Dual-energy CT for Characterization of Renal Masses as Enhancing or Non-enhancing: Can Iodine Quantification Replace Enhancement Measurements?

PURPOSE To evaluate the diagnostic accuracy of two different dual-energy CT algorithms to quantify the iodine uptake, as enhancement measurements and iodine quantification, for characterization of renal masses as enhancing or nonenhancing in a single phase nephrographic image. METHOD AND MATERIALS The Institutional Review Board approved this retrospective study conducted from data found in institutional patient databases and archives. Forty-nine renal masses were characterized as enhancing or nonenhancing using measurements of enhancement (in HU) and iodine quantification (in mg/ml). Calculated iodine concentrations were compared with known iodine concentration in a phantom model. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and diagnostic accuracy of DE enhancement measurements and iodine quantification were calculated, with histopathology or imaging follow-up as reference standard. Receiver operating characteristic (ROC) analysis were used to compare diagnostic performances of the two approaches. Calculated iodine concentration was correlated to known iodine concentration by Pearson correlation. Error in measurement of iodine concentrations was determined by Bland-Altman method. Statistical significance was assumed for P < .05. RESULTS Sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy for enhancement measurements and iodine quantification were 77.7%, 100%, 100%, 61.9%, 84% and 100%, 84.6%, 94.7, 100%, 96%, respectively; corresponding areas under ROC curve were 0.982 and 1.000 (P < .001). An excellent correlation between calculated and known iodine concentration (r2 = 0.999; P < .001) was found, with a mean error of 0.14 mg/mL. CONCLUSION Compared with DE enhancement measurements, iodine quantification improves the diagnostic accuracy of renal masses characterization as enhancing or nonenhancing. CLINICAL RELEVANCE/APPLICATION Iodine quantification at dual energy CT may be considered as a new diagnostic paradigm for the characterization of renal masses, reducing the cost of additional tests.