Attenuation and Scattering of Light in the Skull

The skull’s heterogeneous bone matrix presents a highly scattering and absorptive barrier to near-infrared light. Variations in cortical and trabecular bone layers lead to spatially non-uniform reduced scattering coefficients (μ_s') and absorption coefficients (μ_a), which attenuate and diffuse photons before they reach the brain surface. These effects degrade the sensitivity and spatial specificity of transcranial optical imaging.

Accurate modeling of photon migration through the skull uses Monte Carlo simulations and diffusion theory to predict optical pathlengths and sensitivity profiles. Knowledge of skull optical properties informs optode placement, source-detector separations, and correction algorithms that mitigate superficial signal contamination, thereby improving the fidelity of cerebral hemodynamic measurements.