RESUMO
Objective: To investigate the effect of multi-material artifact reduction (MMAR) technique on the maxillofacial CT images of patients with metallic dental implants. Methods: The data of 30 patients with metal denture implants who underwent maxillofacial wide-detector CT scans in the Department of Radiology of the First Affiliated Hospital of Zhengzhou University from March 2019 to February 2020 were retrospectively collected. The images of the lesion sites of patients were all affected by the metal implants artifacts. The 120 kV-like, virtual monoenergetic images (VMI) (70, 90, 110 keV), VMI (70, 90, 110 keV)+MMAR images were reconstructed at venous phase by energy spectrum scanning. A total of 7 image sequences were obtained for each patient. The CT value and noise value of the lesion and the longus capitis muscle on the same plane were measured, and the artifact index (AI) of lesion was calculated.Friedman test and Wilcoxon test were used to evaluate image quality objectively and subjectively. Results: There were significant differences in SD and AI among the 7 groups (χ2=133.800,P<0.001;χ2=92.147,P<0.001). The SD[10 (8, 12)] and AI [6 (5, 9)]of VMI 110 keV+M images were the lowest, but there were no significant differences in AI between VMI 110 keV+M and VMI 90 keV+M image (P= 0.271). The SD and AI of VMI+M group were lower than those in VMI group (all P<0.05). There was significant difference in image score among the 7 groups (χ 2 = 151.199, P<0.001). The image scores of VMI (70, 90, 110 keV)+M group were higher than those of VMI group (Z=-4.583, P = 0.000; Z=-3.742, P = 0.000; Z =-2.449, P = 0.014). The subjective score of VMI 90 keV+M [4 (3, 4)] was the highest, higher than those of other 6 groups (all P<0.05), in 26 out of 30 cases, lesions displayed clear contrast, and the artifacts eliminated completely. Conclusion: The MMAR technique of wide-detector CT might effectively remove the metallic dental implants artifacts and improve the image quality. VMI 90 keV+MMAR images could achieve the best artifact removal effect and good tissue contrast.