The best monochromatic imaging for reducing spinal metal artifacts with gemstone spectral imaging

Objective To observe the application value of monochromatic imaging in reducing the metal artifacts of spine with gemstone spectral imaging(GSI),and to find the best monochromatic imaging of image quality.Methods Nineteen patients with metal implants of spine received GSI examination.The spectrum analysis was used to obtain the monochromatic images by special gemstone spectral imaging(GSI) viewer.Eleven groups of monochromatic images were obtained from 40 to 140 keV.For each patient,images with heaviest artifacts level(A) and no or less artifacts level(B)were selected in every group.CT value and SD value of ROI were measured and analyzed(named CT1,CT2 and SD1,SD2),and the artifact index(AI) was calculated.Paired t-test was applied to determine the CT value,and the AI value was compared using LSD-t test.Results In the monochromatic images at 120 keV,CT value of A and B levels were([41.41±9.48]HU) and([41.91±7.97]HU).There was no significant difference(t=-0.21,P0.05).CT value of A and B levels in the other 10 groups were significantly different(all P0.05).There was no significant difference among CT value of A and B levels in 70 to 140 keV(all P0.05).For 40 to 60 keV,AI value were significantly different with that of the other groups(all P0.05).Conclusion HDCT can effectively reduce artifacts of spine metal implants using spectral imaging acquisition technique.When 120 keV was the best point for quality of monochromatic imaging,70 keV was the boundary for reducing metal artifacts.