J Korean Assoc Oral Maxillofac Surg 2017; 43(4): 256~261
Recording natural head position using an accelerometer and reconstruction from computed tomographic images
Il Kyung Park1,3, Keun Young Lee2, Yeong Kon Jeong1,3, Rae Hyong Kim3, Dae Gun Kwon3, Sunghee Yeon3, Kyung-Hwan Kwon1
Departments of 1Oral and Maxillofacial Surgery and 2Orthodontics, College of Dentistry, Wonkwang University, 3College of Dentistry, Graduate School, Wonkwang University, Iksan, Korea
Kyung-Hwan Kwon
Department of Oral and Maxillofacial Surgery, Wonkwang University Dental Hospital, College of Dentistry, Wonkwang University, 895 Muwangro, Iksan 54538, Korea
TEL: +82-63-859-2921 FAX: +82-63-857-4002 E-mail: kkhoms@hanmail.net ORCID: http://orcid.org/0000-0002-5257-8440
Received June 7, 2017; Revised July 17, 2017; Accepted July 19, 2017.; Published online August 31, 2017.
© Korean Association of Oral and Maxillofacial Surgeons. All rights reserved.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Objectives: The concept of natural head position (NHP) was first introduced by Broca in 1862, and was described as a person’s stable physiologic position “when a man is standing and his visual axis is horizontal.” NHP has been used routinely for clinical examination; however, a patient’s head position is random during cone-beam computed tomography (CBCT) acquisition. To solve this problem, we developed an accelerometer to record patients’ NHP and reproduce them for CBCT images. In this study, we also tested the accuracy and reproducibility of our accelerometer.
Materials and Methods: A total of 15 subjects participated in this study. We invented an accelerometer that measured acceleration on three axes and that could record roll and pitch calculations. Recorded roll and pitch data for each NHP were applied to a reoriented virtual image using three-dimensional (3D) imaging software. The data between the 3D models and the clinical photos were statistically analyzed side by side. Paired t-tests were used to statistically analyze the measurements.
Results: The average difference in the angles between the clinical photograph and the 3D model was 0.04° for roll and 0.29° for pitch. The paired t-tests for the roll data (P=0.781) and the pitch data (P=0.169) showed no significant difference between the clinical photographs and the 3D model (P>0.05).
Conclusion: By overcoming the limitations of previous NHP-recording techniques, our new method can accurately record patient NHP in a time-efficient manner. Our method can also accurately transfer the NHP to a 3D virtual model.
Keywords: Surgical diagnostic techniques, Cone-beam computed tomography, Three-dimensional imaging

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31 December 2017
Vol. 43
No. 6 pp. 361~428

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