Abstract
The metal artifact reduction (MAR) algorithm is used in most CBCT unit to reduce artifact from various dental materials. The performance of MAR program of a CBCT unit according to the dental material type under different imaging mode was evaluated as introducing automatic quantification of the amount of artifact reduced. Four customized phantoms with different dental prostheses (amalgam, gold, porcelain-fused-metal, zirconia) underwent CBCT scanning with and without the MAR option. The imaging was performed under varied scanning conditions; 0.2 and 0.3 mm3 voxel sizes; 70 and 100 kVp. The amount of artifacts reduced by each prosthesis and scanning mode automatically counted using canny edge detection in MATLAB, and statistical analysis was performed. The overall artifact reduction ratio was ranged from 17.3% to 55.4%. The artifact caused by the gold crown was most effectively reduced compared to the other prostheses (p < 0.05, Welch’s ANOVA analysis). MAR showed higher performance in smaller voxel size mode for all prostheses (p < 0.05, independent t-test). Automatic quantification efficiently evaluated MAR performance in CBCT image. The impact of MAR was different according to the prostheses type and imaging mode, suggesting that thoughtful consideration is required when selecting the imaging mode of CBCT.
Highlights
The metal artifact reduction (MAR) algorithm is used in most cone-beam computed tomography (CBCT) unit to reduce artifact from various dental materials
Previous researchers used a method based on gray-level measurements in the region of interest (ROI) of CBCT images to quantitatively evaluate the efficacy of MAR algorithms[16,17,18,19]
Each phantom was equipped with one of four different prostheses in the form used by a dental clinic: (1) dental amalgam restoration (Hg: 50%, Ag: 30%, Sn: 14%, Cu: 8%, 6.8 mm in height) on the right second molar; (2) gold crown (Au: 46%, Pd: 4%, Ag: 37.7%, 7.3 mm in height) on the left first molar; (3) porcelain-fused-metal (PFM) crown made of nickel-chromium ceramic alloy (Ni: 77.9%, Cr: 12.6%, Mo: 5%, Al, Be, Co, 8.1 mm in height) on the first molar; and (4) zirconia crown (ZrO2, 10.4 mm in height) on the left central incisor (Fig. 1)
Summary
The metal artifact reduction (MAR) algorithm is used in most CBCT unit to reduce artifact from various dental materials. The performance of MAR program of a CBCT unit according to the dental material type under different imaging mode was evaluated as introducing automatic quantification of the amount of artifact reduced. These dental prostheses generally consist of materials with a high atomic number The imaging system such as CT or CBCT uses x-ray beam with polychromatic energies and selective attenuation of lower energy photons occurs when the beam passes dental prostheses[4,5]. This phenomenon causes several types of image artifact and one of them, the streaking artifact, appears as dark and bright band across the image and degrades the image quality to the point of being diagnostically unusable. Gray value measurements are not constant between different CBCT machines, unlike CT20,21
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