Noninvasive Differentiation of Uric Acid versus Non-Uric Acid Kidney Stones Using Dual-Energy CT

Andrew N. Primak, Joel G. Fletcher, Terri J. Vrtiska, Oleksandr P. Dzyubak, John C. Lieske, Molly E. Jackson, James C. Williams, Cynthia H. McCollough

Research output: Contribution to journalArticlepeer-review

283 Scopus citations


Rationale and Objectives: To determine the accuracy and sensitivity for dual-energy computed tomography (DECT) discrimination of uric acid (UA) stones from other (non-UA) renal stones in a commercially implemented product. Materials and Methods: Forty human renal stones comprising uric acid (n = 16), hydroxyapatite (n = 8), calcium oxalate (n = 8), and cystine (n = 8) were inserted in four porcine kidneys (10 each) and placed inside a 32-cm water tank anterior to a cadaver spine. Spiral dual-energy scans were obtained on a dual-source, 64-slice computed tomography (CT) system using a clinical protocol and automatic exposure control. Scanning was performed at two different collimations (0.6 mm and 1.2 mm) and within three phantom sizes (medium, large, and extra large) resulting in a total of six image datasets. These datasets were analyzed using the dual-energy software tool available on the CT system for both accuracy (number of stones correctly classified as either UA or non-UA) and sensitivity (for UA stones). Stone characterization was correlated with micro-CT. Results: For the medium and large phantom sizes, the DECT technique demonstrated 100% accuracy (40/40), regardless of collimation. For the extra large phantom size and the 0.6-mm collimation (resulting in the noisiest dataset), three (two cystine and one small UA) stones could not be classified (93% accuracy and 94% sensitivity). For the extra large phantom size and the 1.2-mm collimation, the dual-energy tool failed to identify two small UA stones (95% accuracy and 88% sensitivity). Conclusions: In an anthropomorphic phantom model, dual-energy CT can accurately discriminate uric acid stones from other stone types.

Original languageEnglish (US)
Pages (from-to)1441-1447
Number of pages7
JournalAcademic radiology
Issue number12
StatePublished - Dec 2007


  • Kidney stones
  • dual-energy computed tomography
  • renal calculi
  • uric acid
  • urolithiasis

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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