title: The effect of the virtual monochromatic spectral imaging for the metallic artifact and the pulmonary nodule detection.
abstract: OBJECTIVE
  This study aimed to evaluate whether dual-energy computed tomography can reduce metal artifacts and improve detection of pulmonary nodules.
  
  
  METHODS
  Twelve simulated nodules were randomly placed inside a chest phantom with a pacemaker. Then, dual-energy computed tomography was performed, and 5 virtual monochromatic images at 40, 50, 65, 100, and 140 keV were reconstructed with 5- and 0.625-mm slice thicknesses. Two independent observers assessed the metal artifact (3-point scale from 1, none, to 3, severe) and detection of the nodule (5-point scale from 1, definitely absent, to 5, definitely present). Statistical analysis was performed with a P value of less than 0.01 (0.05/5).
  
  
  RESULTS
  With both slice thicknesses, the metallic artifact increased at 40 or 50 keV and decreased at 100 or 140 keV relative to that at 65 keV (P < 0.01). The nodule detection score was not significantly different between each kiloelectron volt level with the 0.625-mm slice thickness; however, the score was significantly worse at 40 keV compared to 65 keV (P < 0.01) with the 5-mm slice thickness.
  
  
  CONCLUSIONS
  High monochromatic energy images can reduce metal artifacts without a change in nodule detection score. Low monochromatic energy images increase metal artifacts and worsen nodule detection in thick slices.
authors.affiliation: From the *Department of Radiology, Osaka University Graduate School of Medicine, Suita; †Department of Radiology, Osaka Rosai Hospital, Kita-ku, Sakai; ‡Department of Radiology, Osaka Furitsu Kyuseiki Sogo Iryo Center, Sumiyoshi-ku; §Department of Radiology, Osaka University Hospital, Suita; and ∥Department of Radiology, Osaka Medical College, Takatsuki, Osaka, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Gyobu
authors.forename: Osamu
authors.initials: O
authors.lastname: Honda
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Kawata
authors.forename: Ayano
authors.initials: A
authors.lastname: Kikuyama
authors.forename: Hiromu
authors.initials: H
authors.lastname: Miki
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yanagawa
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Sumikawa
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Koyama
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Tomiyama
mesh_terms: D016477:Artifacts; D008670:Metals; D019047:Phantoms, Imaging; D019736:Prostheses and Implants; D011856:Radiographic Image Enhancement / Q000379:methods*; D015900:Radiography, Dual-Energy Scanned Projection / Q000295:instrumentation / Q000379:methods*; D013902:Radiography, Thoracic / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*
chemical_list: D008670:Metals