Korean J Urol.  2006 Jul;47(7):717-721. 10.4111/kju.2006.47.7.717.

Predicting the Composition of Urinary Stone by Non-enhanced Spiral Computed Tomography

• Park SY
• Hong JH
• Jeon SS

• KMID: 2294311
• DOI: http://doi.org/10.4111/kju.2006.47.7.717

Abstract

PURPOSE: We attempted to develop a more accurate set of tools for predicting the composition of urinary stone with using Hounsfield units (HUs) in non-enhanced spiral computed tomography (NESCT).
MATERIALS AND METHODS
We evaluated 141 stones, and each of which was determined to contain the predominant stone component more than 70% (84 calcium oxalate, 35 uric acid, 16 carbonate apatite, 4 cystine and 2 brushite). NESCT was conducted at different collimations that varied between 3.75mm, 5mm and 7mm through the stones. One region of interest (ROI) was acquired for the plane that passed through the widest transverse diameter of the stone at the bone window setting. The mean size of the ROI in which the highest attenuation area was located was determined to be 2.0+/-0.5mm2, and we recorded the mean and maximum HU values. In order to assess the partial volume effects, we used the S/C ratio (stone size/collimation ratio).
RESULTS
As the S/C ratio increased, both mean and maximum HU values increased, as did the ability to differentiate between different stone compositions. Also, under conditions in which the S/C ratio exceeded 2, we proved to be able to differentiate uric acid stones from other stones, with no overlap in attenuation. Maximum HU values also proved to be effective tools for determining stone composition, as compared with the mean HU values.
CONCLUSIONS
In situations in which the S/C ratio exceeded 2, CT HUs proved to be a useful and accurate measurement for predicting uric acid stones.

Keyword

Tomography; Calculi; Urinary tract

MeSH Terms

Calcium Oxalate
Calculi
Carbon
Cystine
Tomography, Spiral Computed*
Uric Acid
Urinary Calculi*
Urinary Tract
Calcium Oxalate
Carbon
Cystine
Uric Acid

Figure

• 

  Fig. 1. Stone composition and Hounsfield unit distributions. (A) Mean Hounsfield unit distributions of each the stone component in all the stones. (B, C) Mean (B) and maximum (C) Hounsfield unit distributions of each stone component on the condition that the S/C was >2.

• 

  Fig. 2. Schematic illustration that shows the relationship between stone size and the collimation width of the computed tomography. (A) In the case in which the stone is smaller than the collimation width (S/C ratio < 1). (B, B’) In the cases in which the stone is larger than the collimation width, but smaller than double the collimation width(12).

Cited by  1 articles

Predicting the Therapeutic Effect of Extracorporeal Shockwave Lithotripsy by Non-enhanced Computed Tomography in Renal Stones
Jung Hoon Kim, Young Tae Moon
Korean J Urol. 2008;49(3):252-256.    doi: 10.4111/kju.2008.49.3.252.

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