大鼠局灶性脑缺血及再灌注磁共振弥散加权像的早期连续动态观察

An early continuous experimental study on magnetic resonance diffusion weighted image of focal cerebral ischemia and reperfusion

目的 利用大鼠大脑中动脉阻塞 (MCAO)及再灌注模型 ,在磁共振弥散加权成像 (magneticresonancediffusion weightedimaging ,DWI)观察中 ,研究各脑区不同时相的缺血改变时空变化规律 ,探讨急性期细胞毒性水肿的演变。方法 健康S D大鼠 15只 ,随机分为 3组。MCAO后 15min开始DWI连续扫描。计算额叶、顶叶、内侧尾壳核、外侧尾壳核等脑区相对平均信号强度值 (relativemeansignalintensity ,RMSI)及DWI高信号区的体积。各组最后一次DWI成像后 ,行T2 加权成像 (T2 WI)观察。结果 缺血 15minDWI即出现高信号 ,随缺血时间延长范围扩大。再灌注 1h ,高信号区大部分恢复正常 ,但仍有部分区域始终保持高信号。顶叶、外侧尾壳核RMSI在缺血及再灌注阶段均大于额叶及内侧尾壳核的RMSI。各组最后T2 WI检查无明显病灶样改变。结论 DWI对急性脑缺血非常敏感 ,可用于评价早期缺血细胞水肿发展过程及时空变化规律。

Objectives To study the chronological and spatial rules of changes during focal cerebral ischemia and reperfusion in different brain regions with magnetic resonance diffusion weighted imaging (DWI) in a rat model of occlusion of middle cerebral artery(MCAO),and to explore the development of cytotoxic edema in acute phase.Methods Fifteen healthy S D rats with MCA occluded by thread emboli were divided randomly into three groups.Fifteen minutes after the operation,the serial scan was began with DWI for all the three groups.The relative mean signal intensity (RMSI) in the frontal lobe,parietal lobe,lateral cauda putamen,medial cauda putamen and the volume of regions of hyperintense signal in DWI were calculated.After the last DWI,T 2WI was performed for all the three groups.Results Fifteen minutes following the ischemia,the rats presented hyperintense signals in DWI,and the regions of hyperintense signals could be enlarged with prolonging ischemia time.The hyperintense signal region returned to normal after reperfusion for 1 hour,with a small part remaining to show hyperintense signal.The RMSI in parietal lobe and lateral cauda putamen was higher than that in the frontal lobe and medial cauda putamen both in ischemia phase and recanalization phase.All the three groups were normal in T 2WI.Conclusions DWI has good sensitivity to acute cerebral ischemia and can be used to study the chronological and spatial rules of development of early cell edema in ischemic regions.