Røhl L, Ostergaard L, Simonsen C Z, Vestergaard-Poulsen P, Andersen G, Sakoh M, Le Bihan D, Gyldensted C
Department of Neuroradiology, Aarhus University Hospital, Aarhus, Denmark.
Stroke. 2001 May;32(5):1140-6. doi: 10.1161/01.str.32.5.1140.
The penumbra of ischemic stroke consists of hypoperfused, but not irreversibly damaged, tissue surrounding the ischemic core. The purpose of this study was to determine viability thresholds in the ischemic penumbra, defined as the perfusion/diffusion mismatch in hyperacute stroke, by the use of diffusion- and perfusion-weighted MRI (DWI and PWI, respectively).
DWI and PWI were performed in 11 patients </=6 hours after the onset of symptoms of acute ischemic stroke. Regions of interest (ROIs) were placed covering the ischemic core (ROI 1), the penumbra that progressed to infarction on the basis of follow-up scans (ROI 2), and the penumbra that recovered (ROI 3). The ratios of relative cerebral blood flow (rCBF), relative cerebral blood volume (rCBV), mean transit time (MTT), and apparent diffusion coefficient were calculated as lesion ROIs relative to the contralateral mirror ROIS:
The post hoc analysis showed that the penumbra progressed to infarction at the following cutoff values: rCBF <0.59 and MTT >1.63. Higher sensitivity and accuracy in predicting outcome of the penumbra were obtained from the rCBF maps compared with the rCBV and MTT maps. The initial rCBV and apparent diffusion coefficient ratios did not differentiate between the part of the penumbra that recovered and the part that progressed to infarction. The mean rCBF ratio was optimal in distinguishing the parts of the penumbra recovering or progressing to infarction.
The thresholds found in this study by combined DWI/PWI might aid in the selection of patients suitable for therapeutic intervention within 6 hours. However, these hypothesized thresholds need to be prospectively tested at the voxel level on a larger patient sample before they can be applied clinically.
缺血性卒中的半暗带由围绕缺血核心的灌注不足但未发生不可逆损伤的组织构成。本研究的目的是通过使用扩散加权磁共振成像（DWI）和灌注加权磁共振成像（PWI）来确定缺血半暗带的存活阈值，缺血半暗带定义为超急性卒中时的灌注/扩散不匹配。
对11例急性缺血性卒中症状发作后≤6小时的患者进行DWI和PWI检查。将感兴趣区（ROI）放置在覆盖缺血核心（ROI 1）、基于随访扫描进展为梗死的半暗带（ROI 2）以及恢复的半暗带（ROI 3）的区域。计算相对脑血流量（rCBF）、相对脑血容量（rCBV）、平均通过时间（MTT）和表观扩散系数相对于对侧镜像ROI的病变ROI比值：
事后分析显示，半暗带在以下临界值时进展为梗死：rCBF<0.59且MTT>1.63。与rCBV和MTT图相比，rCBF图在预测半暗带转归方面具有更高的敏感性和准确性。初始rCBV和表观扩散系数比值无法区分恢复的半暗带部分和进展为梗死的半暗带部分。平均rCBF比值在区分恢复或进展为梗死的半暗带部分方面最为理想。
本研究通过联合DWI/PWI发现的阈值可能有助于选择在6小时内适合进行治疗干预的患者。然而，在这些假设的阈值能够应用于临床之前，需要在更大的患者样本上对体素水平进行前瞻性测试。
