High-resolution imaging of cardiac biomagnetic fields using a low-transition-temperature superconducting quantum interference device microscope

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Abstract
We have developed a multiloop low-temperaturesuperconducting quantum interference devicesensor with a field sensitivity of 450 fT/Hz −1/2 for imaging biomagnetic fields generated by action currents in cardiac tissue. The sensor has a diameter of 250 μm and can be brought to within 100 μm of a room-temperature sample. Magnetic fields generated by planar excitation waves are associated with a current component parallel to the wave front, in agreement with predictions of the bidomain model. Our findings provide a new basis for interpreting the magnetocardiogram.