Definition : Encephalographs designed for recording the variations of the very weak biomagnetic fields caused by the electrical activity of the brain detected externally to the body. The magnetic field is typically picked up with superconductive coils (or gradiometers) externally to the body and then detected with very sensitive sensors, such as an array of superconducting quantum interference devices (SQUIDs). The SQUIDs are housed in a cryogenic container (known as a Dewar) that is configured as a helmet and usually filled with liquid helium and where the patient places their head. After enhancing the signal-to-noise ratio the detected signals are amplified and displayed as magnetic field and/or electric current maps. The equipment also includes a computerized unit with dedicated software (a workstation) to process the magnetic signals; magnetocardiographs should be used inside magnetic shielded locations. Magnetoencephalographs are mainly used for accurate localization of areas associated with brain disorders, such as epilepsy and schizophrenia and/or to find tumors; they are not intended for real-time assessment of the brain conditions.
Entry Terms : "Magnetic Field Encephalographs"
UMDC code : 18332