title: Recording of natural head position using stereophotogrammetry: a new technique and reliability study.
abstract: The purpose of this study was to develop a technique to record physical references and orient digital mesh models to a natural head position using stereophotogrammetry (SP). The first step was to record the digital mesh model of a hanging reference board placed at the capturing position of the SP machine. The board was aligned to true vertical using a plumb bob. It also was aligned with a laser plane parallel to a hanging mirror, which was located at the center of the machine. The parameter derived from the digital mesh model of the board was used to adjust the roll, pitch, and yaw of the subsequent captures of patients' facial images. This information was valid until the next machine calibration. The board placement was repeatable, with standard deviations less than 0.1° for pitch and yaw angles and 0.15° for roll angles.
authors.affiliation: Postdoctoral Fellow, Discipline of Oral and Maxillofacial Surgery, Faculty of Dentistry, The University of Hong Kong, Hong Kong, China.
authors.forename: Tai-Chiu
authors.initials: TC
authors.lastname: Hsung
authors.affiliation: Clinical Assistant Professor, Discipline of Oral and Maxillofacial Surgery, Faculty of Dentistry, The University of Hong Kong, Hong Kong, China. Electronic address: drjohnlo@hku.hk.
authors.forename: John
authors.initials: J
authors.lastname: Lo
authors.affiliation: Resident, Discipline of Oral and Maxillofacial Surgery, Faculty of Dentistry, The University of Hong Kong, Hong Kong, China.
authors.forename: Tik-Shun
authors.initials: TS
authors.lastname: Li
authors.affiliation: Chair and Professor, Discipline of Oral and Maxillofacial Surgery, Faculty of Dentistry, The University of Hong Kong, Hong Kong, China.
authors.forename: Lim-Kwong
authors.initials: LK
authors.lastname: Cheung
mesh_terms: D006257:Head; D006801:Humans; D021621:Imaging, Three-Dimensional; D056888:Patient Positioning; D010780:Photogrammetry / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results