Modeling Polarized Light Transport: Monte Carlo and Tissue Properties

Saturday, 11 September 2010: 13:45-14:30

Prof. Steven Jacques, Oregon Health and Science University

Polarized light measurements offer a characterization of tissue based on short paths of light transport through the tissue. Longer photon paths completely depolarize incident polarized light. Short paths partially depolarize, diattenuate and retard polarized light, hence the polarization state (specified as a Stokes vector) of the escaping light can characterize the tissue properties. A single photon can scatter or retard which modifies its polarization state, but the photon is still fully polarized. In contrast, a population of photons can diverge with respect to the polarization state of its members, and the average behavior exhibits a loss of polarization. Tissues can present local microdomains (10-100 .m) of birefringent fibers that are randomly oriented, which can be modeled as a series of incremental Mueller matrices, enabling study of depolarization due to randomized retardance. Monte Carlo simulations can propagate photons as Stokes vectors that are scattered, enabling study of depolarization due to scattering. In imaging, selecting polarized photons rejects multiply scattered light, yielding images of superficial tissue layers.