P977 Combined F18-FDG-PET-MRI-imaging can predict clinical remission in small bowel Crohn’s disease

Abstract

Abstract Background Diagnostics and follow-up of small bowel Crohn’s disease (CD) can be difficult. Combined PET-MRI enterography (MRE) can be used to evaluate intestinal inflammation. Lack of standardized methods and diagnostic thresholds has limited its clinical use in diagnostics and monitoring of small bowel CD. There is no previous data on the use of PET-MRI in follow-up of small bowel CD. Methods 34 patients with suspected CD in small bowel were recruited from Turku University Hospital’s outpatient clinic. A static PET-MRE was obtained with [18F]-FDG (fluorodeoxyglucose) tracer. CD diagnosis was confirmed with small bowel capsule endoscopy. Patients diagnosed with CD were started with appropriate treatment chosen by clinicians. Endoscopic findings including histopathology, laboratory results (Hb, CRP, serum albumin (Alb) and fecal calprotectin (FC)) and medication data were collected. Patients diagnosed with CD (N=16) went through control PET-MRE median 105 days after initial imaging. Highest SUVmax (standardized uptake value) in small intestine was measured and MRE-images with diffusion weighted imaging (DWI) were analyzed by an experienced abdominal radiologist and severity of inflammation was graded from 1-4. Hb, CRP, Alb and FC were measured from the patients at the time of imaging. Results Median SUVmax was significantly lower after three months of medical treatment (3.2 vs. 2.1) (p=0.016). FC was significantly lower at the time of control imaging (p=0.030) (median 725 ug/g vs. 141 ug/g). 10 patients had FC <250 ug/g at the time of control imaging. Using this as a cut- off for clinical response, ROC-curve showed AUC 0.73 for SUVmax and AUC 0.65 for MRE-grading. Sensitivity and specificity were highest at SUVmax 2.4 (83% and 80%). Conclusion Decreased SUVmax measured after starting CD medication seems to predict clinical remission and a cut-off level 2.4 could be used in diagnostics. Diagnostic yield was higher for SUVmax compared to MRE-grading. Here we have shown for the first time that PET-MRE can be used for disease activity monitoring in small bowel CD.