title: Dual-energy contrast-enhanced computed tomography for the detection of urinary stone disease.
abstract: OBJECTIVE
  To assess the value of dual-energy contrast-enhanced computed tomography (CT) imaging for the detection of urinary stone disease using dual-source CT.
  
  
  METHODS
  Forty consecutive patients (mean age 46.6 +/- 16.2 years, range 27-85 years) suspected of having urinary stone disease underwent dual-source CT of the urinary tract. A 3-phasic CT scan protocol consisting of a standard unenhanced scan, a nephrographic, and an excretory phase of contrast enhancement was performed. The nephrographic phase scan was acquired in the dual-energy mode (80 kV/400 mA and 140 kV/95 mA) allowing reconstruction of virtual unenhanced images. Two blinded readers independently compared standard and virtual unenhanced CT for the number, size, and location of urinary stones. Measurements of anteroposterior abdominal diameters were performed to determine abdominal obesity.
  
  
  RESULTS
  Standard unenhanced CT revealed 35 uroliths in 18 of the 40 patients (18 of 40; 45%), virtual unenhanced CT demonstrated 26 uroliths in 15 of the 40 patients (15 of 40; 38%) ([kappa] value 0.89). Three false-negative and no false-positive ratings occurred using virtual unenhanced CT, and false-negative ratings solely occurred in obese patients. Sensitivity, specificity, positive predictive, and negative predictive values for virtual unenhanced CT for the diagnosis of urinary stone disease were 83%, 100%, 100%, and 88%, respectively.
  
  
  CONCLUSIONS
  Virtual unenhanced CT images reconstructed from contrast-enhanced dual-energy CT allow detection of urinary stones with good sensitivity and excellent specificity, but sensitivity is decreased in abdominal obese patients.
authors.affiliation: Department of Medical Radiology, Institute of Diagnostic Radiology, University of Zurich, Zurich, Switzerland.
authors.forename: Hans
authors.initials: H
authors.lastname: Scheffel
authors.forename: Paul
authors.initials: P
authors.lastname: Stolzmann
authors.forename: Thomas
authors.initials: T
authors.lastname: Frauenfelder
authors.forename: Thomas
authors.initials: T
authors.lastname: Schertler
authors.forename: Lotus
authors.initials: L
authors.lastname: Desbiolles
authors.forename: Sebastian
authors.initials: S
authors.lastname: Leschka
authors.forename: Borut
authors.initials: B
authors.lastname: Marincek
authors.forename: Hatem
authors.initials: H
authors.lastname: Alkadhi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002114:Calcinosis / Q000175:diagnosis / Q000000981:diagnostic imaging; D003287:Contrast Media / Q000008:administration & dosage; D003937:Diagnosis, Differential; D005188:False Negative Reactions; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods; D014545:Urinary Calculi / Q000175:diagnosis* / Q000000981:diagnostic imaging*
chemical_list: D003287:Contrast Media