title: Intraindividual comparison of diagnostic performance in patients with hepatic metastasis of full-dose standard and half-dose iterative reconstructions with dual-source abdominal computed tomography.
abstract: OBJECTIVE
  The objectives of the study were to evaluate the image quality and diagnostic performance of sinogram-affirmed iterative reconstruction (SAFIRE) for detecting hepatic metastasis and to estimate the potential radiation dose reduction at abdominal computed tomography (CT).
  
  
  METHODS
  Fifty-nine consecutive patients (mean age, 59.2 years; range, 42-81 years) who had hepatic metastasis and who underwent dual-source abdominal CT were enrolled in this study. The image noise of the liver was compared between full-dose filtered back projection images (FD-FBP) and simulated half-dose images, which used only single-source projection data, and reconstructed with different strengths of SAFIRE (HD-SAFIRE(1-5)) by 1-way analysis of variance with Bonferroni correction. The diagnostic performance for hepatic metastasis was compared by logistic regression with the weighted least squares method and noninferiority test between the FD-FBP images and the half-dose sinogram-affirmed iterative reconstruction (HD-SAFIRE) images.
  
  
  RESULTS
  As the SAFIRE strength increased, image noise decreased (P < 0.001). The images of HD-SAFIRE(2) showed similar image noise for liver parenchyma (13.4 Hounsfield unit [HU]), signal-to-noise ratio for liver parenchyma (9.2), and lesion-to-liver contrast-to-noise ratio (4.5), compared with the FD-FBP images (12.6 HU, P = 0.668; 9.6, P > 0.999; and 4.5, P > 0.999, respectively). The diagnostic accuracy for hepatic metastasis with the HD-SAFIRE(2) images (87.5%) was not different from that of the FD-FBP images (87.5%, P > 0.999). The diagnostic performance of the HD-SAFIRE(2) images was also noninferior to that of the FD-FBP images (95% confidence interval lower limit difference [-9.16%] excluding the -10% clinical noninferiority limit). The mean (SD) volume CT dose index of FD-FBP was 11.26 (2.66) mGy, and the mean (SD) radiation dose equivalent associated with HD-SAFIRE was estimated to be 5.63 (1.33) mGy.
  
  
  CONCLUSIONS
  By applying SAFIRE2, the radiation dose could be reduced by up to 50% compared with the standard-of-care abdominal CT protocol without increasing image noise and without deteriorating diagnostic performance for the detection of hepatic metastasis.
authors.affiliation: From the *Department of Radiology, Research Institute of Radiological Science, and †Biostatistics Collaboration Unit, Medical Research Center, College of Medicine, Yonsei University, Seoul, South Korea.
authors.forename: Mina
authors.initials: M
authors.lastname: Park
authors.forename: Yong Eun
authors.initials: YE
authors.lastname: Chung
authors.forename: Hye Sun
authors.initials: HS
authors.lastname: Lee
authors.forename: Jin-Young
authors.initials: JY
authors.lastname: Choi
authors.forename: Mi-Suk
authors.initials: MS
authors.lastname: Park
authors.forename: Myeong-Jin
authors.initials: MJ
authors.lastname: Kim
authors.forename: Ki Whang
authors.initials: KW
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008113:Liver Neoplasms / Q000000981:diagnostic imaging* / Q000556:secondary*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods*; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D011860:Radiography, Abdominal / Q000379:methods; D015900:Radiography, Dual-Energy Scanned Projection / Q000379:methods*; D011874:Radiometry; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*