Foetal magnetocardiography with a multi-channel HTS rf SQUID gradiometer

• Published in: Superconductor science & technology 2006-05, Vol.19 (5), p.S266-S270
• Main Authors: Zhang, Y, Wolters, N, Lomparski, D, Zander, W, Banzet, M, Schubert, J, Krause, H-J, Geue, D, van Leeuwen, P
• Format: Article
• Language: English
• ISSN: 0953-2048; 1361-6668
• DOI: 10.1088/0953-2048/19/5/S21

Foetal magnetocardiography (fMCG) is a promising technique for prenatal cardiac diagnosis. In this paper, we discuss the special requirements of a system for fMCG measurements. A SQUID system incorporating five HTS rf SQUID magnetometers has been developed and constructed. Four magnetometers are arranged at the bottom of the cryostat in a 4 cm X 4 cm square configuration. One reference magnetometer is located 20 cm above the plane to form four first-order axial gradiometers with the four bottom magnetometers. The magnetometer with a 18 mm diameter flux focuser, which reaches a field sensitivity of 20-30 fT Hz-1/2, proved sufficient for recording foetal magnetocardiograms in a magnetically shielded room. The cardiac activities of two foetuses (31st and 33rd weeks of gestation) were recorded in 90 Hz bandwidth. The foetal QRS peak signals ranged from 4 to 7 pT and could easily be identified in the real-time gradiometer outputs with a signal-to-noise ratio of up to five. Furthermore, the averaged fMCG data enabled the determination of de- and repolarization time intervals. Overall, the fMCG signals proved of sufficient quality to perform foetal heart diagnostics.