Comparison of 270 Versus 320 mg I/mL of Iodixanol in 1 Image Assessment of Both Renal Arteries and Veins With Dual-Energy Spectral CT Imaging in Late Arterial Phase and Their Influence on Renal Function

Computed Tomography Urography: State of the Art and Beyond

Computed Tomography Urography (CTU) is a multiphase CT examination optimized for imaging kidneys, ureters, and bladder, complemented by post-contrast excretory phase imaging. Different protocols are available for contrast administration and image acquisition and timing, with different strengths and limits, mainly related to kidney enhancement, ureters distension and opacification, and radiation exposure. The availability of new reconstruction algorithms, such as iterative and deep-learning-based reconstruction has dramatically improved the image quality and reducing radiation exposure at the same time. Dual-Energy Computed Tomography also has an important role in this type of examination, with the possibility of renal stone characterization, the availability of synthetic unenhanced phases to reduce radiation dose, and the availability of iodine maps for a better interpretation of renal masses. We also describe the new artificial intelligence applications for CTU, focusing on radiomics to predict tumor grading and patients' outcome for a personalized therapeutic approach. In this narrative review, we provide a comprehensive overview of CTU from the traditional to the newest acquisition techniques and reconstruction algorithms, and the possibility of advanced imaging interpretation to provide an up-to-date guide for radiologists who want to better comprehend this technique.

Detection and Characterization of Atypical Renal Cysts and Solid Renal Masses in Kidney Transplant Patients by Use of Dual-Energy CT Iodine Maps

OBJECTIVE. The purpose of this study was to evaluate whether dual-energy CT follow-up of kidney transplant recipients performed with only two contrast-enhanced phases and reconstructed material maps has the same diagnostic efficiency as triphasic conventional CT in detection and characterization of atypical renal cysts and renal masses. MATERIALS AND METHODS. In a retrospective study, 175 renal transplant patients underwent dual-energy CT as part of their follow-up (monoenergetic unenhanced, late contrast-enhanced, and tubular contrast-enhanced dual-energy phases). An unenhanced virtual series and material separation maps were reconstructed. ROIs were marked on theses lesions, the bladder, and the psoas muscle. Material suppressed iodine was used to record attenuation measurements on the unenhanced and virtual unenhanced series in the tubular and late phases, and material concentration measurements were obtained on the iodine density images. The delivered doses for each series were registered. RESULTS. One hundred one renal lesions (spontaneous attenuation > 20 HU, size > 10 mm) were detected. An iodine concentration threshold greater than 1500 μg/mL was associated with excellent diagnostic performance (sensitivity, 100%; specificity, 92.55%; positive predictive value, 50%; negative predictive value, 100%) for detection of suspect lesions (enhancement > 20 HU). The two lesions with an iodine concentration greater than 5000 μg/mL corresponded to the only two histologically proven cancers. CONCLUSION. Iodine concentration maps obtained with dual-energy CT perform as well as enhanced images obtained at conventional CT in the detection and characterization of tissue and atypical cystic renal lesions in kidney transplant recipients. Use of this method could reduce radiation dose, especially by avoiding the unenhanced series.

Dual-Energy CT Urography With 50% Reduced Iodine Dose Versus Single-Energy CT Urography With Standard Iodine Dose

OBJECTIVE

The purpose of this study was to compare dual-energy CT (DECT) urography with a 50% reduced iodine dose to single-energy CT (SECT) urography with a standard iodine dose with respect to attenuation of renal vascular and urinary tract structures and with respect to image quality.

SUBJECTS AND METHODS

The study included 62 patients undergoing evaluation of urinary tract lithiasis, tumor, or hematuria. Thirty-one patients underwent DECT urography with a 50% reduced iodine dose and reconstruction at 50 and 77 keV. These subjects were sex, age, and size matched to a group of 31 patients who underwent 120-kVp SECT urography with a standard iodine dose. The mean iodine dose was 22 g for DECT and 44 g for SECT. Attenuation was measured at seven locations in the renal arteries, renal veins, and urinary tract. Two reviewers subjectively scored the image quality parameters image noise, sharpness of urinary tract contours, enhancement of urinary structures, and streak artifacts.

RESULTS

Mean DECT attenuation at 50 keV was the same as or greater than SECT attenuation at each of the seven locations. Measured image noise was highest at 50-keV DECT but was the same for 77-keV DECT and 120-kVp SECT. Mean subjective scores for DECT image quality parameters were the same as or higher than those of SECT, except for streak artifact and sharpness of urinary tract contours.

CONCLUSION

DECT urography with a 50% reduced iodine dose may result in measured renal vascular and urinary tract attenuation the same as or higher than and image quality measurements and scores similar to those obtained with 120-kVp SECT urography with a standard iodine dose.