MRIsafety.com

171
Coils, Filters, Stents, and Grafts

Coils, stents, filters and vascular grafts have been evaluated relative to the use of MR systems. Several of these demonstrated magnetic field interactions. Fortunately, the devices that exhibited positive magnetic field interactions typically become incorporated securely in tissue within six weeks after implantation due to ingrowth and other mechanisms. Therefore, for most coils, filters, stents and grafts that have been tested, it is unlikely that these implants would become moved or dislodged as a result of exposure to MR systems operating at 1.5-Tesla or less. Additionally, many of these items have been evaluated at 3-Tesla (see below). MRI-related heating may also be of concern for certain configurations or shapes for coils, stents, filters, and vascular grafts. To date, there has been no reported case of excessive heating in association with MRI and these types of implants.

Many coils, filters, stents and grafts are made from nonferromagnetic materials, such as the LGM IVC filter (Vena Tech) used for caval interruption and the Wallstent biliary endoprosthesis (Schneider, Inc.) used for treatment of biliary obstruction. As such, these implants are acceptable for patients undergoing MR procedures relative to the use of the particular field strength utilized in the ex vivo testing (for specific information, see The List). Notably, it is unnecessary to wait after surgery to perform an MR procedure in a patient with a “passive” metallic implant that is made from a nonmagnetic material (see Guidelines for the Management of the Post-Operative Patient Referred for a Magnetic Resonance Procedure). In fact, there are reports in the peer-reviewed literature that describe placement of vascular stents or other similar devices using MR-guidance at 1.5-Tesla and 3-Tesla. Interestingly, some of these vascular implants (e.g., vascular stent grafts and stainless steel embolization coils) display high magnetic field interactions in association with 1.5- and 3-Tesla MR systems, yet have MR Conditional labeling approved by the Food and Drug Administration.

Patients with the specific coils, stents, filters and vascular grafts indicated in The List have had procedures using MR systems operating at static magnetic field strengths of 3-Tesla or less without reported injuries or other problems.

A study by Taal, et al. (1997) supports the fact that not all stents are safe for patients undergoing MR procedures. This investigation was performed to evaluate potential problems for four different types of stents: the Ultraflex (titanium alloy), the covered Wallstent (Nitinol), the Gianturco stent (Cook), and the modified Gianturco stent (Song) - the last two are made from stainless steel. Taal, et al. reported “an appreciable attraction force and torque” found for both types of Gianturco stents. Taal, et al. stated, “the Gianturco (Cook) stent pulled toward the head with a force of 7 g…however, it is uncertain whether this is a potential risk for dislodgment.” In consideration of these results, the investigators advised, “…specific information on the type of stent is necessary before a magnetic resonance imaging examination is planned.”

MRI at 3-Tesla and Coils, Stents, Filters and Vascular Grafts. Different coils, stents, filters and vascular grafts have been evaluated at 3-Tesla. Of these implants, two displayed magnetic field interactions that exceeded the American Society for Testing and Materials (ASTM) International guideline for safety (i.e. the deflection angles were greater than 45 degrees). However, similar to other comparable implants, tissue ingrowth and other mechanims are sufficient to prevent them from posing a substantial risk to a patient or individual in the 3-Tesla MR environment. Please refer to The List for specific information related to coils, stents, filters and vascular grafts.

MRI at 3-Tesla: Bare Metal and Drug Eluting Coronary Stents. Patients with coronary artery disease are often treated by percutaneous transluminal coronary angioplasty (PTCA). Re-narrowing at the angioplasty site, or restenosis, occurs in as many as 50% of patients following PTCA. Therefore, after coronary artery intervention, either a bare metal or drug eluting stent may be placed in an effort to prevent restenosis.

MRI information has been obtained for many bare metal and drug eluting coronary artery stents, which have been reported to be acceptable for patients undergoing MR procedures at 3-Tesla or less (i.e. based on assessments of magnetic field interactions and MRI-related heating). Of note is that, for these coronary artery stents, patients may undergo MRI procedures immediately after placement. Please refer to The List for specific information.

REFERENCES

Ahmed S, Shellock FG. Magnetic resonance imaging safety: Implications for cardiovascular patients. Journal of Cardiovascular Magnetic Resonance 2001;3:171-181.

Audet-Griffin A, Pakbaz S, Shellock FG. Evaluation of MRI issues for a new, liquid embolic device. J Neurointervent Surg 2014;6:624-629.

Bueker A, et al. Real-time MR fluoroscopy for MR-guided iliac artery stent placement. J Magn Reson Imag 2000;12:616-622.

Girard MJ, et al. Wallstent metallic biliary endoprosthesis: MR imaging characteristics. Radiology 1992;184:874-876.

Green SR, Gianchandani YB. Wireless magnetoelastic monitoring of biliary stents. Journal of Microelectromechanical Systems 2009;18:64-78.

Hennemeyer CT, et al. In vitro evaluation of platinum Guglielmi detachable coils at 3-T with a porcine model: Safety issues and artifacts. Radiology 2001;219:732-737.

Hiramoto JS, et al. Long-term outcome and reintervention after endovascular abdominal aortic aneurysm repair using the Zenith stent graft. J Vasc Surg 2007;45:461-452.

