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.
Keywords: atypical cysts; dual-energy CT; iodine concentration map; kidney transplant; renal cancer.