Value of dual-energy CT parameters DER and DEI in predicting calcium-containing urinary stones and differentiating pure calcium oxalate monohydrate.

OBJECTIVE

To investigate the diagnostic value of quantitative parameters (including dual-energy ratio (DER) and dual-energy index (DEI)) from dual-source dual-energy computed tomography (DECT) in predicting calcium-containing urinary stone subtypes and differentiating pure calcium oxalate monohydrate (COM) stones.

METHODS

We conducted a retrospective analysis of 311 patients with urinary stones diagnosed between May 2022 and September 2024, including 119 patients with uric acid (UA) stones and 192 patients with non UA calcium-containing stones according to Fourier-transform infrared spectroscopy. All patients underwent DECT, and CT attenuation values were measured on virtual monoenergetic images at 40 keV and 80 keV. Multiple parameters were calculated from these measurements: dual-energy density (DED), DER, DEI, and effective atomic number (Eff-Z). Infrared spectroscopy was used as the gold standard for stone composition analysis. ROC curve analysis was used to test the diagnostic efficacy of CT-based parameters. A confusion matrix was then constructed to comprehensively evaluate diagnostic performance, including sensitivity, specificity, and accuracy.

RESULTS

When evaluating the ability of various imaging parameters to differentiate between uric acid stones and calcium-containing stones, Eff-Z demonstrated the strongest discriminative ability, with an AUC of 0.938 and an accuracy of 88.42%. DER and DEI followed closely, with slightly lower diagnostic efficacy but still significant. In the comparison between COM and non-COM stones, after adjusting for orientation, DER (AUC 0.854, accuracy 80.21%) and DEI (AUC 0.760, accuracy 70.31%) still provided effective differential diagnostic criteria. There were statistical differences in DER and DEI measurements (both P<0.001).

CONCLUSION

DER, DEI, and Eff-Z from dual-source CT can effectively differentiate between uric acid stones and calcium-containing stones, with Eff-Z being the best indicator. DER and DEI can further help identify pure COM stones, providing value for preoperative non-invasive assessment.