Abstract: Objective To evaluate the practical value of gemstone spectral imaging(GSI)in reducing the metal artifacts of orbital implants.Methods GSI examination were performed in 32 patients with metal implants of orbit,and the polychromatic images(140 kVp)were obtained.Gemstone spectral imaging(GSI)viewer was used to obtain 11 sets of monochromatic images(40-140 keV with interval of 10 keV).Subjective image quality of two methods was assessed by 3 radiologists in consensus.CT value and noise value(SD)of ROI were measured at the most obvious and non-artifact level of each image,and contrast noise ratio(CNR)and artifact index(AI)were calculated.The SD,CNR and AI values were compared between polychromatic images and monochromatic images.Results Among the 11 sets of monochromatic images,the noise value(SD)and artifact index(AI)of 110 keV images were the smallest,and the contrast noise ratio(CNR)was the best.Compared with the polychromatic images,the artifacts of orbital metal implants were removed significantly,and the image quality was improved significantly.Conclusion Gemstone spectral CT can effectively reduce artifacts of orbital metal implants and will provide high image quality in the area of metal implants.110 keV is the best monochromatic imaging point for the image quality of patients with orbital metal implant.

Key words: Gemstone spectral imaging, Orbit, Metal artifacts