Noninvasive measurement of physiological functions in a living body by transillumination

With the view toward the non-invasive imaging of biological functions with light, a fundamental study has been conducted. Using a near-infrared light, the transillumination images of the head of a rat were obtained. The change in the image was investigated, when the oxygen fraction of inhalation gas was changed and when the brain circulation was changed by occluding the carotid artery. It was found that the changes in the brain blood volume and in the brain oxygenation state can be detected using multiple wavelengths of light. Further, the spatial distribution of these changes can be visualized in the transillumination images of a brain. Through this study, the feasibility of optical trans-body imaging of physiological functions was verified