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

为利用多波长超短光脉冲实现生物功能的透照和CT成像进行了基础性研究。通过本课题的研究，取得了以下进展：(1)通过理论和实验研究表明，利用近红外区多波长的光可以获得动物体内发生的功能变化的图像。基于该原理，研制了一套透光成像系统。利用这一系统，我们尝试用小型实验动物对大脑功能进行成像。因此，我们可以成功地成像在施加体感刺激时定位于大鼠脑内的传递变化。证实这种变化出现在刺激肢体对侧左右大脑半球的对称位置。在…看来，这一结果研制了光学CT系统，并尝试在横断面图像上进行功能成像。利用该系统可以检测到小鼠腹部CT图像中肾脏的氧合变化。(4)利用飞秒激光和条纹相机搭建了超短光脉冲实验系统。这使得我们能够分析来自破碎介质的时间分辨光脉冲。(5)发展了一种新的重建技术，利用后向散射光获得高散射介质的截面图像。在计算机模拟和模型实验中，验证了该方法的有效性。(6)研究了超短光脉冲时间分辨分析中透射光中的散射成分。阐明了蛇形光子或近轴散射光沿入射光束光轴传播的行为和特性。基于这一结果，发现了比传统的时间门控方法更有效地抑制散射效应的可能性。较少

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