Metal Artifact Reduction in Virtual Monoenergetic Spectral Dual-Energy CT of Patients With Metallic Orthopedic Implants in the Distal Radius

Abstract

OBJECTIVE. The purpose of this study was to evaluate the image quality of virtual monoenergetic images obtained from dual-layer-detector spectral CT of patients with metallic orthopedic implants of the distal radius. MATERIALS AND METHODS. A retrospective analysis was performed between April 2016 and January 2017. Forty-three consecutively registered patients (33 women, 10 men; mean age, 50.7 +/- 15.4 years) with metallic implants for distal radius fractures underwent dual-layer-detector spectral CT. Sixteen virtual monoenergetic image sets ranging from 50 to 200 keV were generated from the single slice with the most pronounced low-attenuation artifact from implants. Image quality was quantitatively assessed on the basis of the attenuation of the artifacts and reference tissue, background image noise, and artifact index. Qualitative assessment included degree of artifact, diagnostic image quality of the periimplant bones, and delineation of fracture lines. The Friedman rank sum test and kappa analysis were used for statistical analysis. RESULTS. There were statistically significant differences in quantitative and qualitative parameters at different monoenergy levels (all p < 0.001). Artifact index was the lowest at 120 keV. Low-attenuation artifacts in the periimplant regions were least pronounced at 110 keV, and the diagnostic image quality of periimplant bone was best at 130 keV. Fracture lines were well delineated in all cases at 80-110 keV (p < 0.001). CONCLUSION. The optimal energy setting for incurring the fewest metallic artifacts and obtaining the best diagnostic image quality from distal radius implants during dual-layer-detector spectral CT is the range of 110-130 keV.