(18)F-FDG-PET-MRI for the assessment of acute intestinal graft-versus-host-disease (GvHD)

BACKGROUND: Graft versus host disease (GvHD) is a frequent complication of allogeneic stem cell transplantation (alloSCT), significantly increasing mortality. Previous imaging studies focused on the assessment of intestinal GvHD with contrast-enhanced MRI/CT or (18)F-FDG-PET imaging alone. The objective of this retrospective study was to elucidate the diagnostic value of a combined (18)F-FDG-PET-MRI protocol in patients with acute intestinal GvHD. METHODS: Between 2/2015 and 8/2019, 21 patients with acute intestinal GvHD underwent (18)F-FDG-PET-MRI. PET, MRI and PET-MRI datasets were independently reviewed. Readers assessed the number of affected segments of the lower gastrointestinal tract and the reliability of the diagnosis on a 5-point Likert scale and quantitative PET (SUVmax, SUVpeak, metabolic volume (MV)) and MRI parameter (wall thickness), were correlated to clinical staging of acute intestinal GvHD. RESULTS: The detection rate for acute intestinal GvHD was 56.8% for PET, 61.4% for MRI and 100% for PET-MRI. PET-MRI (median Likert-scale value: 5; range: 4–5) offers a significantly higher reliability of the diagnosis compared to PET (median: 4; range: 2–5; p = 0.01) and MRI alone (median: 4; range: 3–5; p = 0.03). The number of affected segments in PET-MRI (r(s) = 0.677; p < 0.001) and the MV (r(s) = 0.703; p < 0.001) correlated significantly with the clinical stage. SUVmax (r(s) = 0.345; p = 0.14), SUVpeak (r(s) = 0.276; p = 0.24) and wall thickening (r(s) = 0.174; p = 0.17) did not show a significant correlation to clinical stage. CONCLUSION: (18)F-FDG-PET-MRI allows for highly reliable assessment of acute intestinal GvHD and adds information indicating clinical severity.