title: A novel method for measuring the torque on implantable cardiovascular devices in MR static fields.
abstract: OBJECTIVE
  To propose a novel quantitative method for measuring the torque acting on mechanical heart valve prostheses subjected to a high static magnetic field in a MR scanner.
  
  
  METHODS
  Torque measurements were performed with a torsion balance, implemented with a copper wire. The reaction torque exerted by the static magnetic field on the device was measured optically from the deflection angle of a laser beam spot on a graduate scale. Three different types of mechanical valves (two bileaflet and one monoleaflet) were tested at different locations of a small bore 4.7 tesla system.
  
  
  RESULTS
  The method proved to be particularly sensitive (detectability limit lower than 10(-6) N x m), reliable and yielded quantitative reproducible results. The equivalent force of the torque measured for the three valves was at least 10(3)-fold lower than the force exerted by the beating heart.
  
  
  CONCLUSIONS
  The proposed method provides a quantitative evaluation of the torque induced on prosthetic device by a MR scanner operating at high magnetic field.
authors.affiliation: Department of Technology and Health, Istituto Superiore di Sanità, Rome, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: D'Avenio
authors.forename: Rossella
authors.initials: R
authors.lastname: Canese
authors.forename: Franca
authors.initials: F
authors.lastname: Podo
authors.forename: Mauro
authors.initials: M
authors.lastname: Grigioni
mesh_terms: D001807:Blood Vessel Prosthesis; D004574:Electromagnetic Fields; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006350:Heart Valve Prosthesis; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D019415:Torque; D014159:Transducers