The experimental phantom study of spectral CT metal artifact reduction technique in reducing the artifacts of different types of spinal implants / 中华放射学杂志

ABSTRACT

Objective:To evaluate spectral CT metal artifacts reduction (MAR) technique in reducing metal artifacts of spinal implants in a phantom.Methods:Ovine spines were chosen as anthropomorphic phantom. The phantom including the pedicle screws, 3D-printed vertebral body (VB) and mesh cage were examined using spectral CT. Postoperative CT images were reconstructed at 70—140 keV with 10 keV interval of MAR and non-MAR. Artifact index (AI) and signal-to-noise ratio (SNR) were evaluated by CT and SD values in ROIs around the implants. Visibility of bony structures, the artifacts of pedicle screw, 3D-printed VB and mesh cage were subjectively evaluated. Plotting curves of AI and SNR with the increasing keV were drawn. The AI and SNR were compared at lower (70 keV), medium (100 keV) and high (130 keV) level between MAR and non-MAR images using the paired t-test, and the subjective scores were compared using Wilcoxon signed rank-sum test. Results:The AI values around pedicle screws (anterior, posterior and lateral), 3D-printed VB and mesh cage decreased with the increase of keV, while SNR improved in MAR and non-MAR images. The AI values in the anterior, lateral and posterior pedicle screws and lateral titanium implants were significantly lower in MAR than those in non-MAR ( P<0.05). The AI value in posterior 3D-printed vertebral was lower in MAR than that of non-MAR only at 70 keV ( P<0.001). The SNR values in the anterior and posterior pedicle screws, 3D-printed VB increased with the increase of keV, but decreased in other ROIs. In the subjective evaluation, the image scores of MAR were higher than those of non-MAR ( P<0.05). Conclusion:Spectral CT using the MAR reconstruction can effectively reduce metal artifacts of spinal implants. The effect is better in pedicle screw and mesh cage than 3D-printed VB.