title: Effect of iterative reconstruction on variability and reproducibility of epicardial fat volume quantification by cardiac CT.
abstract: BACKGROUND
  The epicardial fat volume (EFV) measured by cardiac CT has emerged as an important parameter for understanding the pathophysiology of coronary atherosclerosis.
  
  
  OBJECTIVE
  We investigated the variability and reproducibility of EFV measurements and evaluated the effect of model-based type iterative reconstruction (M-IR) on measurement results.
  
  
  METHODS
  Non-contrast cardiac CT data (tube voltage 120-kVp, tube current time product 32 mAs) of 30 consecutive patients were reconstructed with filtered back projection (FBP), hybrid type iterative reconstruction (H-IR), and M-IR using a slice thickness of 3.0 mm. CT attenuation and image noise was measured for all reconstructions. Two observers independently quantified EFV using semi-automated software and interobserver agreement was evaluated.
  
  
  RESULTS
  There was no significant difference in the CT attenuation of the ascending aorta among the three reconstructions. The mean image noise on FBP-, H-IR-, and M-IR images was 48.0 ± 7.9 HU, 29.6 ± 4.8 HU, and 9.3 ± 1.3 HU, respectively; there was a significant difference among all comparison combinations for the three reconstructions (p < 0.01). FBP yielded the highest EFV among the three reconstructions (171.0 ± 54.9 cm(3) [FBP], 153.8 ± 53.1 cm(3) [H-IR], and 134.0 ± 46.4 cm(3) [M-IR]). For all three reconstructions, interobserver correlations were excellent (r = 0.91 [FBP], 0.93 [H-IR], and 0.96 [M-IR]). Interobserver comparisons showed that the lowest Bland-Altman limit of agreement was with M-IR (mean difference 2.0 ± 4.9%, 95% limit of agreement, -24.0 to 28.0%) followed by H-IR (-2.6 ± 7.1%, -39.8 to 34.6%) and FBP (-0.2 ± 8.6%, -45.3- to 45.0%).
  
  
  CONCLUSIONS
  For the quantification of epicardial fat by cardiac CT, model-based iterative reconstruction can improve the image quality and lessen measurement variability.
authors.affiliation: Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, 1-1-1 Honjyo, Chuo-ku, Kumamoto, 860-8556, Japan. Electronic address: seisei0430@nifty.com.
authors.forename: Seitaro
authors.initials: S
authors.lastname: Oda
authors.affiliation: Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, 1-1-1 Honjyo, Chuo-ku, Kumamoto, 860-8556, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Utsunomiya
authors.affiliation: Department of Medical Physics, Faculty of Life Sciences, Kumamoto University, 1-1-1 Honjyo, Chuo-ku, Kumamoto, 860-8556, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Funama
authors.affiliation: Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, 1-1-1 Honjyo, Chuo-ku, Kumamoto, 860-8556, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Yuki
authors.affiliation: Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, 1-1-1 Honjyo, Chuo-ku, Kumamoto, 860-8556, Japan.
authors.forename: Masafumi
authors.initials: M
authors.lastname: Kidoh
authors.affiliation: Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, 1-1-1 Honjyo, Chuo-ku, Kumamoto, 860-8556, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nakaura
authors.affiliation: Department of Diagnostic Radiology, Kumamoto Chuo Hospital, 1-5-1 Tainoshima, Minami-ku, Kumamoto, 862-0965, Japan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Takaoka
authors.affiliation: Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, 1-1-1 Honjyo, Chuo-ku, Kumamoto, 860-8556, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Matsumura
authors.affiliation: Department of Diagnostic Radiology, Kumamoto Chuo Hospital, 1-5-1 Tainoshima, Minami-ku, Kumamoto, 862-0965, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Katahira
authors.affiliation: Department of Cardiology, Kumamoto Chuo Hospital, 1-5-1 Tainoshima, Minami-ku, Kumamoto, 862-0965, Japan.
authors.forename: Katsuo
authors.initials: K
authors.lastname: Noda
authors.affiliation: Department of Cardiology, Kumamoto Chuo Hospital, 1-5-1 Tainoshima, Minami-ku, Kumamoto, 862-0965, Japan.
authors.forename: Shuichi
authors.initials: S
authors.lastname: Oshima
authors.affiliation: CT Clinical Science, Philips Electronics Japan, Kohnan 2-13-37, Minato-ku, Tokyo, 108-8507, Japan.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Tokuyasu
authors.affiliation: Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, 1-1-1 Honjyo, Chuo-ku, Kumamoto, 860-8556, Japan.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Yamashita
mesh_terms: D000273:Adipose Tissue / Q000000981:diagnostic imaging* / Q000503:physiopathology; D050154:Adiposity; D000368:Aged; D000369:Aged, 80 and over; D001331:Automation; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography; D015588:Observer Variation; D010496:Pericardium / Q000000981:diagnostic imaging* / Q000503:physiopathology; D011237:Predictive Value of Tests; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012189:Retrospective Studies
keywords: Cardiac CT; Epicardial fat volume; Image quality; Iterative reconstruction; Measurement variability