Magnetocardiography System With Self-Shielding Coils for High-Quality Cardiac Magnetic Signal Acquisition

To establish a near-zero magnetic environment for accurate magnetocardiography (MCG) measurements, a magnetically shielded cylinder (MSC) is commonly used in combination with active magnetic compensation coils. However, the coupling effect between the field from internal coils and the magnetic shielding layer can distort the distribution of ideal magnetic field and degrade the quality of cardiac magnetic signals. To address this issue, this article proposes a design approach for self-shielding coils featuring curved structures that integrate the target-field method with the pigeon-inspired optimization algorithm. The results indicate that the optimized coils maintain nonuniformity error below 1% in the internal region with a side length of 0.2 m and attain an attenuation error below 5% in the external area. This means that the coils are not easily affected by ferromagnetic materials and are suitable for MSCs of different sizes. An optically pumped magnetometer-based magnetocardiography (OPM-MCG) system, using two sets of single-axis curved coils, is used to compensate for the background field interference, resulting in an improved signal-to-noise ratio (SNR) for cardiac magnetic signals. Within the frequency range of 1–40 Hz, the average sensitivity of the OPM-MCG compensation system improves from 810.59 to 97.63 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{fT/Hz}^{1/2}$ </tex-math></inline-formula>, and it achieves 9.19 dB of noise suppression. Based on the enhanced MCG system, the collected MCG signals reveal significant SNR gains of 6.44 and 5.89 dB in the R-wave and T-wave segments, which lays a foundation for further exploration of cardiac electrophysiological information and assisted cardiac treatment.