局灶性脑缺血后细胞反应性增生的MR和病理表现

MR Features and Pathological Changes of Cellular Responses Following Local Cerebral Ischemia in Rats

目的:动态追踪局灶性脑缺血MR T_2、ADC信号变化,探讨脑缺血后细胞反应性增生的影像特点。方法:线栓法阻塞大鼠左侧大脑中动脉,模型制作后6h、1d、3d、7d行俯卧位冠状面磁共振T_2WI、T_2map和DWI扫描,测量ADC、T_2值,取脑切片进行病理观察。结果:MR图像6h已经显示缺血灶;1d时病理表现为脑水肿、组织坏死,T_2WI为高信号,ADC值降低;3d时病变组织以片状坏死为主,出现细胞增生,T_2信号增高的程度较前有所降低,ADC值有所回升;反应性细胞增生于第7天更为明显,T_2高信号强度进一步降低,而ADC值增高,并超过对侧。结论:脑缺血后不同MR参数时间空间变化存在一定规律,MR成像能够在一定程度上活体反映脑缺血后细胞反应性增生过程。

Purpose：To discuss the imaging character of cellular responses following focal cerebral ischemia in the middle cerebral artery territory.Methods：Healthy male Sprague - Dawley rats（n = 28）, whose left middle cerebral arteries were occluded,were included in our study.The MR T_2WI,DWI and T_2 map sequences were performed on 6h,1d,3d and 7d by using a 3.0 T MR scanner.After that,the brains of the rats were extracted and sliced up for pathological observation.Results：Six hours after cerebral ischemia,the ischemic lesions were shown on MRI.On 1d following cerebral ischemia,the brain edema was significant and the cellar necrosis was presented.The lesions showed high signal intensity on T_2WI and low signal intensity on ADC map.The T_2WI high signal of ischemic lesion was lowered slightly on 3d,and the ADC value was began to return back.The cellular response was obviously shown on 7d, and the T_2 WI high signal intensity was continued to decline,but the ADC value was increased to exceed the normal level.None of the brains of sham - operated animals showed any noteworthy abnormality. Conclusion：MR could reflect the pathological changes in some extent,and display the cellular responses following cerebral ischemia in vivo.