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Purpose To assess the usefulness of various metal artifact reduction (MAR) methods in patients with hip prostheses. Materials and Methods This retrospective study included 47 consecutive patients who underwent hip arthroplasty and dual-energy CT. Conventional polyenergetic image (CI), orthopedic-MAR (O-MAR), and virtual monoenergetic image (VMI, 50–200 keV) were tested for MAR. Quantitative analysis was performed in seven regions around the prostheses. Qualitative assessments included evaluation of the degree of artifacts and the presence of secondary artifacts. Results The lowest amount of image noise was observed in the O-MAR, followed by the VMI. O-MAR also showed the lowest artifact index, followed by high-keV VMI in the range of 120–200 keV (soft tissue) or 200 keV (bone). O-MAR had the highest contrast-to-noise ratio (CNR) in regions with severe hypodense artifacts, while VMI had the highest CNR in other regions, including the periprosthetic bone. On assessment of the CI of pelvic soft tissues, VMI showed a higher structural similarity than O-MAR. Upon qualitative analysis, metal artifacts were significantly reduced in O-MAR, followed by that in VMI, while secondary artifacts were the most frequently found in the O-MAR (p < 0.001). Conclusion O-MAR is the best technique for severe MAR, but it can generate secondary artifacts. VMI at high keV can be advantageous for evaluating periprosthetic bone. [ABSTRACT FROM AUTHOR]

Purpose To assess the feasibility of spectral detector CT (SDCT) with axial maximum-intensity projection (MIP) reconstruction for the evaluation of lumbar CT discography. Materials and Methods We retrospectively evaluated 44 disc levels from 18 patients who underwent CT discography on a dual-layer SDCT between May 2016 and July 2017. We compared the distribution of contrast material between conventional CT and SDCT-based iodine maps using the Jaccard index (JI) and Dice similarity coefficient (DSC). Qualitative analysis of the post-discogram features was done according to the Dallas discogram description, and changes in reading time and diagnostic confidence were analyzed. Results The intermethod variability between conventional CT and SDCT was good, with a mean DSC of 0.93 and a mean JI of 0.87. The mean sensitivity and positive predictive value of the SDCT-based method were 90% and 96%, respectively. The addition of SDCT-based axial MIP iodine maps increased the diagnostic confidence (p = 0.025) and reduced the reading time in both reviewers (p < 0.001). Conclusion SDCT discography demonstrates the distribution of contrast medium within the disc similarly to conventional CT. Additionally, axial MIP iodine maps using SDCT allow for the fast evaluation of disc pathology with reduced reading time and can increase diagnostic confidence. [ABSTRACT FROM AUTHOR]