Reproducibility of Dynamic Contrast-Enhanced MRI in Renal Cell Carcinoma A Prospective Analysis on Intra- and Interobserver and Scan-Rescan Performance of Pharmacokinetic Parameters

The objective of this study was to investigate the intra- and interobserver as well as scan-rescan reproducibility of quantitative parameters of renal cell carcinomas (RCCs) with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI).A total of 21 patients with clear cell RCCs (17 men, 4 woman; age 37-69 years, mean age 54.6 years, mean size, 5.02.2cm) were prospectively recruited from September 2012 to November 2012. Patients underwent paired DCE-MRI studies on a 3.0 T MR system with an interval of 48 to 72 hours. The extended-Tofts model and population-based arterial input function were used to calculate kinetic parameters. Three observers defined the 2-dimensional whole-tumor region of interest at the slice with the maximum diameter of the RCC. Intraobserver and scan-rescan differences were assessed using paired t tests, whereas interobserver differences using two-way analysis of variance. Intra- and interobserver reproducibility and scan-rescan reproducibility were evaluated using within-subject coefficient of variation (wCoV) and intraclass correlation coefficient (ICC).There were no significant intra-, interobserver, or scan-rescan differences in parameters (all P>0.05). All ICCs for intra- and interobserver agreements were >0.75 (P<0.05), whereas the scan-rescan agreement was moderate to good; V-e (0.764, 95% confidence interval [CI]: 0.378-0.925) and K-ep (0.906, 95% CI: 0.710-0.972) had higher ICC than K-trans (0.686; 95% CI: 0.212-0.898) and V-p (0.657; 95% CI: 0.164-0.888). In intra- and interobserver variability analyses, all parameters except V-p had low wCoV values. K-trans and V-e had slightly lower intraobserver wCoV (1.2% and 0.9%) compared with K-ep (3.7%), whereas all 3 of these parameters had similar interobserver wCoV values (2.5%, 3.1%, and 2.9%, respectively). Regarding scan-rescan variability, K-trans and K-ep showed slightly higher variation (15.6% and 15.4%) than V-e (10.1%). V-p had the largest wCoV in all variability analyses (all >30%).DCE-MRI demonstrated good intra- and interobserver reproducibility and moderate to good scan-rescan performance in the assessment of RCC using K-trans, K-ep, and V-e as parameters under noncontinuous scanning mode. V-p showed poor reproducibility, and thus may not be suitable for this scanning protocol.