Dependence of Reflectance on Optical Properties at Short Distance (Part A: Adaptation of Monte Carlo Simulations)

Accurate description of light propagation in tissue is a primary requirement in most optical imaging techniques, and enables to quantify for example the oxygen saturation. The Monte Carlo (MC) method, employing Henyey-Greenstein (HG) phase function, is a classical numerical approach to simulate the path of photons in tissue. However, it loses accuracy when describing short light propagation distances (<10 mm), where scattering is anisotropic. The aim of this work was to develop and test different approaches to mitigate this deficiency, employing the modified Henyey-Greenstein (MHG) and Gegenbauer (GB) phase functions. The updated scattering angle probability was implemented in the MC toolbox MCXLAB, written in CUDA and callable in MATLAB. Simulations were performed at source-detector distances from 1.5 to 5 mm, to test the behavior of the new solutions. We observed higher adaptability of the simulated curve due to employing MHG and GB phase functions compared to the conventional HG, due to the presence of the additional γ parameter in the equation that enables to adjust for the anisotropy.