Split-bolus CT urography after microwave ablation of renal cell carcinoma improves image quality and reduces radiation exposure

Objective To compare image quality and radiation dose between single-bolus 2-phase and split-bolus 1-phase CT Urography (CTU) performed immediately after microwave ablation (MWA) of clinically localized T1 (cT1) RCC. Methods Forty-two consecutive patients (30 M, mean age 67.5 ± 9.0) with cT1 RCC were treated with MWA from 7/2013 to 12/2013 at two academic quaternary-care institutions. Renal parenchymal enhancement, collecting system opacification and distention and size-specific dose estimate (SSDE) were quantified and image quality subjectively assessed on single-bolus 2-phase versus split-bolus 1-phase CTU. Kruskal–Wallis and Pearson’s Chi-squared tests were performed to assess differences in continuous and categorical variables, respectively. Two-sample T test with equal variances was used to determine differences in quantitative and qualitative image data. Results Median tumor diameter was larger [2.9 cm (IQR 1.7–5.3) vs 3.6 cm (IQR 1.7–5.7), p = 0.01] in the split-bolus cohort. Mean abdominal girth ( p = 0.20) was similar. Number of antennas used and unenhanced CTs obtained before and during MWA were similar ( p = 0.11–0.32). Renal pelvis opacification (2.5 vs 3.5, p