Contrast-enhanced Ultrasound (CEUS)-based Characterization Solid Renal Masses: A role for quantitative imaging approaches

In this prospective study, forty patients with solid renal masses who underwent contrast-enhanced ultrasound (CEUS) examinations were selected. Using the ImageJ software, renal masses and adjacent normal tissue were manually segmented from CEUS cine exams obtained using the built-in RS85 Samsung scanner software. For the radiomics analysis, one frame representing precontrast, early, peak, and delay enhancement phase were selected post segmentation from each CEUS clip. From each region of interest (ROI) within a tumor tissue normalized renal mass, 112 radiomic metrics were extracted using custom Matlab (R) code. For the time-intensity curve (TIC) analysis, the segmented ROIs were plotted as a function of time, and the data were fit to a washout curve. From these time-signal intensity curves, perfusion quantitative parameters, were generated. Wilcoxon rank sum test or univariate independent t-test depending on data normality were used for descriptive analyses. Agreement was analyzed using Kappa statistic. Of the 40 solid masses, 31 (77.5%) were malignant, 9 (22.5%) were benign based on histopathology. Excellent agreement was found between histopathological confirmation and visual assessment based on CEUS in discriminating solid renal masses into benign vs. malignant categories (kappa=0.89 95% confidence interval ( CI): (0.77,1)). The total agreement between the two was 92.5%. The sensitivity and specificity of CEUS-based visual assessment was found to be 100% and 66.7%, respectively. Quantitative analysis revealed TIC metrics revealed statistically significant differences between the malignant and benign groups and between clear cell renal cell carcinoma (ccRCC) and papillary renal cell carcinoma (pRCC) subtypes. The study shows excellent agreement between visual assessment and histopathology, but with the room to improve in specificity.