Yang Haodi, Klotz Thomas, Gizzi Leonardo, Lu Hongyu, Monittola Gianpiero, Schneider Urs, Siegel Markus, Marquetand Justus
Department of Neural Dynamics and Magnetoencephalography, Hertie-Institute for Clinical Brain Research, University of Tübingen, Otfried-Müller-Str.47, 72076, Tübingen, Germany.
MEG-Center, University of Tübingen, Tübingen, Germany.
Sci Rep. 2025 Jun 20;15(1):20225. doi: 10.1038/s41598-025-06545-1.
Magnetomyography (MMG) can be used as a contactless modality to study the neuromuscular system. On the one hand, being contactless is a practical advantage as there is no need to prepare skin or attach electrodes as in electromyography (EMG). On the other hand, it is also a disadvantage because the magnetic field decays with increasing distance. However, the effect of sensor-to-source distance in MMG has not been systematically studied. Comparative in vivo and in silico experiments of the effect of sensor-to-source distance were performed. In vivo, muscle activity was recorded using simultaneous surface EMG and one triaxial optically pumped magnetometer (OPM). For the simulations, an established multiscale muscle model was used to predict how distance affects the signal-to-noise ratio (SNR) and the signal's spectral content. Given an environmental noise level of 0.5-1 pT root-mean-square (RMS) from 10 to 350 Hz, it was impossible to robustly detect muscle activity of one finger flexor muscle beyond a distance of two centimeters using OPM technology. In silico experiments showed a high SNR between 8 and 29 for MMG at 0.5 cm distance. Increasing the distance increases the MMG's median frequency content. The simulations uncovered that this is due to the effect of noise. For distances greater than two centimeters, measuring MMG of voluntary contractions in medium-sized muscles with current OPM technology and conventional magnetic shielding cannot be recommended.
磁肌图(MMG)可作为一种非接触式方法来研究神经肌肉系统。一方面,非接触式是一个实际优势,因为无需像肌电图(EMG)那样准备皮肤或附着电极。另一方面,这也是一个劣势,因为磁场会随着距离增加而衰减。然而,MMG中传感器与源距离的影响尚未得到系统研究。我们进行了关于传感器与源距离影响的体内和计算机模拟对比实验。在体内,使用同步表面肌电图和一个三轴光泵磁力计(OPM)记录肌肉活动。对于模拟,使用一个已建立的多尺度肌肉模型来预测距离如何影响信噪比(SNR)和信号的频谱内容。在环境噪声水平为0.5 - 1皮特斯拉均方根(RMS)、频率范围为10至350赫兹的情况下,使用OPM技术在超过两厘米的距离时无法可靠地检测到一根手指屈肌的肌肉活动。计算机模拟实验表明,在0.5厘米距离时,MMG的SNR在8至29之间。增加距离会增加MMG的中频含量。模拟结果表明,这是由于噪声的影响。对于大于两厘米的距离,不建议使用当前的OPM技术和传统磁屏蔽来测量中等大小肌肉的自主收缩的MMG。