title: Targeted dual-energy single-source CT for characterisation of urinary calculi: experimental and clinical experience.
abstract: OBJECTIVE
  To assess the accuracy of targeted dual-energy single-source multi-detector CT (MDCT) for characterisation of urinary calculi.
  
  
  METHODS
  For proof of principle, 71 ex-vivo calculi underwent single-source 256-slice MDCT. Low-dose CT was performed in 154 patients with suspected urinary calculi. In 104 patients with urinary calculi targeted dual-energy imaging within one breath-hold was added. 46 patients with sufficient material for infrared-spectroscopy were analysed. Potential anatomical misregistrations between 80- and 140-kV(p)-images and HU-values were measured. DEIs (dual-energy-indices) were compared with the standard of reference. Effective doses were calculated.
  
  
  RESULTS
  In 26 of 46 patients no misregistration was present. Mean deviations were 2.7 mm in the z-axis (16 patients) and 4.3 mm in the axial plane (10 patients). The DEIs were 0.018 ± 0.016 for uric acid (UA), 0.035 ± 0.015 for mixed UA and 0.102 ± 0.015 for calcified stones in-vitro and 0.017 ± 0.002 for UA, 0.050 ± 0.019 for mixed UA and 0.122 ± 0.024 for calcified calculi in-vivo. Significant differences were noted among calcium, mixed UA and UA stones (p < 0.05). For the low-dose examination mean effective dose was 3.11 mSv. Targed dual-energy resulted in an extra dose of 1.84 mSv (additional 59.1%).
  
  
  CONCLUSIONS
  Targeted dual-energy imaging within one breath-hold is feasible for characterisation of urinary calculi using single-source MDCT allowing minimal anatomical discordance.
authors.affiliation: Institute of Radiology, Klinikum rechts der Isar, Technische Universität München, Ismaninger Str. 22, 81675 Munich, Germany. matthias.eiber@tum.de
authors.forename: Matthias
authors.initials: M
authors.lastname: Eiber
authors.forename: Konstantin
authors.initials: K
authors.lastname: Holzapfel
authors.forename: Markus
authors.initials: M
authors.lastname: Frimberger
authors.forename: Michael
authors.initials: M
authors.lastname: Straub
authors.forename: Heike
authors.initials: H
authors.lastname: Schneider
authors.forename: Ernst J
authors.initials: EJ
authors.lastname: Rummeny
authors.forename: Martin
authors.initials: M
authors.lastname: Dobritz
authors.forename: Armin
authors.initials: A
authors.lastname: Huber
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods; D014527:Uric Acid / Q000032:analysis*; D014545:Urinary Calculi / Q000000981:diagnostic imaging* / Q000473:pathology; D055815:Young Adult
chemical_list: D014527:Uric Acid