The role of third-generation dual-source dual-energy computed tomography in characterizing the composition of renal stones with infrared spectroscopy as the reference standard

Purpose
The aim of our study was to prospectively evaluate the role of third-generation, dual-source, dual-energy computed tomography (DECT) in the characterization of renal calculi, with ex vivo renal stone evaluation using Fourier transform infrared spectroscopy (IS) as the reference standard.

Material and methods
In our study 50 patients with history suggestive of renal calculi were subjected to DECT using 100 kVp and Sn150 kVp. With DECT, renal stone attenuation at low and high kVp was attained, and the attenuation ratios were measured. The result of DECT was compared with IS to identify the chemical composition of the extracted renal stones. IBM SPSS version 22 was used for statistical analysis.

Results
In our study, the mean attenuation ratio of the renal stone was 1.57 ± 0.25. Out of 50 patients, the stones of 39 patients were predicted as calcium-containing stones, in 4 patients as cystine stones, and in 7 as uric acid stones on DECT. In IS analysis, 43 patients had calcium-containing stones, and 7 patients had uric acid stones. The accuracy rate of DECT for detecting calcium and uric acid stones in our study were 90% and 100%, respectively. The positive predictive value for the DECT to assess the chemical composition of renal calculi was found to be 92%.

Conclusions
Third-generation DECT scan had 100% accuracy in differentiating uric acid stones from non-uric acid stones in our study. Because the treatment is different for different chemical compositions of stones, identification of specific chemical components is very important, and it can be accurately done by DECT.