title: Four-channel multidetector CT in facial fractures: do we need 2 x 0.5 mm collimation?
abstract: OBJECTIVE
  Our aim was to optimize acquisition protocols and multiplanar reformation algorithms for the evaluation of facial fractures using multidetector CT (MDCT) and to determine whether 2 x 0.5 mm collimation is necessary.
  
  
  METHODS
  A cadaveric head with artificial blunt facial trauma was examined using a four-channel MDCT scanner. The influence of acquisition parameters (collimation, 2 x 0.5 mm, 4 x 1 mm, 4 x 2.5 mm; tube current, 120 mAs, 90 mAs, 60 mAs), image reconstruction algorithms (standard vs ultra-high-resolution modes; reconstructed slice thicknesses, 0.5 mm, 1 mm, 3 mm; increment, 0.3 mm, 0.6 mm, 1.5 mm), and reformation algorithms (slice thicknesses, 0.5 mm, 1 mm, 3 mm; overlap, 0.5 mm, 1 mm, 3 mm) on detectability of facial fractures in multiplanar reformations with MDCT was analyzed.
  
  
  RESULTS
  Fracture detection was significantly higher with thin multiplanar reformations (0.5 and 0.5 mm, 1 and 0.5 mm, and 1 and 1 mm) (p < or = 0.014) acquired with 2 x 0.5 mm collimation (p < or = 0.046) in ultra-high-resolution mode (p < 0.0005) with 120 mAs (p < or = 0.025). Interobserver variability showed very good agreement (kappa > or = 0.942). Non-ultra-high-resolution mode, lower milliampere-seconds, and thick multiplanar reformations (3 and 0.5 mm, 3 and 1 mm, and 3 and 0.5 mm) showed significantly decreased fracture detectability.
  
  
  CONCLUSIONS
  Although thin multiplanar reformations obtained from thin collimation (2 x 0.5 mm) are statistically superior for the detection of subtle fractures, 4 x 1 mm collimation is sufficient for routine diagnostic evaluation. Ultra-high-resolution mode with 120 mAs is mandatory for detection of clinically relevant fractures.
authors.affiliation: Department of Radiology, Division of Surgery, University of Vienna Medical School, General Hospital Vienna, Waehringer Guertel 18-20, Austria.
authors.forename: Marcel O
authors.initials: MO
authors.lastname: Philipp
authors.forename: Martin A
authors.initials: MA
authors.lastname: Funovics
authors.forename: Frederick A
authors.initials: FA
authors.lastname: Mann
authors.forename: Andreas M
authors.initials: AM
authors.lastname: Herneth
authors.forename: Michael H
authors.initials: MH
authors.lastname: Fuchsjaeger
authors.forename: Florian
authors.initials: F
authors.lastname: Grabenwoeger
authors.forename: Gerhard
authors.initials: G
authors.lastname: Lechner
authors.forename: Viktor M
authors.initials: VM
authors.lastname: Metz
mesh_terms: D000368:Aged; D000465:Algorithms; D005147:Facial Bones / Q000000981:diagnostic imaging* / Q000293:injuries*; D005151:Facial Injuries / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D015588:Observer Variation; D012680:Sensitivity and Specificity; D012887:Skull Fractures / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed; D015599:Trauma Severity Indices