[The Acceleration of Monte Carlo Simulation for Optical Transmission in Large Space Biological Tissue].

Typically, it is time-consuming to use Monte Carlo simulation to model light propagation in turbid media, such as breasts, mainly because of the thick simulated tissue and the large number of photons required by the stochastic nature of MC simulations. In this paper, in view of the light source and the receiver in a straight line, the transmitted light received by optical fiber model is analyzed; in terms of the optical properties of biological tissue itself, implementation of boundary constraint conditions and restriction of the number of backscatter events have been developed to reduce the simulation time. It is verified that the calculation is relatively simple by many experiments, when the position after two scattering is regarded as the demarcation and the boundary constraint conditions are efficiently solved by optical parameters of tissue respectively. At the same time, considering the actual situation in incident and emergent position, the boundary constraint conditions are expanded. The number of backscatter of every photon that received by optical fiber in the same position are recorded and tissues are selected different thickness and the similar optical parameters in the simulations. Additionally, it is found that the number of backscatter would increase as the depth of tissue or scattering coefficient increases, or as absorption coefficient or anisotropic factor decreases. Therefore, the time is saved further through limiting the number of backscatter. The simulation results show the combination of those new methods reduces the operation time of the MC simulation by 50% on a typical desktop computer. Those new methods are especially suitable for MC simulations of the thick tissue or the scatterer with a complex boundary. This acceleration method is applicable when light source and receiver are in a straight line the biological tissue is thicker and scattering coefficient is large. It can effectively save needed time and be beneficial to analyze the transmission imaging.