title: Dual-energy liver CT: effect of monochromatic imaging on lesion detection, conspicuity, and contrast-to-noise ratio of hypervascular lesions on late arterial phase.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the effect of use of dual-energy CT monochromatic imaging in the late hepatic arterial phase on hyperenhancing focal lesion detection and lesion conspicuity.
  
  
  METHODS
  This prospective study included 72 patients imaged with a single-source dual-energy CT scanner. Late arterial phase imaging was performed with dual energies of 140 and 80 kVp, and the portal venous and delayed phases were performed with a single energy of 120 kVp. Two deidentified image sets were created: set A consisted of 77-keV images only, and set B consisted of 40-, 50-, 70-, and 77-keV images and iodine-based contrast material decomposition images. Two independent reviewers identified hypervascular lesions and subjectively scored lesion conspicuity. Contrast-to-noise ratios were calculated, and radiation dose (volume CT dose index) was recorded.
  
  
  RESULTS
  The 128 lesions identified had a mean size of 1.7 ± 1.4 cm. There was no difference in lesion detection between the two reviewers or the two image sets. The contrast-to-noise ratio at 50 keV was 72% greater than that at 77 keV (p < 0.0001). Subjective conspicuity was statistically greatest at 50 keV (p < 0.0001). There was no statistical difference in mean volume CT dose index between the dual-energy (12.8 mGy) and the two single-energy (14.4 and 14.2 mGy) phases.
  
  
  CONCLUSIONS
  Viewing dual-energy CT images may result in the greatest subjective lesion conspicuity and measured contrast-to-noise ratio at 50 keV with equal detection of hyperenhancing liver lesions compared with viewing 77-keV images alone. In addition, the radiation doses of dual-energy CT may be similar to those of single-energy CT.
authors.affiliation: 1 All authors: Department of Radiology, University of Washington School of Medicine, Box 357115, 1959 NE Pacific St, Seattle, WA 98195.
authors.forename: William P
authors.initials: WP
authors.lastname: Shuman
authors.forename: Douglas E
authors.initials: DE
authors.lastname: Green
authors.forename: Janet M
authors.initials: JM
authors.lastname: Busey
authors.forename: Lee M
authors.initials: LM
authors.lastname: Mitsumori
authors.forename: Eunice
authors.initials: E
authors.lastname: Choi
authors.forename: Kent M
authors.initials: KM
authors.lastname: Koprowicz
authors.forename: Kalpana M
authors.initials: KM
authors.lastname: Kanal
mesh_terms: D005260:Female; D006801:Humans; D008103:Liver Cirrhosis / Q000150:complications / Q000000981:diagnostic imaging*; D008113:Liver Neoplasms / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000209:etiology; D008297:Male; D008875:Middle Aged; D009389:Neovascularization, Pathologic / Q000000981:diagnostic imaging* / Q000209:etiology; D015588:Observer Variation; D011169:Portal Vein / Q000000981:diagnostic imaging; D011230:Precancerous Conditions / Q000000981:diagnostic imaging*; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015900:Radiography, Dual-Energy Scanned Projection / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D059629:Signal-To-Noise Ratio; D014057:Tomography, X-Ray Computed / Q000379:methods
keywords: cirrhosis; dual-energy CT; fast kilovoltage switching; hepatocellular carcinoma; liver CT