Development of noise correction method of environmental magnetic field with reference magnetic sensor for magnetocardiography

Abstract

AbstractIn recent years, a magnetocardiography (MCG) with superconducting quantum interference device with noise level of 50 fT/√ Hz is used for arrhythmia diagnosis. The MCG is usually installed in a multilayered magnetically shielded room (MSR). In the MCG close to some magnetic noise sources like direct current (dc)‐electrified railway, the MCG can stably measure the magnetic field by increasing the number of layers of MSR. However, increasing the number of layers in the MSR increases the cost and weight. We developed the method to correct the environmental magnetic field (EMF) in the MCG that considers the reduction response of each EMF reduction technology of the MCG including the MSR by referring to the signal measured by the reference magnetic sensor outside the MSR. The effect of the correction was evaluated for each channel of the MCG by using the EMF signal from the dc‐electrified railway as the magnetic noise source. The average value of the correction effect was 18.1 dB, the standard deviation (SD) was 4.1 dB, and the 2SD range was from 9.8 to 26.4 dB. From these results, it is suggested that the developed method has the possibility to improve the EMF in the MCG by more than 9 dB.