Kernel Flow: a high channel count scalable time-domain functional near-infrared spectroscopy system

Abstract

. Significance: Time-domain functional near-infrared spectroscopy (TD-fNIRS) has been considered as the gold standard of noninvasive optical brain imaging devices. However, due to the high cost, complexity, and large form factor, it has not been as widely adopted as continuous wave NIRS systems. Aim: Kernel Flow is a TD-fNIRS system that has been designed to break through these limitations by maintaining the performance of a research grade TD-fNIRS system while integrating all of the components into a small modular device. Approach: The Kernel Flow modules are built around miniaturized laser drivers, custom integrated circuits, and specialized detectors. The modules can be assembled into a system with dense channel coverage over the entire head. Results: We show performance similar to benchtop systems with our miniaturized device as characterized by standardized tissue and optical phantom protocols for TD-fNIRS and human neuroscience results. Conclusions: The miniaturized design of the Kernel Flow system allows for broader applications of TD-fNIRS.

Functional near‐infrared spectroscopy is a useful tool for multi‐perspective psychobiological study of neurophysiological correlates of parenting behaviour

“…Modules are organized into four plates on each side of the head, covering the frontal, parietal, temporal and occipital cortices. Each module consists of a central laser source surrounded by six hexagonally arranged detectors, each 10 mm from the source (Ban et al, 2022).…”

“…The use of wearable devices may represent a further step forward in optical neuroimaging (Frijia et al, 2021) and will provide further data on human neuroscience (Ban et al, 2022). Although fNIRS technology has had a significant improvement in recent years, motion artefacts still represent a significant component of the measured fNIRS signal.…”

Concurrent fNIRS and EEG for Brain Function Investigation: A Systematic, Methodology-Focused Review

“…In particular, conventional concurrent fNIRS–EEG studies usually connect separate fNIRS and EEG systems for data recording, which reduces the mobility of both systems and constrains the applications of concurrent fNIRS and EEG. Recent advances have been made toward fiberless and wearable integrated fNIRS–EEG systems that allows for broader research scenarios such as social interaction and outdoor activity [ 127 , 128 ]. However, further improvement of fNIRS and EEG instruments is necessary when applying these systems in clinical cohorts with psychological or psychiatric disorders.…”

Reliable Fast (20 Hz) Acquisition Rate by a TD fNIRS Device: Brain Resting-State Oscillation Studies

“…A commercial solution, named “Flow”, was presented recently by Kernel (Kernel, Los Angeles, CA, USA, (accessed on 22 December 2022)). They showed a multichannel wearable headset that measures brain activity [ 18 ], which potentially allows measurements up to a 100 Hz acquisition rate in the single channel, but now limited to 7.1 Hz to avoid cross-talk effects among channels. They also reported measurements performed at a 6 cm source-detector distance, but with a limited count rate (~10 4 counts/s).…”