Development of optical CT imaging system using multi-wavelength and short pulse of light

为了实现光学CT，本研究开发了一种利用多波长和超短脉冲光获取生理信息的先进测量技术。通过本研究，得到以下结果：1)提出了抑制生物组织中强散射的原理。利用这一原理，我们可以检测到通常埋在强散射分量中的弱近轴散射分量。2)应用超短脉冲时间分辨测量技术检测近轴散射光。提出了一种计算入射光束沿光轴方向吸收积分的方法。3)利用上述技术开发了实验系统。在实验中，得到了该系统在散射介质中的吸收分布。利用该技术，重构图像的空间分辨率得到了显著提高。此外，对吸收分布的定量测量也成为可能，这在没有这种技术的情况下是很困难的。4)针对无法检测到透射光的身体部位，新提出了背散射光横断面成像原理。为了利用这一原理，开发了一种测量技术。通过仿真研究，阐明了该技术的有效性和特性。利用这种技术开发了一个实验系统。重建了生物组织模型体的吸收分布。结果表明，重构图像与给定的分布在质量上符合较好。然而，在定量测量方面还需要进一步改进。同时发现测量误差的影响是不可忽略的。为了克服这些问题，提出了一种利用多波长和超短脉冲光的重建算法。仿真和实验验证了该方法的有效性。少

With a view toward the realization of an optical CT, this study was conducted to develop an advanced measurement technique to obtain physiological information using multi wavelength and ultra-short pulse of light. Through this study, the following results were obtained.1) A principle to suppress the strong scattering in biological tissue was developed. With this principle, we can detect a weak near-axis scattered component of light which is usually buried in a strong scattered component.2) A time-resolved measurement technique with an ultra-short pulse was applied to the detection of the near-axis scattered light. A technique to obtain the integral of absorption along the optical axis of the incident beam of light was developed.3) An experimental system was developed to use the above technique. In the experiment with this system, the absorption distribution in a scattering medium was obtained. With this technique, the spatial resolution of the reconstructed image was improved significa … More ntly. In addition, the quantitative measurement of absorption distribution became possible, which had been difficult without this technique.4) A principle of cross-sectional imaging using backscattered light was newly developed for the body part in which transmitted light could not be detected. To utilize this principle, a measurement technique was developed. In a simulation study, the effectiveness and the property of this technique were clarified.5) An experimental system was developed to use this technique. The absorption distribution in a model phantom of biological tissue was reconstructed. As a result, the reconstructed image agreed well qualitatively with the given distribution. However, further improvement was required for the quantitative measurement. It was also found that the effect of measurement error was not negligible. A new reconstruction algorithm was developed to overcome these problems by the use of multi-wavelength and ultra-short pulse of light. In the simulation and experiment, the effectiveness of this new technique was verified. Less