Measurement of somatosensory evoked magnetic fields at room temperature using a TMR sensor system

• Published in: Transactions of Japanese Society for Medical and Biological Engineering Vol. Annual59; no. Proc; pp. 752 - 753
• Main Authors: Ando, Yasuo, Nakasato, Nobukazu, Fujiwara, Kosuke, Matsuzaki, Hitoshi, Kanno, Akitake, Oogane, mikihiko
• Format: Journal Article
• Language: Japanese
• Published: Japanese Society for Medical and Biological Engineering 2021; 公益社団法人 日本生体医工学会
• ISSN: 1347-443X; 1881-4379
• DOI: 10.11239/jsmbe.Annual59.752

Measurement of somatosensory magnetic evoked fields (SEFs), using a magnetoencephalography (MEG) system with superconducting quantum interference devices (SQUIDs), are one of the most popular diagnostic tools to evaluate and localize brain function in human. However, wall size of liquid helium container for SQUIDs has been constituting a barrier to minimize sensor-source distance, the most important factor for spatial resolution. We recently achieved a success to measure human magneto-cardiogram and spontaneous alpha activity of MEG at room temperature using newly developed tunnel magneto-resistive (TMR) sensors. Here we applied a TMR sensor system to measure SEFs, challenging MEG signals due to their weakness. In a normal volunteer subject, using a standard stimulation protocol of median nerve stimulus, a TMR sensor system combined with magnetic flux concentrators, and a signal averaging technique up to 5,000 times, we successfully demonstrated a clear N20m peak, the first and weakest component of SEFs.