Mitral and aortic valve replacement is a procedure which is common in cardiac surgery. Some of these replacement valves are mechanical and contain moving metal parts in the disc or leaflets. When exposed to MRI there is a potentially hazardous interaction between the moving metal parts and the static magnetic field due to the Lenz Effect. The Lenz Effect is a result of the current (induced by the metallic component moving in a static magnetic field) changing as the valve rotates; this causes a secondary field to be set up which opposes the original field and consequently opposes the motion of the component. A simple 'worst case' analysis of the potential hazard has been performed previously (1). However the differential nature of the delaying effect of the motion of the mechanical valve on the Lenz effect itself was not assessed. In this paper a differential model of a ring-strengthener valve type has been developed to take account of the interplay between the Lenz Effect and disc motion.
|Title of host publication||Proc. 9th Annual Meeting of the International Society of Magnetic Resonance in Medicine (ISMRM)|
|Subtitle of host publication||21-27 April 2001, Glasgow, Scotland|
|Publication status||Published - 2001|