Visualizing Microvascular Remodeling for Precise Staging of Inflammatory Bowel Disease via Ultralow-Dose Magnetic Resonance Enterography.

Accurate staging of inflammatory bowel disease (IBD) using magnetic resonance enterography (MRE) remains challenging because of limited precision. Although microvascular remodeling is a pivotal driver of IBD progression, its contribution to imaging-based activity assessment remains insufficiently characterized owing to the rapid extravasation and short intravascular residence of current contrast agents. Here, an ultralow-dose MRE strategy is developed using a long-circulating (half-life ≈ 5 h), high-relaxivity (r1 = 40.89 mM-1 s-1 at 3.0 T) ultrasensitive nanoprobe to enable direct visualization and quantitative characterization of intestinal microvascular remodeling in vivo. In a rat colitis model, this approach reveals dynamic microvascular alterations during inflammatory progression and generates enhancement patterns that reflect both vascular retention and permeability-associated changes. Quantitative analysis of vascular imaging features enabled the development of a microvascular feature index (MFI), which was significantly associated with histopathological inflammatory activity. Integration of MFI with conventional MR metrics improved disease activity stratification by distinguishing low-activity lesions from moderate-to-severe inflammatory activity. This work establishes inflammation-associated vascular remodeling as an imaging-accessible biological process and demonstrates that contrast kinetics engineering can enable its quantitative characterization as an imaging biomarker. The resulting microvascular-centered framework complements conventional MRE and provides a biologically informed approach for inflammatory activity assessment in IBD.