Fiehler J, Knab R, Reichenbach J R, Fitzek C, Weiller C, Röther J
Department of Neurology, University Hospital Hamburg-Eppendorf, University of Hamburg, Germany.
J Cereb Blood Flow Metab. 2001 May;21(5):577-84. doi: 10.1097/00004647-200105000-00012.
Perfusion-and diffusion-weighted magnetic resonance imaging scans are thought to allow the characterization of tissue at risk of infarction. The authors tested the hypothesis that the apparent diffusion coefficient (ADC) decrease should be associated with the severity of the perfusion deficit in ischemic tissue of acute stroke patients. Perfusion-and diffusion-weighted scans were performed in 11 patients with sudden onset of neurologic deficits within the last 6 hours and T2-weighted magnetic resonance imaging scans were obtained after 6 days. Parameter images of the maximum of the contrast agent concentration, time to peak, relative cerebral blood volume, relative cerebral blood flow, and relative mean transit time were computed from the perfusion-weighted data. A threshold function was used to identify tissue volumes with stepwise ADC decreases. An onionlike distribution of successively decreasing ADC values was found, with the lowest ADC in the center of the ischemic region. Correspondingly, tissue perfusion decreased progressively from the periphery toward the ischemic core. This effect was most pronounced in the time-to-peak maps, with a linear association between ADC decrease and time-to-peak increase. Apparent diffusion coefficient values decreased from the periphery toward the ischemic core, and this distribution of ADC values was strongly associated with the severity of the perfusion deficit.
灌注加权磁共振成像扫描和扩散加权磁共振成像扫描被认为能够对有梗死风险的组织进行特征描述。作者检验了这样一个假设：急性中风患者缺血组织中表观扩散系数（ADC）的降低应与灌注缺损的严重程度相关。对11例在过去6小时内突然出现神经功能缺损的患者进行了灌注加权扫描和扩散加权扫描，并在6天后进行了T2加权磁共振成像扫描。从灌注加权数据中计算出对比剂浓度最大值、达峰时间、相对脑血容量、相对脑血流量和相对平均通过时间的参数图像。使用阈值函数来识别ADC值呈逐步下降的组织体积。发现ADC值呈依次递减的洋葱样分布，缺血区域中心的ADC值最低。相应地，组织灌注从周边向缺血核心逐渐降低。这种效应在达峰时间图中最为明显，ADC降低与达峰时间增加之间呈线性关联。表观扩散系数值从周边向缺血核心降低，且这种ADC值分布与灌注缺损的严重程度密切相关。
