Various hemostatic vascular clips, other types of clips, fasteners, and staples evaluated for magnetic field interactions were not attracted by static magnetic fields of MR systems operating at 3-Tesla or less. These implants were made from nonferromagnetic materials such as tantalum, commercially pure titanium, and nonferromagnetic forms of stainless steel. Additionally, some forms of ligating, hemostatic, or other types of clips are made from biodegradable materials. Therefore, patients that have the implants made from nonmagnetic or “weakly” magnetic materials listed in The List are not at risk for injury during MR procedures. Importantly, for the devices that have been tested to date, there has been no report of an injury to a patient in association with a hemostatic vascular clip, other type of clip, fastener, or staple associated with the MR environment. Patients with nonferromagnetic versions of these implants may undergo MR procedures immediately after they are placed.

Vascular grafts frequently have clips or fasteners applied that may present problems for MR imaging because of the associated artifacts. Weishaupt, et al. (2000) evaluated the artifact size on three-dimensional MR angiograms as well as the MR issues for 18 different commercially available hemostatic and ligating clips. All of the clips were acceptable or safe at 1.5-Tesla insofar as there was no substantial magnetic field interactions or heating measured for these implants.

Specific MRI-related labeling statements for certain hemostatic clips that require further attention during the pre-MRI screening procedure are, as follows:

Long Clip, HX-600-090L. The Long Clip HX-600-090L (Olympus Medical Systems Corporation) is indicated for placement within the gastrointestinal tract for the purpose of endoscopic marking, hemostasis, or closure of GI tract luminal perforations within 20-mm as a supplementary method. Currently, the Long Clip HX-600-090L is labeled, as follows: “Do not perform MRI procedures on patients who have clips placed within their gastrointestinal tracts. This could be harmful to the patient.”

Additional information: Olympus endoscopic clips have been shown to remain in the patient an average of 9.4 days, but retention is based on a variety of factors and may result in a longer retention period. Prior to MRI, the physician should confirm there are no residual clips in the GI tract. The following techniques may be used for confirmation:

View the lesion under radiologic imaging. Olympus clip fixing devices are radiopaque. By using x-ray, the physician can determine if any residual clips are in the gastrointestinal tract. If no clips are evident under radiologic imaging, MRI may be accomplished.

Endoscopically examine the lesion. If no clips remain at the lesion, MRI may be accomplished.

QuickClip2, HX-201LR-135 & HX-201UR-135. The QuickClip2, HX-201LR-135 & HX-201UR-135 (Olympus Medical Systems Corporation) are indicated for placement within the gastrointestinal tract for the purpose of endoscopic marking, hemostasis, or closure of GI tract luminal perforations within 20-mm as a supplementary method. Currently, the QuickClip2 (HX-201LR-135 & HX-201UR-135) is labeled, as follows: “Do not perform MRI procedures on patients who have clips placed within their gastrointestinal tracts. This could be harmful to the patient.”

Additional information: Olympus endoscopic clips have been shown to remain in the patient an average of 9.4 days, but retention is based on a variety of factors and may result in a longer retention period. Prior to MRI, the physician should confirm there are no residual clips in the GI tract. The following techniques may be used for confirmation:

View the lesion under radiologic imaging. Olympus clip fixing devices are radiopaque. By using x-ray, the physician can determine if any residual clips are in the gastrointestinal tract. If no clips are evident under radiologic imaging, MRI may be accomplished.

Endoscopically examine the lesion. If no clips remain at the lesion, MRI may be accomplished.

QuickClip2 Long, HX-201LR-135L & HX-201UR-135L. The QuickClip2 Long, HX-201LR-135L & HX-201UR-135L (Olympus Medical Systems Corporation) are indicated for placement within the gastrointestinal tract for the purpose of endoscopic marking, hemostasis, or closure of GI tract luminal perforations within 20-mm as a supplementary method. The QuickClip2 Long (HX-201LR-135L & HX-201UR-135L) is labeled, as follows: “Do not perform MRI procedures on patients who have clips placed within their gastrointestinal tracts. This could be harmful to the patient.”

