Hybrid Molecular Imaging Using PET/CT and PET/MRI in Inflammatory Bowel Disease: Current Applications, Challenges, and Future Perspectives.

Hybrid molecular imaging is increasingly recognized as a valuable tool for the precision management of inflammatory bowel disease (IBD). Driven by the treat-to-target paradigm, the noninvasive quantification of transmural inflammation and the accurate differentiation of stricture phenotypes remain key clinical challenges. Current evidence indicates that although 2-deoxy-2-¹⁸F-fluoro-D-glucose (¹⁸F-FDG) positron emission tomography (PET) can effectively quantify the overall inflammatory burden, the integration of fibroblast activation protein inhibitor (FAPI)-targeted PET imaging provides important complementary value for characterizing fibro-inflammatory remodeling and distinguishing fibrotic strictures. By combining high metabolic sensitivity with high-resolution multiparametric soft-tissue characterization, PET/magnetic resonance imaging (MRI) has demonstrated potential advantages in assessing penetrating complications and facilitating longitudinal therapeutic monitoring. Pediatric and young adult patients requiring long-term follow-up may derive substantial benefit from the reduced radiation exposure offered by integrated PET/MRI systems. To overcome conventional method limitations, including physiologic intestinal uptake and attenuation-correction artifacts, the field is actively exploring novel molecularly targeted tracers, ultra-low-dose long-axial-field-of-view whole-body systems, and artificial intelligence-based image reconstruction techniques. Given that substantial current evidence is derived from small, single-center cohorts and experimental studies, these advanced modalities currently serve as adjunctive, problem-solving tools rather than routine replacements for standard endoscopy or conventional cross-sectional imaging. This review comprehensively evaluates the clinical performance, applicability, and translational barriers of hybrid molecular imaging in IBD, underscoring the urgent need to establish standardized, multicenter consensus protocols that can guide its future implementation in individualized therapeutic strategies.