In-Vivo Remote Manipulation of Modified Capsule Endoscopes Using An External Magnetic Field

Abstract

Background: Remote control of wireless capsule movement would enhance diagnostic accuracy and might allow targeted biopsy. The efficacy and safety of remote manipulation of modified capsule endoscopes using external magnetic fields were assessed in in-vivo survival studies in pigs as part of a European FP6 project called NEMO. Methods: Model and real wireless capsules (Colon & ESO, by Given Imaging Ltd) were modified to include magnetic material aligned to give different field patterns and strength when exposed to an external magnetic field. The magnetic reed switch in the capsule was inactivated to allow continuous real-time viewing. Capsules were placed in the esophagus and stomach of anesthetised pigs (n = 8, 34-78 kg). An external magnet was used to manipulate the capsule with gastroscopic visualisation. Capsules were attached to a thread to allow withdrawal through the cardio-esophageal junction and to measure forces needed to overcome magnetic attraction and peristaltic forces. The ability of a magnetic field to prevent retropulsion of an electrostimulation capsule causing esophageal contraction was tested. Anterior, lateral and posterior external magnet positions and movements were studied with the animals on the back, left lateral and prone positions. Results: An external plate magnet was effective in holding the capsule in specific locations in the esophagus. Swivel motions were particularly effective using small rotations of the external hand-held plate magnet allowing multiple axial panning circular views of the squamo-columnar junction to be obtained. Caudo-cranial axial magnet rotations caused capsules to somersault in the esophagus. Water lubrication enhanced esophageal capsule movement. In the stomach capsules could be manipulated at will throughout the stomach. It was possible but difficult to drive capsules through the cardio-esophageal junction and move capsules into the pylorus but not to release them in the duodenum by removing the magnetic field. Somersaulting and rapid exploration of the stomach was easy. The magnetic field prevented esophageal retropulsion of an electrostimulation capsule. All pigs were well, eating immediately after recovery - esophagus and stomach looked normal at follow up endoscopy. Left lateral position with a posterior hand held magnet was the best for most manipulations. Conclusions: Magnetic capsules could be swivelled, somersaulted, stopped and moved when constrained by an external magnetic field. Such movements were especially effective in enhancing visualization in the esophagus and stomach and were safe when the internal magnetic arrangement was matched to the external magnet and the size of the animal.