DETERMINATION OF THE RATE OF CEREBRAL OXYGEN-CONSUMPTION AND REGIONAL CEREBRAL BLOOD-FLOW BY NONINVASIVE O-17 INVIVO NMR-SPECTROSCOPY AND MAGNETIC-RESONANCE-IMAGING .2. DETERMINATION OF CMRO2 FOR THE RAT BY O-17 NMR, AND CMRO2, RCBF AND THE PARTITION-COEFFICIENT FOR THE CAT BY O-17 MRI

The rate of oxygen consumption (CMRO2) in intact rat and cat brains was calculated by novel data analysis methods from data obtained in in vivo O-17 NMR spectroscopy and imaging inhalation studies. Data analysis methods of O-17 inhalation measurements are applied to the calculation of CMRO2, regional cerebral blood flow (rCBF), the reflow (R), the arterial venous difference (AVD) and the partition coefficient (lambda). Several of the applied methods for the determination of CMRO2 do not require measurements of regional cerebral blood flow and (H2O)-O-17 arterial concentration. The proposed methods have been tested, and the results obtained by the different methods are in very good agreement. It is shown that O-17 NMR is unique in providing the rate of blood water flow, where the natural abundance O-17 NMR signal consists of an internal reference and that lambda is essentially 1. The average values of CMRO2 for rats and cats were found to be 2.09 +/- 0.35 and 1.18 +/- 0.58 (mumol/O2/g tissue)/min, respectively. The average value for rCBF for the cat was found to be 0.38 +/- 0.12 {(mg/g)/min}. The average value for lambda was found to be 1.00 +/- 0.04. The ratio of AVD due to organs other than the brain to AVD due to the brain is smaller than 1 for the rat and the cat. The time and spatial resolution accuracy of the spectroscopic and imaging methods are compared, discussed and statistically analysed. It is concluded that the accuracy of determination of CMRO2 for the rat is higher than for the cat by a factor of 8.