Gastric activity studies using a magnetic tracer

Abstract

A magnetic pulse generator has been set up in order to study gastric activity. Two coils 1.05 m in diameter, arranged in a Helmholtz configuration, were used. The system generated magnetic field pulses higher than 15 mT, of duration 17.3 ± 1.2 ms. Measurements were performed in 11 male volunteers, with average age 29.3 ± 6.4 years and body mass index 26.0 ± 4.8 kg m−2. Magnetite (Fe3O4) particles with diameters from 75 to 125 µm were used as magnetic tracers, which were mixed in 250 ml of yogurt in concentrations from 2 to 5 g. Signals were registered by using a high speed 3 axis fluxgate digital magnetometer and processed to determine the relaxation of the magnetic tracers by fitting a first-order exponential function to the data, a mean relaxation constant κ = 116 ± 40 s−1 was obtained. Also, an average gastric peristaltic frequency was measured; a value of 3.2 ± 0.3 cpm was determined.