title: Characterization of Urinary Stone Composition by Use of Third-Generation Dual-Source Dual-Energy CT With Increased Spectral Separation.
abstract: OBJECTIVE
  The purpose of this phantom study was to determine the utility of a third-generation dual-source CT scanner with increased dual-energy spectral separation in differentiating urinary stone composition.
  
  
  METHODS
  Eighty-seven urinary stones from humans were scanned in 35-, 40-, 45-, and 50-cm wide anthropomorphic phantoms with a third-generation dual-source scanner (system A) with a high-energy beam of 150 kV plus 0.6-mm tin filtration (Sn). The low-energy data were acquired at 70, 80, 90, and 100 kV. A second-generation dual-source scanner (system B) was used to acquire data at 140 kV plus 0.4-mm Sn for the high-energy and 80 or 100 kV for the low-energy images. Volume CT dose index was matched for a given phantom size. CT number ratios were calculated and used to differentiate uric acid from non-uric acid stones and oxalate from apatite stones in an ROC analysis.
  
  
  RESULTS
  The area under the curve (AUC) of the ROC curve for uric acid versus non-uric acid stones increased for large phantoms. For example, for imaging of the 45-cm wide phantom with system A at the 100- and 150-kV Sn low- and high-energy combination, the AUC was 0.99, whereas for system B at the 100- and 140-kV Sn combination, the AUC was 0.86. At each phantom size and for all energy combinations, the AUC values for oxalate versus apatite stones were higher for system A than they were for any energy combination for system B.
  
  
  CONCLUSIONS
  Compared with use of second-generation dual-source CT, use of third-generation dual-source CT at the energy combination of 100 and 150 kV Sn improved classification of urinary stones across a wide range of phantom sizes and increased the ability to differentiate oxalate from apatite stones.
authors.affiliation: 1 Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905.
authors.forename: Xinhui
authors.initials: X
authors.lastname: Duan
authors.affiliation: 1 Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905.
authors.forename: Zhoubo
authors.initials: Z
authors.lastname: Li
authors.affiliation: 1 Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905.
authors.forename: Lifeng
authors.initials: L
authors.lastname: Yu
authors.affiliation: 1 Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905.
authors.forename: Shuai
authors.initials: S
authors.lastname: Leng
authors.affiliation: 2 Siemens Medical Solutions, Malvern, PA.
authors.forename: Ahmed F
authors.initials: AF
authors.lastname: Halaweish
authors.affiliation: 1 Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905.
authors.forename: Joel G
authors.initials: JG
authors.lastname: Fletcher
authors.affiliation: 1 Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905.
authors.forename: Cynthia H
authors.initials: CH
authors.lastname: McCollough
mesh_terms: D006801:Humans; D019047:Phantoms, Imaging; D011857:Radiographic Image Interpretation, Computer-Assisted; D015900:Radiography, Dual-Energy Scanned Projection / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014545:Urinary Calculi / Q000737:chemistry* / Q000000981:diagnostic imaging*
keywords: CT; dual-energy CT; phantom; spectral separation; urinary stones