Key result
Novel 4.7T MR balance shows mechanical valve torque is ~1000-fold below cardiac forces.
Why the study?
A quantitative method for measuring the torque on mechanical heart valve prostheses in high static magnetic fields of MR scanners was needed.
A novel torsion balance method can accurately measure the torque induced on mechanical heart valves by high-field MRI, demonstrating forces significantly lower than those exerted by the beating heart.
May support high-field MRI evaluation in mechanical valve patients; leaves open clinical translation pending human studies.
PURPOSE: 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. MATERIALS AND 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. CONCLUSION: The proposed method provides a quantitative evaluation of the torque induced on prosthetic device by a MR scanner operating at high magnetic field.
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D’Avenio et al. (2007) studied Mechanical heart valve prostheses (n=3). Torsion balance method was evaluated on Torque acting on mechanical heart valve prostheses. A novel torsion balance method reliably measured torque on mechanical heart valves in a 4.7T MR scanner, showing the equivalent force was at least 1000-fold lower than the beating heart's force.
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