Magnetomyography

For the first attempt, David Cohen used a point-contact superconducting quantum interference device (SQUID) magnetometer in a shielded room to measure the MCG.

At the time, the abundance of physical, technical, and mathematical limitations prevented quantitative comparisons of theories and experiments involving human electrocardiograms and other biomagnetic records.

In the past three decades, a great deal of research has been conducted to measure and analyze the magnetic field generated by the flow of ex vivo currents in isolated axons and muscle fibers.

These measurements have been supported by some complex theoretical studies and the development of ultra-sensitive room temperature amplifiers and neuromagnetic current probes.

In a seminal work of Cohen and Gilver in 1972, they discovered and recorded MMG signals using Superconducting QUantum Interference Devices (SQUIDs).

In the last several years, optically pumped magnetometers (OPMs) have been rapidly developed to study the innervation of the hand nerves and muscles as proof-of-concept investigations.

[11][15][16] The OPMs with small physical size have been improved their LODs significantly during recent years, especially from competing manufacturers e.g. QuSpin Inc., FieldLine Inc. and Twinleaf.

For instance, the amplitude of the Earth magnetic field is about five million times larger and environmental noise from power lines can reach a level of nano-Tesla.

Additionally, current experiments based on SQUIDs and OPMs for MMG sensing are conducted in heavily shielded rooms, which are expensive and bulky for personal daily use.