In functional near-infrared spectroscopy (fNIRS) superficial hemodynamics can mask optical signals related to brain activity. We present a method to separate superficial and cerebral absorption changes based on the analysis of changes in moments of time-of-flight distributions and a two-layered model. The related sensitivity factors were calculated from individual optical properties. The method was validated on a two-layer liquid phantom. Absorption changes in the lower layer were retrieved with an accuracy better than 20%. The method was successfully applied to in vivo data and compared to the reconstruction of homogeneous absorption changes.
Keywords: (120.3890) Medical optics instrumentation; (170.1470) Blood or tissue constituent monitoring; (170.3880) Medical and biological imaging; (170.5280) Photon migration; (170.6510) Spectroscopy, tissue diagnostics; (170.6920) Time-resolved imaging.