High-Resolution Monitoring of the Gastrointestinal Transit of a Magnetically Marked Capsule

Abstract

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.

A Review of Localization Systems for Robotic Endoscopic Capsules

“…One of the earliest systems that has employed such a technique for monitoring the gastrointestinal transit of a capsule is the tracking system presented by Weitschiles et al [29][30]. The Magnetic Marker Monitoring (MMM) implemented in their method utilized a 37-channel, Superconducting Quantum Interference Device (SQUID) sensor system above a volunteer's abdomen.…”

Sensors for Catheter Applications

“…For example, the cylindrical magnet used by Schlageter et al [74] is U 6 × 7 mm and the generated field may be detected at distances as large as 14 cm, using highly sensitive Hall sensors with integrated flux concentrators. Weitschies et al [75] used a cylindrical capsule of U 5.7 × 16.1 mm, which was detected by means of a superconducting quantum interference device (SQUID) at distances as large as 20 cm. Another bar magnet having dimensions U 7.8 × 25 mm was used by Prakesh and Spelman [76], while Ilmoniemi et al [77] employed a magnetic object of U 0.2 × 15 mm that was detected by means of a SQUID.…”

“…A detection distance of 14 cm was achieved, while the position error was found to be within a few millimeters. A similar device, implemented for the same medical application, makes use of a SQUID magnetometer to establish the trajectory of the magnetic marker [75,83], with a spatial resolution within a range of millimeters.…”

Position tracking using inertial and magnetic sensing aided by permanent magnet

“…Some authors tried using these distortions for detection and low accuracy tracking of metallic objects [16], [17]. Magnetic field produced by permanent magnets locally overshadow earth's, thus extensive research have been done on reverse problem of tracking permanently magnetised markers with relation to magnetometer and (most often) arrays of magnetometers [18], [19], [20], [21].…”