title: Fetal magnetocardiography measurements with an array of microfabricated optically pumped magnetometers.
abstract: Following the rapid progress in the development of optically pumped magnetometer (OPM) technology for the measurement of magnetic fields in the femtotesla range, a successful assembly of individual sensors into an array of nearly identical sensors is within reach. Here, 25 microfabricated OPMs with footprints of 1 cm(3) were assembled into a conformal array. The individual sensors were inserted into three flexible belt-shaped holders and connected to their respective light sources and electronics, which reside outside a magnetically shielded room, through long optical and electrical cables. With this setup the fetal magnetocardiogram of a pregnant woman was measured by placing two sensor belts over her abdomen and one belt over her chest. The fetal magnetocardiogram recorded over the abdomen is usually dominated by contributions from the maternal magnetocardiogram, since the maternal heart generates a much stronger signal than the fetal heart. Therefore, signal processing methods have to be applied to obtain the pure fetal magnetocardiogram: orthogonal projection and independent component analysis. The resulting spatial distributions of fetal cardiac activity are in good agreement with each other. In a further exemplary step, the fetal heart rate was extracted from the fetal magnetocardiogram. Its variability suggests fetal activity. We conclude that microfabricated optically pumped magnetometers operating at room temperature are capable of complementing or in the future even replacing superconducting sensors for fetal magnetocardiography measurements.
authors.affiliation: National Institute of Standards and Technology, 325 Broadway, Boulder, CO 80305, USA. University of Colorado, Boulder, CO 80309, USA.
authors.forename: Orang
authors.initials: O
authors.lastname: Alem
authors.forename: Tilmann H
authors.initials: TH
authors.lastname: Sander
authors.forename: Rahul
authors.initials: R
authors.lastname: Mhaskar
authors.forename: John
authors.initials: J
authors.lastname: LeBlanc
authors.forename: Hari
authors.initials: H
authors.lastname: Eswaran
authors.forename: Uwe
authors.initials: U
authors.lastname: Steinhoff
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Okada
authors.forename: John
authors.initials: J
authors.lastname: Kitching
authors.forename: Lutz
authors.initials: L
authors.lastname: Trahms
authors.forename: Svenja
authors.initials: S
authors.lastname: Knappe
mesh_terms: D000465:Algorithms; D005260:Female; D005318:Fetal Heart / Q000502:physiology*; D005323:Fetal Monitoring / Q000379:methods*; D006340:Heart Rate, Fetal; D006801:Humans; D053798:Magnetocardiography / Q000379:methods*; D055616:Microtechnology / Q000379:methods*; D011247:Pregnancy; D012815:Signal Processing, Computer-Assisted; D059629:Signal-To-Noise Ratio