Renal stones composition in vivo determination: comparison between 100/Sn140 kV dual-energy CT and 120 kV single-energy CT.

The objective of this study is to compare in vivo, the accuracy of single-energy CT (SECT) and dual-energy CT (DECT) in renal stone characterization. Retrospective study approved by the IRB. 30 patients with symptomatic urolithiasis who underwent CT on a second-generation dual-source scanner with a protocol that included low-dose 120 kV scan followed by 100/Sn140 kV dual-energy scan have been included. Stone composition was classified as uric acid, cystine or calcium oxalates, and phosphates according to attenuation values at 120 kV and to 100/Sn140 kV attenuation ratios and compared with the infrared spectroscopy analysis. 50 stones were detected in 30 patients. SECT correctly assessed stone composition in 52 % of the cases, DECT in 90 %. Sensitivity, specificity, positive predictive value, and negative predictive value in differentiating uric acid vs. non-uric acid stones were 0.94, 0.72, 0.64, and 0.96 for SECT and 1.00, 0.94, 1.00, and 0.96 for DECT, respectively. DECT significantly performs better than SECT in characterising renal stones in vivo, and may represent a useful tool for treatment planning.