Accurate registration of cone-beam computed tomography scans to 3-dimensional facial photographs.
BACKGROUND
Registering a 3-dimensional (3D) facial surface scan to a cone-beam computed tomography (CBCT) scan has various advantages. One major advantage is to compensate for the inaccuracy of the CBCT surface data. However, when registering CBCT and 3D facial scans, changes in facial expression, spatial soft-tissue changes, and differences in the patient's positioning can decrease the accuracy of the registration. In this study, we introduce a new 3D facial scanner that is combined with a CBCT apparatus. Our goal was to evaluate the registration accuracy of CBCT and 3D facial scans, which were taken with the shortest possible time between them.


METHODS
The experiment was performed with 4 subjects. Each patient was instructed to hold as still as possible while the CBCT scan was taken, followed immediately by the 3D facial surface scan. The images were automatically registered with software. The accuracy was measured by determining the degree of agreement between the soft-tissue surfaces of the CBCT and the 3D facial images.


RESULTS
The average surface discrepancy between the CBCT facial surface and 3D facial surface was 0.60 mm (SD, 0.12 mm). Registration accuracy was also visually verified by toggling between the images of the CBCT and 3D facial surface scans while rotating the registered images.


CONCLUSIONS
Registration of consecutively taken CBCT and 3D facial images resulted in reliable accuracy.
Postgraduate student, Department of Orthodontics, School of Dentistry, Kyung Hee University, Seoul, Korea.
Kyung-Yen
KY
Nahm
Research assistant, Department of Orthodontics, School of Dentistry, Kyung Hee University, Seoul, Korea.
Yong
Y
Kim
Associate professor and chairman, Department of Oral and Maxillofacial Radiology, School of Dentistry, Kyung Hee University, Seoul, Korea.
Yong-Suk
YS
Choi
Professor, School of Computer Science & Engineering, Soongsil University, Seoul, Korea.
Jeongjin
J
Lee
Associate professor and chairman, Department of Orthodontics, School of Dentistry, Kyung Hee University, Seoul, Korea. Electronic address: bravortho@khu.ac.kr.
Seong-Hun
SH
Kim
Clinical professor and interim chair, Division of Orthodontics, Department of Orofacial Science, University of California, San Francisco, Calif.
Gerald
G
Nelson
D054893:Cone-Beam Computed Tomography / Q000706:statistics & numerical data*; D005145:Face / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D005147:Facial Bones / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D005149:Facial Expression; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000706:statistics & numerical data*; D021621:Imaging, Three-Dimensional / Q000706:statistics & numerical data*; D008297:Male; D061848:Optical Imaging / Q000706:statistics & numerical data; D010781:Photography / Q000706:statistics & numerical data*; D011187:Posture; D015203:Reproducibility of Results; D012984:Software