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

用医用气体分析仪和质谱仪测量了氙气扩散系数（Dxe）。当实验系统中加入10%~ 15%的氦气时，Dxe发生显著变化。Dxe的变化取决于两个腔室中氧气浓度的差异。利用这些数据，开发了用于动物实验的CT扫描计算机程序。第一次用兔子做的实验没有成功，主要是因为它们的大脑很小。经眶夹闭猪的大脑中动脉并用作中风模型。猪被麻醉并吸入氙、氦、氧和氮的混合物。通过连续CT扫描测量脑组织的去饱和常数（K）。结果发现，当动物吸入含氦的混合气体时，K值明显小于不含氦的混合气体。K常数的降低在缺血脑中更为明显，这与在氦、氙、氧和氮的混合气体中氙气扩散常数（Dxe·He）的显著增加有关。将用于动物实验的原始CT扫描计算机程序转换为临床使用，并为该方法建立了患者CT扫描的时间表。该CT扫描技术为同时测定局部脑氧代谢指标和血流量提供了一种安全有效的方法。这些结果与我们的体外扩散实验结果一致。

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.