title: Landmark identification errors on cone-beam computed tomography-derived cephalograms and conventional digital cephalograms.
abstract: BACKGROUND
  In this study, we investigated the landmark identification errors on cone-beam computed tomography (CBCT)-derived cephalograms and conventional digital cephalograms.
  
  
  METHODS
  Twenty patients who had both a CBCT-derived cephalogram and a conventional digital cephalogram were recruited. Twenty commonly used lateral cephalometric landmarks and 2 fiducial points were identified on each cephalogram by 11 observers at 2 time points. The mean positions of the landmarks identified by all observers were used as the best estimate to calculate the landmark identification errors. In addition to univariate analysis, regression analysis of landmark identification errors was conducted for identifying the predicting variables of the observed landmark identification errors. To properly handle the multilayer correlations among the clustered observations, a marginal multiple linear regression model was fitted to our correlated data by using the well-known generalized estimating equations method. In addition to image modality, many variables potentially affecting landmark identification errors were considered, including location and characteristics of the landmark, seniority of the observer, and patient information (sex, age, metallic dental restorations, and facial asymmetry).
  
  
  RESULTS
  Image modality was not the significant variable in the final generalized estimating equations model. The regression coefficient estimates of the significant landmarks for the overall identification error ranged from -0.99 (Or) to 1.42 mm (Ba). The difficulty of identifying landmarks on structural images with multiple overlapping--eg, Or, U1R, L1R, Po, Ba, UMo, and LMo--increased the identification error by 1.17 mm. In the CBCT modality, the identification errors significantly decreased at Ba (-0.76 mm).
  
  
  CONCLUSIONS
  The overall landmark identification errors on CBCT-derived cephalograms were comparable to those on conventional digital cephalograms, and Ba was more reliable on CBCT-derived cephalograms.
authors: Department of Dentistry, National Taiwan University Hospital, Taipei, Taiwan.
authors: Zwei-Chieng
authors: ZC
authors: Chang
authors: Fu-Chang
authors: FC
authors: Hu
authors: Eddie
authors: E
authors: Lai
authors: Chung-Chen
authors: CC
authors: Yao
authors: Mu-Hsiung
authors: MH
authors: Chen
authors: Yi-Jane
authors: YJ
authors: Chen
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D059925:Anatomic Landmarks; D002508:Cephalometry / Q000379:methods*; D054893:Cone-Beam Computed Tomography; D003951:Diagnostic Errors; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D055361:Multilevel Analysis; D019252:Radiography, Dental, Digital; D018709:Statistics, Nonparametric; D055815:Young Adult