FDG-PET: A novel non-invasive method to detect affected bowel segments in Crohn's disease?

Abstract

Crohn's disease is a chronic granulomatous disease of the gastrointestinal tract that causes discontinuous inflammation. MRI studies allow detailed analysis of affected small bowel fragments but are limited in their capacity to unequivocally determine all inflamed lesions. In the present study, we performed a prospective clinical study on the use of FDG-PET to localize affected bowel segments in patients with chronic active Crohn's disease (planned n= 50). Patients underwent endoscopy for assessment of colonic involvement, FDG-PET (370 MBq F-18 FDG and 100 MBq F-18), an examination with granulocyte antibodies (GR-AK: SPECT 4 + 24 hours poi. of 800 MBq Tc99m-GR-AK BW 250/193) and MRI analysis (HydroMRI with mannitol). A combined evaluation of MRI and PET was made by computer analysis. Among the 16 analyzed patients so far there were more positive pathologic results in FDG-PET compared to the examination with granulocyte antibodies. Furthermore, the average length of the affected bowel segments was longer in FDG-PET analysis. No case with pathologic granulocyte antibody scan but negative FDG-PET scan was noted. The ratio pathologic finding/ liver signal was on average 2,64 +/1,01 in the studies using granulocyte antibodies. The SUVmax for PET-positive lesions was on average 4,13 +/-1,03. In more than 90% of the pathologic PET findings a corresponding thickening of the small bowel wall was detected by MRI. The comparison of PET data for colonic involvement and the data obtained by endoscopic analysis showed a high correlation between PET-detected lesions and endoscopically affected areas. Taken together, these data suggest that FDG-PET analysis has a higher sensitivity to detect affected bowel wall fragments than studies with a granulocyte antibody. In contrast to MRI, PET studies also allowed the effective analysis of colonic involvement in patients with Crohn' s disease. Furthermore, FOG-PET analysis was helpful to determine the inflammatory activity in MRI-detected stenoses in Crohn's disease. Thus, FDG-PET might provide a novel reliable method for the detection and analysis of affected bowel segments in patients with chronic active Crohn's disease.