Design and Application of a Wearable OPM-MMG System via Motion Artifacts Suppression

The magnetomyography system utilizing an optically pumped magnetometer (OPM-MMG) is applicable for the electrophysiological study of the brachial plexus. In this article, the suppression method of motion artifacts is proposed by optimal design of magnetic shielding barrel (MSB) and the gradient measurement of arrayed OPMs. First, multiparameter optimization design of the magnetic shield barrel is carried out. The purpose of the design is to meet the requirements of residual magnetic field and magnetic noise of the OPM-MMG system by optimizing several parameters of the magnetic shield barrel. The experimental results show that the center residual field of the magnetic shield barrel is 8.64 ± 0.5 nT, and the magnetic noise is lower than 10 ${\mathrm {fT}}/{\mathrm {Hz}}^{{1}/{2}}$ , which can provide an excellent near-zero magnetic environment for MMG experiment. Furthermore, the gradiometer mode is used to measure the magnetic field of muscle for suppressing the motion artifacts. Experimental results show that the signal-to-noise ratio (SNR) of the extensor digitorum muscle’s signal is increased from 12.1 to 47.8 dB compared with magnetometer mode. Consequently, the enhanced OPM-MMG system is capable of producing clearer MMG images.