title: Metal artifacts reduction using monochromatic images from spectral CT: evaluation of pedicle screws in patients with scoliosis.
abstract: OBJECTIVE
  To evaluate the effectiveness of spectral CT in reducing metal artifacts caused by pedicle screws in patients with scoliosis.
  
  
  METHODS
  Institutional review committee approval and written informed consents from patients were obtained. 18 scoliotic patients with a total of 228 pedicle screws who underwent spectral CT imaging were included in this study. Monochromatic image sets with and without the additional metal artifacts reduction software (MARS) correction were generated with photon energy at 65keV and from 70 to 140keV with 10keV interval using the 80kVp and 140kVp projection sets. Polychromatic images corresponded to the conventional 140kVp imaging were also generated from the same scan data as a control group. Both objective evaluation (screw width and quantitative artifacts index measurements) and subjective evaluation (depiction of pedicle screws, surrounding structures and their relationship) were performed.
  
  
  RESULTS
  Image quality of monochromatic images in the range from 110 to 140keV (0.97±0.28) was rated superior to the conventional polychromatic images (2.53±0.54) and also better than monochromatic images with lower energy. Images of energy above 100keV also give accurate measurement of the width of screws and relatively low artifacts index. The form of screws was slightly distorted in MARS reconstruction.
  
  
  CONCLUSIONS
  Compared to conventional polychromatic images, monochromatic images acquired from dual-energy CT provided superior image quality with much reduced metal artifacts of pedicle screws in patients with scoliosis. Optimal energy range was found between 110 and 140keV.
authors.affiliation: Department of Radiology, The Affiliated Nanjing Drum Tower Hospital of Nanjing University Medical School, Nanjing 210008, China. wangzhang227@163.com
authors.forename: Yang
authors.initials: Y
authors.lastname: Wang
authors.forename: Bangping
authors.initials: B
authors.lastname: Qian
authors.forename: Baoxin
authors.initials: B
authors.lastname: Li
authors.forename: Guochu
authors.initials: G
authors.lastname: Qin
authors.forename: Zhengyang
authors.initials: Z
authors.lastname: Zhou
authors.forename: Yong
authors.initials: Y
authors.lastname: Qiu
authors.forename: Xizhao
authors.initials: X
authors.lastname: Sun
authors.forename: Bin
authors.initials: B
authors.lastname: Zhu
mesh_terms: D000293:Adolescent; D016477:Artifacts; D001863:Bone Screws; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D008670:Metals; D011856:Radiographic Image Enhancement / Q000379:methods*; D015203:Reproducibility of Results; D012600:Scoliosis / Q000000981:diagnostic imaging* / Q000601:surgery*; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome
chemical_list: D008670:Metals