FEM Analysis of Photon Migration in Biological Tissues

Abstract

Time-resolved spectroscopy is expected to be developed for optical imaging of biological tissues which strongly scatter and weakly absorb light. It is strongly required to establish the temporal behaviors of the reflectance and/or transmittance of light impulses incident on such scattering and absorbing media. One of the analytical methods to solve the photon diffusion equation numerically is the finite element method (FEM). This paper reports the FEM results of temporal profiles of the transmittance of light impulses through scattering slabs and cylinders. Time courses of transmittances through homogeneously scattering and absorbing slabs are obtained by FEM and compared with those obtained by the Monte Carlo method which is believed to provide more accurate results with much longer computation time. The results of cylinders with homogeneous scattering and in-homogeneous absorption coefficients are also presented. Temporal variations of the cross-sectional profiles of the fluence rate generated by impulses incident on a surface are shown by contour plotting, and the effect of the location and size of the localized absorbing volume on the transmittances are discussed.