Recording of biomagnetic fields, especially magnetocardiogram and magnetogastrogram, using a high-temperature (-196ﾟC) superconducting quantum interference device

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In the present study, magnetocardiogram and magnetogastrogram were recorded using a high-temperature (-196ﾟC) superconducting quantum interference device (SQUID). This is the first multi-channel high-Tc SQUID system and its operation is much simpler than that of the conventional SQUID system that uses liquid helium.1 Magnetocardiogram : In this study, magnetocardiogram were recorded in 144 positions (16 channels * 9 scans) of the anterior chest wall and isomagnetic maps were constructed at the ventricular depolarization and repolarization phases. The isomagnetic maps examined in this study indicated the instantaneous current source of the heart by applying the "Biot-Savart Law". At the phase in QRS and T waves, the deduced current dipoles were coincide well with those from the conventional SQUID sensor.2 Magnetogastrogram : In this study, a magnetic field generated by the movement of magnetized material positional in the stomach was detected. A magnetized steel ball was attached to the tip of a stomach tube. The steel ball (OD,1.3 mm) was positioned in the antrum in a fasting or fed state. A magnetic sensor was placed above the epigastric region and magnetic signals produced by gastric motility were measured in magnetically shielded room. After the magnetic recording bandwidth at DC-0.1 Hz was filtered out, the regular3-cycle/min signal, which indicated gastric motility, was clearly visible. the magnetic field was larger after ingestion of food than in the fasting state. The peak frequency of gastric motility was not statistically different between the two states.3 Conclusions : This new method is expected to contribute to the diagnosis and the management of various cardiac and gastric disorders.