Multichannel heart scanner based on high-T/sub c/ SQUIDs

A 7-channel magnetometer for magnetocardiography based on high-T/sub c/ SQUIDs has been realized. This magnetometer is used for test experiments in the development of a multichannel high-T/sub c/ SQUID based heart-scanner for clinical applications. The intrinsic noise level of the channels in the 7-channel system is typically 120 fT//spl radic/(Hz) down to 1 Hz. Magnetocardiograms were recorded inside a magnetically shielded room. Introductory experiments were performed on the suppression of noise by combining magnetometers to form planar gradiometers. The noise suppression that can be established appeared to be limited by the imbalance of the gradiometric configuration, which is roughly 2%. This relatively poor balance of the system is caused by inaccuracies in the transfer functions of the individual SQUID magnetometers, and by deviations from the planar geometry.