Development and validation of a low-cost, wearable near-infrared spectroscopy system for quantifying tissue water fraction in the human brain.
- 1Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts, United States.
Abstract
Cerebral water fraction is physiologically relevant to brain fluid dynamics, glymphatic function, cerebral edema, and dehydration, yet it is not routinely measured in wearable neuroimaging. We aimed to develop and validate a low-cost, wearable, light-emitting diode (LED)-based continuous-wave near-infrared spectroscopy system capable of concurrently monitoring changes in cerebral hemoglobin concentration and water fraction from the forehead. Our device, called the GS-FlexNIRS, contains nine LEDs spanning 740 to 1050 nm mounted on a flexible printed circuit board. Three of these wavelengths (i.e., 910, 940, and 1050 nm) fall within the water absorption window. A wavelength-weighted fitting algorithm incorporates measured LED emission spectra and photodiode responsivity to enable accurate chromophore recovery despite spectrally broad LED illumination. Performance was characterized in liquid phantoms and in five healthy participants during respiratory maneuvers. The system achieved a dynamic range of ∼100 dB , gain linearity ( R2>0.99997 ), and signal-to-noise ratio of 67 to 90 dB. Phantom experiments confirmed independent tracking of hemoglobin deoxygenation and water fraction changes. Hemoglobin responses in human measurements were consistent with prior work. The GS-FlexNIRS ( ∼$350/unit ) and its wearable design may support future longitudinal and naturalistic monitoring of cerebral hemodynamics and brain fluid dynamics, enabling investigation in sleep, glymphatic research, and cerebral edema monitoring.
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BibTeX
@article{wu2026development,
title = {{Development and validation of a low-cost, wearable near-infrared spectroscopy system for quantifying tissue water fraction in the human brain.}},
author = {Kuan Cheng Wu and Marco Renna and Nikola Otic and Zachary Starkweather and Olivia S Kierul and Christopher Smith and Maria Angela Franceschini and Mitchell B Robinson},
journal = {Journal of biomedical optics},
year = {2026},
month = oct,
doi = {10.1117/1.jbo.31.10.106006},
url = {https://europepmc.org/article/MED/42953459},
note = {CC BY},
}
RIS
TY - JOUR
TI - Development and validation of a low-cost, wearable near-infrared spectroscopy system for quantifying tissue water fraction in the human brain.
AU - Kuan Cheng Wu
AU - Marco Renna
AU - Nikola Otic
AU - Zachary Starkweather
AU - Olivia S Kierul
AU - Christopher Smith
AU - Maria Angela Franceschini
AU - Mitchell B Robinson
PY - 2026
DA - 2026/10/28
JO - Journal of biomedical optics
DO - 10.1117/1.jbo.31.10.106006
UR - https://europepmc.org/article/MED/42953459
AB - Cerebral water fraction is physiologically relevant to brain fluid dynamics, glymphatic function, cerebral edema, and dehydration, yet it is not routinely measured in wearable neuroimaging. We aimed to develop and validate a low-cost, wearable, light-emitting diode (LED)-based continuous-wave near-infrared spectroscopy system capable of concurrently monitoring changes in cerebral hemoglobin concentration and water fraction from the forehead. Our device, called the GS-FlexNIRS, contains nine LEDs spanning 740 to 1050 nm mounted on a flexible printed circuit board. Three of these wavelengths (i.e., 910, 940, and 1050 nm) fall within the water absorption window. A wavelength-weighted fitting algorithm incorporates measured LED emission spectra and photodiode responsivity to enable accurate chromophore recovery despite spectrally broad LED illumination. Performance was characterized in liquid phantoms and in five healthy participants during respiratory maneuvers. The system achieved a dynamic range of ∼100 dB , gain linearity ( R2>0.99997 ), and signal-to-noise ratio of 67 to 90 dB. Phantom experiments confirmed independent tracking of hemoglobin deoxygenation and water fraction changes. Hemoglobin responses in human measurements were consistent with prior work. The GS-FlexNIRS ( ∼$350/unit ) and its wearable design may support future longitudinal and naturalistic monitoring of cerebral hemodynamics and brain fluid dynamics, enabling investigation in sleep, glymphatic research, and cerebral edema monitoring.
SN - 1083-3668
SN - 1560-2281
ER -