Endourology and StonesDual-energy vs Conventional Computed Tomography in Determining Stone Composition
Section snippets
Materials and Methods
Thirty-two renal stones with a known, pure composition, as determined by infrared spectroscopy, were placed in a water bath measuring 25 cm high × 40 cm wide to simulate the scatter from a normal body habitus. Stone size ranged from 1-10 mm and consisted of pure uric acid, cystine, struvite, and calcium oxalate monohydrate.
The stones were scanned using conventional imaging techniques at 120 kV(p) and subsequently using fast kV-switching DECT, using the same scanner (GE Healthcare Discovery 750
Results
Included were 27 stones large enough to allow a ROI that fit completely within the stone. Stones sized <3 mm could not fit the ROI and were therefore excluded. The size and composition of each stone is summarized in Table 1. The mean attenuation values of each stone subtype compared with the reference range are reported in Table 2.
The accuracy for each stone phenotype is compared in Figure 2. For single-energy measurements, the blinded clinician accurately identified 14 of 27 stones of all
Comment
Knowledge of a stone's composition can be a decisive factor in determining optimal management, yet there is no reliable method of determining composition until the stone has been retrieved or passed. Ideally, knowledge of stone phenotype before treatment would allow optimal management and thus improve patient outcomes. This may include treating uric acid stones with medical dissolution therapy, which has reported success rates as high as 70%-80%9 and could spare patients from potentially
Conclusion
When compared in a blinded, prospective fashion, DECT performed superiorly to conventional single-energy CT in classifying calcium oxalate, cystine, struvite, and uric acid stones. In addition, there appears to be a distinct advantage in differentiating nonuric acid from uric acid stones.
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Financial Disclosure: The authors declare that they have no relevant financial interests.