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: 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 () 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 considering the deepest of light. Of the detected photon packages scalp and bone absorbed and absorbed of the energy. The mean volume was negatively correlated () with the SCD and frontal sinus volume () and was reduced by in subjects with relatively large compared to small frontal sinus. Head circumference was significantly positively correlated with the mean SCD () and the traversed frontal sinus volume (). Sulcal morphology had no significant impact on . 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.

A review on continuous wave functional near-infrared spectroscopy and imaging instrumentation and methodology

“…For a single source-detector arrangement, it was shown the light intensity is~10-20 times (depending on the model for estimating the hemodynamic signals and the SDS) more sensitive to the extracerebral compartment compared to the cerebral compartment (Al-Rawi et al, 2001;Liebert et al, 2004). The tissue-specific energy of light absorbed in the head by using a 3 cm SDS was investigated by Haeussinger et al (2011) by a Monte Carlo simulation based on three-dimensional segmented structural MRI data. They showed that the main part of the energy is absorbed by the extracerebral compartment (scalp:~76%), skull: 20%, CSF:~0.4%) compared to the cerebral one (gray matter:~3%, white matter:~0.0005%).…”

Hemodynamic and EEG Time-Courses During Unilateral Hand Movement in Patients with Cortical Myoclonus. An EEG-fMRI and EEG-TD-fNIRS Study

“…The hemodynamic signals in the EPM1 patients, who typically lack b-ERS, had a similar time course but were significantly lessened, possibly because of their mild cortical atrophy. Heinzel et al 2013 have recently reported that up to 41 % of the variance in the HHb signal and up to 18 % of the variance in the O 2 Hb signal in frontal regions can be explained by individual grey matter volume; moreover, differences in the distance between the scalp and cortex may affect the sensitivity of fNIRS (Haeussinger et al 2011). As in previous studies of EPM1 patients (Koskenkorva et al , 2012, we found that motor area CT was moderately reduced in our patients, and correlated with the reduction in the hemodynamic signals.…”

Transcranial Light Emitting Diode Therapy (TCLT) and its Effects on Neurological Disorders

“…Haeussinger et al [43] determined that the amount of radiation absorbed by the brain gray matter is in the order of 3% when a certain amount of radiation is applied to the scalp. Naeser and Hamblin advocated that red/near-infrared photons can penetrate deeply into the skull and reach the cortex.…”