Cone-Beam Angle Dependency of 3D Models Computed from Cone-Beam CT Images

Abstract

Cone-beam dental CT can provide high-precision 3D images of the teeth and surrounding bones. From the 3D CT images, 3D models, also called digital impressions, can be computed for CAD/CAM-based fabrication of dental restorations or orthodontic devices. However, the cone-beam angle-dependent artifacts, mostly caused by the incompleteness of the projection data acquired in the circular cone-beam scan geometry, can induce significant errors in the 3D models. Using a micro-CT, we acquired CT projection data of plaster cast models at several different cone-beam angles, and we investigated the dependency of the model errors on the cone-beam angle in comparison with the reference models obtained from the optical scanning of the plaster models. For the 3D CT image reconstruction, we used the conventional Feldkamp algorithm and the combined half-scan image reconstruction algorithm to investigate the dependency of the model errors on the image reconstruction algorithm. We analyzed the mean of positive deviations and the mean of negative deviations of the surface points on the CT-image-derived 3D models from the reference model, and we compared them between the two image reconstruction algorithms. It has been found that the model error increases as the cone-beam angle increases in both algorithms. However, the model errors are smaller in the combined half-scan image reconstruction when the cone-beam angle is as large as 10 degrees.

Smartphone-Based Facial Scanning as a Viable Tool for Facially Driven Orthodontics?

“…However, the cone-beam angle-dependent artifacts, mostly caused by the incompleteness of the projection data acquired in the circular cone-beam scan geometry, can induce significant errors in the 3D models." [40]. Even research of Pojda et al 2021 confirms necessity of cheaper and more convenient alternatives to orthodontic facial 3D imaging [41].…”

3D Digital Modeling of Dental Casts from Their 3D CT Images with Scatter and Beam-Hardening Correction

“…However, we need further studies to compare digital models directly derived from CBCT scans or intraoral optical scans of patients without taking physical impressions. In a CT scan of a patient without a dental cast, other types of artifacts stemming from projection data truncation [ 36 ], wide cone beam angle [ 7 ], limited scan angle in a half scan [ 37 ], metal artifacts [ 35 , 38 ], and motion artifacts [ 39 ] should be addressed.…”

“…The virtual models can be adjusted digitally to simulate different treatment options or to fabricate custom-made aligners or crowns [ 6 ]. However, there are some challenges associated with CT scanning of dental casts, such as scatter and beam-hardening artifacts [ 7 ]. These artifacts can significantly degrade the accuracy of the resulting 3D models [ 8 ].…”

Smartphone-Based Facial Scanning as a Viable Tool for Facially Driven Orthodontics?

“…According to the recent study of Cho et al, 2022, “From the 3D CT images, 3D models, also called digital impressions, can be computed for CAD/CAM-based fabrication of dental restorations or orthodontic devices. However, the cone-beam angle-dependent artifacts, mostly caused by the incompleteness of the projection data acquired in the circular cone-beam scan geometry, can induce significant errors in the 3D models.” [ 50 ]. Even research of Pojda et al, 2021, confirms the necessity of cheaper and more convenient alternatives to orthodontic facial 3D imaging [ 51 ].…”