Evaluation of Quantitative PET/MR Enterography Biomarkers for Discrimination of Inflammatory Strictures from Fibrotic Strictures in Crohn Disease.

PURPOSE To retrospectively evaluate positron emission tomography (PET)/magnetic resonance (MR) enterography for the differentiation of fibrotic strictures from inflammatory strictures in patients with Crohn disease. MATERIALS AND METHODS This HIPAA-compliant retrospective study was approved by the institutional review board. Patients gave their written informed consent for study enrollment. PET/MR enterography images were evaluated in 19 patients with Crohn disease who had strictures that underwent surgical resection with pathologic confirmation. Two radiologists and a nuclear medicine physician in consensus evaluated the following bowel wall PET/MR enterography biomarkers: signal intensity (SI) on T2-weighted images, apparent diffusion coefficient (ADC), PET maximum standardized uptake value (SUVmax), SI on T2-weighted images × SUVmax, and ADC × SUVmax values at levels that corresponded to pathologic specimens. MR, PET, and hybrid PET/MR biomarkers were compared, and the performance for differentiation of inflammatory strictures from fibrotic strictures was assessed. Mixed-model regression analysis was used to compare the mean imaging parameters between groups; the P values were corrected for the five comparisons by using the Bonferroni method. RESULTS Three of the PET/MR enterography biomarkers, SUVmax, SI on T2-weighted images × SUVmax, and ADC × SUVmax, showed significant differences in the fibrosis group compared with the fibrosis with active inflammation group and the active inflammation only group. The best discriminator between fibrosis and active inflammation was the combined PET/MR enterography biomarker ADC × SUVmax cutoff of less than 3000, which was associated with accuracy, sensitivity, and specificity values of 0.71, 0.67, and 0.73, respectively. CONCLUSION PET/MR enterography offers a potential noninvasive technique for the differentiation of purely fibrotic strictures from mixed or inflammatory strictures. A hybrid biomarker that incorporates both MR and PET information performed better for stricture evaluation than either modality alone.