Missile effect - MRI safety

Missile effect (or projectile effect) denotes the attraction exerted by the static magnetic field of the MRI scanner on ferromagnetic objects accidentally introduced into the MRI-scanner room (i.e. oxygen bottles, scissors, chairs, etc). This effect involves the risk of impact with the patient (or the radiographer) or with the MRI-gantry. Thus it is a major risk factor for both patient and personnel safety, and could also result in severe material damage.

Specifically, the "force" with which the ferromagnetic object is attracted to the center of the magnet is directly proportional to the intensity of the static magnetic field (B0), to the mass of the object and, inversely proportional to the distance cube.