The Utility of Mesenteric T1 Mapping on MR Enterography in Crohn's Disease: A Preliminary Study.

Crohn's disease (CD) is a chronic disorder characterized by transmural bowel wall involvement and mesenteric changes, including inflammation and fibrosis. Although Magnetic Resonance Imaging (MRI)-based scoring systems have been proposed for the quantitative assessment of bowel wall changes in Magnetic Resonance enterography (MRE), there has been limited discussion regarding methods for the quantitative evaluation of mesenteric involvement. T1 mapping is an emerging MRI technique, potentially reflecting inflammation and fibrosis. This study aimed to assess the clinical utility of mesenteric T1 mapping in patients with CD. We retrospectively analyzed 71 adults with CD who underwent MRE from October 2024 to May 2025. Mesenteric native T1, post-contrast T1 relaxation times, their difference (ΔT1), and the extracellular volume (ECV) fraction were measured. Regions of interest were placed in mesenteric tissue adjacent to affected bowel segments, avoiding lymph nodes and artifacts. The Crohn's Disease Activity Index (CDAI) was used to classify disease activity. Group differences and correlations with CDAI were evaluated. Native T1 values were significantly higher in active CD than inactive disease (414.3 ms vs. 355.2 ms, < 0.001). ΔT1 was also elevated in active disease (122.5 ms vs. 55.9 ms, < 0.001), while post-contrast T1 and ECV did not differ significantly. Native T1 and ΔT1 showed significant positive correlations with CDAI (r = 0.53 and r = 0.46, respectively), while ECV had a weaker correlation (r = 0.27, = 0.025). Mesenteric T1 mapping shows potential as a non-invasive biomarker of mesenteric involvement in CD. With further validation, mesenteric T1 mapping could enable more comprehensive disease assessment and improve the accuracy of clinical characterization in patients with Crohn's disease.