Establishment of estimating method of the brain function by near infra-red light computed tomography and its application

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1. Measurement by body oxygen monitoring apparatusUnder anesthesia and artificial breathing, absorption of near infra-red light (600-1000 nm) was measured before and after the ischemic condition in the head. It was found that the deoxygenated form of hemoglobin increased after the ischemic condition. We observed a change in the absorption indicating that the administration of a brain blood flow improving drug caused an increase in the hemoglobin content in the brain.2. Measurement by near infra-red light CT apparatusThe near infra-red light CT apparatus was made using semiconductor laser near infra-red lights (780 nm, 805 nm and 830 nm) and photomultipliers. Using this apparatus following results were obtained. (1) Resolution. Measuring the absorption of different phantoms which had 10 mm sqaure surface, it was found that the limit of the resolution of this apparatus was less than 10 mm. (2) CT image of rat abdomen. When CT image was obtained by the absorption of the light of 780 nm, t … More he resolution was not good because of the surface reflection and edge amplification. Thus, the image was made by the difference between absorptions at 780 nm and 805 nm, and the image of the left lobe of the liver was successfully obtained. (3) CT image of rat brain. Under the ischemic condition, the blood was exchanged for an artificial plasma and images of brain and muscles in the head using the difference between absorptions at 780 nm and 805 nm (this yields mainly informations about oxygenation of hemoglobin and hemoglobin content) was successfully obtained. Images of brain and muscles in the head using the difference between absorptions at 805 nm and 830 nm (this yields mainly the information about reduction of cytochrome oxidase) was successfully obtained under a condition of inspiring air with low oxygen concentration and hypoglycemia after exchanging blood for artificial plasma. These findings indicate the possibility that the blood content, oxygen concentration and oxidoreductive condition of cytochrome oxidase can be measured by near infra-red light CT apparatus. Less