Lin W, Paczynski R P, Celik A, Hsu C Y, Powers W J
Mallinckrodt Institute of Radiology, Department of Electrical Engineering, Washington University, St. Louis, Missouri 63110, USA.
J Cereb Blood Flow Metab. 1998 Sep;18(9):1018-21. doi: 10.1097/00004647-199809000-00011.
T2*-weighted gradient echo magnetic resonance images of rat brain were obtained dynamically during acute hypoxemic hypoxia to investigate the relations between changes in cerebral blood oxygen saturation (deltaYb), blood hematocrit (Hct), and R2* (deltaR2*). Images from hypoxemic rats with normal Hct (42.8%+/-2.33%; n=12) were compared with those from hypoxemic rats with mild (33.4%+/-1.88%; n=8) or moderate (27.14%+/-2.7%; n=10) reduction of Hct. A linear relation between deltaYb and deltaR2* was obtained for all three groups. However, the slopes of the linear regressions were statistically different from one another (P < 0.001), with the slopes of the regression lines increasing inversely with Hct; that is, the slope for normal Hct is less than the slope for mildly reduced Hct, which is less than the slope for moderately reduced Hct. These data suggest that for any given reduction in the oxygen saturation of cerebral blood, the deltaR2* will be of a lesser magnitude when the hemoglobin concentration is reduced; the data are consistent with existing theoretical models of deoxyhemoglobin content-dependent effects in T2*-weighted magnetic resonance imaging.
在急性低氧性缺氧期间动态获取大鼠脑的T2加权梯度回波磁共振图像，以研究脑血氧饱和度变化（deltaYb）、血细胞比容（Hct）和R2（deltaR2*）之间的关系。将正常Hct（42.8%±2.33%；n = 12）的低氧大鼠的图像与轻度（33.4%±1.88%；n = 8）或中度（27.14%±2.7%；n = 10）降低Hct的低氧大鼠的图像进行比较。所有三组均获得了deltaYb与deltaR2之间的线性关系。然而，线性回归的斜率在统计学上彼此不同（P < 0.001），回归线的斜率与Hct呈反比增加；也就是说，正常Hct的斜率小于轻度降低Hct的斜率，轻度降低Hct的斜率小于中度降低Hct的斜率。这些数据表明，对于任何给定的脑血氧量饱和度降低，当血红蛋白浓度降低时，deltaR2的幅度将较小；这些数据与T2*加权磁共振成像中脱氧血红蛋白含量依赖性效应的现有理论模型一致。
