Lin W, Paczynski R P, Celik A, Kuppusamy K, Hsu C Y, Powers W J
Mallinckrodt Institute of Radiology, Washington University, St. Louis, Missouri 63110, USA.
Magn Reson Med. 1998 Mar;39(3):474-81. doi: 10.1002/mrm.1910390318.
A two-dimensional T2*-weighted gradient-echo sequence was used to image the rat brain before and during graded hypoxemia. Changes in R2* (deltaR2*) with respect to the control state were calculated for brain parenchyma and were compared with changes in hemoglobin saturation measured from both arterial and jugular venous blood samples. DeltaR2* was first correlated with the changes in arterial (deltaYa) and venous (deltaYv) hemoglobin saturations individually. Although a general trend toward a linear relationship with deltaR2* was observed for both deltaYa and deltaYv, neither alone was strong (correlation coefficients r=0.71 and 0.75 for deltaYa and deltaYv, respectively, and standard errors of the regression (SER)=0.52 and 0.48 for deltaYa and deltaYv, respectively). However, when an "effective" cerebral blood hemoglobin saturation change (deltaYb) was constructed that takes into account the approximate weighting of the contributions from the arterial and venous phases of the circulation (deltaYb = 0.75 x deltaYv + 0.25 x deltaYa), a stronger correlation with deltaR2* was obtained and there was less variance (r=0.87 and SER=0.35). It is concluded that an appropriate weighting of the contributions of arterial and venous phases of the circulation must be taken into account in modeling the volume susceptibility effects of deoxyhemoglobin on R2* of brain parenchyma. In this way, a more accurate relationship between deltaR2* and deltaYb can be obtained.
采用二维T2加权梯度回波序列对大鼠大脑在分级低氧血症前和期间进行成像。计算脑实质相对于对照状态的R2变化（ΔR2*），并与从动脉和颈静脉血样中测得的血红蛋白饱和度变化进行比较。首先分别将ΔR2与动脉（ΔYa）和静脉（ΔYv）血红蛋白饱和度变化进行相关性分析。尽管观察到ΔYa和ΔYv与ΔR2均呈线性关系的总体趋势，但单独来看两者的相关性都不强（ΔYa和ΔYv的相关系数r分别为0.71和0.75，回归标准误差（SER）分别为0.52和0.48）。然而，当构建一个“有效”的脑血血红蛋白饱和度变化（ΔYb）时，该变化考虑了循环中动脉和静脉相贡献的近似权重（ΔYb = 0.75×ΔYv + 0.25×ΔYa），则与ΔR2的相关性更强且方差更小（r = 0.87，SER = 0.35）。得出的结论是，在模拟脱氧血红蛋白对脑实质R2的体积磁化率效应时，必须考虑循环中动脉和静脉相贡献的适当权重。通过这种方式，可以获得ΔR2*与ΔYb之间更准确的关系。
