Turning OPM-MEG into a Wearable Technology

Rhodes, Natalie; Holmes, Niall; Hill, Ryan; Barnes, Gareth; Bowtell, Richard; Brookes, Matthew; Boto, Elena

Abstract

This chapter explores the use of optically pumped magnetometers (OPMs) as a tool for magnetoencephalography (MEG). Conventional MEG systems use superconducting quantum interference devices (SQUIDs) to measure the femto-Tesla-level magnetic fields at the head surface that are generated by synchronised (dendritic) neural current flow in the brain. SQUIDs require cryogenic cooling to maintain a low operating temperature and must be bathed in liquid helium and held in a rigid helmet with thermal insulation to protect the participant. Scanners are therefore large, cumbersome, and one-size-fits-all; movement of the participant relative to the fixed array degrades quality of data. Conversely, OPMs exploit the spin properties of alkali atoms to measure local magnetic field. They can be constructed with an external surface at close to body temperature, while maintaining a small, light, and flexible form. In this chapter, we show how commercial OPMs can form the basis of a MEG system that allows sensors to get closer to the scalp surface, improving signal strength and spatial specificity. Further, OPMs allow the flexibility to adapt a sensor array to any head shape or size and even facilitate natural movement throughout MEG acquisition. We explain why OPMs are emerging as a stand-out replacement for SQUIDs and how nascent sensor designs enable multi-axis measurements. We look at the practical requirements for designing sensor arrays that facilitate high spatial resolution imaging. We further describe how allowing movement requires additional background magnetic field suppression. Finally, we review recent literature to demonstrate how OPM-MEG has been used to enable novel neuroscientific experimentation.

Citation

Rhodes, N., Holmes, N., Hill, R., Barnes, G., Bowtell, R., Brookes, M., & Boto, E. (2022). Turning OPM-MEG into a Wearable Technology. In E. Labyt, T. Sander, & R. Wakai (Eds.), Flexible High Performance Magnetic Field Sensors: On-Scalp Magnetoencephalography and Other Applications (195-223). Springer International Publishing. https://doi.org/10.1007/978-3-031-05363-4_11

• Online Publication Date: Aug 27, 2022
• Publication Date: Aug 27, 2022
• Deposit Date: Sep 14, 2022
• Publicly Available Date: Aug 28, 2024
• Pages: 195-223
• Book Title: Flexible High Performance Magnetic Field Sensors: On-Scalp Magnetoencephalography and Other Applications
• ISBN: 9783031053627
• DOI: https://doi.org/10.1007/978-3-031-05363-4_11
• Public URL: https://nottingham-repository.worktribe.com/output/11195633
• Publisher URL: https://link.springer.com/chapter/10.1007/978-3-031-05363-4_11
• Contract Date: Mar 24, 2022