Hiramoto JS, et al. The effect of magnetic resonance imaging on stainless-steel Z-stent-based abdominal aortic prosthesis. J Vasc Surg 2007;45:472-474.

Hug J, et al. Coronary arterial stents: Safety and artifacts during MR imaging. Radiology 2000;216:781-787.

Karacozoff AM, Shellock FG, Wakhloo AK. A next-generation, flow-diverting implant used to treat brain aneurysms: In vitro evaluation of magnetic field interactions, heating and artifacts at 3-T. Magnetic Resonance Imaging 2013;31:145-9.

Kaya MG, et al. Long-term clinical effects of magnetic resonance imaging in patients with coronary artery stent implantation. Coron Artery Dis 2009; 20:138-42.

Kiproff PM, et al. Magnetic resonance characteristics of the LGM vena cava filter: Technical note. Cardiovasc Intervent Radiol 1991;14:254-255.

Leibman CE, et al. MR imaging of inferior vena caval filter: Safety and artifacts. Am J Roentgenol 1988;150:1174-1176.

Manke C, et al. MR imaging-guided stent placement in iliac arterial stenoses: A feasibility study. Radiology 2001;219:527-534.

Marshall MW, et al. Ferromagnetism and magnetic resonance artifacts of platinum embolization microcoils. Cardiovasc Intervent Radiol 1991;14:163-166.

Nehra A, et al. MR safety and imaging of Neuroform Stents at 3-T. Am J Neuroradiol 2004;25:1476-1478.

Patel M, et al. Acute myocardial infarction: Safety of cardiac MR imaging after percutaneous revascularization with stents. Radiology 2006;240:674-680.

Porto I, et al. Safety of magnetic resonance imaging one to three days after bare metal and drug-eluting stent implantation. Am J Cardiol 2005;96:366-8.

Rutledge JM, et al. Safety of magnetic resonance immediately following Palmaz stent implant: A report of three cases. Catheter Cardiovasc Interv 2001;53:519-523.

Shellock FG. MR Safety at 3-Tesla: Bare Metal and Drug Eluting Coronary Artery Stents. Signals No. 53, Issue 2, pp. 26-27, 2005.

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, Detrick MS, Brant-Zawadski M. MR-compatibility of the Guglielmi detachable coils. Radiology 1997;203:568-570.

Shellock FG. Forder J. Drug eluting coronary stent: In vitro evaluation of magnetic resonance safety at 3-Tesla. Journal of Cardiovascular Magnetic Resonance 2005;7:415-419.

Shellock FG, Giangarra CJ. Assessment of 3-Tesla MRI issues for a bioabsorbable, coronary artery scaffold with metallic markers. Magnetic Resonance Imaging 2014;32:163-167.

Shellock FG, Gounis M, Wakhloo A. Detachable coil for cerebral aneurysms: In vitro evaluation of magnet field interactions, heating, and artifacts at 3-Tesla. Am J Neuroradiol 2005;26:363-366.

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

Shellock FG, Shellock VJ. Stents: Evaluation of MRI safety. Am J Roentgenol 1999;173:543-546.

Slesnick TC, et al. Safety of magnetic resonance imaging after implantation of stainless steel embolization coils. Pediatr Cardiol 2015 Epub ahead of print.

Sommer T, et al. High field MR imaging: Magnetic field interactions of aneurysm clips, coronary artery stents and iliac artery stents with a 3.0 Tesla MR system. Rofo 2004;176:731-8.

Spuentrup E, et al. Magnetic resonance-guided coronary artery stent placement in a swine model. Circulation 2002;105:874-879.

Taal BG, et al. Potential risks and artifacts of magnetic resonance imaging of self-expandable esophageal stents. Gastrointestinal Endoscopy 1997;46;424-429.

Teitelbaum GP, et al. MR imaging artifacts, ferromagnetism, and magnetic torque of intravascular filters, stents, and coils. Radiology 1988;166:657-664.

Teitelbaum GP, et al. Ferromagnetism and MR imaging: Safety of cartoid vascular clamps. Am J Neuroradiol 1990;11:267-272.

Teitelbaum GP, Ortega HV, Vinitski S, et al. Low artifact intravascular devices: MR imaging evaluation. Radiology 1988;168:713-719.

Teitelbaum GP, et al. Evaluation of ferromagnetism and magnetic resonance imaging artifacts of the Strecker tantalum vascular stent. Cardiovasc Intervent Radiol 1989;12:125-127.

Titterington B, Shellock FG. A new vascular coupling device: Assessment of MRI issues at 3-Tesla. Magn Reson Imaging 2014;32:585-9.

Watanabe AT, Teitelbaum GP, Gomes AS, et al. MR imaging of the bird’s nest filter. Radiology 1990;177:578-579.

Winter L, et al. On the RF heating of coronary stents at 7.0 Tesla MRI. Magn Reson Med 2015;74.

www.cookmedical.com

  Shellock R & D Services, Inc. email: Frank.ShellockREMOVE@MRIsafety.com.
  Copyright © 2024 by Shellock R & D Services, Inc. and Frank G. Shellock, Ph.D. All rights reserved.