Kyung-Yen Nahm1, Yong Kim2, Yong-Suk Choi3, Jeongjin Lee4, Seong-Hun Kim5, Gerald Nelson6. 1. Postgraduate student, Department of Orthodontics, School of Dentistry, Kyung Hee University, Seoul, Korea. 2. Research assistant, Department of Orthodontics, School of Dentistry, Kyung Hee University, Seoul, Korea. 3. Associate professor and chairman, Department of Oral and Maxillofacial Radiology, School of Dentistry, Kyung Hee University, Seoul, Korea. 4. Professor, School of Computer Science & Engineering, Soongsil University, Seoul, Korea. 5. Associate professor and chairman, Department of Orthodontics, School of Dentistry, Kyung Hee University, Seoul, Korea. Electronic address: bravortho@khu.ac.kr. 6. Clinical professor and interim chair, Division of Orthodontics, Department of Orofacial Science, University of California, San Francisco, Calif.
Abstract
INTRODUCTION: 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.
INTRODUCTION: 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.