title: Reducing cone beam CT scan height as a method of radiation reduction for photorealistic three-dimensional orthognathic planning.
abstract: OBJECTIVE
  To determine the superimposition accuracy of full-face stereophotographic images with 22 cm and 13 cm cone beam computed tomography (CBCT) scans.
  
  
  METHODS
  22 cm CBCT scans and corresponding stereophotographic images (3 dMD) for 30 subjects requiring orthognathic surgery were randomly selected. A 13 cm CBCT scan was generated from the 22 cm scan for each subject. All scans and images were converted into STL format. For each subject, the 22 cm and 13 cm CBCT scans were imported into CAD/CAM software and each superimposed with the corresponding 3 dMD image. A one-sample t-test was used to test the null hypothesis that the difference in the 90th percentile of the mean absolute distance between the two 3dMD images when aligned on the 22 cm and the 13 cm CBCT scans was not clinically significant (<0.5 mm).
  
  
  RESULTS
  The 90th percentile of the mean absolute distance between the two 3 dMD surfaces using the 22 cm and 13 cm CBCT scans was significantly less than 0.5 mm (p < 0.001; 0.2 ± 0.2 mm; 95% CI, 0.16-0.30 mm).
  
  
  CONCLUSIONS
  There is no difference in the accuracy of superimposition of a stereophotogrammetry image with a 22 cm CBCT scan or a 13 cm CBCT scan. It should now be possible to use a 13 cm CBCT scan and a full-face stereophotogrammetry image during 3D orthognathic planning to reduce radiation exposure.
authors.affiliation: Paediatric Dentistry and Orthodontics, Faculty of Dentistry, The University of Hong Kong, Hong Kong.
authors.forename: Cze-Yin
authors.initials: CY
authors.lastname: Lin
authors.affiliation: Discipline of Oral and Maxillofacial Surgery, Faculty of Dentistry, The University of Hong Kong, Hong Kong.
authors.forename: Tai-Chiu
authors.initials: TC
authors.lastname: Hsung
authors.affiliation: Paediatric Dentistry and Orthodontics, Faculty of Dentistry, The University of Hong Kong, Hong Kong. Electronic address: bkhambay@hku.hk.
authors.forename: Balvinder
authors.initials: B
authors.lastname: Khambay
mesh_terms: D059925:Anatomic Landmarks / Q000000981:diagnostic imaging; D017076:Computer-Aided Design; D054893:Cone-Beam Computed Tomography / Q000295:instrumentation / Q000706:statistics & numerical data*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000706:statistics & numerical data; D021621:Imaging, Three-Dimensional / Q000706:statistics & numerical data*; D055171:Nasal Cartilages / Q000000981:diagnostic imaging; D009666:Nose / Q000000981:diagnostic imaging; D056948:Orthognathic Surgical Procedures / Q000379:methods*; D010347:Patient Care Planning; D010780:Photogrammetry / Q000706:statistics & numerical data; D011829:Radiation Dosage; D012984:Software; D014584:User-Computer Interface
keywords: 3D planning; Cone beam; Extended field of view; Stereophotogrammetry; Superimposition