The ferromagnetic pillow: a potential MR hazard not detectable by a hand-held magnet

This paper describes an incident in which an apparently normal hospital pil low became a ferromagnetic missile when brought into the proximity of a 1.5 T MR system owing to a fine internal spring system within the pillow. Meas urements revealed that the 1 kg pillow reached a maximum velocity of 33.7 k m h(-1) after undergoing a maximum acceleration of 9.9g. Nonpathological ce rvical spines should sustain the measured forces and torques without signif icant injury. However, the effect could be injurious or even fatal to patie nts suffering from an existing cervical instability, for example due to rhe umatoid arthritis. Of more general concern is the fact that the use of a po werful hand-held magnet did not reveal the presence of ferromagnetic compon ents in this instance. Large objects containing sparsely distributed ferrom agnetic materials may not be deflected by such a magnet but could still rep resent a hazard in the MR environment.