Measurement and Simulation of Light Distribution in Biological Tissue

• Main Authors: Yang Yi-Feng, 楊宜峰
• Other Authors: Tsai Cheng-Lun
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/08691567364754731311

碩士 === 中原大學 === 醫學工程學系 === 88 === Optical measurement is widely used in biomedical and clinical applications. It has the advantages of electrically safe and none invasive. For many applications, it is important to have the accurate values of optical properties of biological tissues (such as absorption coefficient, scattering coefficient, and anisotropy coefficient) in order to estimate the distribution of light in tissue as well as its propagation paths. However, the measurement of optical properties itself remains a great challenge to the researchers. This study proposes a new method for studying the distribution of light in biological tissue on a cross section image. A 623 nm red light emission diode (LED) was used as the light source. The light was coupled into an optical fiber with diameter of 0.5 mm and guided to the tissue sample. Light distribution on tissue surface was filmed with a digital camera. The two-dimension image applies more information than traditional one-dimension measurements. The distribution of light in different kinds of soft tissue (muscle, skin, and fat) was studied. The results also show the effect of muscle fiber direction and temperature on the light distribution. Monte Carlo simulation was carried out to simulate the light distribution of measurements. In the model, the anisotropy coefficient was assumed to change with the propagation direction of photon to simulate the effect of muscle direction. By comparing the results of measurement and simulation, the anisotropy coefficient does change with the direction of muscle fiber direction and has an obvious influence on the light distribution in the near field. The increase of tissue temperature from 23°C to 42°C caused a decrease of scattering property of fat tissue, whereas an increase of scattering in muscle and skin tissue. Future work of this study will be to match the simulation of light distribution with the measurement by modifying the optical coefficients. This reverse method will be helpful in acquiring more accurate values of optical coefficients of biological tissue.