Study on simultaneously measurement of local cerebral oxygen metabolism indexes and blood flow by CT scan

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A Medical gas analyser equipped with a mass spectrometer was used to measure xenon gas diffusion coefficient (Dxe) in experiments with two gas diffusion chambers. Dxe significantly changed when 10 to 15% of helium gas was added in the experimental system. The change of Dxe eas dependent on difference of oxygen gas concentration between two chambers. With these data, a CT scan computer program was developed for animal experiments. First session of experiments with rabbits was unsuccessful mainly because of their minute brains. The middle cerebral artery of a pig was clipped transorbitally and used as a stroke model. Pigs were anesthetized and inhaled a mixture of xenon, helium, oxygen and nitrogen. Desaturation constant (K) of the brain tissue was measured by taking serial CT scans. It was found that K was significantly smaller when the animal inhaled a mixture of gas with helium than without helium. The decrease of K constant was more apparent in the ischemic brain and this eas associated with a significant increase in a xenon gas diffusion constant (Dxe.He) in a mixed gas with helium, xenon, oxygen and nitrogen. The original CT scan computer program for animal experiments was converted for a clinical use and a schedule was established for CT scanning of the patient for this method. This CT scan technique has provided a safe and effective method for simultaneous measurement of local cerebral oxgen metabolism indexes and blood flow. These results were in good agreement with our results of in vitro diffusion experiments.