High-Tc Squids Prodice Magnetocardiograms

High-Tc SQUIDS produce magnetocardiograms that are clinically practical. SQUIDs (superconducting quantum interference devices) can detect incredibly small magnetic fields, even those produced by nerve signals in the brain or heart. Arrays of SQUIDs have been used to make magnetic maps of the heart in the past but only with models using the lower-critical-temperature superconductors that must be chilled in liquid helium, and operated in a room-sized enclosure needed to shield against extraneous magnetic fields. Now, for the first time, a group of scientists at Hitachi in Japan has produced a magnetocardiograph machine based on high-temperature superconductors which can be chilled with much more tractable liquid nitrogen, and magnetically shielded by a much smaller cylindrical enclosure. The Hitachi device employs a 4 x 4 SQUID array to map the heart's magnetism at field strengths as small as 50 pico-tesla, a million times weaker than Earth's field. One of the authors, Koichi Yokosawa (+81-42-323-1111), suggests that magnetocardiography will prove to be one of the forefront applications of high-Tc superconductor technology. (Yokosawa et al., Applied Physics Letters, 30 June 2003)