title: Reliability and reproducibility of landmarks on three-dimensional soft-tissue cephalometrics using different placement methods.
abstract: BACKGROUND
  Affixing markers on the face in vivo with an optical surface imaging system and placing landmarks on a computed tomographic reconstructive facial model represent two helpful approaches prevailing in three-dimensional cephalometric analysis of facial aesthetics. In this study, the authors determine the suitability of these methods for soft-tissue evaluation along with the reproducibility and reliability of landmark placement.
  
  
  METHODS
  Thirty-seven soft-tissue landmarks were investigated in 35 normal healthy volunteers who underwent cephalometric analysis by direct and indirect placement methods. Two operators performed the analysis twice for each method at a 1-week interval. Landmark positions were measured on the three-dimensional coordinates, and data were standardized and converted into landmark placement errors for the estimation, by two-way random intraclass correlation coefficients.
  
  
  RESULTS
  Using the direct method, 86.5 percent of the landmarks had a higher intraclass correlation coefficient than 0.75, and 67.6 percent were higher than 0.90. The authors found that 75.7 percent were higher than 0.75 and 43.2 percent were higher than 0.90 with the indirect method. Both methods showed good reliability in identifying midline-related structures, although the correlations of markers surrounding eyelashes and lips were better using the direct method. The direct method had a significantly smaller landmark placement error and better reproducibility than that identified indirectly (p<0.05).
  
  
  CONCLUSIONS
  When evaluating well-defined contours and the natural texture of the face, the direct placement method shows better accuracy than the indirect method. The three-dimensional evaluation emphasizes the eye, lip, and some structures more laterally, therefore providing comprehensive analysis for clinical diagnosis.
  
  
  METHODS
  Diagnostic, II.
authors.affiliation: Guangdong, People's Republic of China; and Cleveland, Ohio From the Department of Orthodontics, Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Stomatology; and Case Western Reserve University.
authors.forename: Han
authors.initials: H
authors.lastname: Lin
authors.forename: Ping
authors.initials: P
authors.lastname: Zhu
authors.forename: Yi
authors.initials: Y
authors.lastname: Lin
authors.forename: Yuxi
authors.initials: Y
authors.lastname: Zheng
authors.forename: Yue
authors.initials: Y
authors.lastname: Xu
mesh_terms: D002508:Cephalometry / Q000379:methods*; D005145:Face / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D015203:Reproducibility of Results; D055815:Young Adult