Measurement of Triaxial Magnetocardiography Using High Sensitivity Tunnel Magnetoresistance Sensor

Abstract

Three-axis components of magnetocardiography (MCG) signals are measured with a high sensitivity tunnel magnetoresistance (TMR) sensor in this paper. From the measurement result, the R-wave and QRS-complex of MCG associated with the cardiac cycle are clearly observable without need of averaging. The T-wave is at the noise level and the weaker P-wave is drowned in noise. It is a great progress comparing with the previous MCG measurement with TMR sensor, where averaging was required to reliably detect R-wave. The amplitude of R-peak observed by the TMR sensor in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$x$ </tex-math></inline-formula> -direction is 200 pT, which is consistent with the measurement of superconducting quantum interference device (SQUID) considering the effect of distance from the observation point to the magnetic field source. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$y$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$z$ </tex-math></inline-formula> components R-peak are about 550 pT. 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.