Theoretical investigation of near-infrared light path in multi-layer brain models for three DOT systems

The optical path of near-infrared light propagation in multi-layer brain models was investigated by theoretical and computational analysis for three DOT systems. The brain models are comprised a three-layer slab or three-layer semi-sphere intersected by a same size three-layer slab. In each model, the light penetration depths and the shapes of light paths for different source and detector pairs were analyzed with a numerical diffusion forward model based on the finite element method. The simulation results revealed that the light path was affected by source and detector distance, and varied in the different brain models. Specifically, the effective penetration depths were different for the different DOT systems and deeper penetration depth was observed using a fast time-domain DOT system.