Abstract:

 A Monte Carlo method was used to study the light distribution in biotissues with a collimated light beam. The track of photons propagation, the energy intensity distribution with optical parameters, the absorption energy density and internal fluence with depths and radius, the change of radially and angularly resolved diffuse reflectances were analyzed. The propagation of the Gaussian beam and circularly flat beam in biotissues was simulated by using convolution. The results showed that when a collimated light beam propagated in the tissue, the energy was mainly concentrated in the vicinity of the central axis. The photons forward movement was enhanced when the g factor was increased. When the absorption coefficient became larger, the distribution of photons was reduced along the vertical and horizontal axis. The internal fluence changed more smoothly than the absorption energy density. The energy distribution of the Gaussian beam had a larger concentration than that of a circularly flat beam, changed more rapidly and had a larger energy absorption in the center.

Key words:  Monte Carlo method, bio-tissue, absorption energy density, diffuse reflectance