Single energy metal artifact reduction performs better than virtual monoenergetic dual-energy reconstruction in CT of the equine proximal phalanx

Josephine E Faulkner, Bart J G Broeckx, Ann Martens, Els Raes, Hanna Haardt, Katrien Vanderperren

Background: The page is an article from the journal Veterinary Radiology & Ultrasound, published in July 2023. It reports on a study that evaluated the use of single energy metal artifact reduction (SEMAR) and virtual monoenergetic (VM) dual-energy CT (DECT) for reducing metal artifacts from stainless steel screws in the equine proximal phalanx.

Study: The study was a prospective experimental study that used 18 cadaver limbs from six horses, with two screws surgically inserted in each limb. The limbs were scanned with seven different CT acquisition types: Helical +SEMAR, Volume +SEMAR, Standard Helical, Standard Volume, and VM DECT at 135, 120, and 105 keV. The images were subjectively and objectively evaluated for the severity and diagnostic impact of metal artifacts by three reviewers.

Methods: The subjective evaluation used a five-point Likert scale and a seven-point ranking scale for the adjacent and distant tissues, as well as the overall preference for clinical use. The objective evaluation measured the width of the hyperattenuating region associated with the screws to assess the blooming artifact. Statistical analysis was performed using linear mixed models and post hoc comparisons.

Results: The results showed that SEMAR performed the best at reducing metal artifacts, followed by VM DECT. However, VM DECT performance varied with energy level and was associated with decreased image quality in distant tissues and artifactual overcorrection of metal artifacts at high energy levels. The Standard Helical and Standard Volume acquisitions had the worst metal artifacts. There were significant differences between the reviewers and the planes of measurement for the subjective and objective evaluations, respectively.

Limitations: The limitations of the study included the use of only one type of surgical implant, the variability of performance between different CT systems and algorithms, the lack of evaluation of soft tissue kernel reconstructions, and the challenges of positioning large animals within the CT bore.

Conclusions: The study concluded that SEMAR and VM DECT can be used in the equine distal limb for reducing metal artifacts, with SEMAR being the preferred method. VM DECT should be used with caution and at an optimal energy level of 120 keV. Further research is needed to determine the efficacy of these techniques in soft tissues and in other types of metal implants.

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