A Superconducting Quantum Interference Device Magnetometer with a Room-Temperature Pickup Coil for Measuring Impedance Magnetocardiograms

Abstract

To measure an impedance magnetocardiogram (I-MCG) signal, we have developed a superconducting quantum interference device (SQUID) magnetometer with a room-temperature pickup coil. The pickup coil (30-mm diameter) is set outside the cryostat and is connected to the input coil in the SQUID. The noise level of the magnetometer is 90 fT Hz-1/2 at 10 kHz. Using the magnetometer, we measured I-MCG signals (below 15 pT)–which were obtained by applying an ac current (10 kHz) with constant amplitude (7 mA, peak-to-peak) to a subject–from the heart.