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Assessment of magnetic field (4.7 T) induced forces on prosthetic heart valves and annuloplasty rings

Edwards, MB; Ordidge, RJ; Hand, JW; Taylor, KM; Young, IR; (2005) Assessment of magnetic field (4.7 T) induced forces on prosthetic heart valves and annuloplasty rings. J MAGN RESON IMAGING , 22 (2) 311 - 317. 10.1002/jmri.20373.

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Abstract

Purpose: To assess the magnetic field interactions on 11 heart valve prostheses and 12 annuloplasty rings subjected to a 4.7 T MR system.Materials and Methods: Ex vivo testing was performed to evaluate translational and rotational forces using previously described techniques.Results: Seventeen out of 23 prostheses showed zero interaction with the magnetic field. Translational forces with deflection angles of 2-20 degrees were demonstrated in six prostheses. Only two heart valves and two annuloplasty rings demonstrated rotational forces. The Carpentier Edwards (CE) Physio Ring, which contains Elgiloy, demonstrated deflection angles three times greater than those previously measured at 1.5 T. Furthermore, there was a direct relationship between increasing prosthesis size and increasing translational force. All heart valve prostheses attracted to the magnetic field were slightly paramagnetic/weakly ferromagnetic.Conclusion: Twenty-three heart valve prostheses evaluated for MRI are considered safe in static fields up to 4.7 T based on cur-rent safety criteria. However, the CE Physio Ring appeared to develop an increasing magnetism upon re-entry into the MR system. We conclude that prostheses made from Elgiloy may not be acceptable for patients in an MR environment of 4.7 T. Further investigations are required to confirm the safety of Elgiloy.

Type:Article
Title:Assessment of magnetic field (4.7 T) induced forces on prosthetic heart valves and annuloplasty rings
DOI:10.1002/jmri.20373
Keywords:heart valves, annuloplasty rings, magnetic resonance imaging, MRI safety, Elgiloy, MR SYSTEM, ANEURYSM CLIPS, IMPLANTS, DEVICES, ARTIFACTS
UCL classification:UCL > School of BEAMS > Faculty of Engineering Science > Medical Physics and Bioengineering

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