MRI estimation of global brain oxygen consumption rate.

Measuring the global cerebral metabolic rate of oxygen (CMRO(2)) is a valuable tool for assessing brain vitality and function. Measurement of blood oxygen saturation (HbO(2)) and flow in the major cerebral outflow and inflow vessels can provide a global estimate of CMRO(2). We demonstrate a rapid noninvasive method for quantifying CMRO(2) by simultaneously measuring venous oxygen saturation in the superior sagittal sinus with magnetic resonance susceptometry-based oximetry, a technique that exploits the intrinsic susceptibility of deoxygenated hemoglobin, and the average blood inflow rate with phase-contrast magnetic resonance imaging. The average venous HbO(2), cerebral blood flow, and global CMRO(2) values in eight healthy, normal study subjects were 64%+/-4%, 45.2+/-3.2 mL per 100 g per minute, and 127+/-7 micromol per 100 g per minute, respectively. These values are in good agreement with those reported in literature. The technique described is noninvasive, robust, and reproducible for in vivo applications, making it ideal for use in clinical settings for assessing the pathologies associated with dysregulation of cerebral metabolism. In addition, the short acquisition time (approximately 30 seconds) makes the technique suitable for studying the temporal variations in CMRO(2) in response to physiologic challenges.