Reconstruction of light absorption changes in the human head using analytically computed photon partial pathlengths in layered media

VERA, DEMIÁN; GARCÍA, HÉCTOR; WAKS SERRA, MARIA; CARBONE, NICOLÁS; IRIARTE, DANIELA; POMARICO, JUAN

JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION - (Print)

OPTICAL SOC AMER

Año: 2023

1084-7529

Functional Near Infrared Spectroscopy has been used in the last decades to sense and quantify changes in hemoglobin concentrations in the human brain. This non invasive technique can deliver useful information concerning brain cortex activation associated with different motor/cognitive tasks or external stimuli. This is usually accomplished by considering the human head as a homogeneous medium; however, this approach does not explicitly takes into account the detailed layered structure of the head and thus, extracerebral signals can mask those arising at the cortex level. This work improves this situation by considering layered models of the human head during the reconstruction of the absorption changes in layered media. To this end, analytically calculated mean partial pathlengths of photons are used, which guarantees fast and simple implementation in real-time applications. Results obtained from synthetic data generated by Monte Carlo simulations in two- and four-layered turbid media suggest that a layered description of the human head greatly outperforms the typical homogeneous reconstructions, with errors, in the first case, bounded up to $sim$ 20% maximum, while in the second case the error is usually larger than 75%. Experimental measurements on dynamic phantoms support this conclusion.