title: Head orientation in CBCT-generated cephalograms.
abstract: OBJECTIVE
  To determine the reliability of obtaining two-dimensional cephalometric measurements using two virtual head orientations from cone-beam computed tomography (CBCT) models.
  
  
  METHODS
  CBCT scans of 12 patients (6 class II and 6 class III) were randomly selected from a pool of 159 patients. An orthodontist, a dental radiologist, and a third-year dental student independently oriented CBCT three-dimensional (3D) renderings in either visual natural head position (simulated NHP) or 3D intracranial reference planes (3D IRP). Each observer created and digitized four CBCT-generated lateral cephalograms per patient, two using simulated NHP and two using 3D IRP at intervals of at least 3 days. Mixed-effects analysis of variance was used to calculate intraclass correlation coefficients (ICCs) and to test the difference between the orientations for each measure.
  
  
  RESULTS
  ICC indicated good reliability both within each head orientation and between orientations. Of the 50 measurements, the reliability coefficients were > or =0.9 for 45 measurements obtained with 3D IRP orientation and 36 measurements with simulated NHP. The difference in mean values of the two orientations exceeded 2 mm or 2 degrees for 14 (28%) of the measurements.
  
  
  CONCLUSIONS
  The reliability of both virtual head orientations was acceptable, although the percentage of measurements with ICC >0.9 was greater for 3D IRP. This may reflect the ease of using the guide planes to position the head in the 3D IRP during the simulation process.
authors.affiliation: Department of Orthodontics, University of North Carolina, UNC School of Dentistry, Chapel Hill, NC 27599-7450, USA. cevidanl@dentistry.unc.edu
authors.forename: Lucia
authors.initials: L
authors.lastname: Cevidanes
authors.forename: Ana E F
authors.initials: AE
authors.lastname: Oliveira
authors.forename: Alexandre
authors.initials: A
authors.lastname: Motta
authors.forename: Ceib
authors.initials: C
authors.lastname: Phillips
authors.forename: Brandon
authors.initials: B
authors.lastname: Burke
authors.forename: Donald
authors.initials: D
authors.lastname: Tyndall
mesh_terms: D002508:Cephalometry / Q000379:methods*; D054893:Cone-Beam Computed Tomography; D006257:Head / Q000000981:diagnostic imaging* / Q000502:physiology; D006801:Humans; D021621:Imaging, Three-Dimensional; D008312:Malocclusion, Angle Class II / Q000000981:diagnostic imaging; D008313:Malocclusion, Angle Class III / Q000000981:diagnostic imaging; D015588:Observer Variation; D056888:Patient Positioning; D011187:Posture; D011856:Radiographic Image Enhancement; D012886:Skull / Q000000981:diagnostic imaging*
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