Determination of the rate of cerebral oxygen consumption and regional cerebral blood flow by non-invasive 17O in vivo NMR spectroscopy and magnetic resonance imaging: Part 2. Determination of CMRO2, for the rat by 17O NMR, and CMRO2, rCBF and the partition coefficient for the cat by 17O MRI

Abstract

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 ¹⁷O NMR spectroscopy and imaging inhalation studies. Data analysis methods of ¹⁷O 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 (λ). Several of the applied methods for the determination of CMRO₂ do not require measurements of regional cerebral blood flow and H₂ ¹⁷O 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 ¹⁷O NMR is unique in providing the rate of blood water flow, where the natural abundance ¹⁷O NMR signal consists of an internal reference and that » 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 (μmol/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 » 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 compareddiscussed 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. [Neurol Res 1993; 15: 7-22].