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

在两个气体扩散室的实验中，利用配备质谱仪的医用气体分析仪测量氙气体扩散系数（Dxe）。当实验系统中加入10% ~ 15%的氦气时，Dxe发生了显著变化。Dxe的变化取决于两腔间氧气浓度的差异。有了这些数据，我们开发了一个用于动物实验的CT扫描计算机程序。第一次用兔子做实验失败的主要原因是它们的大脑很小。经眶夹取猪大脑中动脉作为脑卒中模型。猪被麻醉并吸入氙气、氦气、氧气和氮气的混合物。通过连续CT扫描测量脑组织去饱和常数(K)。结果发现，当动物吸入含有氦气的混合气体时，K值明显小于不含氦气的气体。K常数的降低在缺血脑中更为明显，这与氦、氙、氧和氮混合气体中氙气体扩散常数（Dxe.He）的显著增加有关。将原用于动物实验的CT扫描计算机程序转换为临床使用，并制定了该方法对患者进行CT扫描的时间表。该CT扫描技术为同时测量局部脑氧代谢指标和血流提供了一种安全有效的方法。这些结果与我们体外扩散实验的结果很好地吻合。

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.