Time-resolved Light Distribution Properties And The Optical Parameters Measurement In Bio-tissue

The diffusion light detected from tissue surface contains the tissue optical parameters information. So the tissue optical parameters can be obtained indirectly by the diffusion light measuring, then the optical parameters resolved tissue structure, the physiologic and pathologic state information can be obtained finally. Therefore, the study of tissue optical properties, the propagation rule of light in tissue and how to extract tissue optical parameters with accuracy play significant role in optical examine and diagnosis.Firstly, the ultra-short pulse light propagation rule in tissue is investigated by time-resolved Monte Carlo (MC) simulation method, and the relationship between the light distribution rule in semi-infinite homogeneous tissue surface and the absorption coefficient μ_a, the reduced scattering coefficient μ'_s the anisotropy factor g and the detected angle θ are obtained respectively. Additionally, the relationship between the reflectance light distribution in tissue surface and the thickness of a homogeneous tissue is also studied, and some analyses are made based on the results above. Then some valuable conclusions are obtained to have the time-resolved transport theory of tissue enriched.Secondly, a nonlinear least square fitting algorithm based on a simplex search method is used to display the fitting accuracy influenced by the fitting start time and the fitting end time, the two parameters (μ_a μ'_s) fitting and the three parameters (μ_ μ'_s amplitude factor A) fitting on the basis of MC simulation. In addition, a comparison is made between the results that to use the diffusion reflectance data with a certain detected angle to fit to the diffusion reflectance formula based on full angle detecting and to fit to the diffusion formula based on corresponding detected angle respectively. And, the influence of different nonlinear least square fitting algorithm to the fitting accuracy and to the fitting time is also discussed. Then, some significant results are made to improve the fitting accuracy of tissue optical parameters.Finally, for the finite thickness homogenous tissue, a single parameter (μ'_s) fitting method and a double parameters (μ'_s A or μ'_s, A) fitting method on the basis of the least square Newton fitting algorithm are used to demonstrate that the rest term in...