Non-Invasive Functional-Brain-Imaging with an OPM-based Magnetoencephalography System

Abstract

A non-invasive functional-brain-imaging system based on optically-pumped-magnetometers (OPM) is presented. The OPM-based magnetoencephalography (MEG) system features 20 OPM channels conforming to the subject's scalp. Due to proximity (12 mm) of the OPM channels to the brain, it is anticipated that this MEG system offers an enhanced spatial resolution as it can capture finer spatial features compared to traditional MEG systems employing superconducting quantum interference device (SQUID). We have conducted two MEG experiments on three subjects: somatosensory evoked magnetic field (SEF) and auditory evoked magnetic field (AEF) using our OPM-based MEG system and a commercial SQUID-based MEG system. We have cross validated the robustness of our system by calculating the distance between the location of the equivalent current dipole (ECD) yielded by our OPM-based MEG system and the ECD location calculated by the commercial SQUID-based MEG system. We achieved sub-centimeter accuracy for both SEF and AEF responses in all three subjects.

A conformal array of microfabricated optically-pumped first-order gradiometers for magnetoencephalography

“…Building off of previous designs [12][13][14][15], we demonstrate a multichannel OPM system capable of synchronously operating 48 microfabricated SERF magnetometers in an array of 24 radial first-order gradiometers. Several MEG recordings have been published to date with conformal OPM arrays with more than 10 channels [13,[16][17][18][19]. While most OPM arrays consist of magnetometers, a system of planar gradiometers, measuring both transverse components of the magnetic field, has been developed by the Sandia group [16,17,20].…”

“…Several MEG recordings have been published to date with conformal OPM arrays with more than 10 channels [13,[16][17][18][19]. While most OPM arrays consist of magnetometers, a system of planar gradiometers, measuring both transverse components of the magnetic field, has been developed by the Sandia group [16,17,20]. In contrast, the gradiometers in this work measure the radial component and radial gradient with a 2 cm baseline and can be adjusted such that their position conforms to the shape of a human head.…”

Recent advances in the noninvasive detection of high-frequency oscillations in the human brain

“…OPMs is less affected by the head movement compared to conventional MEG, and can be worn more conveniently because of the sensors' positions on the scalp (Boto et al 2019). Although OPMs is not yet used clinically, there have been some recent studies using OPMs in several areas (Barry et al 2019;Borna et al 2020;Boto et al 2019;Elzenheimer et al 2020;Hill et al 2020;Iivanainen et al 2020;Lin et al 2019;Nardelli et al 2019). OPMs has not yet been used in HFO research, but this is a very promising future application of this technology.…”

Overview of Magnetoencephalography—Brief History of its Sensors and Hardware

“…Many articles on MEG using optically pumped magnetic sensors have already been published [45][46][47][48][49][50][51][52][53], but the most well known system was reported by Boto et al [49] in 2018, which is a MEG allowing head movement . The system comprises 13 optically pumped magnetic sensors (QuSpin) with sensitivity of 15 fT/ Hz which are mounted on the scalp surface, and a magnetic shield made of material with high magnetic permeability combined with a 3-axis multi-layered active shield, which creates a uniform magnetic eld space (within this space, the error of uniformity of the eld is within 5%) of 40 cm 3 around the head of the subject wearing the sensors.…”