The new helmet-shaped wearable device monitors brain activity.
Modern brain imaging techniques allow for high-resolution, precise observations of the brain’s functions. Functional near-infrared spectrum (fNIRS), a popular noninvasive imaging method, uses near-infrared (wavelength >700nm) light to determine the relative hemoglobin concentration in the brain. This is done by comparing hemoglobin’s light absorption patterns.
Noninvasive brain scanning systems rely on continuous-wave fNIRS. This is where tissue is exposed to a constant stream of photons. These systems can’t distinguish between scattered and absorption photons. Time-domain (TD-fNIRS) is a recent improvement to this technique. It uses picosecond pulses and fast detectors to determine photon scattering in tissues. These systems are costly and complicated, and they have a significant form factor that limits their widespread adoption.
Kernel, a company in neurotechnology, created a wearable headset based on TD-fNIRS technology to overcome these problems. The device is called Kernel Flow and weighs 2.05kg. It contains 52 modules that are arranged in four plates. These plates can be attached to either side of the head. The Journal of Biomedical Optics reports the specifications and performance of Kernel Flow.
Two laser sources are used to generate pulses of laser light that are less than 150 picoseconds in width. The photons are then reflected onto a prism and combined in a source pipe that directs it to the scalp. Six detector light pipes with spring-loaded detectors that measure 2 mm in diameter capture the laser pulses and transmit them to six sensors placed 10 mm from the source. The detectors can record photon arrival times and convert them into histograms. They can also handle high photon count rates (photons exceeding 1 x 10 9 counts per minute).
The Kernel Flow system recorded brain signals from two participants during a finger-tapping task to demonstrate its effectiveness. To measure changes in the concentrations of oxyhemoglobin or deoxyhemoglobin, histograms were taken from more than 2000 channels.
It was found that the system performed as well as conventional TD-fNIRS devices. Ryan Field, Chief Technology Officer at Kernel and co-author of the study, said that the system performed similarly to benchtop systems using our miniaturized device.
Field acknowledged that the results were promising but added that more testing is needed because near-infrared radiation is absorbed differently by different hair and skin types. Kernel Flow is collecting data to show additional applications of neuroscience for humans. He says the system is also evaluated with varying hair and skin types.
Kernel Flow packs large-scale TD/fNIRS systems in a wearable form and delivers the next generation of noninvasive optical brain imaging devices. Kernel Flow systems will make neuroimaging more accessible and enable many benefits in science and health. The FDA approved a recent study using Kernel Flow to measure the psychedelic effects of ketamine on the brain.
JBO guest editor Dimitris Gorpas from Helmholtz Zentrum Munich (a German research center for environmental and health) comments, “This is the world’s first wearable, full-head coverage TD–an fNIRS system that maintains/improves on existing benchtop systems. It has the potential to make neuro measurements mainstream.” I look forward to seeing what the brain will reveal.