title: Blast and ballistic trajectories in combat casualties: a preliminary analysis using a cartesian positioning system with MDCT.
abstract: OBJECTIVE
  The purpose of this study is to determine the agreement with which radiologists identify wound paths in vivo on MDCT and calculate missile trajectories on the basis of Cartesian coordinates using a Cartesian positioning system (CPS).
  
  
  METHODS
  Three radiologists retrospectively identified 25 trajectories on MDCT in 19 casualties who sustained penetrating trauma in Iraq. Trajectories were described qualitatively in terms of directional path descriptors and quantitatively as trajectory vectors. Directional descriptors, trajectory angles, and angles between trajectories were calculated based on Cartesian coordinates of entrance and terminus or exit recorded in x, y image and table space (z) using a Trajectory Calculator created using spreadsheet software. The consistency of qualitative descriptor determinations was assessed in terms of frequency of observer agreement and multirater kappa statistics. Consistency of trajectory vectors was evaluated in terms of distribution of magnitude of the angles between vectors and the differences between their paraaxial and parasagittal angles.
  
  
  RESULTS
  In 68% of trajectories, the observers' visual assessment of qualitative descriptors was congruent. Calculated descriptors agreed across observers in 60% of the trajectories. Estimated kappa also showed good agreement (0.65-0.79, p < 0.001); 70% of calculated paraaxial and parasagittal angles were within 20° across observers, and 61.3% of angles between trajectory vectors were within 20° across observers.
  
  
  CONCLUSIONS
  Results show agreement of visually assessed and calculated qualitative descriptors and trajectory angles among observers. The Trajectory Calculator describes trajectories qualitatively similar to radiologists' visual assessment, showing the potential feasibility of automated trajectory analysis.
authors.affiliation: Department of Radiology, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892, USA.
authors.forename: Les R
authors.initials: LR
authors.lastname: Folio
authors.forename: Tatjana
authors.initials: T
authors.lastname: Fischer
authors.forename: Paul
authors.initials: P
authors.lastname: Shogan
authors.forename: Michael
authors.initials: M
authors.lastname: Frew
authors.forename: Andrew
authors.initials: A
authors.lastname: Dwyer
authors.forename: James M
authors.initials: JM
authors.lastname: Provenzale
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D001753:Blast Injuries / Q000000981:diagnostic imaging*; D005107:Explosions; D044709:Forensic Ballistics; D006801:Humans; D021621:Imaging, Three-Dimensional; D054542:Iraq War, 2003-2011; D008297:Male; D008889:Military Personnel; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014948:Wounds, Gunshot / Q000000981:diagnostic imaging*