Fetal magnetocardiography provides the requisite precision for diagnostic measurement of electrophysiological events in the fetal heart. Despite its significant benefits, this technique with current cryogenic based sensors has been limited to few centers, due to high cost of maintenance. In this study, we show that a less expensive non-cryogenic alternative, optically pumped magnetometers, can provide similar electrophysiological and quantitative characteristics when subjected to direct comparison with the current technology. Further research can potentially increase its clinical use for fetal magnetocardiography. © 2016 John Wiley & Sons, Ltd.

The objective of this study was to quantify the number of segments that have contractile activity and determine the propagation speed from uterine electrophysiological signals recorded over the abdomen. The uterine magnetomyographic (MMG) signals were recorded with a 151 channel SARA (SQUID Array for Reproductive Assessment) system from 36 pregnant women between 37 and 40 weeks of gestational age. The MMG signals were scored and segments were classified based on presence of uterine contractile burst activity. The sensor space was then split into four quadrants and in each quadrant signal strength at each sample was calculated using center-of-gravity (COG). To this end, the cross-correlation analysis of the COG was performed to calculate the delay between pairwise combinations of quadrants. The relationship in propagation across the quadrants was quantified and propagation speeds were calculated from the delays. MMG recordings were successfully processed from 25 subjects and the average values of propagation speeds ranged from 1.3–9.5 cm/s, which was within the physiological range. The propagation was observed between both vertical and horizontal quadrants confirming multidirectional propagation. After the multiple pairwise test (99% CI), significant differences in speeds can be observed between certain vertical or horizontal combinations and the crossed pair combinations. The number of segments containing contractile activity in any given quadrant pair with a detectable delay was significantly higher in the lower abdominal pairwise combination as compared to all others. The quadrant-based approach using MMG signals provided us with high spatial-temporal information of the uterine contractile activity and will help us in the future to optimize abdominal electromyographic (EMG) recordings that are practical in a clinical setting.

Aims: To characterize levator ani muscle (LAM) activity in nulligravidas using magnetomyography (MMG) and define MMG characteristics associated with LAM activity with and without accessory muscle contributions. Methods: MMG data were collected from eight nulligravidas during rest and voluntary LAM contractions (Kegels) of varying intensity. We utilized simultaneous vaginal manometry and surface electromyography (sEMG) to evaluate for accessory muscle recruitment. Moderate Kegel (MK) MMG trials were sub-selected based on the presence or absence of accessory muscle interaction. Amplitude and spectral-related indicators were calculated across MK epochs: root-mean square (RMS) amplitude, percentage amplitude relative to rest, and relative power spectrum density (rPSD) in three frequency bands (low, middle, high). Ternary diagram characterized rPSD from selected Kegels and ROC analysis was performed to identify cut-points to differentiate MKs from interacting MKs. Results: Nineteen MMG recordings were obtained. Amplitude and spectral parameters were significantly different between isolated and interacting MK epochs.Mean RMS and power values of the isolated MK were, respectively, 120.66 ± 43.8 fT and 1.72 ± 1.44 (T 2 /Hz)*10 −28 . Amplitudes of MK were 64% and 117 higher than baseline activities for the isolated and interacting epochs, respectively. ROC curves reveled cut-off points on low and middle frequency bands that achieved perfect separation (ROC-AUC = 1.0) between isolated and interacting MK. Conclusions: Our study demonstrates that MMG, a novel biomagnetic technique, allows precise detection and characterization of normal female pelvic floor function.Results show that isolated moderate voluntary contraction of the LAMs produces distinct MMG amplitude and spectral characteristics compared with Kegels involving co-activation of other muscle groups. K E Y W O R D S electromyography, intra-vaginal pressure, Kegel, magnetomyography, pelvic floor muscles Neurourology and Urodynamics. 2019;38:151-157.wileyonlinelibrary.com/journal/nau

Objective: Fetal magnetocardiography (fMCG) is a non-invasive biomagnetic technique that provides detailed beat-to-beat fetal heart rate analysis, both in normal rhythm as well as in fetal arrhythmias. New cryogenic-free sensors called optically pumped magnetometers (OPMs) have emerged as a less expensive and more geometrically flexible alternative to traditional Superconducting Quantum Interference Device (SQUID) technology for performing fMCG. The objective of the study was to show the ability of OPMs to record fMCG using flexible geometry while seeking to preserve signal quality, and to quantify fetal heart rate variability (FHRV). Approach: Biomagnetic measurements were performed with OPMs in 24 healthy pregnant women with uncomplicated singleton pregnancies between 28 and 38 weeks gestation (GA). A total of 96 recordings were analyzed from OPM data that was collected using sensors placed in two different maternal configurations over the abdomen. The fMCG signals were extracted and the quality of the recordings were quantified by peak amplitudes and signal-to-noise ratio (SNR). R peaks were used to perform both time and frequency domain FHRV analysis. FHRV measures obtained from OPMs were compared descriptively to the same measures obtained from GA-matched existing SQUID data. Main results: The fMCG derived from OPMs were observed in 21 of the 24 participants. Higher detection rates (85%) of fMCG signals were observed in the data sets recorded at GA >32 weeks. Peak amplitudes and SNR values were similar between two maternal configurations, but peak amplitudes were significantly higher (p = 0.013) in late GA compared to early GA. FHRV indicators were successfully extracted and their values overlapped substantially with those obtained from SQUID recordings. Significance: Taking advantage of the geometric flexibility of the OPMs, we have demonstrated their ability to record and quantify fMCG in different maternal positions as opposed to rigid SQUID configurations.

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