Validation of the simplified magnetic resonance index of activity by using DWI without gadolinium enhancement to evaluate bowel inflammation in Crohn’s disease

Objectives To validate the modified simplified magnetic resonance index of activity (sMARIA) score using DWI on non-contrast magnetic resonance enterography (MRE) to evaluate active inflammation in patients with Crohn’s disease (CD), compared to the original sMARIA scoring system, with and without contrast enhancement. Methods This retrospective study included 275 bowel segments from 55 CD patients who underwent ileocolonoscopy and MRE within a 2-week period. Two blinded radiologists evaluated original sMARIA on both conventional MRE (CE-sMARIA) and non-contrast MRE (T2-sMARIA). Modified sMARIA was then evaluated using non-contrast MRE, replacing ulcerations with DWI grades. Three scoring systems were compared for diagnostic accuracy of active inflammation, correlation with simple endoscopic score (SES)-CD, and interobserver reproducibility. Results The AUC of modified sMARIA for detecting active inflammation (0.863, 95% confidence interval [0.803–0.923]) was significantly higher than T2-sMARIA (0.827 [0.773–0.881], p = 0.017), and comparable to CE-sMARIA (0.908 [0.857–0.959], p = 0.122). CE-sMARIA, T2-sMARIA, and modified sMARIA all showed moderate correlation with SES-CD ( r = 0.795, 0.722, and 0.777, respectively). Interobserver reproducibility of diffusion restriction ( κ , 0.686 [0.602–0.770]) was significantly better than ulcers on conventional MRE ( κ , 0.382 [0.212–0.552]; p = 0.001) and T2-weighted image ( κ , 0.312 [0.034–0.590]; p = 0.012). Conclusions Modified sMARIA using DWI can improve the diagnostic performance of sMARIA on non-contrast MRE, showing comparable performance to sMARIA using contrast-enhanced MRE. Key Points • DWI can improve the diagnostic performance of non-contrast magnetic resonance enterography (MRE) for assessing active inflammation in patients with Crohn’s disease. • Modified simplified magnetic resonance index of activity (sMARIA) using DWI grades in place of ulcers showed comparable diagnostic performance to sMARIA using conventional MRE with contrast-enhanced sequences.