Gallium-68-labeled Fibroblast Activation Protein Inhibitor-46 (68Ga-FAPI-46) PET in Crohn's Disease Patients: a Case-control Study Designed to Illuminate the Spectrum of Fibrostenosis in Patients With Small Bowel Crohn's Disease

This study is a prospective, case-control study evaluating whether the PET radiotracer 68Ga-FAPI-46 can detect fibrostenosing Crohn's disease in the small bowel. The goal is to determine whether areas of early or developing fibrosis ("pre-stricture" changes) demonstrate uptake of the tracer, which binds to fibroblast activation protein (FAP).

Participants with small bowel Crohn's disease will be assigned to either a case or control group based on CT or MR enterography findings at enrollment.

Cases will include participants who have a small bowel stricture or probable stricture, with or without penetrating complications.

Controls will include participants with small bowel Crohn's disease without strictures. Controls may have active inflammatory disease, luminal narrowing, or no active inflammation (including postoperative or chronic changes), as long as no stricture is present.

Because most radiologic strictures represent more advanced fibrostenosis, the study aims to enroll a larger proportion of controls to better characterize early fibrotic changes. Approximately one-third to one-half of participants will be cases, and the remainder controls. This design will allow comparison of FAPI uptake patterns in patients with and without strictures to understand how FAP expression relates to the development of small bowel fibrosis.