg）and injection speed of 0.7 ml/s. One observer recorded quantitative and morphologic information, which included measurement of the area of the lumen and main plaque components （calcification, hemorrhage, loose matrix ）; fibrous cap status （thick, thin, or ruptured）; reformed MR lesion type （types Ⅰ-Ⅷ） based on American Heart Association （AHA）. Plaques associated with neurologic symptoms（transient ischemic attack, amaurosis fugax, or stroke appropriate to the distribution of the index carotid artery）and asymptomatic plaques were compared with Independent-sample T test on luminal stenosis, chi square test on occurrence rate of main plaque components and fibrous cap rupture respectively and regression analysis for the connection strength between plaque components and clinical symptoms. Results 64 carotid artery enrolled in the symptomatic group and 131 carotid artery enrolled in the asymptomatic group. Compared with asymptomatic plaques, symptomatic plaques had a smaller lumen area （P＆lt;0.01） and a higher incidence of fibrous cap rupture （P＆lt;0.01）, intraplaque hemorrhage or thrombus （P＆lt;0.05） and complicated AHA type VI lesions （P＆lt;0.01）. No significant differences between symptomatic and asymptomatic plaques were found for occurrence rate of the calcification and the loose matrix. According to the connection strength between plaque components and clinical symptoms, fibrous cap rupture is the most strongly connected component among the foresaid 5 factors. Luminal stenosis is the factor second in order from the connection strength. Loose matrix, hemorrhage and calcification have weak or none correlation with clinical symptoms. Conclusion This study revealed significant differences between symptomatic and asymptomatic plaques, and the manifest dependability between intraplaque composition and occurrence of clinical symptoms. It is probable to provide early-warning information before the presence of stock if its risk can be predict through composition analysis by MR examination.