MR Imaging and Quantification of CMRO2, CBF and OEF in Human Visual Cortex at Rest and during Activation
Introduction Oxygen consumption occurs in the mitochondrial respiratory chain to form ATP for supporting the energy needs in the brain and other aerobic organs. In vivo O MRS/I has unique ability for assessing cerebral oxygen metabolism via imaging the dynamic change of the metabolic H2O during an inhalation of Oisotope labeled oxygen gas (O2) 1 4 according to the reaction of 4H 4e O2 2H2O. However, the cerebral metabolic rate of oxygen (CMRO2) in human is difficult to quantify due to the large body size and slow exchange between the labeled and non labeled oxygen gases in the lung as compare to small animals. This issue could become more problematic for a short O2 inhalation experiment. In this study, a simple and practical approach was proposed for measuring gas exchange rate of lung, which was incorporated into a comprehensive modeling for simultaneously determining three important physiology parameters of CMRO2, CBF and OEF in the human brain with a brief O2 inhalation time of 2 3 minutes. This new approach was tested in the human visual cortex under resting and visual stimulation conditions. Theory The quantification method is based on following mass balance equation 2 4 dCb(t)