Focused Dual-energy CT Maintains Diagnostic and Compositional Accuracy for Urolithiasis Using Ultralow-dose Noncontrast CT

Urology. 2015 Dec;86(6):1097-102. doi: 10.1016/j.urology.2015.06.052. Epub 2015 Sep 14.


Objective: To evaluate the diagnostic accuracy of a new energy and radiation dose-reduced protocol for noncontrast computed tomography (NCCT) with dual-energy CT (DECT) analysis and its potential for the compositional analysis of uric acid (UA)- or non-uric acid (N-UA)-containing calculi.

Methods: A retrospective evaluation was carried out in 61 patients who underwent dose-reduced DECT (tube A: 140 kV/55 mAs; tube B: 80 kV/303 mAs) with a tube current 38.8% lower than that set by the manufacturer. A protocol combining low-dose CT and targeted DE scans was used. Urinary stones were detected and classified as UA- or N-UA-containing or mixed based on DE software results. The accuracy of the compositional analysis was controlled by correlation with conventional infrared-based analysis.

Results: The compositional stone differentiation was correct in 58 of 61 (95.1%) patients. The sensitivity of detecting pure UA-containing and pure N-UA-containing stones was 100%. The specificity of detecting UA- and pure N-UA-containing stones was 100% and 78.57%, respectively, as 3 of 7 mixed urinary stones (small fragments <4 mm) were classified as N-UA calculi. The total radiation dose in patients with body mass index <25 and >25 kg/m(2) was 1.2 and 2.5 mSv, respectively.

Conclusion: Lowering the DECT tube current by up to 38% of the manufacturer's recommendations allows a reduced radiation dose without impairing detection accuracy and stone compositional analysis. Compared with previous studies, this protocol might significantly decrease patient radiation exposure without affecting the quality of results.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Body Mass Index
  • Female
  • Humans
  • Kidney Calculi / chemistry*
  • Kidney Calculi / diagnostic imaging*
  • Male
  • Middle Aged
  • Radiation Dosage*
  • Radiography, Dual-Energy Scanned Projection
  • Retrospective Studies
  • Sensitivity and Specificity
  • Spectrophotometry, Infrared
  • Tomography, X-Ray Computed / methods*
  • Ureteral Calculi / chemistry*
  • Ureteral Calculi / diagnostic imaging*
  • Uric Acid / analysis


  • Uric Acid