title: Cone beam computed tomography registration for 3-D airway analysis based on anatomic landmarks.
abstract: OBJECTIVE
  Explore craniofacial landmarks reliability to superimpose cone beam computed tomography (CBCT) images and assess impact of plane reorientation on airway parameters.
  
  
  METHODS
  10 CBCTs were marked 3 times at baseline, 3 T1, to test landmark reliability. Measurement errors of new coordinate system were tested using 3 T1, and other 10 paired CBCT images, at T1 and T2. Effect on upper airway was assessed using volume, surface area, and point-based analysis.
  
  
  RESULTS
  Tips of nasal bone and clivus and foramina spinosa defined the new coordinate system. Plane reorientation didn't affect landmark identification reliability and significantly reduced interlandmark distances from T1-T2. Airway volume changed by 25.76 ± 24.9%, surface area by 13.85 ± 10.8%, and mean part analysis was 0.43 ± 0.3 mm. Strong correlation (R(2) > 65%) was found between airway analysis and large distances in second and third cervical vertebrae.
  
  
  CONCLUSIONS
  Coordinate transformation significantly reduced measurement errors in longitudinal CBCT data; however, it is not designed to correct for large neck flexion.
authors.affiliation: Department of Dentistry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada. Electronic address: Alsufyan@ualberta.ca.
authors.forename: Noura A
authors.initials: NA
authors.lastname: Alsufyani
authors.affiliation: Mechanical Engineering, Faculty of Engineering, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Nicholas H
authors.initials: NH
authors.lastname: Dietrich
authors.affiliation: Orthodontic Graduate Program, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Manuel O
authors.initials: MO
authors.lastname: Lagravère
authors.affiliation: Mechanical Engineering, Faculty of Engineering, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Jason P
authors.initials: JP
authors.lastname: Carey
authors.affiliation: Department of Dentistry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada.
authors.forename: Paul W
authors.initials: PW
authors.lastname: Major
mesh_terms: D000293:Adolescent; D059925:Anatomic Landmarks / Q000000981:diagnostic imaging*; D054893:Cone-Beam Computed Tomography; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D007830:Larynx / Q000000981:diagnostic imaging*; D008297:Male; D056888:Patient Positioning; D010614:Pharynx / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results; D012189:Retrospective Studies