A New Generation of OPM for High Dynamic and Large Bandwidth MEG: The [sup.4]He OPMs—First Applications in Healthy Volunteers

• Published in: Sensors (Basel, Switzerland) Switzerland), 2023-03, Vol.23 (5)
• Main Authors: Gutteling, Tjerk P, Bonnefond, Mathilde, Clausner, Tommy, Daligault, Sébastien, Romain, Rudy, Mitryukovskiy, Sergey, Fourcault, William, Josselin, Vincent, Le Prado, Matthieu, Palacios-Laloy, Agustin, Labyt, Etienne, Jung, Julien, Schwartz, Denis
• Format: Article
• Language: English
• Subjects: Superconductors
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s23052801

MagnetoEncephaloGraphy (MEG) provides a measure of electrical activity in the brain at a millisecond time scale. From these signals, one can non-invasively derive the dynamics of brain activity. Conventional MEG systems (SQUID-MEG) use very low temperatures to achieve the necessary sensitivity. This leads to severe experimental and economical limitations. A new generation of MEG sensors is emerging: the optically pumped magnetometers (OPM). In OPM, an atomic gas enclosed in a glass cell is traversed by a laser beam whose modulation depends on the local magnetic field. MAG[sup.4]Health is developing OPMs using Helium gas ([sup.4]He-OPM). They operate at room temperature with a large dynamic range and a large frequency bandwidth and output natively a 3D vectorial measure of the magnetic field. In this study, five [sup.4]He-OPMs were compared to a classical SQUID-MEG system in a group of 18 volunteers to evaluate their experimental performances. Considering that the [sup.4]He-OPMs operate at real room temperature and can be placed directly on the head, our assumption was that [sup.4]He-OPMs would provide a reliable recording of physiological magnetic brain activity. Indeed, the results showed that the [sup.4]He-OPMs showed very similar results to the classical SQUID-MEG system by taking advantage of a shorter distance to the brain, despite having a lower sensitivity.