Active Crohn's disease in the small bowel: Evaluation by diffusion weighted imaging and quantitative dynamic contrast enhanced MR imaging

Purpose: To determine relative diagnostic value of MR diffusion and perfusion parameters in detection of active small bowel inflammation in patients with Crohn's disease (CD). Materials and Methods: We reviewed 18 patients with active CD of terminal ileum (TI) who underwent MR enterography (MRE; including dynamic contrast enhanced MRI and diffusion-weighted MRI). Conventional MRI findings of TI were recorded. Regions of interest were drawn over TI and normal ileum to calculate apparent diffusion coefficient (ADC), the volume transfer constant (K^trans) and the contrast media distribution volume (v _e). Receiver operating characteristic analysis was used to determine their diagnostic performance. Results: Among conventional MR findings, mural thickening and increased enhancement were present in all actively inflamed small bowel. K^trans, v_e, and ADC values differed significantly between actively inflamed TI and normal ileum (0.92 s^-1 versus 0.36 s^-1; 0.31 versus 0.15 ± 0.08; 0.00198 mm²/s versus 0.00311 mm²/s; P < 0.001). Area under the curve (AUC) for K ^trans, ve, and ADC values ranged from 0.88 to 0.92 for detection of active inflammation. Combining K^trans and ADC data provided an AUC value of 0.95. Conclusion: Dynamic contrast-enhanced MRI (DCE-MRI) and diffusion-weighted imaging (DWI) provide quantitative measures of small bowel inflammation that can differentiate actively inflamed small bowel segments from normal small bowel in CD. DWI provides better sensitivity compared with DCE-MRI and combination of ADC and Ktrans parameters for analysis can potentially improve specificity.