Patent ID: 7446304

Claim:
A method of detecting collisions between a medical device and a second object in a medical procedure comprising: wherein the medical device comprises a magnet for use in magnetic resonance imaging, the magnet having a cylindrical bore surrounding a longitudinal axis of the magnet and an end face lying in a radial plane of the longitudinal axis; wherein the magnet is movable along its longitudinal axis in a direction toward and away from the second object; mounting on the magnet a detection device responsive to impacts between the magnet and the second object; the detection device comprising a flexible body within which is mounted at least one optical fiber arranged such that the impact causes bending of the optical fiber; and detecting changes in light transmission through the at least one optical fiber to detect the bending and thus the collision; wherein the flexible body is a ring attached to the radial end face of the magnet with an end face of the ring being parallel to the end face of the magnet, an inner face of the ring being located in a common cylindrical surface with the bore and an outer edge of the ring spaced outwardly of the bore and inwardly of an outer edge of the end face of the magnet.