Differentiation of Benign Solid Renal Lesions from Malignant Lesions Using Dual-Energy CT

Objective: To evaluate the quantitative measurement of effective atomic number (Zeff) and iodine density reconstructed from dual-energy computed tomography (CT) in the discrimination of malignant renal lesions from benign renal lesions. Materials and Methods: The present study was a retrospective study that included patients with renal lesions who underwent dual-energy CT between January 2017 and June 2020. All subjects had a pathological diagnosis or follow-up imaging of at least 24 months. Two observers independently measured the Zeff, iodine density, and conventional CT attenuation of the renal lesions. Associations between the different tumor types and the quantitative CT measurements reconstructed from dual-energy CT were assessed, and interobserver agreement was evaluated. Results: Sixty-one renal lesions from 48 patients were included in the present study. No statistical differences were found in mean Zeff, iodine density, or CT attenuation between the benign renal lesions and the malignant renal lesions. However, significant differences were observed in Zeff, iodine density, and CT attenuation between the renal cell carcinoma (RCC) and the other malignant tumors, and between the clear cell RCC and the papillary RCC. The optimal thresholds for Zeff, iodine density, and CT attenuation for distinguishing RCC from other malignant tumors were 8.22, 1.71 mg/mL, and 79.50 HU, respectively, which provided sensitivity of 76%, 76%, and 80%, respectively. Conclusion: Benign solid renal lesions cannot be differentiated from malignant renal tumors by Zeff and iodine density measurements alone. However, dual-energy Zeff and iodine density have potential for the non-invasive differentiation of RCC from the other malignant renal tumors, and for the differentiation of RCC subtypes. Keywords: Dual-energy CT; Spectral CT; Renal cell carcinoma; Renal mass; Iodine density; Effective atomic number