Characterization of Mixed Urinary Stone Compositions with Dual-Source Dual-Energy Computed Tomography in Vivo Compared to Infrared Spectroscopy

Background: Most previous studies have demonstrated the possibility of using dual-source dual-energy computed tomography (DSDECT) to distinguish pure stones with high accuracy. While stones are usually composed of a mixture of substances, very few studies have focused on these stone compositions. Objectives: To retrospectively evaluate the diagnostic accuracy of DSDECT in predicting the composition of mixed urinary calculi in vivo compared to the postoperative infrared spectroscopy (IRS) for stone analysis. Patients and Methods: We retrospectively included 111 patients with 117 mixed urinary stones, detected by IRS, who underwent DSDECT between June 2018 and March 2020. Patients diagnosed with urolithiasis were examined by DSDECT preoperatively. The final stone composition was detected by IRS in vitro postoperatively. Also, the stone composition predicted by DSDECT was compared to the IRS results, known as the reference standard. Results: According to the results of IRS, 117 mixed urinary calculi, composed of a main constituent and minor admixtures, were divided into four groups: calcium oxalate (CaOx)-hydroxyapatite (HA) (n = 70); HA-CaOx (n = 36); uric acid (UA)-CaOx (n = 8); and cystine (CYS)-HA (n = 3). The accuracy of DSDECT in predicting different components of mixed urinary stones was 68.4%, 64.1%, 97.4%, and 97.5% for the CaOx-HA, HA-CaOx, UA-CaOx, and CYS-HA stones, respectively. The imaging characteristics of different mixed urinary stones, as shown by DSDECT, revealed that the CaOx-HA ratio value was lower than that of HA-CaOx (1.59 ± 0.11 vs. 1.66 ± 0.22; P < 0.05). Meanwhile, the computed tomography (CT) values of CaOx-HA under 150 kV were higher than those of HA-CaOx (915.41 ± 226.84 vs .799.56 ± 252.01; P < 0.05). Conclusion: Although DSDECT has a relatively low accuracy for predicting the components of CaOx-HA and HA-CaOx in vivo, its combination with the measured ratio and CT values may help differentiate these stones.