High-resolution monitoring of the gastrointestinal transit of a magnetically marked capsule.

The purpose of this study was to demonstrate that it is possible to continuously monitor the gastrointestinal transit of magnetically marked, solid, oral dosage forms with multichannel biomagnetic measuring equipment and by magnetic source imaging (MSI) methods. For the investigations presented, a sucrose pellet was coated with powdered magnetite (Fe3O4) in poly(methyl methacrylate). Then, the pellet was enclosed in a capsule prepared from silicone rubber and magnetized to obtain a net magnetic dipole moment. After ingestion of the capsule, its magnetic field distribution over the abdomen was recorded for several time intervals with a 37-channel superconducting quantum interference device (SQUID) magnetometer. At each time point, the position of the capsule within the gastrointestinal tract was calculated from the measured field distribution, assuming a magnetic dipole model. The data presented here demonstrate that with this noninvasive method of magnetic marker monitoring it is possible to investigate the gastrointestinal transit of a solid oral dosage form with a temporal resolution in the order of milliseconds and a spatial resolution within a range of millimeters.