A Monte Carlo study of Mueller matrix decomposition in complex tissue-like turbid media

Abstract

Extraction / unique interpretation of the intrinsic polarization parameters in optically thick turbid media such as tissues is complex due to multiple scattering effects and due to simultaneous occurrences of many polarization effects (the most common polarimetry effects in tissues are depolarization, linear birefringence and optical activity). Each of these polarimetry characteristics, if separately extracted, holds promise as a useful biological metric. We have recently investigated the use of an expanded Mueller matrix decomposition method to tackle this problem, with early indications showing promise. However, for further insight and for practical realization of this approach, it is essential to have quantitative understanding of the confounding effects of scattering, the propagation path of multiply scattered photons and detection geometry on the Mueller matrix-derived polarization parameters (parameters of particular biomedical importance are linear retardance, optical rotation and depolarization). The effect of the ordering of the individual matrices in the decomposition analysis on the derived polarization parameters also needs to be studied. We have therefore investigated these issues by decomposing the Mueller matrices generated with a polarization sensitive Monte Carlo model, capable of simulating all the simultaneous optical (scattering and polarization) effects. The results show that with appropriate choice of detection position, indeed the inverse decomposition analysis enables one to decouple and quantify the individual intrinsic polarimetry characteristics despite their simultaneous occurrence, even in the presence of the numerous complexities due to multiple scattering. The details of these results are presented and the implications of these in diagnostic photomedicine are discussed.