title: Modified method of recording and reproducing natural head position with a multicamera system and a laser level.
abstract: BACKGROUND
  As computer-assisted surgical design becomes increasingly popular in maxillofacial surgery, recording patients' natural head position (NHP) and reproducing it in the virtual environment are vital for preoperative design and postoperative evaluation. Our objective was to test the repeatability and accuracy of recording NHP using a multicamera system and a laser level.
  
  
  METHODS
  A laser level was used to project a horizontal reference line on a physical model, and a 3-dimensional image was obtained using a multicamera system. In surgical simulation software, the recorded NHP was reproduced in the virtual head position by registering the coordinate axes with the horizontal reference on both the frontal and lateral views. The repeatability and accuracy of the method were assessed using a gyroscopic procedure as the gold standard.
  
  
  RESULTS
  The interclass correlation coefficients for pitch and roll were 0.982 (0.966, 0.991) and 0.995 (0.992, 0.998), respectively, indicating a high degree of repeatability. Regarding accuracy, the lack of agreement in orientation between the new method and the gold standard was within the ranges for pitch (-0.69°, 1.71°) and for roll (-0.92°, 1.20°); these have no clinical significance.
  
  
  CONCLUSIONS
  This method of recording and reproducing NHP with a multicamera system and a laser level is repeatable, accurate, and clinically feasible.
authors.affiliation: Doctor, Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, Beijing, China.
authors.forename: Xiao-jing
authors.initials: XJ
authors.lastname: Liu
authors.affiliation: PhD student, Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, Beijing, China.
authors.forename: Qian-qian
authors.initials: QQ
authors.lastname: Li
authors.affiliation: PhD student, Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Md.
authors.forename: Yuan-jie
authors.initials: YJ
authors.lastname: Pang
authors.affiliation: PhD student, Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, Beijing, China.
authors.forename: Kai-yue
authors.initials: KY
authors.lastname: Tian
authors.affiliation: PhD student, School of Public Health, Peking University Health Science Center, Beijing, China.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Xie
authors.affiliation: Professor, Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, Beijing, China. Electronic address: kqlzl@sina.com.
authors.forename: Zi-li
authors.initials: ZL
authors.lastname: Li
mesh_terms: D003198:Computer Simulation; D054893:Cone-Beam Computed Tomography / Q000706:statistics & numerical data; D005240:Feasibility Studies; D057918:Fiducial Markers; D006257:Head / Q000033:anatomy & histology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000706:statistics & numerical data; D021621:Imaging, Three-Dimensional / Q000706:statistics & numerical data; D007834:Lasers; D019047:Phantoms, Imaging; D010780:Photogrammetry / Q000706:statistics & numerical data; D010781:Photography / Q000295:instrumentation / Q000706:statistics & numerical data*; D011187:Posture; D015203:Reproducibility of Results; D014584:User-Computer Interface