Department of Radiology, University of Minnesota and Hennepin County Medical Center, Minneapolis, MN 55415, USA.
AJR Am J Roentgenol. 2009 Dec;193(6):1629-38. doi: 10.2214/AJR.09.2664.
The purpose of this study was to evaluate cerebral blood flow, cerebral blood volume, mean transit time, time to peak, and delay in a selected sample of patients with visually normal or increased cerebral blood volume to facilitate detection of a postischemic CT perfusion hyperperfusion-reperfusion phenomenon that may mask subacute and acute infarcts.
Ten patients were included who had visually normal or elevated cerebral blood volume in infarcts larger than 1.5 cm confirmed on diffusion-weighted MR images within 48 hours of perfusion CT. The cases were selected from 371 perfusion CT studies of stroke patients (99 associated with positive diffusion-weighted imaging findings) reviewed over 2.5 years on a 64-MDCT scanner. The perfusion CT images were fused to the diffusion-weighted images for measurement of cerebral blood volume, cerebral blood flow, mean transit time, time to peak, and delay in each infarct versus the contralateral hemisphere. Two neuroradiologists reviewed the images in consensus.
The mean time between symptom onset and perfusion CT was 3.9 days. Infarcts were in the middle cerebral artery (n = 7) and posterior cerebral artery (n = 3) distributions. Significant differences versus the contralateral finding were found in cerebral blood volume (p = 0.016; mean increase, 30.0%), mean transit time (p = 0.007; mean increase, 38.1%), time to peak (p = 0.005; mean increase, 17.7%), and delay (p = 0.030; mean increase, 124.9%). The difference in cerebral blood flow (p = 0.785; mean increase, 1.8%) was not statistically significant. Infarcts became enhanced on the dynamic perfusion CT images of eight of 10 patients and on the contrast-enhanced T1-weighted MR images of six of nine patients.
Visual inspection of cerebral blood volume and cerebral blood flow maps alone is insufficient in the evaluation of infarcts. Mean transit time, time to peak, and delay maps also should be reviewed with dynamic source images to prevent misinterpretation of findings as false-negative. This phenomenon is unlikely to occur hyperacutely (< 8 hours after onset).
本研究旨在评估选择的视诊显示脑血容量正常或增加的患者的脑血流、脑血容量、平均通过时间、达峰时间和延迟时间，以利于发现可能掩盖亚急性和急性梗死的缺血后 CT 灌注高灌注-再灌注现象。
10 例患者入选，这些患者的脑梗死体积大于 1.5cm，在灌注 CT 后 48 小时内行弥散加权 MR 成像证实，且视诊显示脑血容量正常或增加。这些病例选自 2.5 年内在 64 层 MDCT 扫描仪上进行的 371 例卒中患者的灌注 CT 研究（99 例与阳性弥散加权成像结果相关）。将灌注 CT 图像与弥散加权图像融合，以测量每个梗死灶与对侧半球相比的脑血容量、脑血流量、平均通过时间、达峰时间和延迟时间。2 名神经放射学家共同进行图像回顾。
症状发作至灌注 CT 的平均时间为 3.9 天。梗死灶位于大脑中动脉（n=7）和大脑后动脉（n=3）分布区。与对侧发现相比，脑血容量（p=0.016；平均增加 30.0%）、平均通过时间（p=0.007；平均增加 38.1%）、达峰时间（p=0.005；平均增加 17.7%）和延迟时间（p=0.030；平均增加 124.9%）有统计学差异。脑血流量的差异（p=0.785；平均增加 1.8%）无统计学意义。10 例患者中有 8 例的动态灌注 CT 图像和 9 例患者中的 6 例的对比增强 T1 加权 MR 图像显示梗死灶强化。
单独观察脑血容量和脑血流量图不足以评估梗死灶。还应结合动态源图像来观察平均通过时间、达峰时间和延迟时间图，以防止错误解读为假阴性。这种现象不太可能超急性（发病后<8 小时）发生。
