SU‐E‐I‐21: Metal Artifact Redcution in CT for Surgical Screws: Comparison Between Two Commercially Available Software Packages

Purpose: To compare the performance between two available metal artifact reduction software (MAR) packages from different CT vendors to determine applicability for surgical screws, even though such use is not supported. Methods: Two vertebral screws (Al and stainless steel) were placed in the center of a water phantom (20 cm × 15 cm), with long axis perpendicular to the scan direction. Scans were performed using a GE Discovery HD750 with Dual Energy (DE) and MARS software, and Philips iCT with iDose4 and OMAR software. Reconstruction was performed with and without MAR. Assessment was performed qualitatively and quantitatively by measuring the SD in areas surrounding the screws. For the GE scanner, mono‐energy reconstructions were performed for 70, 127, and 140 keV in addition to the MARS routine. Thickness of the screws was also measured and compared to the expected size. Results: DE reduced streak artifacts and MARS further reduced artifacts for both screws. However, a portion of the middle was distorted. SD of region next to the screw tips was reduced up to 97%; whereas SD in the region under the long axis increased in some MARS images by more than 50%. O‐MAR reduced streak artifacts but less effectively than MARS but with no loss of the middle section. With OMAR, in general most images showed reduced SD in both regions by 2% to 54%. Additionally, width was significantly reduced (20% to 50%) by MARS. This effect was not noted with O‐MAR. Conclusion: Performance of MARS and O‐MAR differed considerably. MARS effectively reduced streaks along the long axis but introduced distortions in regions near the center of the screw. With O‐MAR, streaks were reduced by a lesser degree than MARS along the screws axis, but by higher degree above and below the screws with no distortion at the center.