Supplementary Material for: Intralesional Patterns of MRI ADC Maps Predict Outcome in Experimental Stroke

<b><i>Background:</i></b> After acute ischemia, the tissue that is at risk of infarction can be detected by perfusion-weighted imaging/diffusion-weighted imaging (PWI/DWI) mismatch but the time that is needed to process PWI limits its use. As DWI is highly sensitive to acute ischemic tissue damage, we hypothesized that different ADC patterns represent areas with a different potential for recovery. <b><i>Methods:</i></b> In a model of permanent middle cerebral artery occlusion (pMCAO), Sprague-Dawley rats were randomly distributed to sham surgery and pMCAO. We further separated the pMCAO group according to intralesional ADC pattern (homogeneous or heterogeneous). At 24 h after ischemia induction, we analyzed lesion size, functional outcome, cell death expression, and brain protection markers including ROS enzyme NOX-4. MRI included DWI (ADC maps), DTI (tractography), and PWI (CBF, CBV and MTT). <b><i>Results:</i></b> The lesion size was similar in pMCAO rats. Animals with a heterogeneous pattern in ADC maps showed better functional outcome in Rotarod test (p = 0.032), less expression of cell death (p = 0.014) and NOX-4 (p = 0.0063), higher intralesional CBF (p = 0.0026) and larger PWI/DWI mismatch (p = 0.007). <b><i>Conclusions:</i></b> In a rodent model for ischemic stroke, intralesional heterogeneity in ADC maps was related to better functional outcome in lesions of similar size and interval after pMCAO. DWI ADC maps may assist in the early identification of ischemic tissue with an increased potential for recovery as higher expression of acute protection markers, lower expression of cell death, increased PWI/DWI mismatch, and higher intralesional CBF were present in animals with a heterogeneous ADC pattern.

**背景**：急性缺血发生后，可通过灌注加权成像/弥散加权成像（perfusion-weighted imaging/diffusion-weighted imaging, PWI/DWI）不匹配检出存在梗死风险的脑组织，但PWI的图像处理耗时限制了其临床应用价值。鉴于弥散加权成像对急性缺血性脑组织损伤具有高度敏感性，本研究假设不同的表观扩散系数（apparent diffusion coefficient, ADC）模式可反映脑组织恢复潜能的差异。
**方法**：本研究采用永久性大脑中动脉闭塞（permanent middle cerebral artery occlusion, pMCAO）大鼠模型，将斯普拉格-道利（Sprague-Dawley）大鼠随机分为假手术组与pMCAO造模组。随后根据病灶内ADC模式（均质性或异质性）对pMCAO造模组进行二次分组。于缺血诱导后24小时，分析各组的病灶体积、功能预后、细胞死亡表达水平，以及包括活性氧（reactive oxygen species, ROS）相关酶NOX-4在内的脑保护标志物表达情况。MRI检测涵盖弥散加权成像（ADC图）、弥散张量成像（diffusion tensor imaging, DTI，纤维束追踪）及灌注加权成像（脑血流量cerebral blood flow, CBF、脑血容量cerebral blood volume, CBV与平均通过时间mean transit time, MTT）。
**结果**：pMCAO造模大鼠的初始病灶体积无显著组间差异。ADC图呈异质性模式的大鼠，其转棒实验（Rotarod test）中的功能预后更佳（p=0.032），细胞死亡表达水平更低（p=0.014），NOX-4表达量更少（p=0.0063），病灶内CBF水平更高（p=0.0026），且PWI/DWI不匹配范围更广（p=0.007）。
**结论**：在缺血性脑卒中啮齿类动物模型中，当病灶体积与缺血间隔时间一致时，ADC图上的病灶内异质性与更佳的功能预后相关。鉴于ADC图呈异质性模式的大鼠，其急性保护标志物表达水平更高、细胞死亡表达更低、PWI/DWI不匹配范围更广且病灶内CBF更高，因此弥散加权成像ADC图或可辅助早期识别具有更高恢复潜能的缺血脑组织。