Study of the Influence of Implant Material on Magnetocardiography Measurements Using SQUID Sensors

Abstract

Magnetocardiography system is a medical device that diagnoses cardiac disease by measuring magnetic fields generated from electric currents flowing through the myocardium. However, the accuracy of measurement data can be degraded if strong magnetic materials are present or magnetic field changes occur near the MCG system. With the widespread use of implants, the number of patients with metallic implants is increasing, but there is a lack of in-depth research on the potential impact of implant materials on the results of the MCG examination. This study aims to analyze the effect of implant materials on MCG measurements and establish relevant criteria. In this study, a 96-channel MCG system employing Superconducting Quantum Interference Device sensors, specifically first-order gradiometers based on the Double Relaxation Oscillation SQUID method, and a Magnetically Shielded Room were utilized. Ti6Al4V ELI was selected as the representative implant material sample. Experiments were conducted under extreme conditions, where a sample significantly larger than an actual implant was placed as close as possible to the sensors. As a result, when the implant material was at the minimum distance to the sensor, the noise increase was approximately 0.7 fT/$\sqrt{\mathrm{Hz}}$, which satisfies the sensitivity criteria for MCG. Furthermore, since these results were obtained under severely adverse conditions designed to maximize the noise impact, it is anticipated that the effect would be even more negligible in actual clinical settings. In conclusion, it was confirmed that common implant materials have little to no effect on MCG measurements. However, as the experiments were not conducted with the material inserted into the human body, unlike actual clinical environments, the generation of magnetic fields due to micromotion has not been verified, thus requiring further experimentation.