Model of light propagation in cerebrospinal fluid for brain function measurement

The direct hybrid Monte Carlo-diffusion method (DHMDM) has been used to calculate the light propagation in the head model with a low-scattering CSF layer. In calculation of the DHMDM, the surface radiance to the CSF layer should be replaced by the light source for Monte-Carlo calculation of light propagation in the CSF layer. In this study, the influence of asymmetric distribution of the surface radiance toward the CSF layer on the light propagation in the head model is investigated to improve the accuracy of the DHMDM. The light propagation in the head model with thin superficial layer is considerably affected by the asymmetric of the surface radiance. The model considering the asymmetric of the surface radiance in calculation of light propagation in the CSF layer by Monte-Carlo calculation improves the accuracy of DHMDM.