Usefulness of a metal artifact reduction algorithm for orthopedic implants in abdominal CT: phantom and clinical study results

OBJECTIVE. The purpose of this study was to evaluate the usefulness of a metal artifact reduction (MAR) algorithm for orthopedic prostheses in phantom and clinical CT. MATERIALS AND METHODS. An agar phantom with two sets of spinal screws was scanned at various tube voltage (80-140 kVp) and tube current-time (34-1032 mAs) settings. The orthopedic MAR algorithm was combined with filtered back projection (FBP) or iterative reconstruction. The mean SDs in three ROIs were compared among four datasets (FBP, iterative reconstruction, FBP with orthopedic MAR, and iterative reconstruction with orthopedic MAR). For the clinical study, the mean SDs of three ROIs and 4-point scaled image quality in 52 patients with metallic orthopedic prostheses were compared between CT images acquired with and without orthopedic MAR. The presence and type of image quality improvement with orthopedic MAR and the presence of orthopedic MAR-related new artifacts were also analyzed. RESULTS. In the phantom study, the mean SD with orthopedic MAR was significantly lower than that without orthopedic MAR regardless of dose settings and reconstruction algorithms (FBP versus iterative reconstruction). The mean SD near the metallic prosthesis in 52 patients was significantly lower on CT images with orthopedic MAR (28.04 HU) than those without it (49.21 HU). Image quality regarding metallic artifact was significantly improved with orthopedic MAR (rating of 2.60 versus 1.04). Notable reduction of metallic artifacts and better depiction of abdominal organs were observed in 45 patients. Diagnostic benefit was achieved in six patients, but orthopedic MAR-related new artifacts were seen in 30 patients. CONCLUSION. Use of the orthopedic MAR algorithm significantly reduces metal artifacts in CT of both phantoms and patients and has potential for improving diagnostic performance in patients with severe metallic artifacts.