Alexandra Schmiedel MD, PRESENTER: Nothing to Disclose

Abstract: HTML Purpose: To evaluate the MR compatibility of various CA stents with respect to magnetic attraction and RF-related heating at 3.0 Tesla. Methods and Materials: 34 commonly used CA stents were studied in a 3.0 T system (Intera, PMS, NL): 1. NIR Primo, 2. NIR Royal, 3. Radius, 4. Express, 5. Express 2 (Boston Scientific Europe), 6. Palmaz, 7. Crown, 8. Crossflex , 9. Palmaz , 10. BX Velocity, 11. Crossflex (Cordis), 12. ACS RX Multilink, 13. ML Tetra , 14. Herculink, 15. ML Tristar, 16. ACS Multilink Duett, 17.Multilink Ultra, 18. Multilink Pixel, 19. Multilink Penta, 20. Multilink RX Zeta, 21. Multilink Tetra (Guidant), 22. beStent , 23. Wiktor (Medtronic), 24. Sirius Carbostent, 25. Tecnic, 26. Syncro (Sorin Biomedica), 27. Jostent Flex (Jomed), 28. Flex AS (Phytis), 29. BiodivYsio (Biocompatibles), 30. Jostent StentGraft (Jomed), 31. SitoStent (Sitomed), 32. Wallstent (Schneider), 33. Coronary Stent (Mansfield), 34. Micro Stent (AVE). Each stent was evaluated for: 1. magnetic deflection forces: The stents were suspended by a fine string and placed in the magnet bore at the location of the greatest magnetic field gradient. The deflection angle was measured 3 times and deflection forces were calculated. 2. magnetic field-induced torque: Each stent was placed on a plastic Petri dish in a position perpendicular to the static magnetic field (position 90°) and slowly moved on the MR table into the center of the magnetic bore. Any possible displacement or rotation of the stents was noted. The stent was turned in steps of 45°, and the procedure was repeated to encompass a full 360° rotation of positions. 3. heating: The stents were implanted in a cadaveric porcine heart and placed in a rectangular plastic phantom filled with 0.9% saline solution. A fiber-optic temperature probe was attached directly to the stents to measure temperature continuously during MR imaging. To simulate a worst case heating condition a fast spin echo sequence - producing an estimated whole -body averaged absorption rate of 3.9 W/kg (body coil as sending coil)- was applied for 15 min. Results: Magnetic deflection force: In all devices tested the deflection force (range 0.01 - 0.18 mN, mean 0.08 mN ± 0.03 {SD}) was less than the gravitational force (i.e. the clips weight). Torque: None of the clips aligned to or rotated in the magnetic field at any of the various 45°-interval positions. Heating: Maximum temperature increase of the clips ranged from 0.1°C to 1.1°C (mean 0.3°C +/- 0.21). Conclusion: MR imaging at 3.0 Tesla may be performed safely in pts with any of the 34 different CA stents evaluated in this study.      

Schmiedel MD, A, High-Field Strength MR Imaging and Coronary Artery Stents (CA stents): In Vitro Evaluation of Magnetic Attraction Forces and Radio Frequency Related Heating at 3.0 Tesla.  Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL. http://archive.rsna.org/2003/3102357.html