title: Metal artifact reduction using virtual monochromatic images for patients with pedicle screws implants on CT.
abstract: To evaluate the effect of spectral CT for metal artifact reduction in patients with pedicle screw.
  
  
  
  45 patients with 119 pairs of pedicle screws underwent spectral CT examination. One set of conventional (140 kVp) polychromatic image and nine sets of virtual monochromatic images (60-140 keV) were obtained. The standard deviation (SD) of CT number in 12 locations around the implant and 1 on homogenous fat was measured to generate artifact index (AI). Objective assessment including AI, CT number and SD value was performed with independent t test and paired sample t test. Two radiologists independently reviewed the image quality, and Wilcoxon signed-rank test and kappa analysis were used for the subjective scores of image quality.
  
  
  
  The artifact index (AI) of all the regions decreased as keV increased. AIs of 100-140 keV were lower than that of 140 kVp images. At 120 keV there was no significant difference in CT numbers of psoas major muscle and vertebral canal between pedicle screw level and pedicle level, but a significant difference in SD value was determined between the two levels. The subjective scores at 100-140 keV were higher than the images at 140 kVp, and the highest subjective score of two observers and excellent interobserver agreement were found at 120 keV (κ = 0.889).
  
  
  
  Virtual monochromatic images at high-energy levels have a well-concordant effect of removing metal artifacts, and 120 keV monochromatic images provided an accurate CT number and good subjective score.
authors.affiliation: Department of Radiology, The First Affiliated Hospital of Dalian Medical University, Dalian, 116011, Liaoning, China. dyy1026@sina.com.|Department of Radiology, LiaoNing Cancer Hospital, DaLian Medical University Clinical Oncology College, Shenyang, 110042, Liaoning, China. dyy1026@sina.com.
authors.forename: Yue
authors.initials: Y
authors.lastname: Dong
authors.affiliation: Department of Radiology, The First Affiliated Hospital of Dalian Medical University, Dalian, 116011, Liaoning, China.
authors.forename: Ai Jun
authors.initials: AJ
authors.lastname: Shi
authors.affiliation: Department of Radiology, Affiliated ZhongShan Hospital of Dalian University, Dalian, 116001, Liaoning, China.
authors.forename: Jian Lin
authors.initials: JL
authors.lastname: Wu
authors.affiliation: Department of Radiology, The First Affiliated Hospital of Dalian Medical University, Dalian, 116011, Liaoning, China.
authors.forename: Ru Xin
authors.initials: RX
authors.lastname: Wang
authors.affiliation: Department of Radiology, The First Affiliated Hospital of Dalian Medical University, Dalian, 116011, Liaoning, China.
authors.forename: Li Fei
authors.initials: LF
authors.lastname: Sun
authors.affiliation: Department of Radiology, The First Affiliated Hospital of Dalian Medical University, Dalian, 116011, Liaoning, China.
authors.forename: Ai Lian
authors.initials: AL
authors.lastname: Liu
authors.affiliation: Department of Radiology, The First Affiliated Hospital of Dalian Medical University, Dalian, 116011, Liaoning, China.
authors.forename: Yi Jun
authors.initials: YJ
authors.lastname: Liu
mesh_terms: D016477:Artifacts; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008670:Metals; D065289:Pedicle Screws; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D008670:Metals
keywords: Computed tomography; Metal artifacts; Pedicle screw; Spectral imaging; Virtual monochromatic image