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Accurate estimation of the radiation distribution in the adult human head requires realistic head models generated from magnetic resonance imaging (MRI) scans with true optical properties of each layer of the head. In this study, a complex three-dimensional structural data obtained by MRI are introduced in a three-dimensional Monte Carlo code, with varying optical properties and arbitrary boundary condition, to calculate the spatial sensitivity profile of photon in head, so-called banana-shaped. It is therefore a better model to incorporate the contribution of cerebrospinal fluid (CSF) when modeling the head. The spatial sensitivity of near-infrared spectroscopy measurement to regions in the brain, as well as the effect of optical fiber arrangement on the regions of measurement are investigated. It is shown that the detected signal in brain imaging measurements is greatly affected by the heterogeneity of the head tissue and its scattering properties.

The purpose of this study was to design a near infrared spectroscopy (NIRS) sensor head to continuously monitor visual cortex activation. Visual cortex activation regions as a result of eye movements were localized using functional magnetic resonance imaging (FMRI). Once the region was determined we placed the NIRS sensor head on that region and emulated the same task performed in the FMRI experiment. The eye movement chosen for our current validation study was saccades. One subject was instructed to move their eyes in a saccadic fashion for 30 seconds then fixate for 30 seconds. We were able to see changes in oxyhemoglobin and deoxyhemoglin using the NIRS design. These preliminary results suggest that NIRS can be used as a monitoring tool, guided by FMRI in patients who may have visual disorders.