Alignment of magnetic sensing and clinical magnetomyography

Abstract

Neuromuscular diseases are a prevalent cause of prolonged and severe suffering for patients, and with the global population aging, it is increasingly becoming a pressing concern. To assess muscle activity in NMDs, clinicians and researchers typically use electromyography (EMG), which can be either non-invasive using surface EMG, or invasive through needle EMG. Surface EMG signals have a low spatial resolution, and while the needle EMG provides a higher resolution, it can be painful for the patients, with an additional risk of infection. The pain associated with the needle EMG can pose a risk for certain patient groups, such as children. For example, children with spinal muscular atrophy (type of NMD) require regular monitoring of treatment efficacy through needle EMG; however, due to the pain caused by the procedure, clinicians often rely on a clinical assessment rather than needle EMG. Magnetomyography (MMG), the magnetic counterpart of the EMG, measures muscle activity non-invasively using magnetic signals. With super-resolution capabilities, MMG has the potential to improve spatial resolution and, in the meantime, address the limitations of EMG. This article discusses the challenges in developing magnetic sensors for MMG, including sensor design and technology advancements that allow for more specific recordings, targeting of individual motor units, and reduction of magnetic noise. In addition, we cover the motor unit behavior and activation pattern, an overview of magnetic sensing technologies, and evaluations of wearable, non-invasive magnetic sensors for MMG.

Magnetomyography: A novel modality for non-invasive muscle sensing

“…The magnetic field of a dipole falls off as a cube of the distance from the source, the field from a finite wire as the square of the distance, and the field from an infinite wire as the inverse of the distance. Although muscle fibers are often modeled as finite wires, the drop-off is typically considered to be the cube of the distance when recording very close to the source to become the inverse of the distance when further from the source (Arekhloo et al, 2023;Wijesinghe, 1991).…”

Neuromuscular Magnetic Field Measurement Based on Superconducting Bio-Sensors

“…Some international research teams have pointed out that the neuromuscular magnetic field has potential advantages in disease diagnosis, health detection, rehabilitation and robot control [ 21 , 22 ]. Compared with EMG, MMG, with a higher signal-to-noise ratio, non-invasive property, higher signal accuracy, and being insensitive to surrounding muscle tissues can simultaneously measure multiple dimensions for source localization [ 23 ].…”