Magnetic field measurements of gastrointestinal activity

Motility is the electro-mechanical processes by which gastrointestinal (GI) muscle is stimulated to contract, resulting in propulsion of contents. Assessment of motility must involve evaluation of GI smooth muscle electrical activity. In this study, the magnetic field corresponding to electrical activity was measured over the abdominal region using a 37 channel SQUID gradiometer system. Three females and two males with no history of GI dysfunction participated in this study. After fasting for 8 hours a 1 hour recording was made. The measurement was repeated after ingestion of a standard test meal. Signals were examined with respect to frequency content, spatial distribution and time dependence. Four frequency bands, corresponding to activity in the stomach and small bowel, were studied (45-55, 90-105, 140-160 and 190-205 mHz). The spatial distribution of power was observed to be different in each of these bands. Gastric and intestinal signals exhibited maximum power at distinct times after ingestion.