Light diffusion in stochastically perturbed media

In a medium such as biological tissue, the optical parameters may vary widely within a small volume. These small-scale variations cause variations in the light dose. A method is presented that quantifies (in the diffusion approximation) the average value and the standard deviation of the light fluence rate in a medium with stochastic optical parameters. Four optical parameters ({mu}{sub a}, {mu}{sub s}, g, and {mu}{sub s}{prime}) are modeled separately at each point in the medium as samples of correlated distributions. We find that the mean value differs only slightly from the fluence rate calculated with the average optical parameters. When the standard deviation of the optical parameter is {approximately}30%, the standard deviation of the stochastic fluence rate is of the same order of magnitude as the average fluence rate itself. Relative to the average value of the fluence rate, the standard deviation increases steadily with distance from the source: the fluence rate is more noisy deep in the medium. 23 refs., 7 figs., 1 tab.