Development of CT Imaging Technique Using Multi-wavelengh and Ultra-short Light Pulse

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A fundamental study was conduced to realize the transilumination and the CT imaging of biological functions using multi-wavelength and ultra-short light pulse. Through this research the following progresses were made.(1) Through theoretical and experimental study, it was shown that we can get the image of functional change occurred inside an animal body using the light of multiple wavelengths in near-infrared region. The imaging can be perfomed noninvasively with a relatively simple apparatus.(2) A transilumination imaging system was developed based on the proposed principle. Using this system, the imaging of brain functions was attempted using small experimental animals. As a result, we could succeeded in imaging the transmission change localized in the rat brain when a somatosensory stimulation was applied. It was confirmed that the change appeared in symmetrical positions of left and right cerebral hemispheres at the contra-lateral side of the stimulated limbs. This result seems to … More be the first case which verified the feasibility of transilumination imaging of the cerebral functions.(3) An optical CT system was developed, and the functional imaging in the crosssectional image was attempted. Using this system, we could detect the oxygenation change of the kidney in the CT image of the mouse abdomen.(4) An experimental system of an ultra-short light pulse was constructed with a femto-second laser and a streak camera. This enabled us to analyze a time-resolved light pulse from a svattering medium.(5) A reconstruction technique was newly developed to obtain crosssectional image of highly scattering medium using backscattered light. In computer simulations and phantom experiments, the effectiveness of this technique was confirmed.(6) The scattered component in transmitted light was investigated in the time-resolved analysis of an ultra-short light pulse. The behavior and prepertes of a snake photon or near-axis scattered light which propagates along the optical axis of the incident beam of light were clarified. Based on this result, the possibility was found to suppress the scattering effect much more effective than the conventional time-gating method. Less