title: A new method to orient 3-dimensional computed tomography models to the natural head position: a clinical feasibility study.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the clinical feasibility of a new method to orient 3-dimensional (3D) computed tomography models to the natural head position (NHP). This method uses a small and inexpensive digital orientation device to record NHP in 3 dimensions. This device consists of a digital orientation sensor attached to the patient via a facebow and an individualized bite jig. The study was designed to answer 2 questions: 1) whether the weight of the new device can negatively influence the NHP and 2) whether the new method is as accurate as the gold standard.
  
  
  METHODS
  Fifteen patients with craniomaxillofacial deformities were included in the study. Each patient's NHP is recorded 3 times. The first NHP was recorded with a laser scanning method without the presence of the digital orientation device. The second NHP was recorded with the digital orientation device. Simultaneously, the third NHP was also recorded with the laser scanning method. Each recorded NHP measurement was then transferred to the patient's 3D computed tomography facial model, resulting in 3 different orientations for each patient: the orientation generated via the laser scanning method without the presence of the digital orientation sensor and facebow (orientation 1), the orientation generated by use of the laser scanning method with the presence of the digital orientation sensor and facebow (orientation 2), and the orientation generated with the digital orientation device (orientation 3). Comparisons are then made between orientations 1 and 2 and between orientations 2 and 3, respectively. Statistical analyses are performed.
  
  
  RESULTS
  The results show that in each pair, the difference (Δ) between the 2 measurements is not statistically significantly different from 0°. In addition, in the first pair, the Bland-Altman lower and upper limits of the Δ between the 2 measurements are within 1.5° in pitch and within a subdegree in roll and yaw. In the second pair, the limits of the Δ in all 3 dimensions are within 0.5°.
  
  
  CONCLUSIONS
  Our technique can accurately record NHP in 3 dimensions and precisely transfer it to a 3D model. In addition, the extra weight of the digital orientation sensor and facebow has minimal influence on the self-balanced NHP establishment.
authors.affiliation: Department of Oral and Maxillofacial Surgery, The Methodist Hospital Research Institute, Houston, TX, USA. jxia@tmhs.org
authors.forename: James J
authors.initials: JJ
authors.lastname: Xia
authors.forename: J Kevin
authors.initials: JK
authors.lastname: McGrory
authors.forename: Jaime
authors.initials: J
authors.lastname: Gateno
authors.forename: John F
authors.initials: JF
authors.lastname: Teichgraeber
authors.forename: Brian C
authors.initials: BC
authors.lastname: Dawson
authors.forename: Kathleen A
authors.initials: KA
authors.lastname: Kennedy
authors.forename: Robert E
authors.initials: RE
authors.lastname: Lasky
authors.forename: Jeryl D
authors.initials: JD
authors.lastname: English
authors.forename: Chung H
authors.initials: CH
authors.lastname: Kau
authors.forename: Kathleen R
authors.initials: KR
authors.lastname: McGrory
mesh_terms: D000704:Analysis of Variance; D016302:Centric Relation; D002508:Cephalometry / Q000295:instrumentation*; D003627:Data Interpretation, Statistical; D004867:Equipment Design; D005240:Feasibility Studies; D006257:Head / Q000000981:diagnostic imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007834:Lasers; D019767:Maxillofacial Abnormalities / Q000000981:diagnostic imaging*; D008953:Models, Anatomic; D056888:Patient Positioning / Q000295:instrumentation*; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*