Dual-Energy CT (DECT) Color-Coded Iodine Overlay in the Diagnosis of Complex Cystic Renal Masses

PURPOSE To define the diagnostic value of DECT color-coded iodine overlay (CCIO) in the evaluation of complex cystic renal masses and calculate the potential dose reduction of this technique. METHOD AND MATERIALS Forty-nine patients (20 women, 29 men; age range 33-78 years; mean age, 57 years ± 5) with an ultrasonographic diagnosis of complex cystic renal mass, were prospectively studied with a CT protocol that included true nonenhanced (TNE) phase acquired in the single-energy (SE) mode, cortico-medullary phase acquired in the DE mode, and nephrographic phase acquired in the SE mode. We considered radiation doses, both in vitro and in vivo, comparing a combined SE/DE dual-phase protocol (VNE-DE cortico-medullary and SE nephrographic phases) with a standard SE triple- phase protocol (TNE, cortico-medullary and nephrographic phases). VNE images were evaluated during a first session, considering TNE images as standard of reference; DE images with CCIO, were read during a second session, with DE blended images data set as standard of reference. RESULTS Dose reduction by using a combined DE/SE study protocol was 28% in vitro and 18% in vivo. VNE and TNE images were comparable in all cases with regard to diagnostic informations, and the interobserver agreement was almost perfect (k = 0.986). The depiction of enhancement was found in the same 35 out of 43 (81.3%) lesions, and an almost perfect interobserver agreement (k = 0.991) was demonstrated. The diagnostic accuracy of DECT with CCIO was: 100% sensitivity, 100% specificity, NPV value of 100% and PPV value of 100%. CONCLUSION The use of CCIO technique in DECT and using a combined DE/SE study protocol results in an increased diagnostic confidence for differentiating cysts and enhancing masses with a dose reduction of 18%. CLINICAL RELEVANCE/APPLICATION A combined DE/SE study protocol with the use of CCIO allows an accurate discrimination of cysts and enhancing renal masses with a considerable radiation dose reduction.