title: Dual-energy MDCT in hypervascular liver tumors: effect of body size on selection of the optimal monochromatic energy level.
abstract: OBJECTIVE
  The purpose of this article is to investigate the effect of body size on the selection of optimal monochromatic energy level for maximizing the conspicuity of hypervascular liver tumors during late hepatic arterial phase using dual-energy MDCT.
  
  
  METHODS
  An anthropomorphic liver phantom in three body sizes and iodine-containing inserts simulating low- and high-contrast hypervascular lesions was imaged with dual- and single-energy MDCT at various energy levels (80, 100, 120, and 140 kVp). Dual-energy MDCT was also performed in 48 patients with 114 hypervascular liver tumors; virtual monochromatic images were reconstructed at energy levels from 40 to 140 keV. The effect of body size and lesion iodine concentration on noise and tumor-to-liver contrast-to-noise ratio was compared among different datasets for phantoms and patients.
  
  
  RESULTS
  The highest tumor-to-liver contrast-to-noise ratio was noted at 80 kVp for all phantom sizes. On virtual monochromatic images, the minimum noise was noted at 70 keV for small and medium phantoms and at 80 keV for the large phantom. Tumor-to-liver contrast-to-noise ratio was highest at 50 keV for small and medium phantoms and at 60 keV for the large phantom (p<0.0001). Compared with 80-kVp images, an optimal monochromatic energy level yielded a significantly higher (p<0.0001) tumor-to-liver contrast-to-noise ratio for high-contrast lesions in the large body size and for low-contrast lesions in all phantom sizes. In patients, the optimal monochromatic energy level for tumor-to-liver contrast-to-noise ratio increased proportionally along with body size (p<0.0001).
  
  
  CONCLUSIONS
  Selection of the optimal monochromatic energy level for maximizing the conspicuity of hypervascular liver tumors is significantly affected by patient's body size.
authors.affiliation: 1 Department of Radiology, Duke University Medical Center, Box 3808, 2301 Erwin Rd, Durham, NC 27710.
authors.forename: Achille
authors.initials: A
authors.lastname: Mileto
authors.forename: Rendon C
authors.initials: RC
authors.lastname: Nelson
authors.forename: Ehsan
authors.initials: E
authors.lastname: Samei
authors.forename: Kingshuk Roy
authors.initials: KR
authors.lastname: Choudhury
authors.forename: Tracy A
authors.initials: TA
authors.lastname: Jaffe
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Wilson
authors.forename: Daniele
authors.initials: D
authors.lastname: Marin
mesh_terms: D049628:Body Size; D006801:Humans; D008113:Liver Neoplasms / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D061330:Multidetector Computed Tomography / Q000295:instrumentation / Q000379:methods*; D009389:Neovascularization, Pathologic / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D015900:Radiography, Dual-Energy Scanned Projection / Q000295:instrumentation / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D059629:Signal-To-Noise Ratio
keywords: MDCT; body size; dual-energy CT; hypervascular liver tumors; virtual monochromatic imaging