A hybrid MC-FEM model for analysis of light propagation in highly scattering medium

Abstract

The hemodynamic change related to the brain activation can be located by the diffuse optical tomography (DOT) using the near-infrared spectroscopy (NIRS) signals and the spatial sensitivity profiles (SSP). Monte Carlo (MC) method and finite element method (FEM) have been used to predict the SSPs. The computation time for MC method is much longer than that for the FEM, however, the accurate solution in the region close to the light source cannot be obtained by FEM solutions of the diffusion equation. In this study, a hybrid MC-FEM model is proposed for fast and accurate simulation of light propagation in a highly scattering medium. In the hybrid model, the solution in the region close to the light source is calculated by the MC method whereas that in the region far from the light source is calculated by the FEM. The solutions by the FEM in hemispherical models were compared with thoseby the MC method to determine the region in which diffusion approximation does not hold and the number of photons for the MC method for the hybrid model. The results demonstratethat theproposed hybrid model can calculatethe accurate solutionswithin reasonable computation time for a multi-layered model.