Recent advances in brain imaging techniques facilitate accurate high-resolution observations of the brain and its functions. For example, functional near-infrared spectroscopy (fNIRS) is a widespread non-invasive imaging technique that uses near-infrared light (wavelength> 700 nm) to determine the relative concentration of hemoglobin in the brain via differences in hemoglobin light absorption patterns.
Most non-invasive brain scanning systems use continuous wave fNIRS, where the tissue is irradiated by a constant stream of photons. However, these systems cannot distinguish between scattered and absorbed photons. A recent advancement to this technique is time domain (TD) -fNIRS, which uses picosecond pulses of light and fast detectors to estimate photon scattering and absorption in tissues. However, such systems are expensive and complex and have a large form factor, which limits their widespread use.
To overcome these challenges, researchers from Kernel, a neurotechnology company, have developed a portable headset based on TD-fNIRS technology. This device, called the "Kernel Flow", weighs 2.05 kg and contains 52 modules arranged in four plates that fit on each side of the head. Kernel Flow system specifications and performance are reported in Journal of Biomedical Optics (JBO).
The headset modules have two laser sources that generate laser pulses with a width of less than 150 picoseconds. The photons are then reflected from a prism and combined in a source fluorescent tube that directs the beam to the scalp. After passing through the scalp, the laser pulses are captured by six spring-loaded detector fluorescents 2 mm in diameter and then sent to six hexagonal located detectors 10 mm away from the laser source. The detectors record the arrival times of the photons in histograms and are able to handle high photon counting speeds (those over 1 × 109 counter per second).
To demonstrate its performance, researchers used the Kernel Flow system to record the brain signals of two participants who performed a finger tapping task. During the test session, histograms from more than 2,000 channels were collected from the entire brain to measure the changes in the concentrations of oxyhemoglobin and deoxyhemoglobin.
The system was found to match conventional TD-fNIRS systems. "We demonstrated 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," explains Ryan Field, Chief Technology Officer at Kernel and the corresponding author of the study.
Although the results are promising, Field recognizes the need for more tests, as near-infrared light is absorbed differently by certain hair and skin types. "We are currently collecting data with Kernel Flow to demonstrate additional human neuroscience applications. We are also in the process of evaluating system performance with different hair and skin types," he says.
Kernel Flow packs large-scale TD-fNIRS systems in a portable form and delivers the next generation of non-invasive optical imaging devices. Systems like Kernel Flow will make neuroimaging much more accessible to enable widespread benefits in health and science. For example, the FDA recently approved a study using the Kernel Flow system to measure the psychedelic effect of ketamine on the brain.
JBO guest editor Dimitris Gorpas of the German Research Center for Environmental Health states: "This is the world's first full-coverage TD-fNIRS portable system that maintains or improves the performance of existing table systems and has the potential to achieve its mission of making neuro measurements mainstream. I'm really looking forward to what the brain has not yet revealed. "
Citation: Kernel Flow: A portable device for non-invasive optical brain imaging (2022, January 18) Retrieved January 19, 2022 from https://phys.org/news/2022-01-kernel-wearable-device-noninvasive-optical. html
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