Theoretical study on light distribution in biological

Radiance in biological tissue with strong absorption is studied, by solving the steady-state Boltzmann transport equation in P-3 approximation for an isotropy point source. We compare the diffusion solution to the total reflectance and the first two terms of the reflectance in P-3 approximation respectively, and find that P-3 approximation can improve the accuracy, especially in cases of strong absorption. Light radial distribution at the surface is also studied, it is shown that light centralizes in a small area as absorption tends strong. Through many calculations we have drawn a relation between radial width of light distribution and the absorption coefficient.