Toward noninvasive monitoring of ongoing electrical activity of human uterus and fetal heart and brain

S Lew,M.S Hämäläinen,Y Okada

doi:10.1016/j.clinph.2017.08.026

Abstract

ObjectiveTo evaluate whether a full-coverage fetal-maternal scanner can noninvasively monitor ongoing electrophysiological activity of maternal and fetal organs. MethodsA simulation study was carried out for a scanner with an array of magnetic field sensors placed all around the torso from the chest to the hip within a horizontal magnetic shielding enclosure. The magnetic fields from internal organs and an external noise source were computed for a pregnant woman with a 35-week old fetus. Signal processing methods were used to reject the external and internal interferences, to visualize uterine activity, and to detect activity of fetal heart and brain. ResultsExternal interference was reduced by a factor of 1000, sufficient for detecting signals from internal organs when combined with passive and active shielding. The scanner rejects internal interferences better than partial-coverage arrays. It can be used to estimate currents around the uterus. It clearly detects spontaneous activity from the fetal heart and brain without averaging and weaker evoked brain activity at all fetal head positions after averaging. ConclusionThe simulated device will be able to monitor the ongoing activity of the fetal and maternal organs. SignificanceThis type of scanner may become a novel tool in fetal medicine.

Highlights

We still know relatively little about the electrophysiology of the human uterus and the fetal heart and brain during pregnancy
We tested an idea that the quality of biomagnetic signals can be improved significantly by using a full-coverage, whole-body sensor array instead of a partial-coverage sensor array as in existing biomagnetic instruments. This idea is based on our experience in rejecting external magnetic field noise sources for the wholehead 375-channel pediatric MEG system (‘‘babyMEG”) we have developed recently (Okada et al, 2016)
We present evaluation of an eventual FM scanner with a full-coverage sensor array wrapped around the torso of a pregnant woman to help readers understand the methods we evaluated for rejecting the interference from external noise sources and internal organs and how we determined the anticipated performance level of a full-coverage sensor array

Summary

Introduction

We still know relatively little about the electrophysiology of the human uterus and the fetal heart and brain during pregnancy. Electrical potential measurement techniques can be used to monitor the activity of maternal heart and other organs. The contractions of the uterus can be measured mechanically (tocodynamometry - Bakker et al, 2010) and its electrical activity can be measured with electrohysterogram (EHG) (Alamedine et al, 2013; Alexandersson et al, 2015). This field is still in its infancy and we know relatively little of where the contraction may be initiated and how it propagates during preterm and normal labor. The physiology during the quiescent period before the onset of labor is even less understood

Methods

Results

Discussion

Conclusion