Reliability of brain metrics derived from a Time-Domain Functional Near-Infrared Spectroscopy System

Abstract

With the growing interest in establishing brain-based biomarkers for precision medicine, there is a need for noninvasive, scalable neuroimaging devices that yield valid and reliable metrics. Kernel's second-generation Flow2 Time-Domain Functional Near-Infrared Spectroscopy (TD-fNIRS) system meets the requirements of noninvasive and scalable neuroimaging, and uses a validated modality to measure brain function. In this work, we investigate the test-retest reliability (TRR) of a set of metrics derived from the Flow2 recordings. We adopted a repeated-measures design with 49 healthy participants, and quantified TRR over multiple time points, different headsets, and different experimental conditions including a resting state, a sensory, and a cognitive task. Results demonstrated high reliability in resting state features including hemoglobin concentrations, head tissue light attenuation, amplitude of low frequency fluctuations, and functional connectivity. Additionally, passive auditory and Go/No-Go inhibitory control tasks each exhibited similar activation patterns across days. Notably, areas with the highest reliability were in auditory regions during the auditory task, and right prefrontal regions during the Go/No-Go task, consistent with prior literature. This study underscores the reliability of Flow2-derived metrics, supporting its potential to actualize the vision of using brain-based biomarkers for diagnosis, treatment selection and treatment monitoring of neuropsychiatric and neurocognitive disorders.

Time-Domain Diffuse Optical Tomography for Precision Neuroscience

“…Further, those channels that exhibited the most statistically significant responses to task conditions revealed strong task-locked modulations. It is worth noting that we previously demonstrated the stability of such task-evoked metrics in a larger-scale study with the Flow2 device ( 34 ). Taken together, these findings uphold the two pillars of device performance for research and clinical-use: validity and reliability.…”

“…Additionally, as with other optical neuroimaging devices, hair can limit signal quality, as it absorbs light which reduces signal at the detectors. We have found that at least 1000 usable channels are available over the head for most participants ( 34 ) there is still room for improvement in mechanical design to ensure good optical coupling by working through all hair types and making contact with the scalp at all locations. Moreover, as with all diffuse optical systems, deep brain structures remain inaccessible.…”