Supplementary Material for: Digital Probabilistic Atlas of the Border Region between the Middle and Posterior Cerebral Arteries

Background and Purpose: The diagnosis of external borderzone infarction is made when the stroke is located at the border between the arterial territories. Recent studies have raised questions regarding the location of this borderzone given the variability in the arterial territories. We examined the location of this region using a digital approach and its correspondence with the ‘traditional’ template. Methods: Infarcts resulting from occlusion of the middle cerebral artery (MCA) or posterior cerebral artery (PCA) trunk or branches were segmented from T2-weighted MR images and linearly registered into a common stereotaxic coordinate space. For MCA infarcts and PCA infarcts, maps of voxels in a rim surrounding the infarct were created. The maps of individual rims were averaged to create images of the probability of each voxel lying in the MCA and PCA rims. The MCA and PCA rims were used to create a digital atlas of the probability of each voxel lying concurrently in both rims. Results: The MCA group consisted of 36 patients (16 males) with a median age of 73 (range 25–87) years. The PCA territory group consisted of 30 patients (24 males) with a median age of 61 (range 22–86) years. The probability of involvement in the digital atlas was higher in the posterior putamen (probability 0.12–0.29) and optic tract (probability 0.13–0.0.20) than in the angular gyrus (probability 0.01). Conclusion: We have created a digital model of the border region between the MCA and PCA territories. This approach may be useful for evaluating the likelihood of a stroke mechanism from topography.

背景与目的：当卒中病灶位于动脉供血区域之间的边缘带时，即可诊断为边缘带脑梗死（external borderzone infarction）。近期有研究针对该边缘带的位置提出质疑，原因在于动脉供血区域存在个体差异性。本研究采用数字化方法对该区域的位置进行了分析，并探究其与“传统”模板的对应关系。

方法：从T2加权磁共振成像（T2-weighted MR images）中分割出因大脑中动脉（middle cerebral artery, MCA）、大脑后动脉（posterior cerebral artery, PCA）干或分支闭塞所致的脑梗死病灶，并将其线性配准至统一的立体定向坐标空间。针对大脑中动脉梗死与大脑后动脉梗死病灶，分别构建环绕病灶边缘区域的体素（voxels）概率图。将所有个体病灶的边缘区域概率图进行平均，得到每个体素分别属于大脑中动脉供血区边缘带、大脑后动脉供血区边缘带的概率图像。进一步基于大脑中动脉与大脑后动脉的边缘带概率图，构建同时处于两类边缘带内的体素概率数字化图谱（digital atlas）。

结果：大脑中动脉梗死组共纳入36例患者（男性16例），中位年龄为73岁（年龄范围25~87岁）。大脑后动脉供血区梗死组共纳入30例患者（男性24例），中位年龄为61岁（年龄范围22~86岁）。数字化图谱中，后壳核（posterior putamen）与视束（optic tract）的受累概率（0.12~0.29、0.13~0.20）高于角回（angular gyrus）的受累概率（0.01）。

结论：本研究构建了大脑中动脉与大脑后动脉供血区域之间边缘带的数字化模型。该方法可用于基于病灶位置评估卒中发生机制的可能性。