Demonstration of Unshielded Fetal Magnetocardiography System Using Two-Dimensional Gradiometers

We performed fetal magnetocardiography (fMCG) measurements in an unshielded hospital environment to demonstrate our developed fMCG system using two-dimensional (2D) gradiometers based on low- T c superconducting quantum interference devices. The subjects were 25 pregnant women, including two subjects with twin pregnancies, or 27 fetuses, in this study. The 2D gradiometer was optimized for fMCG measurements and detected both the axial second-order gradient and planar-first-order gradient of a magnetic field. Depth of the fetal heart was also measured by using ultrasonography before fMCG measurement. As a result, the QRS peaks of the fMCG waveform were detected in real time for 15 cases including early fetal gestational periods as 24 and 25 weeks. Moreover, the P and T waves were also detected in some cases by averaging. These results demonstrate that the developed unshielded fMCG system can detect fMCG waveforms in an unshielded hospital environment.