Assessment of Crohn’s disease activity by FDG-PET/CT through a novel quantitative approach

Objectives The goal of this study was to determine the feasibility of assessment of Crohn’s disease (CD) activity by FDG-PET/CT through a novel quantitative approach.

Methods 22 subjects (mean age 37) with CD who had undergone FDG-PET/CT followed by ileocolonoscopy within 1 week were prospectively studied. The CD endoscopy index of severity (CDEIS) for various bowel segments was calculated. The CD activity index (CDAI) was evaluated and fecal calprotectin was measured before endoscopy. On PET, FDG-avid regions in large and small bowel were segmented with an adaptive thresholding method, and metabolically active volume (MAV), partial-volume corrected (PVC) SUVmean (cSUVmean), SUVmax, and PVC metabolic-volumetric-product (cMVPmean = MAV × cSUVmean) were measured (ROVER software, ABX GmbH, Germany). Global CD Activity Score (GCDAS) was calculated as the sum of cMVP over all FDG-avid regions in each subject. Correlations between regional PET quantification measures (SUVmax, SUVmean, cMVP) and CDEIS were calculated. Correlations between global PET quantification (GCDAS) and CDAI and fecal calprotectin were calculated.

Results SUVmax, cSUVmean, and cMVPmean significantly correlated with CDEIS (r=0.50, r=0.69, r=0.31, respectively; p<0.05). GCDAS significantly correlated with CDAI and fecal calprotectin (r=0.64, r=0.51 respectively; p<0.05).

Conclusions Through this approach, we were able to calculate indices of regional and global CD activity which correlate well with both clinical and pathological disease activity measures. This may be of use clinically to measure disease burden and treatment response in patients with CD