Directly extracting the optical transport coefficients of a turbid medium via time-resolved diffuse reflectance: a Monte Carlo study

An empirical approach to estimate the reduced scattering (μ_s') and absorption (μ_a) coefficients of a turbid medium from time-resolved diffuse reflectance detected at multiple source-detector separations (SDS) is described. The dependence of the temporal point spread function (TPSF) on the medium's optical properties has been previously well studied. Here, we exploit these findings by using the difference in photon arrival-times obtained from a pair of SDS at the (a) peak intensity and (b) longer-time trailing edge of the TPSF to estimate the transport coefficients. This difference may have little dependence on the instrument response functions (IRF). Consequently, real-time quantitation is possible since the method does not depend on non-linear fitting of measured reflectance and/or deconvolving the IRF. The approach uses Monte Carlo simulations to directly translate the difference in arrival times of the temporal reflectance profiles at multiple SDS into the medium's optical properties. Here, we show that a small range in the optical properties could be defined using a pair of time differences in the TPSF.