Stochastic View of Photon Migration in Turbid Media
  Light propagation in an infinite uniform turbid medium is treated as a Markov stochastic process of photons to provide an intuitive framework for photon migration. The macroscopic physical quantities of photon migration are shown to be completely determined by the microscopic statistics of the photon propagation direction in direction space and a generalized Poisson distribution of the number of scattering events that includes an exponential decay absorption factor. A proper diffusion solution is derived with an exact time-dependent central position and half width of photon migration in this framework. The diffusion coefficient is found to be absorption-independent. 
M. Xu, W. Cai, M. Lax and R. R. Alfano