Abstract
.Functional near-infrared spectroscopy (fNIRS) is a noninvasive brain imaging technique that uses scalp-placed light sensors to measure evoked changes in cerebral blood oxygenation. The portability, low overhead cost, and ability to use this technology under a wide range of experimental environments make fNIRS well-suited for studies involving infants and children. However, since fNIRS does not directly provide anatomical or structural information, these measurements may be sensitive to individual or group level differences associated with variations in head size, depth of the brain from the scalp, or other anatomical factors affecting the penetration of light into the head. This information is generally not available in pediatric populations, which are often the target of study for fNIRS. Anatomical magnetic resonance imaging information from 90 school-age children (5 to 11 years old) was used to quantify the expected effect on fNIRS measures of variations in cerebral and extracerebral structure. Monte Carlo simulations of light transport in tissue were used to estimate differential and partial optical pathlengths at 690, 780, 808, 830, and 850 nm and their variations with age, sex, and head size. This work provides look-up tables of these values and general guidance for future investigations using fNIRS sans anatomical information in this child population.
Highlights
Functional near-infrared spectroscopy is a noninvasive neuroimaging technique that uses low levels of red to near-infrared light (650 to 950 nm) to measure changes in the optical absorption of tissue due to hemoglobin
We examine the effects on the optical differential pathlength factor (DPF) and partial pathlength factor (PPF) using Monte Carlo modeling of the optical transport model
We used 90 segmented magnetic resonance imaging (MRI) volumes from children ages 5 to 11 years to model the intersubject variations in head and brain anatomy and their effects on the sensitivity of Functional near-infrared spectroscopy (fNIRS) measurements
Summary
Functional near-infrared spectroscopy (fNIRS) is a noninvasive neuroimaging technique that uses low levels of red to near-infrared light (650 to 950 nm) to measure changes in the optical absorption of tissue due to hemoglobin. Variations between individuals in the cortical folding of the brain, head-size, skull thickness, or layers of cerebral spinal fluid (CSF) can influence the recorded fNIRS signals and the sensitivity to underlying brain activity This is a limiting situation since one of the advantages of fNIRS technology is often cited as its portability, low cost, and ability to record brain activity from pediatric or other special subject populations for whom magnetic resonance imaging (MRI) may be difficult or contraindicated. The objective of this current work is to investigate how these factors affect fNIRS measurements in school-age children and to systematically examine the quantitative effect of age, head-size, and sex on fNIRS measurements. A dataset of structural MRI volumes from 90 children (58 to 131 months) is examined in this work
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