Title :
Multichannel SQUID system for detecting fetal magnetocardiograms
Author :
Kandori, Akihiko ; Tsukada, Keiji ; Horigome, Hitoshi ; Asaka, Mitsuhiro ; Shigemitsu, Sadahiko ; Takahashi, Miho ; Terada, Yasushi ; Kubo, Takeshi ; Matsui, Akira ; Mitsui, Toshio
Author_Institution :
Central Res. Lab., Hitachi Ltd., Tokyo, Japan
Abstract :
A nine-channel SQUID magnetometer system is developed to detect weak magnetic fields generated by fetal cardiac activity. The nine 20-mm-diameter axial first-order gradiometers are mounted at intervals of 30 mm. A baseline length of 60 mm is applied to the pickup coil to measure the weak magnetic field from a fetal heart in a deep position. The SQUID is operated with a flux-locked loop (FLL) circuit and the FLL output is recorded at 1 kHz by a computer. Fetal magneto-cardiograms (FMCG) were measured for 109 fetuses of 20 to 39 weeks´ gestation. In most cases, maternal MCG interference was negligible. R-wave peaks were detected in 81% of all subjects. The results of FMCG measurements and Fourier analysis of fetal the R-R interval are shown in this paper
Keywords :
Fourier analysis; SQUID magnetometers; magnetocardiography; medical signal processing; obstetrics; 1 kHz; 20 mm; 20 to 39 w; 30 mm; 60 mm; R-wave peaks; axial first-order gradiometers; fetal magnetocardiograms detection; maternal MCG interference; medical instrumentation; multichannel SQUID system; pickup coil; weak magnetic field; Circuits; Coils; Fetal heart; Frequency locked loops; Interference; Length measurement; Magnetic analysis; Magnetic field measurement; Position measurement; SQUID magnetometers;
Conference_Titel :
Bioelectromagnetism, 1998. Proceedings of the 2nd International Conference on
Conference_Location :
Melbourne, Vic.
Print_ISBN :
0-7803-3867-7
DOI :
10.1109/ICBEM.1998.666429
