Utility of Spectral CT Monochromatic Imaging with Metal Artifacts Reduction (MAR) for the Reduction of Metal Artifacts of Embolization Coil Implants

Purpose: To evaluate the utility of monochromatic imaging combined with metal artifacts reduction (MAR) for metal artifacts reduction of embolization coil implants using Quantitative Standard Pulsating Phantom with spectral computed tomography. Method and materials: Iodine solutions with eight different concentrations were prepared with different mix ratios of iohexol and sodium chloride. 20mL of these concentrations of iodine solutions were contained in eight tubes and inserted into the Quantitative Standard Pulsating Phantom to simulate different degrees of enhancement in organs of human anatomy. The embolization coil with a diameter of 8mm was placed in an intermediate cylinder of the QSP that contains sodium chloride solution. Two scan protocols were performed using spectral CT: Group A (conventional CT scan mode); Group B adopts Gemstone Spectral Imaging mode and after a post-processing workstation to obtain one set of 120kVp images, MAR images (68keV), 11 sets of monochromatic images (40-140keV, interval of 10keV), 11 sets of MonoE+MAR images. The CT values and SD values of artifacts areas are measured respectively. Calculation the artifact index of the region of interest and beam hardening artifact reduction rate. The ANOVA test and Paired T test was used to compare the artifact index and beam hardening artifact reduction rate of the group A and B of images. The difference was statistically significant at P<0.05. Results: Compared with conventional CT images, the high and low density artifacts artifact index of MAR image, MonoE images, MonoE+MAR images were all reduced, P<0.05, and the differences were statistically significant. The high and low density artifacts beam hardening artifact reduction rate of MAR images were 82%, 92%; High and low density artifact beam hardening artifact reduction rate of MonoE, MAR+MonoE images increases with single energy enhanced, while MAR+140keV MonoE image were highest. Conclusion: Spectral CT using the MAR, MonoE, and MAR+MonoE reconstruction methods can reduce metal implant artifacts to varying degrees. The MAR+MonoE reconstruction method in the three methods is the best way to reduce metal artifacts.