Dual-Energy Dual-Source CT With Additional Spectral Filtration Can Improve the Differentiation of Non–Uric Acid Renal Stones: An Ex Vivo Phantom Study

Abstract

Purpose To determine the ex vivo ability of dual-energy, dual-source computed tomography (DE-DSCT) with additional tin filtration to differentiate between five groups of human renal stone types. Methods Forty-three renal stones of ten types were categorized into five primary groups based on effective atomic numbers, which were calculated as the weighted average of the atomic numbers of constituent atoms. Stones were embedded in porcine kidneys and placed in a 35cm water phantom. DE-DSCT scans were performed with and without tin filtration at 80/140kV. The CT number ratio [CTR=CT(low)/CT(high)] was calculated on a volumetric voxel-by-voxel basis for each stone. Statistical analysis was performed and receiver operating characteristic (ROC) curves were plotted to compare the difference in CTR with and without tin filtration, and to measure the discrimination between stone groups. Results CTR of non-uric acid stones increased on average by 0.17 (range 0.03–0.36) with tin filtration. The CTR values for non-uric acid stone groups were not significantly different (p>0.05) between any of the two adjacent groups without tin filtration. Use of the additional tin filtration on the high-energy x-ray tube significantly improved the separation of non-uric acid stone types by CTR (p<0.05). The area under the ROC curve increased from 0.78–0.84 without fin filtration to 0.89–0.95 with tin filtration. Conclusion Our results demonstrated better separation between different stone types when additional tin filtration was used on DE-DSCT. The increased spectral separation allowed a 5-group stone classification scheme. Some overlapping between particular stone types still exists, including brushite and calcium oxalate.

In vivo characterization of urinary calculi on dual-energy CT: going a step ahead with sub-differentiation of calcium stones

“…Further characterization of calcium calculi remains even more difficult because of overlap in their attenuation values (13,16). With the introduction of second-generation dual-source DECT with added tin filtration, a few in vitro studies have shown that further characterization of calcium calculi may be possible (17)(18)(19)(20) whereas a few others have concluded otherwise (21).…”

Characterization of Urinary Tract Stones with Dual Energy Computed Tomography

“…11 Qu et al also demonstrated better separation of different types of stones ex vivo as well. 12 The characterization of various stone is based on the dual energy ratio and x ray attenuation or HU.…”

Evaluation of ureteric jet flow with Doppler ultrasonography during manual compression

“…[14][15][16][17] Conventional US is the first-line modality for evaluating the urinary tract. However, sound beam attenuation in obesity and superposition of colonic gas may prevent optimal visualization for diagnosis.…”