Verheul H B, Berkelbach van der Sprenkel J W, Tulleken C A, Tamminga K S, Nicolay K
Department of Neurosurgery, University Hospital Utrecht, The Netherlands.
Brain Topogr. 1992 Winter;5(2):171-6. doi: 10.1007/BF01129046.
The present study was undertaken to characterize the formation of ischemic brain edema using diffusion-weighted and T2-weighted magnetic resonance imaging in a rat model of focal ischemia. The extent of edema formation was measured from multislice diffusion-weighted and T2-weighted spin-echo images acquired at various times after ischemia. The spin-spin relaxation time (T2) and the apparent diffusion coefficient in normal and ischemic tissue were also determined. The results show that on the diffusion-weighted images the lesion was clearly visible at 30 minutes after ischemia, while on the T2-weighted images it became increasingly evident after 2-3 hours. On both types of images the hyperintense area increased in size over the first 48 hours. After 1 week the hyperintensity on the diffusion-weighted images rapidly disappeared and evolved as a hypointense lesion in the chronic phase. These results confirm the high sensitivity of diffusion-weighted MRI for the detection of early ischemia. The temporal course of the edema observed on T2W-images is in agreement with the reported increase of total water content occurring in this model. The increase of the lesion observed on the diffusion-weighted images during the first 2 days points to an aggravation of cytotoxic edema that parallels the changes in free water shown by the T2-weighted images. It is shown that the highly elevated T2's of the infarcted area several days after ischemia can substantially contaminate the diffusion-weighted images.
本研究旨在利用弥散加权和T2加权磁共振成像技术，在局灶性脑缺血大鼠模型中对缺血性脑水肿的形成进行特征描述。从缺血后不同时间获取的多层弥散加权和T2加权自旋回波图像测量水肿形成的程度。还测定了正常组织和缺血组织中的自旋-自旋弛豫时间（T2）和表观扩散系数。结果显示，在弥散加权图像上，缺血后30分钟病变清晰可见，而在T2加权图像上，2-3小时后病变变得越来越明显。在这两种类型的图像上，高强度区域在最初48小时内大小均增加。1周后，弥散加权图像上的高强度迅速消失，并在慢性期演变为低强度病变。这些结果证实了弥散加权磁共振成像对早期缺血检测的高敏感性。在T2加权图像上观察到的水肿的时间进程与该模型中报道的总含水量增加一致。在最初2天内，弥散加权图像上观察到的病变增加表明细胞毒性水肿加剧，这与T2加权图像显示的游离水变化平行。结果表明，缺血几天后梗死区域高度升高的T2值可严重影响弥散加权图像。
