Optimization of Monoenergetic Extrapolations in Dual-Energy CT for Metal Artifact Reduction in Different Body Regions and Orthopedic Implants.

RATIONALE AND OBJECTIVES: To define an optimal monoenergetic extrapolation (ME) in dual-energy computed tomography (DECT) for metal artifact reduction (MAR) including different body regions and orthopedic implants.

MATERIAL AND METHODS: DECT scans were acquired with dual-source CT (SOMATOM Force, Siemens, Germany) at tube voltage A 80-100 kV/B Sn150 kV from 39 patients (mean 54.1 ± 20.7 years, 23 male vs. 16 female) with orthopedic implants ranging from wires to joint implants. Scans were assembled in four groups based on scan regions and volume. Single- and weighted-energy images at a ratio of 0.3 and MEs at 100, 130, 160, and 190 keV were produced using vendor-specific postprocessing software (Syngo.Via, Siemens, Germany). Artifact degree was assessed quantitatively by metal-induced Hounsfield unit changes in relation to reference tissues. Visibility of screw-bone interface, hardware integrity, adjacent bone, and soft tissues were visually rated on a four-point Likert scale (0, none; 3, strong artifacts with nondiagnostic quality). Optimal energy was visually determined by side-by-side comparisons. Artifact degree was statistically compared between regions and energies.

RESULTS: Metal-induced attenuation changes were most severe in large scan volume groups for all energies. Reference tissue attenuation outside metal artifacts was not affected by ME (p = 0.57). Independent of region, ME at 130-190 keV quantitatively performed significantly better for MAR than the remainder. ME 130 keV showed the highest frequency (54%) in optimal energy ratings based on qualitative image criteria.

CONCLUSION: DECT significantly reduces image artifacts in patients with orthopedic hardware and prospective choice of ME at 130 keV may suit best for optimal MAR, independent of region or implant.