Noninvasive quantification of whole-brain cerebral metabolic rate of oxygen (CMRO₂) by MRI

Cerebral metabolic rate of oxygen (CMRO₂) is an important marker for brain function and brain health. Existing techniques for quantification of CMRO₂ with positron emission tomography (PET) or MRI involve special equipment and/or exogenous agents, and may not be suitable for routine clinical studies. In the present study, a noninvasive method is developed to estimate whole-brain CMRO₂ in humans. This method applies phase-contrast MRI for quantitative blood flow measurement and T₂-relaxation-under-spin- tagging (TRUST) MRI for venous oxygenation estimation, and uses the Fick principle of arteriovenous difference for the calculation of CMRO₂. Whole-brain averaged CMRO₂ values in young, healthy subjects were 132.1 ± 20.0 μmol/100 g/min, in good agreement with literature reports using PET. Various acquisition strategies for phase-contrast and TRUST MRI were compared, and it was found that nongated phase-contrast and sagittal sinus (SS) TRUST MRI were able to provide the most efficient and accurate estimation of CMRO₂. In addition, blood flow and venous oxygenation were found to be positively correlated across subjects. Owing to the noninvasive nature of this method, it may be a convenient and useful approach for assessment of brain metabolism in brain disorders as well as under various physiologic conditions.