title: Emphysema Quantification Using Ultralow-Dose CT With Iterative Reconstruction and Filtered Back Projection.
abstract: OBJECTIVE
  The purpose of this study was to evaluate agreement between standard-dose CT (SDCT) and ultralow-dose CT (ULDCT) findings with respect to emphysema quantification. ULDCT images were reconstructed with and without iterative reconstruction (IR). Adaptive iterative dose reduction with 3D processing was used for IR.
  
  
  METHODS
  Fifty patients who underwent SDCT and ULDCT were included. The tube current for SDCT was 250 mA, and that for ULDCT was 10 mA. SDCT, ULDCT without IR, and ULDCT with IR were used for emphysema quantification. The low-attenuation volume percentage (LAV%) in the lungs at four thresholds (-970, -950, -930, and -910 HU), mean lung attenuation, and total lung volume were computed. Concordance correlation coefficients (CCC) were used to assess the agreement of emphysema quantification between SDCT and ULDCT.
  
  
  RESULTS
  The LAV% CCC values were 0.310-0.789 between SDCT and ULDCT without IR and 0.934-0.966 between SDCT and ULDCT with IR. The agreement of LAV% improved when IR was used for ULDCT. The mean lung attenuation CCC value between SDCT and ULDCT without IR was substantial (0.957), whereas that between SDCT and ULDCT with IR was poor (0.890). The total lung volume CCC values were substantial (0.982 with IR, 0.983 without IR).
  
  
  CONCLUSIONS
  ULDCT with and without IR can substitute for SDCT in emphysema quantification.
authors.affiliation: 1 Clinical PET Center, Institute of Biomedical Research and Innovation, 2-2, Minatojimaminamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan.|2 Department of Radiology, Division of Functional and Diagnostic Imaging Research, Kobe University Graduate School of Medicine, Kobe, Hyogo, Japan.|3 Advanced Biomedical Imaging Research Center, Kobe University Graduate School of Medicine, Kobe, Hyogo, Japan.
authors.forename: Mizuho
authors.initials: M
authors.lastname: Nishio
authors.affiliation: 4 Department of Radiology, Kobe University Graduate School of Medicine, Kobe, Hyogo, Japan.
authors.forename: Hisanobu
authors.initials: H
authors.lastname: Koyama
authors.affiliation: 2 Department of Radiology, Division of Functional and Diagnostic Imaging Research, Kobe University Graduate School of Medicine, Kobe, Hyogo, Japan.|3 Advanced Biomedical Imaging Research Center, Kobe University Graduate School of Medicine, Kobe, Hyogo, Japan.
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Ohno
authors.affiliation: 5 Center for Radiology and Radiation Oncology, Kobe University Hospital, Kobe, Hyogo, Japan.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Negi
authors.affiliation: 4 Department of Radiology, Kobe University Graduate School of Medicine, Kobe, Hyogo, Japan.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Seki
authors.affiliation: 2 Department of Radiology, Division of Functional and Diagnostic Imaging Research, Kobe University Graduate School of Medicine, Kobe, Hyogo, Japan.|3 Advanced Biomedical Imaging Research Center, Kobe University Graduate School of Medicine, Kobe, Hyogo, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yoshikawa
authors.affiliation: 4 Department of Radiology, Kobe University Graduate School of Medicine, Kobe, Hyogo, Japan.
authors.forename: Kazuro
authors.initials: K
authors.lastname: Sugimura
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D011656:Pulmonary Emphysema / Q000000981:diagnostic imaging*; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed
keywords: COPD; CT; emphysema; quantitative evaluation; radiation dose