Safety of endoclips for magnetic resonance imaging.

BACKGROUND

A fatal incident in which magnetic resonance (MR) may be involved and the appearance of strong MR attraction experienced by some MR-conditional endoclips have cast confusion over the MR safety of MR-conditional endoclips, which may lead to unnecessary delay or denial of MRI to some patients. On the other hand, there are endoclips that are MRI-unsafe, yet not all MRI facilities screen patients for endoclips.

PURPOSE: Our purpose is to promote a better understanding of the MRI risks associated with endoclips to facilitate proper management of MRI exams involving patients with endoclips.

METHODS

Deflection angle measurements were conducted on three models of MR-conditional endoclips on a 1.5T and a 3T MRI system to assess the magnetic forces on the endoclips. Detachment force measurements were also performed on porcine stomach mucosa specimens to evaluate the attachment force. Besides, detachment tests were conducted inside the magnet bore to evaluate the effect of magnetic-induced torque.

RESULTS

The measured detachment force was much larger than the magnetic force for each clip tested, with the ratios of the two forces being 87.3-251 at 1.5T and 46.7-130 at 3T, indicating low detachment risk for these clips. This was further supported by the detachment tests inside the magnet bore in which no endoclip detached.

CONCLUSIONS

This study reinforces the MR conditional labeling on endoclips, demonstrating that the appearance of strong magnetic force does not necessarily imply an endoclip is MR unsafe. If the counter force (i.e., the detachment force) provided by an endoclip is much larger than the MRI magnetic force, as observed in this study, the risk of clip detachment during MRI is low. This paper should assist in facilitating proper management of MRI exams involving patients with endoclips, preventing unnecessary denial of MRI examinations to patients while protecting patient safety.