Fetal MCG and fetal MEG measurements with a 3-channel SQUID system.
Since the high costs of common large array SQUID system may hinder widespread application of fetal magnetoencephalography (fMEG) and magnetocardiography (fMCG), we intended to investigate a small non-commercial 3-channel SQUID system. The system comprises 3 axial first order gradiometers with 7 cm base length, 2 cm diameter and 2x2 windings of niobium wire, dc-SQUIDs (UJ-111), and current locked mode SQUID electronics that form an equal length triangle (22.5 mm). The system is mounted in a Cryostat BFH-7 model 16 with 5 mm "warm"-"cold" distance. System noise is about 10 fT/Hz1/2. The fMEG and fMCG were recorded between 29 - 40 weeks of gestation after sonographic localization of the fetal head and heart using a 31-channel biomagnetometer (Philips) and the 3-channel-system, both in the same magnetically shielded room. The fMEG was recorded continuously over 500 sec (500 auditory stimuli, 100 dB SPL, 500 Hz, 50 ms, ISI 0.8-1.2/1.6-2.4 sec, trigger channel, maternal ECG lead, sampling rate 1 kHz). The fMCG was recorded over a period of 5 minutes after dewar readjustment. The detection rates of cortical auditory evoked responses (CAER) reached 100 % for both systems. Cross confirmation of the components was difficult and may have uncovered false positive component detection. The fMCG was characterized by a systematic increase in SNR under application of the smaller device. The small size array provides a profitable alternative for the fetal applications.
Schneider
U
U
Department of Obstetrics, Friedrich Schiller University, Jena, Germany. uwe.schneider@med.uni-jena.de
Giessler
F
F
Nowak
H
H
Logemann
T
T
Grimm
B
B
Haueisen
J
J
Schleussner
E
E
D015148:Cardiotocography / Q000295:instrumentation* / Q000379:methods; D005260:Female; D005333:Fetus / Q000502:physiology; D006801:Humans; D008280:Magnetics / Q000295:instrumentation*; D015225:Magnetoencephalography / Q000295:instrumentation* / Q000379:methods; D011247:Pregnancy; D012107:Research Design