Adaptable Sensor Arrays for Fetal Magnetocardiographic Measurements Using Optically-Pumped Magnetometers: A Pilot Study

Fetal magnetocardiography (fMCG) is a noninvasive method of measuring magnetic signals generated by the depolarizing heart. fMCG has proved to have superior signal-to-noise ratio characteristics and enables precise detection of the R-R intervals for fetal heart rate variability (FHRV) analysis. FHRV is one of the most useful clinical indicators for investigating fetal neurodevelopment. Currently, fMCG recordings rely on superconducting quantum interference devices (SQUIDs) which require cryogenics leading to a high cost device. New cryogenic-free sensors called optical pump magnetometers (OPMs) have emerged as alternative to SQUIDs. To take advantage of the flexibility of the OPM sensors, we explored the ability of OPM sensors to measure the fMCG at different maternal positions and sensor locations. Data were collected with a 14-channel OPM array using different sitting positions (mother leaning forward, backward, and prone). Projection operator algorithm based on minimum norm (POMN) was applied to extracted fMCG. R peaks were obtained to perform standard FHRV analysis. We were able to configure a standalone array of the OPMs that conforms to the shape of the maternal abdomen to obtain signals with sufficient quality. We extracted and quantified FHRV parameters in three low-risk fetuses. Results showed that FHRV values are in the range of previous SQUID studies.