We present Monte Carlo simulations of the backscattering of polarized light by colon tissue in terms of Mueller matrix. We validated the Monte Carlo code with measurements on aqueous suspensions of polystyrene spheres of different sizes. In a first instance we have modeled a tissue as a monodisperse scattering medium representing the nuclei in cytoplasm; then we included a second layer with monodisperse scatterers to represent the most superficial layers (mucosa and submucosa) while the deeper layers (muscularis and pericolic tissue) were "lumped" into a totally depolarizing lambertian. These simulations failed to reproduce the Rayleigh type scattering (larger depolarization for circular vs. linear incident polarization) systematically observed on all experimentally studied tissue samples. This issue has been solved by modelling tissues as a single layer of bimodal mixtures including large and small scatterers over a lambertian.
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