Impedance magnetocardiogram

We have developed an impedance magnetocardiogram (IMCG) system to detect th e change of magnetic field corresponding to changes in blood volume in the heart. A low magnetic field from the electrical activity of the human heart -the so-called magnetocardiogram (MCG)-can be simultaneously detected by us ing this system. Because the mechanical and electrical functions in the hea rt can be monitored by non-invasive and non-contact measurements, it is eas y to observe the cardiovascular functions from an accurate sensor position. This system uses a technique to demodulate induced current in a subject. A flux-locked circuit of a superconducting quantum interference device has a wide frequency range (above 1 MHz) because a constant current (40 kHz) is fed through the subject. It is shown for the first time that the system cou ld measure IMCG signals at the same time as MCG signals.