Research On Numerical Simulation Of Light Propagation And Optical Measurement For Biological Tissue

The biomedical photonics has been developing rapidly in the recent years, in which the light-biology interaction and light distribution principle have bee n the hot topic of research. Considering that the diversity of biologic structures and the complexity of physiological state, the optical characteristic parameter have to be obtained completely for the establishment of bio-tissue model. Meanwhile the pathological and physiological states are closely related to the optical parameters. Accordingly the measurement of optical coefficients is the key research content in the field of biomedical photonicsThe Monte Carlo algorithm is used to the investigation of t racking particle. This method is highly accurate, which is usually adopted as non-experimental inspection standard towards the theoretical model. The propagation character of photon in tissue has been researched with the method of Monte Carlo in this paper. The basic idea was to simulate the interaction between photons and material particles. And the macroscopic photon transport model could be determined by means of counting the track of photons propagation after several times of independent repeated trials.Firstly the law of light propagation in biological tissue was discussed in the article. Starting from the photon transport theory and the diffusion approximation, the three different boundary conditions were derived. And then the theoretical light distribution under the steady state condition was obtained. The accuracy and the application range of the theoretical model were validated while the Monte Carlo method has been considered as standard results.Secondly the Monte Carlo algorithm was researched aiming at optical propagation in biological tissue. The model of multi-layer tissue was constructed based on the existing steady state Monte Carlo method. At the same time the influence of beam radius on the light distribution was analyzed through the method of convolution. And then the time-resolved Monte Carlo algorithm was improved and programmed to realize the record of the diffuse reflection spectrum, whose precision was compared with the diffusion approximation. The impacts of absorption coefficient, scattering coefficient, anisotropic factor and relative refractive index on simulation results have been discussed with different detection positions.Finally the measuring method for the optical parameters of tissue has been investigated in this paper. The detecting platform of optical parameters was built based on the spatially resolved and time-resolved techniques. At the same time the experimental principle, equipment type and relevant parameters were also presented. Taking the phantom for research object, the diffuse reflectance signal was measured. The Matlab Cftool toolbox and fitting program written were applied respectively to realize the optical parameters inversion aiming at the experimental curve. The choice of fitting theory model and validation of fitting range have been simultaneously discussed in depth, which improve the measurement accuracy effectively. And the results was compared and analyzed with standard value of sample.