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

The magnetomyography system utilizing optically pumped magnetometer (OPM-MMG) is applicable for electrophysiological study of brachial plexus. In this paper, the suppression method of motion artifacts is proposed by optimal design of magnetic shielding barrel and the gradient measurement of arrayed OPMs. Firstly, multi-parameter optimization design of magnetic shield barrel is carried out. The purpose of design is to meet the requirements of residual magnetic field and magnetic noise of OPM-MMG system by optimizing several parameters of magnetic shield barrel. The experimental results show that the center residual field of the magnetic shield barrel is 8.64nT±0.5nT, and the magnetic noise is lower than 10fT/Hz<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup>, which can provide 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 SNR of extensor digitorum muscle’s signal is increased from 12.1dB to 47.8dB compared with magnetometer mode. Consequently, the enhanced OPM-MMG system is capable of producing clearer MMG images.