An Hongyu, Liu Qingwei, Chen Yasheng, Lin Weili
Department of Radiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Stroke. 2009 Jun;40(6):2165-72. doi: 10.1161/STROKEAHA.108.540864. Epub 2009 Apr 9.
A noninvasive MRI method to measure cerebral oxygen metabolism has the potential to assess tissue viability during cerebral ischemia. The purposes of this study were to validate MR oxygenation measurements across a wide range of global cerebral oxygenation and to examine the spatiotemporal evolution of oxygen metabolism during focal middle cerebral artery occlusion in rats.
A group of rats (n=28) under normal, hyperoxic hypercapnia and hypoxia were studied to compare MR-measured cerebral oxygen saturation (O(2)Sat(MRv)) with blood gas oximetry measurements in the jugular vein (O(2)Sat(JV)) and superior sagittal sinus (O(2)Sat(SSS)). In a separate group of rats (n=31), MR-measured cerebral oxygen metabolic index (MR_COMI) was acquired at multiple time points during middle cerebral artery occlusion. Histogram analysis was performed on the normalized MR_COMI (rMR_COMI) to examine evolution of oxygen metabolism during acute ischemia.
Highly linear relationships were obtained between O(2)Sat(MRv) and O(2)Sat(JV)/O(2)Sat(SSS) in rats under global cerebral oxygenation alterations. In the focal ischemia study, rMR_COMI values were significantly lower within the areas of eventual infarction than other regions. Moreover, the rMR_COMI values within the ischemic territory decreased with time, concomitant with an increase in the number of voxels with severely impaired oxygen metabolism.
Accurate estimates of O(2)Sat(MRv) can be obtained across a broad and physiologically relevant range of cerebral oxygenation. Furthermore, this method demonstrates a dynamic alteration of cerebral oxygen metabolism during acute ischemia in rats.
一种用于测量脑氧代谢的无创MRI方法有潜力在脑缺血期间评估组织活力。本研究的目的是在广泛的全脑氧合范围内验证磁共振氧合测量，并研究大鼠大脑中动脉局灶性闭塞期间氧代谢的时空演变。
对一组处于正常、高氧高碳酸血症和低氧状态的大鼠（n = 28）进行研究，以比较磁共振测量的脑氧饱和度（O(2)Sat(MRv)）与颈静脉血氧饱和度测量值（O(2)Sat(JV)）和上矢状窦血氧饱和度测量值（O(2)Sat(SSS)）。在另一组大鼠（n = 31）中，在大脑中动脉闭塞期间的多个时间点获取磁共振测量的脑氧代谢指数（MR_COMI）。对标准化的MR_COMI（rMR_COMI）进行直方图分析，以检查急性缺血期间氧代谢的演变。
在全脑氧合改变的大鼠中，O(2)Sat(MRv)与O(2)Sat(JV)/O(2)Sat(SSS)之间获得了高度线性关系。在局灶性缺血研究中，最终梗死区域内的rMR_COMI值显著低于其他区域。此外，缺血区域内的rMR_COMI值随时间下降，同时氧代谢严重受损的体素数量增加。
在广泛且生理相关的脑氧合范围内可获得O(2)Sat(MRv)的准确估计值。此外，该方法证明了大鼠急性缺血期间脑氧代谢的动态变化。
