Magnetocardiography Measurements with a High Sensitivity Tunnel Magnetoresistance Sensor

The measurement of magneto-cardiography (MCG) is a noninvasive diagnostic technique and an effective supplement to electro-cardiography. In this paper, the three-axial components of MCG signals on a male subject (aged 24) in the supine position are measured by rotating a high sensitivity tunnel magnetoresistance (TMR) sensor. The R-wave and QRS-complex of MCG associated with the cardiac cycle are clearly observable without need of averaging. The amplitude of the R-peak observed in the normal direction is 150 pT, which is consistent with measurements made using a superconducting quantum interference device considering the field attenuation with distance. The tangential components of the R-peak are about 550 pT. The T-wave is at the noise level and the weaker P-wave is drowned in noise. As the TMR sensor can measure MCG at room temperature, potentially it is a promising alternative to cryogenically-cooled superconducting devices to make inexpensive MCG instrumentation for extensive clinical applications.