title: The influence of 1.5 and 3 T magnetic resonance unit magnetic fields on the movement of steel-jacketed projectiles in ordnance gelatin.
abstract: OBJECTIVE
  Ferromagnetic bullets can move in air or gelatin in magnetic resonance (MR) units. According to our experience, ferromagnetic bullets do not always present consistent movement. We examined factors affecting ferromagnetic projectile movement in a 1.5T and a 3T MR unit, focusing in this study on the steel-jacketed Swiss ordnance ammunition 7.5 mm GP11 Suisse.
  
  
  METHODS
  Five 7.5 mm GP11 Suisse bullets were embedded horizontally and vertically in 10 % ordnance gelatin phantoms. Before and after exposing the bullets to 1.5T (Siemens) and 3T (Philips) MR units each bullet's position was documented by a CT scan. In a second phase, the magnetic polarization of the bullets in relation to the MR units was measured by a dry magnetic portable compass (Suunto).
  
  
  RESULTS
  Our results showed that the displacement of the bullets increased when subjected to a stronger magnetic field (max. Movement 1.5T: 24.4 mm vs. 3T: 101.5 mm) and that the position, i.e. orientation of the bullet toward the gantry, strongly influenced its mobility (horizontally embedded projectiles showed poor movement, vertically placed ones strong movement). One of the bullets presented a 180° rotation in the 3T MR unit. Magnetization and changing of the polarization of these ferromagnetic bullets is possible when subjected to MR units.
  
  
  CONCLUSIONS
  In conclusion, the location of a bullet, and its orientation toward the gantry must be taken into account when assessing the risk of performing an MR examination on a gunshot victim in clinical and in forensic cases.
authors.affiliation: Department of Forensic Medicine and Imaging, Institute of Forensic Medicine, University of Zurich, Winterthurerstrasse 190/52, Zurich, 8057, Switzerland.|Department of Radiology, Kantonsspital Baden AG, Baden, Switzerland.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Eggert
authors.affiliation: Department of Radiology, Kantonsspital Baden AG, Baden, Switzerland.
authors.forename: Rahel A
authors.initials: RA
authors.lastname: Kubik-Huch
authors.affiliation: Forensic Institute Zurich, Zurich, Switzerland.
authors.forename: Martin
authors.initials: M
authors.lastname: Lory
authors.affiliation: Federal Institute of Technology, Pharmaceutical Sciences, Zurich, Switzerland.
authors.forename: John M
authors.initials: JM
authors.lastname: Froehlich
authors.affiliation: Department of Forensic Medicine and Imaging, Institute of Forensic Medicine, University of Zurich, Winterthurerstrasse 190/52, Zurich, 8057, Switzerland.
authors.forename: Dominic
authors.initials: D
authors.lastname: Gascho
authors.affiliation: Department of Forensic Medicine and Imaging, Institute of Forensic Medicine, University of Zurich, Winterthurerstrasse 190/52, Zurich, 8057, Switzerland.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Thali
authors.affiliation: Department of Forensic Medicine and Imaging, Institute of Forensic Medicine, University of Zurich, Winterthurerstrasse 190/52, Zurich, 8057, Switzerland. stephan.bolliger@irm.uzh.ch.
authors.forename: Stephan A
authors.initials: SA
authors.lastname: Bolliger
mesh_terms: D005389:Firearms; D044709:Forensic Ballistics; D005780:Gelatin; D006801:Humans; D060526:Magnetic Fields; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008954:Models, Biological; D061330:Multidetector Computed Tomography
chemical_list: D005780:Gelatin
keywords: Bullets; Ferromagnetic foreign bodies; MR; MR safety