Accurate registration of cone-beam computed tomography scans to 3-dimensional facial photographs.

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.