van Gelderen P, de Vleeschouwer M H, DesPres D, Pekar J, van Zijl P C, Moonen C T
Faculty of Applied Physics, University of Technology Delft, The Netherlands.
Magn Reson Med. 1994 Feb;31(2):154-63. doi: 10.1002/mrm.1910310209.
The occlusion of the middle cerebral artery was used as an experimental acute stroke model in 30 cats. The diffusion of water was followed by diffusion-sensitized MRI between 1 and 15 h after induction of stroke. It is demonstrated that images representing the trace of the diffusion tensor provide a much more accurate delineation of affected area than images representing the diffusion in one direction only. The reason is that the strong contrast caused by the anisotropy and orientation of myelin fibers is completely removed in the trace of the diffusion tensor. The trace images show a small contrast between white and gray matter. The diffusion coefficient of white matter is decreased in acute stroke to approximately the same extent as gray matter. It is further shown that the average lifetime of water in extra and intracellular space is shorter than 20 ms both for healthy and ischemic tissue indicating that myelin fibers are permeable to water. The anisotropy contrast did not change before or after induction of stroke, nor after sacrifice. Together, these observations are consistent with the view that the changes in water diffusion during acute stroke are directly related to cytotoxic oedema, i.e., to the change in relative volume of intra- and extracellular spaces. Changes in membrane permeability do not appear to contribute significantly to the changes in diffusion.
在30只猫身上，将大脑中动脉闭塞用作实验性急性中风模型。在中风诱发后1至15小时内，通过扩散敏感磁共振成像跟踪水的扩散情况。结果表明，与仅代表一个方向扩散的图像相比，代表扩散张量轨迹的图像能更准确地描绘受影响区域。原因是髓鞘纤维的各向异性和取向所导致的强烈对比度在扩散张量的轨迹中完全消除。轨迹图像显示白质和灰质之间的对比度较小。在急性中风中，白质的扩散系数降低程度与灰质大致相同。进一步表明，无论是健康组织还是缺血组织，细胞外和细胞内空间中水的平均寿命均短于20毫秒，这表明髓鞘纤维对水具有渗透性。在中风诱发前后以及处死后，各向异性对比度均未改变。这些观察结果共同表明，急性中风期间水扩散的变化与细胞毒性水肿直接相关，即与细胞内和细胞外空间的相对体积变化有关。膜通透性的变化似乎对扩散变化没有显著贡献。
