Magnetically induced displacement force
On an object which is attracted by a magnet, the static magnetic field of the MR scanner induces a force. This force can be quite strong, depending on the material and size of the object.
With this measurement, the strength of this force is determined. For an implant to be considered safe for the use in an MR scanner, this force should be smaller than the gravity force, because gravity of the implant has been empirically shown to be continually tolerated by the body.