title: Translational and rotational forces on heart valve prostheses subjected ex vivo to a 4.7-T MR system.
abstract: OBJECTIVE
  To assess the magnetic field interactions on 60 heart valve prostheses subjected to a 4.7 T MR system. It addresses the question of whether heart valves deemed safe at 1.5 T may pose safety hazards as patients are exposed to increased static magnetic fields.
  
  
  METHODS
  Ex vivo testing was performed to evaluate translational and rotational forces on 60 heart valves using previously described techniques.
  
  
  RESULTS
  Translational forces were detected on 58 heart valves ranging from 0.5 degrees to 7.5 degrees. Seven valves exhibited paramagnetic/weakly ferromagnetic behavior, and 51 valves exhibited diamagnetic behavior. Rotational forces were observed for 46 valves.
  
  
  CONCLUSIONS
  Criteria previously used for safety assessment of heart valve prostheses and expressed in terms of magnetic forces suggest the forces observed in this study are compatible with the safe use of these valves in magnetic resonance (MR) systems with static fields up to 4.7 T.
authors.affiliation: United Kingdom Heart Valve Registry, Department of Cardiothoracic Surgery, Hammersmith Hospital, London, UK. m.b.edwards@ic.ac.uk
authors.forename: Maria-Benedicta
authors.initials: MB
authors.lastname: Edwards
authors.forename: Roger J
authors.initials: RJ
authors.lastname: Ordidge
authors.forename: David L
authors.initials: DL
authors.lastname: Thomas
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Hand
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Taylor
mesh_terms: D006350:Heart Valve Prosthesis; D006358:Hot Temperature; D006801:Humans; D066298:In Vitro Techniques; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008280:Magnetics; D012399:Rotation; D012449:Safety