Time-resolved MRI oximetry for quantifying CMRO(2) and vascular reactivity.

This brief review of magnetic resonance susceptometry summarizes the methods conceived in the authors' laboratory during the past several years. This article shows how venous oxygen saturation is quantified in large draining veins by field mapping and how this information, in concert with simultaneous measurement of cerebral blood flow, yields cerebral metabolic rate of oxygen, the brain's rate of oxygen consumption. The accuracy of this model-based approach in which the blood vessel is approximated as a long, straight cylinder, for which an analytical solution for the induced field exists, is discussed. It is shown that the approach is remarkably robust, allowing for time-resolved quantification of whole-brain metabolism at rest and in response to stimuli, thereby providing detailed information on cerebral physiology in health and disease not previously amenable by noninvasive methods.