Ito Hiroshi, Kanno Iwao, Takahashi Kazuhiro, Ibaraki Masanobu, Miura Shuichi
Department of Radiology and Nuclear Medicine, Akita Research Institute of Brain and Blood Vessels, Akita, Japan.
Neuroimage. 2003 Jul;19(3):1163-9. doi: 10.1016/s1053-8119(03)00156-3.
Cerebral vascular mean transit time (MTT) characterizes the cerebral circulation. MTT has been measured in humans by carotid angiography, x-ray computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET). However, regional distribution of MTT has not been investigated in detail. Thus, we investigated regional distribution of normal human MTT. Regional cerebral blood flow (CBF) and cerebral blood volume (CBV) were measured by PET with H(2)(15)O and (11)CO, respectively, in each of 10 normal subjects. MTT was calculated as MTT = CBV/CBF. MTT for cerebral cortical regions was 3.2 to 4.4 s. These values were in accord with MTT measured by carotid angiography, CT, and MRI. Considered regionally, MTT was longest in the temporooccipital cortex, and shorter in the cerebellum, thalamus, and putamen, than in all other regions. These regional differences in MTT that are inversely proportional to cerebral perfusion pressure might relate to regional differences in cerebral vascular tone. Simulation studies showed that errors in CBF and thus MTT caused by regional differences in regional tracer appearance time, distribution volume, and gray-white matter mixing were negligible.
脑血管平均通过时间（MTT）可表征脑循环。MTT已通过颈动脉血管造影、X射线计算机断层扫描（CT）、磁共振成像（MRI）和正电子发射断层扫描（PET）在人体中进行测量。然而，MTT的区域分布尚未得到详细研究。因此，我们研究了正常人体MTT的区域分布。在10名正常受试者中，分别使用H(2)(15)O和(11)CO通过PET测量局部脑血流量（CBF）和脑血容量（CBV）。MTT计算为MTT = CBV/CBF。大脑皮质区域的MTT为3.2至4.4秒。这些值与通过颈动脉血管造影、CT和MRI测量的MTT一致。从区域角度考虑，MTT在颞枕叶皮质最长，在小脑、丘脑和壳核中比所有其他区域短。MTT的这些区域差异与脑灌注压成反比，可能与脑血管张力的区域差异有关。模拟研究表明，由区域示踪剂出现时间、分布容积和灰白质混合的区域差异引起的CBF误差以及因此导致的MTT误差可忽略不计。