Additional information: Olympus endoscopic clips have been shown to remain in the patient an average of 9.4 days, but retention is based on a variety of factors and may result in a longer retention period. Prior to MRI, the physician should confirm there are no residual clips in the GI tract. The following techniques may be used for confirmation:

View the lesion under radiologic imaging. Olympus clip fixing devices are radiopaque. By using x-ray, the physician can determine if any residual clips are in the gastrointestinal tract. If no clips are evident under radiologic imaging, MRI may be accomplished.

Endoscopically examine the lesion. If no clips remain at the lesion, MRI may be accomplished.

TriClip Endoscopic Clipping Device. An investigation by Gill, et al. (2009) involving excised tissue exposed to a 1.5-Tesla MR system, reported that the TriClip (TriClip Endoscopic Clipping Device, Wilson-Cook Medical Inc., Winston-Salem, NC) demonstrated “detachment from gastric tissue”. Therefore, the TriClip should be considered “unsafe” for MRI.

MRI at 3-Tesla and Hemostatic Clips, Other Clips, Fasteners, and Staples. At 3-Tesla, a variety of hemostatic clips, other clips, fasteners, and staples have been evaluated for MRI issues including magnetic field interactions and MRI-related heating. In general, these devices do not present an additional risk to patients undergoing MR procedures. For example, Gill and Shellock (2012) tested metallic skin closure staples and vessel ligation clips at 3-Tesla to characterize MRI issues in order to ensure patient safety. Clips were selected for testing that represented the largest metallic sizes made from materials with the highest magnetic susceptibilities among 61 other similar implants. Each surgical implant showed only minor magnetic field interactions and heating was not substantial. The results demonstrated that it would be acceptable for patients with these particular metallic surgical implants to undergo MRI at 3-Tesla or less. Because of the materials and dimensions of the skin closure staples and vessel ligation clips that underwent testing, the findings pertained to 61 additional similar implants. Please refer to The List for specific information for other hemostatic clips, other clips, fasteners, and staples.

REFERENCES

Brown MA, et al. Magnetic field effects on surgical ligation clips. Magnetic Resonance Imaging 1987;5:443-453.

Barrafato D, Henkelman RM. Magnetic resonance imaging and surgical clips. Can J Surg 1984;27:509-512.

Gill A, Shellock FG. Assessment of MRI issues at 3-Tesla for metallic surgical implants: Findings applied to 61 additional skin closure staples and vessel ligation clips. J Cardiovasc Magn Reson. 2012;14:3-7.

Gill KR, Pooley RA, Wallace MB. Magnetic resonance imaging compatibility of endoclips. Gastrointest Endosc 2009;70:532-6.

Mavrogenis G, et al. Hemostatic clips and magnetic resonance imaging. Are there any compatibility issues? Endoscopy 2013;45:933.

Raju GS. Endoclips for GI endoscopy. Gastrointestinal Endoscopy 2004;59:267-279.

Shellock FG. Hemostatic Clips and MRI Procedures: Some Safe…Some May Not Be. Signals No. 66, pp. 20-21, 2008.

Shellock FG, Crues JV, Editors. MRI Bioeffects, Safety, and Patient Management. Biomedical Research Publishing Group, Los Angeles, CA, 2014.

Shellock FG. MR imaging of metallic implants and materials: A compilation of the literature. Am J Roentgenol 1988;151:811-814.

Shellock FG. Biomedical implants and devices: Assessment of magnetic field interactions with a 3.0-Tesla MR system. J Magn Reson Imag 2002;16:721-732.

Shellock FG, Crues JV. High-field strength MR imaging and metallic biomedical implants: An ex vivo evaluation of deflection forces. Am J Roentgenol 1988;151:389-392.

Shellock FG, Morisoli S, Kanal E. MR procedures and biomedical implants, materials, and devices: 1993 update. Radiology 1993;189:587-599.

Shellock FG, Swengros-Curtis J. MR imaging and biomedical implants, materials, and devices: An updated review. Radiology 1991;180:541-550.

Weishaupt D, et al. Ligating clips for three-dimensional MR angiography at 1.5-T: In vitro evaluation. Radiology 2000;214:902-907.