Magnetocardiograph based on a 4×4 array of high-temperature superconducting quantum interference devices

A magnetocardiograph, consisting of superconducting quantum interference device (SQUID) magnetometers made of a high-critical-temperature (Tc) superconductor and a compact magnetically shielding cylinder, has been developed. We assembled a sensor array of 4×4-matrix-arranged magnetometers which are treated as 24 electronic first-order gradiometers by taking the differences between the outputs in every pair of adjacent magnetometers. Field gradients generated by P waves were estimated from the results for 21 subjects of a conventional magnetocardiograph made of low-Tc SQUID gradiometers. Every gradiometer of the assembled sensor array was then designed to be sufficiently sensitive to detect the field gradient corresponding to the mean P wave. The clear magnetocardiograms obtained without averaging indicate the clinical applicability of the developed magnetocardiograph.