title: Fairly direct hit! Advances in imaging of shotgun projectiles in MRI.
abstract: OBJECTIVE
  To investigate the magnetic properties of different types of projectiles and qualify the metal artefact reduction technique for diagnostic and/or forensic MRI.
  
  
  METHODS
  Ten different projectiles embedded in ordnance gelatine blocks underwent an in vitro 1.5-T MR study with seven sequences including a recently developed metal artefact reduction sequence (Advanced WARP) combining VAT (view-angle-tilting) and SEMAC (slice-encoding metal-artefact-correction). Resulting image quality (five-point scale: 1=best; 5=worst) was scored. Quantifiable magnetic characteristics were correlated with qualitative rating of the MR sequences and torque dislodgment.
  
  
  RESULTS
  Metal artefact reduction sequence (median: 2.5) significantly (p < 0.001) improves depiction of projectiles in comparison to all other MR pulse sequences (median: 4.75). Images from diamagnetic composed bullets (median: 2) are much less disturbed compared to magnetic attracted ones (median: 5). Correlation (0.623) between deflection angle measurement (ferromagnetic mean 84.2°; paramagnetic 62°; diamagnetic mean 0°) and median qualitative image quality was highly significant (p = 0.027). Torque dislodgement was distinct for elongated magnetic attracted projectiles.
  
  
  CONCLUSIONS
  Significant improvement of MR imaging of projectiles using metal artefact reduction techniques has important implications for diagnostic/forensic work-up. The correlations between magnetic attraction force, deflection-angle results and image properties demonstrate that the MR safety of projectiles can be estimated with one of these methods.
  
  
  CONCLUSIONS
  • Metal artefact reduction sequence improves overall image quality of bullets (p < 0.001). • Deflection angle assessment significantly predicts image quality of bullets (p = 0.027). • Classification of projectiles' magnetic properties based on artefacts' characteristics is possible. • Classifying of bullets has important implications in diagnostic and forensic imaging. • Identification of projectiles' magnetic attributes improves estimation of patients' injury risk.
authors.affiliation: Department of Radiology, Kantonsspital Baden AG, Im Ergel, 5404, Baden, Switzerland, sebastian.eggert@irm.uzh.ch.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Eggert
authors.forename: Rahel A
authors.initials: RA
authors.lastname: Kubik-Huch
authors.forename: Markus
authors.initials: M
authors.lastname: Klarhöfer
authors.forename: Alexander
authors.initials: A
authors.lastname: Peters
authors.forename: Stephan A
authors.initials: SA
authors.lastname: Bolliger
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Thali
authors.forename: Suzanne
authors.initials: S
authors.lastname: Anderson
authors.forename: Johannes M
authors.initials: JM
authors.lastname: Froehlich
mesh_terms: D000328:Adult; D000369:Aged, 80 and over; D016477:Artifacts; D005260:Female; D005389:Firearms; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008670:Metals; D008875:Middle Aged; D019047:Phantoms, Imaging; D011446:Prospective Studies
chemical_list: D008670:Metals