Technology
Biomagnetic signals are extremely weak, but can be recorded using an exotic superconducting detector known as a SQUID (superconducting quantum interference device) magnetometer.
The recordings must be made within a special magnetically-shielded room because the signals are dwarfed by the ambient magnetic interference present in a typical laboratory or hospital environment.
These equipment are highly complex and expensive. In addition to magnetic shielding, we employ specialized signal processing techniques to attenuate environmental and biological interferences.

