Miyabe M, Mori S, van Zijl P C, Kirsch J R, Eleff S M, Koehler R C, Traystman R J
Department of Anesthesiology and Critical Care Medicine, Johns Hopkins Medical Institutions, Baltimore, Maryland, USA.
J Cereb Blood Flow Metab. 1996 Sep;16(5):881-91. doi: 10.1097/00004647-199609000-00012.
Magnetic resonance water diffusion imaging can detect early ischemic changes in stroke. Using a middle cerebral artery occlusion model, we examined which range of values of the orientation-independent diffusion quantity Dav = 1/3Trace(D) = 1/3(Dxx + Dyy + Dzz) is an early noninvasive indicator of reduced cerebral perfusion and focal brain injury. Cats underwent either a 30-min occlusion followed by 3.5 h reperfusion (n = 7) or a 60-min occlusion followed by 4-h reperfusion (n = 6). Repeated measurements of CBF were made with radiolabeled microspheres, and acute focal injury was measured with triphenyltetrazolium chloride (TTC) staining. During occlusion, the decrease in Dav correlated with CBF for caudate [30-min occlusion (n = 13): p < 0.0001: 60-min occlusion (n = 6): p < 0.02] and for cortex [30-min occlusion (n = 12): p < 0.0001: 60-min occlusion (n = 5): p < 0.04]. Variable caudate and hemispheric injury levels were found among cats in both groups. The area of tissue injury demarcated by TTC began to correlate with the area of reduced Dav by 30 min of occlusion (p < 0.02), and this correlation improved (p < 0.0001) at 1, 1.5, and 2.0 h after the onset of occlusion. The time necessary to reach a one-to-one correspondence between the percent of hemisphere injured and the percent of hemispheric area with Dav < 0.65 x 10(-9) m2/s was 2 h after occlusion. Thus, the absolute value of Dav is a good indicator of the risk of tissue injury, whereas the combination of Dav and the length of time of Dav reduction is an excellent predictor of acute focal tissue injury demarcated by TTC staining.
磁共振水扩散成像能够检测出中风早期的缺血性变化。利用大脑中动脉闭塞模型，我们研究了非方向依赖性扩散量Dav = 1/3Trace(D) = 1/3(Dxx + Dyy + Dzz)的哪些取值范围是脑灌注减少和局灶性脑损伤的早期非侵入性指标。猫接受30分钟闭塞后再灌注3.5小时（n = 7）或60分钟闭塞后再灌注4小时（n = 6）。用放射性微球重复测量脑血流量（CBF），并用氯化三苯基四氮唑（TTC）染色测量急性局灶性损伤。在闭塞期间，尾状核的Dav降低与CBF相关[30分钟闭塞（n = 13）：p < 0.0001；60分钟闭塞（n = 6）：p < 0.02]，皮质的情况也是如此[30分钟闭塞（n = 12）：p < 0.0001；60分钟闭塞（n = 5）：p < 0.04]。两组猫的尾状核和半球损伤水平存在差异。TTC划定的组织损伤面积在闭塞30分钟时开始与Dav降低的面积相关（p < 0.02），且在闭塞开始后1、1.5和2.0小时这种相关性增强（p < 0.0001）。闭塞后2小时，半球损伤百分比与Dav < 0.65 x 10(-9) m2/s的半球面积百分比之间达到一一对应所需的时间。因此，Dav的绝对值是组织损伤风险的良好指标，而Dav及其降低时间的组合是TTC染色划定的急性局灶性组织损伤的优秀预测指标。
