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

Metal artifacts in CT negatively impact the evaluation of surgical implants and the surrounding tissues. The aim of this prospective experimental study was to evaluate the ability of a single energy metal artifact reduction (SEMAR (TM), Canon) algorithm and virtual monoenergetic (VM) dual-energy CT (DECT) scanning techniques to reduce metal artifacts from stainless steel screws surgically inserted into the equine proximal phalanx. Seven acquisitions of 18 cadaver limbs were performed on a Canon Aquilion One Vision CT scanner (Helical +SEMAR, Volume +SEMAR, Standard Helical, Standard Volume and VM DECT at 135, 120, and 105 keV) and reconstructed in a bone kernel. Blinded subjective evaluation performed by three observers indicated a significant effect of acquisition in both adjacent tissues (P < 0.001) and distant tissues (P < 0.001) and the best metal artifact reduction was seen with Helical +SEMAR and Volume +SEMAR. The subjective overall preference of CT acquisition type was (1) Helical +SEMAR, (2) Volume +SEMAR, (3) VM DECT 135 keV, (4) VM DECT 120 keV, (5) VM DECT 105 keV, (6) Standard Helical, (7) Standard Volume (P < 0.001). Unblinded objective evaluation performed by one observer showed that VM DECT 120 keV, Helical +SEMAR, and Volume +SEMAR performed similarly and were objectively the best at reducing blooming artifact. Overall, the best metal artifact reduction was obtained with SEMAR, followed by VM DECT. However, VM DECT performance varies with energy level and was associated with decreased image quality in distant tissues and artifactual overcorrection of metal artifacts at high energy levels.