Noninvasive differentiation of uric acid versus non-uric acid kidney stones using dual-energy CT

Acad Radiol. 2007 Dec;14(12):1441-7. doi: 10.1016/j.acra.2007.09.016.


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.

MeSH terms

  • Absorptiometry, Photon / methods
  • Animals
  • Cadaver
  • Calcium Oxalate / analysis
  • Cystine / analysis
  • Durapatite / analysis
  • Humans
  • Image Processing, Computer-Assisted / methods
  • Kidney Calculi / chemistry*
  • Kidney Calculi / diagnostic imaging
  • Phantoms, Imaging
  • Radiation Dosage
  • Swine
  • Tomography, X-Ray Computed / methods*
  • Uric Acid / analysis*


  • Calcium Oxalate
  • Uric Acid
  • Cystine
  • Durapatite