Fig 1.
Field-of-view (yellow box) and imaging plane (green box) on lateral scout images of conventional (A) and open mouth (B) computed tomography.
Table 1.
Definition of visual scores.
Fig 2.
Box-and-whisker plots of the quantified noise level according to the anatomical structures and Computed Tomography (CT) protocols.
The bottom and top of box are the first and third quartiles, the horizontal line represents the median value, and the vertical line represents the difference between the maximum and minimum values. Statistically significant differences with P values less than 0.008 are presented in the figure. CTc = conventional CT; CTc_O = conventional CT with O-MAR processing; CTo = open mouth CT; CTo_O = open mouth CT with O-MAR processing; O-MAR = metal artifact reduction for orthopedic implants.
Table 2.
Quantitative noise measurement.
Fig 3.
Box graphs of the mean values of the visual scores according to the anatomical structures and Computed Tomography (CT) protocols.
The mean values of the 4-point visual scores assessing the degree of streak artifacts are shown in orange box, and the mean values of the 5-point visual scores assessing the overall subjective image quality are shown in the blue box. Statistically significant differences with P values less than 0.008 are presented in the figure. CTc = conventional CT; CTc_O = conventional CT with O-MAR processing; CTo = open mouth CT; CTo_O = open mouth CT with O-MAR processing; O-MAR = metal artifact reduction for orthopedic implants.
Table 3.
Intraclass correlation coefficient for visual scores between two readers.
Table 4.
Qualitative visual scores.
Fig 4.
Post-contrast Computed Tomography (CT) images of a 56-year-old woman with a dental prosthesis.
On the conventional CT image, the mobile tongue is barely seen due to the metallic artifact (A). However, the structure is clearly seen on the open mouth CT image (B), without overlapping dental prosthesis in the same imaging plane. (C) The additional application of O-MAR to conventional CT shows a substantial decrease in the extent of streak artifacts, but there are still remaining streaks. (D) On open mouth CT images with O-MAR processing, the added effect of O-MAR is not noticeable, since the streak artifact is already displaced from the open mouth maneuver. O-MAR = metal artifact reduction for orthopedic implants.
Fig 5.
Post-contrast Computed Tomography (CT) images of a 71-year-old woman with a dental prosthesis.
Bilateral palatine tonsils are completely covered by the metallic artifact from the adjacent dental prosthesis on a conventional CT image (A). However, on the open mouth CT image (B), there is no streak artifact obscuring the bilateral palatine tonsils, because the axis of the streak artifact from the dental prosthesis is tilted. On a conventional CT image with O-MAR processing (C), the bilateral palatine tonsils are partly seen with decreased artifacts, but the image texture becomes blurry. The added effect of O-MAR is not noticeable on the open mouth CT image with O-MAR processing (D) since the streak artifact is already displaced from the open mouth maneuver. O-MAR = metal artifact reduction for orthopedic implants.
Fig 6.
Post-contrast Computed Tomography (CT) images of a 51-year-old woman with a dental prosthesis.
On a conventional CT image with the mouth closed (A) and on the conventional CT image with O-MAR processing (B), the mouth floor with extrinsic tongue muscles are well visualized without any artifacts. Contrarily, the structure is degraded by the metallic artifact from the lower molar prosthesis on the open mouth CT image (C). The streak artifact remains substantial even on the open mouth CT image with O-MAR processing (D). O-MAR = metal artifact reduction for orthopedic implants.