Abstract: Objective To compare the efficacy differences among model-based iterative reconstruction (MBIR),metal artifact reduction(MAR),and noise-optimized virtual monochromatic imaging(VMI+) in the removal of metal artifacts from lumbar spine internal fixation and to propose the best combined scheme.Methods Retrospective collection of lumbar CT raw data of patients after lumbar internal fixation surgery in our hospital,a total of 10 cases.Through orthogonal experimental design,a 3-factor 2-level orthogonal table L8 (27) was designed.The raw data was reconstructed and post-processed according to the scheme of the orthogonal design table,and the CT values and SD values of the high-density metal artifact area near the screw,the low-density metal artifact area on the ventral side of the screw long axis,and the subcutaneous fat control area on the back were measured separately.The Artifact Index (AI) was calculated,followed by intuitive analysis and analysis of variance (ANOVA).Results In the impact on high-density metal artifacts,the order of influence of factors was:C (VMI+) > B (MAR) > A (MBIR);for low-density metal artifacts,the order was:B (MAR) > C (VMI+) > A (MBIR).The effects of different levels of each factor on both high-density and low-density metal artifacts were A2 > A1,B2 > B1,C2 > C1.A (MBIR),B (MAR),and C (VMI+) were significant influencing factors in the removal of high-density and low-density metal artifacts from lumbar spine internal fixation (P<0.001).The interactions between A and B,A and C,and B and C were significant in the impact on high-density metal artifacts (P<0.001);for low-density metal artifacts,the interactions between A and B,and B and C were significant (P<0.05).The optimal combined protocol was identified as A2B2C2.Conclusion Conclusion MBIR,MAR,and VMI+ are significant factors in the removal of metal artifacts from lumbar spine internal fixation.There are differences in the effects of MBIR,MAR,and VMI+ on the removal of metal artifacts:for high-density artifacts,VMI+ > MAR > MBIR;for low-density artifacts,MAR > VMI+ > MBIR.There is an interaction when MBIR,MAR,and VMI+ are used in combination to remove metal artifacts from lumbar spine internal fixation,with the interaction between MAR and VMI+ being the most significant.The best combined scheme of this study is MBIR level 4,130KeV VMI+,MAR.

Key words: model-based iterative reconstruction; metal artifact reduction; noise-optimized virtual monoenergetic imaging; lumbar internal fixation; metal artifacts; orthogonal design