Hybrid model of Monte Carlo simulation and diffusion theory for light reflectance by turbid media

Light reflectance by semi-infinite turbid media is modeled by a hybrid of Monte Carlo simulation and diffusion theory, which combines the accuracy of Monte Carlo simulation near the source and the speed of diffusion theory distant from the source. For example, when the turbid medium has the following optical properties--absorption coefficient 1 cm-1, scattering coefficient 100 cm-1, anisotropy 0.9, and refractive-index-matched boundary--the hybrid simulation is 7 times faster than the pure Monte Carlo simulation (100,000 photon packets were traced), and the difference between the two simulations is within 2 standard deviations of the Monte Carlo simulation.