Translational 18F-FDG PET/CT imaging to monitor lesion activity in intestinal inflammation

In patients with inflammatory bowel disease (IBD) and in murine IBD models, mucosal disease activity is routinely assessed by endoscopy and histologic evaluation. This information is valuable for monitoring treatment response, with mucosal healing being a major treatment goal. The aim of this study was to evaluate the translational potential of noninvasive (18)F-FDG PET/CT for the assessment of mucosal damage in murine dextran sodium sulfate (DSS) colitis and human IBD.

After induction of DSS colitis, (18)F-FDG uptake was serially assessed from colonic volumes of interest defined on PET/CT scans and intraindividually correlated to histologic findings and to infiltrating cell types. In addition, (18)F-FDG PET/CT scans of 25 Crohn disease patients were analyzed, and colonic (18)F-FDG uptake was correlated to endoscopically assessed damage.

At days 4 and 7 after DSS induction, colonic (18)F-FDG uptake was significantly increased, with a distinct peak in the medial colon. (18)F-FDG uptake strongly correlated with histologic epithelial damage. Additionally, (18)F-FDG uptake increased in the bone marrow in the course of the disease, correlating with an increase in intestinal (18)F-FDG uptake. Histology and fluorescence-activated cell sorting analysis of the bone marrow of DSS mice revealed an increased number of immature neutrophils, whereas mucosal polymerase chain reaction suggested a correlation of (18)F-FDG uptake to T cell infiltration. In accordance with the results of (18)F-FDG PET/CT in DSS colitis, an increased (18)F-FDG uptake was found in 87% of deep mucosal ulcerations in IBD patients, whereas mild endoscopic lesions were detected only by (18)F-FDG PET/CT in about 50% of patients assessed.

(18)F-FDG PET/CT is a noninvasive method for evaluation of both experimental colitis and Crohn disease patients and thereby offers promising translational potential.