Spectral metal artifact reduction after posterior spinal fixation in photon-counting detector CT datasets

• Published in: European journal of radiology Vol. 165; p. 110946
• Main Authors: Popp, Daniel, Sinzinger, Andrea X., Decker, Josua A., Braun, Franziska, Bette, Stefanie, Risch, Franka, Haerting, Mark, Garthe, Tarik, Scheurig-Muenkler, Christian, Kroencke, Thomas J., Schwarz, Florian
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier B.V 01.08.2023
• Subjects: Metal artifact reduction; Pedicle screws; Photon-counting computed tomography; Spectral imaging; Spinal fixation; Virtual monoenergetic imaging; Virtual monoenergetic imaging; Spectral imaging; Pedicle screws; FoV; DECT; ROI; AIx; SPP; VMI; Photon-counting computed tomography; Spinal fixation; EID-CT; PCD-CT; Metal artifact reduction; MAR
• ISSN: 0720-048X; 1872-7727
• DOI: 10.1016/j.ejrad.2023.110946

•Virtual monoenergetic image (VMI) reconstructions derived from Photon-counting CT reduce metal artifacts in spinal fixation.•Best overall artifact reduction is obtained with VMI reconstructions at intermediate-keV levels.•Slight adjustments towards higher-keV levels may be preferable in specific anatomic regions adjacent to the pedicle screws.•Future developments should strive for standard integration of VMI settings into common image viewers. To investigate the usefulness of virtual monoenergetic image (VMI) reconstructions derived from scans on a novel photon-counting detector CT (PCD-CT) for artifact reduction in patients after posterior spinal fixation. This retrospective cohort study included 23 patients status post posterior spinal fixation. Subjects were scanned on a novel PCD-CT (NAEOTOM Alpha, Siemens Healthineers, Erlangen, Germany) as part of routine clinical care. 14 sets of VMI reconstructions were derived in 10 keV increments for the interval 60–190 keV. The mean and the standard deviation (SD) of CT-values in 12 defined locations around a pair of pedicle screws on one vertebral level and the SD of homogenous fat were measured and used to calculate an artifact index (AIx). Averaged over all regions, the lowest AIx was observed at VMI levels of 110 keV (32.5 (27.8–37.9)) which was significantly different from those of VMIs ≤ 90 keV (p < 0.001) or ≥160 keV (p < 0.015), respectively. Overall AIx values increased in both lower- and higher-keV levels. Regarding individual locations, either a monotonous AIx-decrease for increasing keV values or an AIx-minimum in intermediate-keV levels (100–140 keV) was found. In locations adjacent to larger metal parts, the increase of AIx values at the high-end of the keV spectrum was mainly explained by a reappearance of streak artifacts. Our findings suggest that 110 keV is the optimal VMI setting for overall artifact suppression. In specific anatomical regions, however, slight adjustments towards higher-keV levels may provide better results.