title: Effect of changing the head position on accuracy of transverse measurements of the maxillofacial region made on cone beam computed tomography and conventional posterior-anterior cephalograms.
abstract: OBJECTIVE
  This study aimed to assess the effect of head position on the accuracy of transverse measurements of the maxillofacial region on CBCT and conventional posteroanterior (PA) cephalograms. The second objective of this study was to find skull positions with the greatest and smallest effect on transverse measurements in the maxillofacial region.
  
  
  METHODS
  PA cephalograms and CBCT scans were obtained from 10 dry human skulls in 7 positions, namely the central position, 10° and 20° rotations, 10° and 20° tilts and 10° and 20° tips. The CBCT scans were converted to PA cephalograms on which distances from six landmarks, namely the nasal cavity, zygomatic arch, jugale, antegonion, condylion and zygomaticofrontal suture to the mid-sagittal plane, were measured on both sides using Dolphin two-dimensional software. The paired t-test was used to compare the mean values separately in each position (for each landmark) with the gold standard (central skull position). The interclass correlation coefficient and the Bland-Altman plot were used to compare the mean values measured by two observers.
  
  
  RESULTS
  The mean values of the distances measured on CBCT PA cephalograms were greater than those measured on conventional PA cephalograms; this difference was statistically significant for some landmarks (p < 0.005). The rotated position (as compared with the central position) caused the greatest change in values for most landmarks on both sides (p < 0.005).
  
  
  CONCLUSIONS
  The CBCT PA cephalogram was more accurate than the conventional PA cephalogram, and landmarks farther from the midline exhibited greater changes on cephalograms compared with those closer to the midline. Patients are at risk of improper positioning when undergoing extraoral radiography such as PA cephalograms. Changes in head position may affect the transverse measurements and thus the treatment plan.
authors.affiliation: 1 Department of Oral and Maxillofacial Radiology, Faculty of Dentistry, Dental Research Center, Hamadan University of Medical Sciences, Hamadan, Islamic Republic of Iran.
authors.forename: Abbas
authors.initials: A
authors.lastname: Shokri
authors.affiliation: 2 Department of Orthodontics, Faculty of Dentistry, Dental Research Center, Hamadan University of Medical Sciences, Hamadan, Islamic Republic of Iran.
authors.forename: Amirfarhang
authors.initials: A
authors.lastname: Miresmaeili
authors.affiliation: 2 Department of Orthodontics, Faculty of Dentistry, Dental Research Center, Hamadan University of Medical Sciences, Hamadan, Islamic Republic of Iran.
authors.forename: Nasrin
authors.initials: N
authors.lastname: Farhadian
authors.affiliation: 3 Department of Oral and Maxillofacial Radiology, Faculty of Dentistry, Kermanshah University of Medical Sciences, Kermanshah, Islamic Republic of Iran.
authors.forename: Sepideh
authors.initials: S
authors.lastname: Falah-Kooshki
authors.affiliation: 4 Department of Epidemiology and Reproductive Health, Reproductive Epidemiology Research Center, Royan Institute for Reproductive Biomedicine, ACECR, Tehran, Islamic Republic of Iran.
authors.forename: Payam
authors.initials: P
authors.lastname: Amini
authors.affiliation: 5 Department of Orthodontics, Faculty of Dentistry, Rafsanjan University of Medical Sciences, Rafsanjan, Islamic Republic of Iran.
authors.forename: Najmeh
authors.initials: N
authors.lastname: Mollaie
mesh_terms: D059925:Anatomic Landmarks; D002508:Cephalometry / Q000379:methods*; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D006801:Humans; D066298:In Vitro Techniques; D056888:Patient Positioning / Q000379:methods*; D012886:Skull / Q000000981:diagnostic imaging*
keywords: CBCT; cephalometry