3-D spatial sensitivity profiles of head model in near-infrared spectroscopy

The heterogeneity of tissue scattering makes determination of sampling volume of near infrared spectroscopy (NIRS) instruments difficult. The 3-D spatial sensitivity profiles, which indicate the volume of tissue sampled by an NIRS instrument, in the head models are predicted by the Monte Carlo method. The spatial sensitivity profile is strongly affected by the clear cerebrospinal fluid (CSF) surrounding the brain. In the model with the CSF, the spatial sensitivity profile spreads over an extensive area in the brain surface between the source and detector but it is confined to a shallow region in the brain.