Miniature Coil Array for Passive Magnetocardiography in Non-Shielded Environments

Existing practices for monitoring heart activity rely heavily on electrocardiography (ECG) approaches, which suffer from low accuracy (as electric fields get impacted by biological tissues); extensive diagnostic times; and lack of comfort (as electrodes are in direct contact with the human body). Though magnetocardiography (MCG) provides more accurate and localized signals while also being non-contact, state-of-the-art equipment for capturing such weak magnetic fields (i.e., SQUIDs) requires extensive shielding and is very expensive. MCG sensing devices that do not require shielding have been reported, but they are sbulky, heavy, and cumbersome to use. In this work, we take a major step forward and propose a novel, miniature, and low-cost MCG sensor for operation in non-shielded environments that breaks the state-of-the-art boundaries in terms of size and weight. Our sensor relies on novel coil design principles and Digital Signal Processing (DSP) algorithms to achieve: (a) 4.67 times smaller diameter, (b) 4.5 times smaller height, and (c) at least 216 times lighter weight than previous passive implementations. In vitro measurements demonstrate that a 4-coil sensor array with 15 minutes of recoding time is sufficient to capture human MCG signals. Discussions indicate that higher number of coils and longer recording times can be employed to improve the signal clarity and fit diverse clinical needs. The proposed coil sensor array provides a convenient method to diagnose several cardiac conditions, such as myocardial ischemia, arrhythmia, right atrial hypertrophy, right ventricular hypertrophy, and the Brugada syndrome.