Diffusion kurtosis MRI versus conventional diffusion-weighted imaging for evaluating inflammatory activity in Crohn's disease

Purpose: To assess the efficacy of diffusion kurtosis imaging (DKI) and to compare DKI-derived parameters with that of conventional diffusion-weighted imaging (DWI) for grading the inflammatory activity of Crohn's disease (CD). Materials and Methods: In all, 38 patients with CD underwent 3T magnetic resonance enterography (MRE) with DKI (b values of 0–2000 s/mm ² ). The inflammatory activity of the bowel segments was graded by magnetic resonance index of activity (MaRIA) as inactive (<7), mild (≥7 and <11), or moderate-severe (≥11). Apparent diffusion for non-Gaussian distribution (D _app ) and apparent kurtosis coefficient (K _app ) on DKI as well as apparent diffusion coefficient (ADC) on DWI were compared. Results: In all, 86 bowel segments including inactive (20), mild (19), and moderate-severe (47) CD were analyzed. The differences in K _app , D _app , and ADC among inactive, mild, and moderate-severe CD were significant (all P < 0.05). K _app (r = 0.862), D _app (r = −0.755), and ADC (r = −0.713) correlated well with MaRIA in all segments. Stronger correlation with MaRIA in moderate-severe CD was found for K _app (r = 0.647) than that of D _app (r = −0.414) and ADC (r = −0.580). Receiver operating characteristic (ROC) curve analysis showed high accuracy of K _app , D _app , and ADC for differentiating active from inactive CD (AUC: 0.953 for K _app , 0.944 for D _app , 0.907 for ADC) as well as differentiating inactive-mild from moderate-severe CD (AUC: 0.946 for K _app , 0.887 for D _app , 0.846 for ADC). The threshold K _app of 0.731 allowed differentiation of active from inactive CD with 89.4% sensitivity and 95% specificity. Conclusion: DKI of CD is clinically feasible and might be superior to conventional DWI for grading the inflammatory activity of CD. Level of Evidence: 2. Technical Efficacy: Stage 2. J. Magn. Reson. Imaging 2018;47:702–709.