A 20-channel magnetoencephalography system based on optically pumped magnetometers

Abstract

We describe a multichannel magnetoencephalography (MEG) system that uses optically pumped magnetometers (OPMs) to sense the magnetic fields of the human brain. The system consists of an array of 20 OPM channels conforming to the human subject’s head, a person-sized magnetic shield containing the array and the human subject, a laser system to drive the OPM array, and various control and data acquisitions systems. We conducted two MEG experiments: auditory evoked magnetic field (AEF) and somatosensory evoked magnetic field (SEF), on three healthy male subjects, using both our OPM array and a 306-channel Elekta-Neuromag superconducting quantum interference device (SQUID) MEG system. The described OPM array measures the tangential components of the magnetic field as opposed to the radial component measured by most SQUID-based MEG systems. Herein, we compare the results of the OPM- and SQUID-based MEG systems on the auditory and somatosensory data recorded in the same individuals on both systems.

Potential of on‐scalp MEG: Robust detection of human visual gamma‐band responses

“…Recent advances in the development of optically pumped magnetometers (OPMs) (Budker & Kimball, 2013;Budker & Romalis, 2007) has enabled their use in MEG (e.g., Borna et al, 2017;Boto et al, 2018;Iivanainen, Zetter, Grön, Hakkarainen, & Parkkonen, 2019;Sheng, Wan, et al, 2017). OPMs, in contrast to SQUIDs, can be placed in very close proximity to the scalp, considerably boosting both spatial resolution and sensitivity to neural sources (Boto et al, 2016;Iivanainen et al, 2017).…”

A 7-channel high-Tc SQUID-based on-scalp MEG system

“…Higher spatial frequencies potentially lead to better spatial resolution, but also require denser spatial sampling. With 12.0 mm vertical and 13.4 mm diagonal center-to-center distances between adjacent sensors, the spatial sampling of the system presented here is higher compared to that of previously reported multi-channel on-scalp MEG systems (18 mm within 4-channel OPM in [23]; not specified in [21,22], but necessarily greater than the 13 mm x 19 mm sensor footprint [24]). Furthermore the sensor-to-head distance, ranging between 1 and 3 mm, is significantly smaller than in previously reported systems (12 mm in [23] and 6.5 mm in [21,22]).…”

“…While on-scalp MEG with multiple single-channel units has been demonstrated with both high-T c SQUIDs [10] and optically pumped magnetometers (OPMs) [21,22], the only previous report of a multi-channel system is with the latter technology [23]. Due to inherent advantages and disadvantages of high-T c SQUIDs compared to OPMs as well as specific design goals described below, our system differs in several key aspects from such on-scalp MEG systems.…”

Multi-Channel Whole-Head OPM-MEG: Helmet Design and a Comparison with a Conventional System

“…Whilst multi-channel systems are available (e.g. (Borna et al, 2017;Boto et al, 2018;Iivanainen et al, 2019b)), most demonstrations still employ small numbers of sensors sited over specific brain regions and the introduction of a whole-head array will be an important step forward. Sensor array coverage (i.e.…”