A novel method for measuring the torque on implantable cardiovascular devices in MR static fields.
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.
D'Avenio
Giuseppe
G
Department of Technology and Health, Istituto Superiore di Sanità, Rome, Italy.
Canese
Rossella
R
Podo
Franca
F
Grigioni
Mauro
M
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