Light Propagation And Light Source Localization In Biotissues

Optical transmission and optical localization problem in biological tissues were an important research area in tissue optics. It played an important role in medical for diseases diagnosing and treating. Localization of light Source in deep tissue was the key issue in this paper, and the main work of this dissertation included establishing optical physical model of tissues, mathematics description of interaction between photons and biological tissues, acquirement of optical parameters of tissues, proposing of equivalence measuring methods, and experimental design and evaluation of the method under lab conditions. Specifically, the research focused on three parts:Firstly, the principles of Mote Carlo simulation of were simply described and the algorithm of Monte Carlo simulation was used to investigate the distribution of light source in the tissue. The 2-dimensional images of photo distribution were constructed by Matlab software from the Monte Carlo simulation results, which obviously displayed the optical field distribution within the tissue. According to that, the relationship between light intensity and relative distance were used to analylize the photon propagation in tissuses. Numerical results were obtained by Monte Carlo method became a non-experimental standards to compare the accuracy of various analytical theories of tissue optics, which derived the following diffusion theory to provide comparative standards.Secondly, from the theory of light transmission, we obtained the light transportation of diffusion approximation equation within biological tissue under diffusion approximation condition, and the answers of diffusion model equation could be obtained when infinitely thin beam normal incidence to semi-infinite and infinite medium, and then, the analytical expression of light distribution within the tissue were given. The results of Matlab simulation of the analytical conditions and the corresponding results of Monte Calo methods were compared to verify the accuracy of the method. The analytical solution of diffusion theory provided theoretical foundation for the equivalence method in the next section.Thirdly, because the tissue optical parameters within the tissue are hard to be obtained accurately, the equivalence method for locating the light source was provided according to the diffusion approximation theory. The simulation results were compared with the theoretical values to verify the correctness of the algorithm, and then the corresponding light detection system was designed according to the algorithm. The light source distributions according to the actual measuring optical parameters from dual-integrating sphere were compared to the localization of light source according to equivalence method. The results showed that the algorithm could localize the light source within the tissue correctly and in realtime.The proposed algorithm theory was valuable for early detection of tumor and the mini-invasive surgical navigation of tumor resection in the future.