title: Simulation of near-infrared light absorption considering individual head and prefrontal cortex anatomy: implications for optical neuroimaging.
abstract: Functional near-infrared spectroscopy (fNIRS) is an established optical neuroimaging method for measuring functional hemodynamic responses to infer neural activation. However, the impact of individual anatomy on the sensitivity of fNIRS measuring hemodynamics within cortical gray matter is still unknown. By means of Monte Carlo simulations and structural MRI of 23 healthy subjects (mean age: 25.0±2.8 years), we characterized the individual distribution of tissue-specific NIR-light absorption underneath 24 prefrontal fNIRS channels. We, thereby, investigated the impact of scalp-cortex distance (SCD), frontal sinus volume as well as sulcal morphology on gray matter volumes (V(gray)) traversed by NIR-light, i.e. anatomy-dependent fNIRS sensitivity. The NIR-light absorption between optodes was distributed describing a rotational ellipsoid with a mean penetration depth of (23.6±0.7) mm considering the deepest 5% of light. Of the detected photon packages scalp and bone absorbed (96.4±9.7)% and V(gray) absorbed (3.1±1.8)% of the energy. The mean V(gray) volume (1.1±0.4) cm3 was negatively correlated (r=-.76) with the SCD and frontal sinus volume (r=-.57) and was reduced by 41.5% in subjects with relatively large compared to small frontal sinus. Head circumference was significantly positively correlated with the mean SCD (r=.46) and the traversed frontal sinus volume (r=.43). Sulcal morphology had no significant impact on V(gray). Our findings suggest to consider individual SCD and frontal sinus volume as anatomical factors impacting fNIRS sensitivity. Head circumference may represent a practical measure to partly control for these sources of error variance.
authors: Department of Psychiatry and Psychotherapy, University of Tuebingen, Tuebingen, Germany.
authors: Florian B
authors: FB
authors: Haeussinger
authors: Sebastian
authors: S
authors: Heinzel
authors: Tim
authors: T
authors: Hahn
authors: Martin
authors: M
authors: Schecklmann
authors: Ann-Christine
authors: AC
authors: Ehlis
authors: Andreas J
authors: AJ
authors: Fallgatter
mesh_terms: D000328:Adult; D006257:Head / Q000033:anatomy & histology*; D006801:Humans; D007259:Infrared Rays; D008279:Magnetic Resonance Imaging; D009010:Monte Carlo Method; D017397:Prefrontal Cortex / Q000033:anatomy & histology*; D019265:Spectroscopy, Near-Infrared