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目的分析兔脑急性缺血组织磁共振弥散成像(DWI)的影像学表现及其与水通道蛋白-4(AQP-4)表达的关系,探讨DWI成像的病理生理基础。方法 58只新西兰大白兔随机分为永久缺血组(A组)和再灌注组(B组),线栓法制作大脑中动脉缺血和缺血1h后再灌注模型。其中A组(A1～A6)分为缺血1h、3h、6h、12h、24h、48h组;B组(B1～B6)又分为再灌注0h、2h、5h、11h、23h和47h组。每组分别于各自时间点进行MRI弥散成像,分别测量表观弥散系数(ADC),并计算相对表观弥散系数(rADC)值。显微镜下观察并记录双侧大脑皮层和纹状体区AQP-4阳性细胞数。结果缺血1h时DWI高信号区内平均ADC值95%可信区间上限为58.75×10-5mm2/s。缺血组DWI高信号区面积随时间延长逐渐增大,rADC值呈先下降后上升的趋势。再灌注组rADC值于再灌注2h趋于正常化,DWI高信号区面积减小;5h rADC值最低;以后rADC值逐渐升高,DWI高信号区面积逐渐扩大。缺血组AQP-4阳性细胞数6h内呈下降趋势,6h后缓慢上升,与rADC值的变化关系密切(r=0.943,P=0.005);再灌注5h内AQP-4变化平稳,之后也出现上升趋势。结论 AQP-4表达水平的高低受缺血程度和持续时间的影响,永久缺血组rADC值的变化趋势与AQP-4表达水平的高低有明显的相关性。
Objective To analyze the imaging manifestations of acute ischemic tissue magnetic resonance imaging (DWI) in rabbits brain and its relationship with the expression of aquaporin-4 (AQP-4), and to explore the pathophysiological basis of DWI imaging. Methods Fifty - eight New Zealand white rabbits were randomly divided into permanent ischemic group (A group) and reperfusion group (B group). The middle cerebral artery ischemia and ischemia 1 h reperfusion model was made by thread occlusion. Group A (A1 ~ A6) was divided into 1h, 3h, 6h, 12h, 24h and 48h after ischemia. Group B (B1 ~ B6) was divided into 0h, 2h, 5h, 11h, 23h and 47h after reperfusion. MRI diffusion imaging was performed at each time point for each group, and the apparent diffusion coefficient (ADC) was measured and the relative apparent diffusion coefficient (rADC) value was calculated. The numbers of AQP-4 positive cells in bilateral cerebral cortex and striatum were observed and recorded under a microscope. Results The mean confidence interval of 95% confidence interval of DWI high signal area at 1 hour after ischemia was 58.75 × 10-5mm2 / s. DWI high signal area of ischemic group increased gradually with time, rADC value decreased first and then increased. The rADC of reperfusion group tended to normalize at 2h after reperfusion, the area of high signal area of DWI decreased and the value of rADC was the lowest at 5h. The area of rADC increased gradually and the area of high signal area of DWI gradually expanded. The number of AQP-4 positive cells in the ischemic group decreased gradually within 6 hours and then gradually increased after 6 hours, which was closely related to the change of rADC (r = 0.943, P = 0.005). AQP-4 changed smoothly within 5 hours after reperfusion, Upward trend. Conclusions The level of AQP-4 is affected by the degree of ischemia and the duration of ischemia. The trend of rADC in permanent ischemia is significantly correlated with the level of AQP-4.