Introducing a Freely Accessible Internet Database for Identification of Cerebral Aneurysm Clips to Determine Magnetic Resonance Imaging Compatibility

MRI in patients with a cerebral aneurysm clip; review of the literature and incident databases and recommendations for the Netherlands

BACKGROUND

In the past ferromagnetic cerebral aneurysm clips that are contraindicated for Magnetic Resonance Imaging (MRI) have been implanted. However, the specific clip model is often unknown for older clips, which poses a problem for individual patient management in clinical care.

METHODS

Literature and incident databases were searched, and a survey was performed in the Netherlands that identified time periods at which ferromagnetic and non-ferromagnetic clip models were implanted. Considering this information in combination with a national expert opinion, we describe an approach for risk assessment prior to MRI examinations in patients with aneurysm clips. The manuscript is limited to MRI at 1.5 T or 3 T whole body MRI systems with a horizontal closed bore superconducting magnet, covering the majority of clinical Magnetic Resonance (MR) systems.

RESULTS

From the literature a list of ferromagnetic clip models was obtained. The risk of movement or rotation of the clip due to the main magnetic field in case of a ferromagnetic clip is the main concern. In the incident databases records of four serious incidents due to aneurysm clips in MRI were found. The survey in the Netherlands showed that from 2000 onwards, no ferromagnetic clips were implanted in Dutch hospitals.

DISCUSSION

Recommendations are provided to help the MR safety expert assessing the risks when a patient with a cerebral aneurysm clip is referred for MRI, both for known and unknown clip models. This work was part of the development of a guideline by the Dutch Association of Medical Specialists.

Magnetic resonance imaging and aneurysm clips

The problem of implanted metals causing tissue damage by movement in patients exposed to MRI fields has produced a confusing welter of erroneous, pseudoscientific publications about magnetics, metals, medical equipment, and tissue compatibility. Quite simply, among the devices made for implantation, only those fabricated of stainless steel have the ferromagnetic properties capable of causing such accidents. The author, who introduced the basic design of the modern aneurysm clip in the late 1960s and then a cobalt nickel alloy as an improvement over steel, while chairing the neurosurgical committee assigned to the task of establishing neurosurgical standards at American Society for Testing and Materials, exposes this flawed information and offers clear guidelines for avoiding trouble.

Magnetic resonance imaging compatibility of endoclips

BACKGROUND

Endoscopic clipping devices are now available for treatment of GI hemorrhage and microperforations. All commercially available endoclips are labeled as magnetic resonance imaging (MRI) incompatible. No data are available about the actual magnetic field strength at which endoclips are first deflected nor the clinical relevance of the magnetic fields on endoclips used in GI endoscopy.

OBJECTIVE

To determine the compatibility of different endoclips with MRI.

DESIGN

Prospective observational study.

SETTING

Experiment on excised pig tissue in an MRI scanner.

INTERVENTIONS

The physical deflection and strength of attraction of endoclips: Resolution Clip, TriClip, QuickClip, and Ethicon Endo-surgery Clip were measured in different positions by using an MRI scanner at a field strength of 1.5 Tesla. Endoclips that demonstrated deflection were attached to a pig stomach and tested for detachment at a 1.5-Tesla MRI field strength.

MAIN OUTCOME MEASUREMENTS

Physical deflection and detachment from pig stomach mucosa in an MRI scanner.

RESULTS

All endoclips except the one made by Ethicon Endo-surgery demonstrated physical deflection under the tested conditions. The magnetic attraction was strongest for the Resolution Clip (0.7 gauss) compared with the TriClip (1.2 gauss) and the QuickClip (26.8 gauss). Only the Triclip demonstrated detachment from the pig gastric tissue under testing conditions.

LIMITATIONS

A pig model and a small number of clips.

CONCLUSIONS

The Ethicon Endo-surgery clip is compatible with MRI. All other clips showed deflection in a magnetic field, but only the TriClip demonstrated detachment from gastric tissue, and hence should be considered MRI incompatible.