Abstract
Quantitative estimates of cerebral metabolic rate of oxygen utilization using magnetic resonance imaging can have profound implications for the understanding of brain metabolic activity as well as the investigation of cerebrovascular disease. In this study, five normal volunteers were studied. All images were acquired on a Siemens 1.5 T scanner (Siemens Medical Systems Inc, Erlangen, Germany). Cerebral blood flow (CBF) was obtained in vivo with a dynamic imaging approach and the acquired images were post-processed with the singular value decomposition method (SVD). In addition, a multi-echo gradient echo/spin echo sequence was employed to provide MR estimates of oxygen extraction fraction (MR_OEF) in vivo. Subsequently, an absolute measure of MR cerebral metabolic rate of oxygen utilization (MR_CMRO(2)) was obtained in all subjects by taking the product of CBF and MR_OEF. A mean MR_CMRO(2) of 28.94 +/- 3.26 ml/min/100 g and 12.57 +/- 3.11 ml/min/100 g was obtained for gray matter and white matter, respectively, suggesting that the gray matter utilizes more oxygen than white matter under normal physiological conditions. These results yield a gray matter to white matter CMRO(2) ratio of 2.37 +/- 0.37, which is comparable to the reported values in the literature. More studies are needed to further improve on the accuracy as well as shortening the required data acquisition time so that the proposed approaches can be utilized in a routine clinical setting.