Quantitative Assessment of Bladder Cancer Reflects Grade and Recurrence: Comparing of Three Methods of Positioning Region of Interest for ADC Measurements at Diffusion-weighted MR Imaging

Purpose: To determine the impact of three different regions of interests (ROIs) positioning methods for apparent diffusion coefficient (ADC) measurements on the assessment of the grade and recurrence and to examine the correlation between ADC value and histopathological grade/ Ki-67 labeling index (LI) in patients with bladder cancer. Materials and Methods: Sixty-one patients with bladder cancer were retrospectively evaluated. Two observers measured mean ADC values using whole-volume-ROIs, single-section-ROI and three-ROIs methods. Interclass correlation coefficient was analyzed to assess interobserver variability. The grade and recurrence in patients with bladder cancer were assessed by calculating the areas under the receiver operating characteristic curves with Az values. Spearman's correlation was used to analyze the correlations of ADC value with grade and Ki-67 LI. Results: For the mean ADC value, the interclass correlation coefficient were excellent with the whole-volume and the single-section method (0.90 [95% CI: 0.84, 0.94] and 0.89 [95% CI: 0.81, 0.93]) and was good with the three-ROIs method (0.72 [95% CI: 0.53, 0.83]). The Az value for determining histological grade and recurrence of bladder cancer were not significantly different from each positioning method (all p > 0.05). There's significant correlation between histological grade and ADC measuring by whole-volume-ROIs and single-section-ROI methods (r = 0.31, p = 0.02; r = 0.37, p < 0.05). The ADC measured by whole-volume-ROIs, single-section-ROI, and three-ROls methods were significantly and inversely correlated with the Ki-67 LI (r = -0.3; r = -0.49; r = -0.40, all p < 0.05). Conclusion: There's no significant difference among any of the ROI positioning methods in evaluation of tumor grade and recurrence. There's significant correlation between histological grade and ADC measuring by whole-volume-ROls and single-section-ROI methods. The ADC value obtained by either of three methods was significantly and inversely correlated with the Ki-67 LI.