脑缺血区水分子扩散变化及其临床应用

目的：研究脑缺血区水分子扩散运动变化的规律。探讨脑缺血区水分子扩散运动变化的可能机制。方法:临床诊断脑缺血或脑梗死患者43 例, 磁共振成像检查距起病6 h之内10例, 7～24 h 12例,2～7 d 7例，8～14 d 8例, 15 d～2个月6例，计算缺血区的水分子扩散速率变化。结果:正常脑灰质区水分子扩散速率为8.61×10－4mm2*s－1。早期缺血区水分子扩散迅速下降为（4.72×10－4+1.51×10－4） mm2*s－1，与对侧相应区的比值为0.55±0.18。随发作与检查间隔延长，水分子扩散速率上升，2～7 d为(5.68×10－4±1.22×10－4) mm2*s－1，比值为0.66±0.14；8～14 d为（9.22×10－4±2.07×10－4） mm2*s－1，比值为1.07±0.24。2个月时扩散值明显升高，与纯水相近, 为(26.42×10－4±9.65×10－4） mm2*s－1。扩散比值与时间呈明显相关(r=0.95, P<0.001) 。ADCv在超早期增加后逐渐下降。结论:超急性期脑缺血区水分子扩散速率下降, 随时间延长扩散值逐渐上升。扩散的各向异性在超早期增加，随病程逐渐下降。DWI可在超急性期(2 h)发现缺血灶的存在，较CT及常规T1、T2WI在脑梗死超早期诊断及演变中更有价值。超早期缺血区水分子扩散变化机制可能是超早期细胞毒性水肿。

Water molecular diffusion changes in cerebral ischemia and the study of its clinical application

Objective： To study the changes of water molecular diffusion in the ischemic region by using MR dephase technique and discuss the potential mechanism of the diffusion changes at early stage. Methods: Totally 43 cases were studied retrospectively. There were 10 cases whose MRI examinations were performed within 6 hours，12 cases from 7－24 hours，7 cases from 2－7 days, 8 cases from 8－14 days, 6 cases from 15 days to 2 months. The apparent diffusion coefficients in the ischemic region were calculated. Results: The ADCav in the grey matter was 8.61×10－4mm2*s－1. The ADCav decreased to (4.72×10－4±1.51×10－4) mm2*s－1 in ischemic region at superacute stage, ADCav ratio to contralateral corresponding region was 0.55±0.18, and ADCav increased to (5.68×10－4±1.22×10－4) mm2*s－1 during the time range of 2-7 days, （9.22×10－4±2.07×10－4） during the time range of 8－14 days, and approaching （26.42×10－4+9.65×10－4） mm2*s－1 during the time range of 2 months. The pearson product- moment correlation between the changes of diffusion value and time was sighificent (r=0.95, P<0.001). ADCv increased at superacute stage and decreased over time. Conclusion: The diffusion of water molecules in ischemic region decreased at superacute stage, and the ADC increased over time. The anisotropy increased at superacute stage and decreased as the course developed. DWI could detect ischemic lesion much earlier than CT and routine MR examination. DWI has great value in the diagnosis of superacute stroke. The mechanism of the diffusion changes at early stage may be the intracellular toxicity edema.