Kernel flow: A wearable device for noninvasive optical brain imaging
A new wearable helmet-shaped device monitors brain activity

Date:
January 18, 2022
Source:
SPIE--International Society for Optics and Photonics
Summary:
Most noninvasive brain scanning systems use continuous-wave
fNIRS, where the tissue is irradiated by a constant stream of
photons. However, these systems cannot differentiate 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, limiting their widespread
adoption. To overcome these challenges, researchers have developed
a wearable headset based on TD-fNIRS technology.



FULL STORY ========================================================================== 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 widely used noninvasive imaging technique that employs near-infrared light (wavelength >700 nm)
to determine the relative concentration of hemoglobin in the brain,
via differences in the light absorption patterns of hemoglobin.


==========================================================================
Most noninvasive brain scanning systems use continuous-wave fNIRS, where
the tissue is irradiated by a constant stream of photons. However, these systems cannot differentiate 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, limiting their widespread
adoption.

To overcome these challenges, researchers from Kernel, a neurotechnology company, developed a wearable headset based on TD-fNIRS technology. This device, called "Kernel Flow," weighs 2.05 kg and contains 52 modules
arranged in four plates that fit on either side of the head. The
specifications and performance of the Kernel Flow system are reported
in the Journal of Biomedical Optics (JBO).

The headset modules feature two laser sources that generate laser pulses
less than 150 picoseconds wide. The photons are then reflected off a
prism and combined in a source light pipe that directs the beam to the
scalp. After passing through the scalp, the laser pulses are captured
by six spring-loaded detector light pipes that are 2 mm in diameter and
then transmitted to six hexagonally arranged detectors 10 mm away from
the laser source. The detectors record the photon arrival times into
histograms and are capable of handling high photon count rates (those
exceeding 1 x 109 counts per second).

To demonstrate its performance, the Kernel Flow system was used to record
the brain signals of two participants who performed a finger-tapping
task. During the testing session, histograms from more than 2,000
channels were collected from across the brain to measure the changes in
the concentrations of oxyhemoglobin and deoxyhemoglobin.

The system was found to match conventional TD-fNIRS systems. "We
demonstrated a 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, the Chief Technology Officer at Kernel and the corresponding
author of the study.

While the results are promising, Field acknowledges the need for more
testing 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 the performance of the system with different hair and skin types," he says.

Kernel Flow packages large-scale TD-fNIRS systems into a wearable form, delivering the next generation of noninvasive optical brain imaging
devices.

Systems like Kernel Flow will make neuroimaging much more accessible,
to enable widespread benefits in health and science. For instance, the
FDA recently authorized 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 remarks, "This is the world's first wearable
full-head coverage TD-fNIRS system that maintains or improves on
the performance of existing benchtop systems and has the potential
to achieve its mission of making neuro measurements mainstream. I am
really looking forward to what the brain has yet to reveal." special
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in this free online course from New Scientist -- Sign_up_now_>>> academy.newscientist.com/courses/science-of-sleep-and-dreams ========================================================================== Story Source: Materials provided by SPIE--International_Society_for_Optics_and_Photonics.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Han Y. Ban, Geoffrey M. Barrett, Alex Borisevich, Ashutosh
Chaturvedi,
Jacob L. Dahle, Hamid Dehghani, Julien Dubois, Ryan M. Field,
Viswanath Gopalakrishnan, Andrew Gundran, Michael Henninger,
Wilson C. Ho, Howard D. Hughes, Rong Jin, Julian Kates-Harbeck,
Thanh Landy, Michael Leggiero, Gabriel Lerner, Zahra M. Aghajan,
Michael Moon, Isai Olvera, Sangyong Park, Milin J. Patel, Katherine
L. Perdue, Benjamin Siepser, Sebastian Sorgenfrei, Nathan Sun,
Victor Szczepanski, Mary Zhang, Zhenye Zhu.

Kernel Flow: a high channel count scalable time-domain functional
near- infrared spectroscopy system. Journal of Biomedical Optics,
2022; 27 (07) DOI: 10.1117/1.JBO.27.7.074710 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220118154852.htm

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