Metal Artifact Reduction in Dental CBCT Images Using Direct Sinogram Correction Combined with Metal Path-Length Weighting

Abstract

Metal artifacts in dental computed tomography (CT) images, caused by highly X-ray absorbing objects, such as dental implants or crowns, often more severely compromise image readability than in medical CT images. Since lower tube voltages are used for dental CTs in spite of the more frequent presence of metallic objects in the patient, metal artifacts appear more severely in dental CT images, and the artifacts often persist even after metal artifact correction. The direct sinogram correction (DSC) method, which directly corrects the sinogram using the mapping function derived by minimizing the sinogram inconsistency, works well in the case of mild metal artifacts, but it often fails to correct severe metal artifacts. We propose a modified DSC method to reduce severe metal artifacts, and we have tested it on human dental images. We first segment the metallic objects in the CT image, and then we forward-project the segmented metal mask to identify the metal traces in the projection data with computing the metal path length for the rays penetrating the metal mask. In the sinogram correction with the DSC mapping function, we apply the weighting proportional to the metal path length. We have applied the proposed method to the phantom and patient images taken at the X-ray tube voltage of 90 kVp. We observed that the proposed method outperforms the original DSC method when metal artifacts were severe. However, we need further extensive studies to verify the proposed method for various CT scan conditions with many more patient images.

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.…”

“…To reduce the cupping artifacts caused by the X-ray beam hardening in dental cast imaging, we have developed a combined algorithm that simultaneously corrects both scatter and beam-hardening artifacts. We initiate the process by applying the DSC algorithm used in our previous work [ 35 ] to the raw projection data. …”

“…We have developed a new method that can effectively reduce both scatter and beam-hardening artifacts. We have modified the model-based scatter correction method proposed by Ohnesorge et al and integrated it with the beam-hardening correction method [ 35 ] to minimize both artifacts in the CT images of plaster dental casts. We have also investigated the effects of artifact correction on the accuracy of the 3D digital models by comparing them with the optical scan-based 3D models.…”

Performance of different cone-beam computed tomography scan modes with and without metal artifact reduction in detection of recurrent dental caries under various restorative materials

“…Radiologists should consider the trade-off between reducing metal artifacts and maintaining image sharpness when selecting MAR algorithms. In some cases, it may be necessary to selectively apply MAR to specific regions of interest rather than the entire image [30][31][32].…”

Nonconvex weighted variational metal artifacts removal via convergent primal-dual algorithms

“…One effective approach is to modify the model by incorporating imaging physics [3][4][5][6][7]. This methodology can mitigate artifacts whilst preserving boundaries and specifics.…”