Magnetocardiograms Taken Inside a Shielded Room With a Superconducting Point-Contact Magnetometer

A point-contact (SQUID) magnetometer was used inside a shielded room to record the magnetic field of the human heart, without noise-averaging. The resulting magnetocardiograms, with the peak signal at about 3 × 10−7 G had a noise level of about 1 × 10−9 G (rms, per root cycle). They approach good medical electrocardiograms in clarity, and are an order-of-magnitude improvement in sensitivity over previous magnetic detectors of the heart. These results suggest new medical uses for this magnetometer.