P0377 Dual-Energy and Photon-Counting Computed Tomography in Crohn’s Disease: Towards Quantitative Imaging Biomarkers. A Systematic Review

Abstract Background Over the last three decades, the role of imaging in Crohn’s disease (CD) has evolved from an ancillary diagnostic tool used in selected settings to a central component of routine, point-of-care management. Advances in computed tomography (CT) technology have led to the development of new acquisition techniques, providing shorter scan times, improved spatial resolution, and superior mucosal detail. These CT modalities have introduced quantitative parameters, such as iodine density (ID) and fat fraction, with potential as reproducible imaging biomarkers of intestinal inflammation. Our aim was to systematically review the diagnostic performance of Dual-Energy CT (DECT) and Photon-Counting CT (PCCT) enterography in assessing disease activity in CD patients. Methods The review protocol was registered in PROSPERO (CRD420251143394). A systematic search was conducted in PubMed, Scopus, and Web of Science (last updated September 6, 2025), in accordance with the PRISMA guidelines. Case reports, reviews, position papers, and preclinical studies were excluded. Results A total of 246 papers were retrieved, and 21 publications were included: 20 investigating DECT and 1 adopting PCCT (Figure 1). All studies were single center; only two were prospectively designed. In 14 studies, regions of interest (ROI) for iodine map assessment were manually defined, whereas semi-automatic software-assisted segmentation was applied in 7. Overall, 1,055 CD patients underwent DECT (n = 1,032) or PCCT (n = 23) enterography. The gold standard for disease activity assessment was represented by endoscopic and/or clinical scores (Harvey–Bradshaw or Clinical Disease Activity Index). In DECT studies, ID demonstrated a significant correlation with reference clinical/endoscopic scores (P < 0.01) across all papers; however, a meta-analysis was not feasible due to heterogeneity in acquisition protocols and outcome reporting (absolute, mean/max/min, or aorta-normalized ID). Data on fat fraction (reported in 3 studies) were inconsistent and inconclusive. In the PCCT study, ID thresholds of 2.7 mg/mL and 3.4 mg/mL could distinguish active and severe disease (accuracy 98% and 87%, respectively). Conclusion Iodine density shows promise as a quantitative biomarker for CD activity; however, the data remain heterogeneous, while manual ROI definition significantly reduces reproducibility. PCCT represents a genuine technological advance in the field, offering superior spatial resolution and lower radiation dose. Preliminary evidence suggests diagnostic thresholds of 2.7 mg/mL for CD activity and 3.4 mg/mL for severity, but larger, prospective studies are warranted to validate these findings and confirm their clinical applicability. References: 1. Kucharzik T, Taylor S, Allocca M, Burisch J, Ellul P, Iacucci M, et al. ECCO-ESGAR-ESP-IBUS Guideline on Diagnostics and Monitoring of Patients with Inflammatory Bowel Disease: Part 1. J Crohns Colitis. 2025;19(7). 2. Yanai H, Feakins R, Allocca M, Burisch J, Ellul P, Iacucci M, et al. ECCO-ESGAR-ESP-IBUS Guideline on Diagnostics and Monitoring of Patients with Inflammatory Bowel Disease: Part 2. J Crohns Colitis. 2025;19(7). 3. Dane B, Duenas S, Han J, O’Donnell T, Ream J, Chang S, et al. Crohn’s Disease Activity Quantified by Iodine Density Obtained From Dual-Energy Computed Tomography Enterography. J Comput Assist Tomogr. 2020;44(2):242-7. 4. Dane B, Qian K, Soni R, Megibow A. Crohn’s disease inflammation severity assessment with iodine density from photon counting CT enterography: comparison with endoscopic histopathology. Abdom Radiol (NY). 2024;49(1):271-8. Conflict of interest: Prof. Merola, Elettra: No conflict of interest Mereu, Sandro: No conflict of interest Dore, Maria Pina: No conflict of interest Scaglione, Mariano: No conflict of interest