IN VIVO 17O NMR STUDIES OF CEREBRAL OXYGEN CONSUMPTION AND BLOOD FLOW

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This project involves the development of new non-invasive approaches for imaging oxygen consumption and blood flow in the brain. These new approaches combine the advantages of magnetic resonance spectroscopy, which can separate signals from different metabolites or "tracers" in the brain, and magnetic resonance imaging, which can localize signals from metabolites and tracers to well-defined regions of the brain. If the animal breathes a gas mixture containing 1702, it will produce 170- labelled water, which is the end product of oxidative metabolism in the brain. If the blood flow is also imaged, the rate of increase in the 170- labelled water signal can be used to calculate the rate of oxygen consumption. In the last year, we have shown that 19F NMR techniques can be used to image cerebral blood flow with a spatial resolution of 0.4 cc, which is approximately the same spatial evolution as PET. We have also shown that 19F NMR approaches can be combined with 170 NMR approaches to image simultaneously cerebral blood flow and oxygen consumption. The 170 NMR approach is very similar to the 150 PET approach for imaging cerebral oxygen consumption and blood flow. At the present time, the spatial resolution of the 170 approach is 0.8cc, which is not as good as the spatial resolution of 150 PET (approximately 0.5 cc). However, the 170 NMR approach has two important advantages: first, 170-labelled compounds are non-radioactive and non-toxic, and second, the interpretation of 170 spectroscopic data is much simpler than the interpretation of 150 PET data.