Quantitative assessment of global and regional inflammation in patients with Crohn’s disease by FDG PET/CT: An inter-reader and intra-reader agreement evaluation study

Objectives There is a growing body of evidence supporting the application of volumetric PET/CT parameters including metabolic active volume (MAV) and total lesion glycolysis (TLG) in malignancies. However, limited data are available about the reliability of these indices in non-malignant diseases. The purpose of this study was to determine the feasibility and inter/intra-reader reproducibility of volumetric PET/CT indices for quantification of Crohn’s disease (CD) activity.

Methods Thirty-six FDG PET/CT scans of patients with clinically active CD were studied. Two nuclear medicine physicians independently assessed the degree of colon inflammation by measuring SUVmax, SUVmean, MAV and TLG=MAV*SUVmean of colon segments with significant FDG-avidity. Global SUVmax (GSUVmax) and Global SUVmean (GSUVmean) were calculated as the average of all regional values. Global lesion glycolysis (GLG) and global metabolic active volume(GMAV) was calculated as the sum of all regional values. Intraclass correlation coefficient (ICC) and Bland-Altman analyses were performed to measure inter-reader and intra-reader agreement of the measurements.

Results In regional assessment, robust agreement of volumetric PET indices was observed where the ICC of SUVmax, SUVmean, MAV, and TLG were 0.95 (95%CI: 0.88-0.96), 0.97 (95%CI: 0.94-0.98), 0.94 (95%CI: 0.91-0.96) and 0.97 (95%CI: 0.93-0.98), respectively. In global assessment, substantial reproducibility was noted while the ICC for GSUVmean, GSUVmax, GMAV and GLG were 0.98 (95%CI: 0.97-0.99), 0.98 (95%CI: 0.96-0.99), 0.96 (95%CI: 0.93-0.97) and 0.97 (95%CI: 0.94-0.98), respectively.

Conclusions SUVmean, MAV, TLG have potential for practical PET-based quantification of inflammation in patients with CD. Therefore, measuring and incorporating these parameters in future studies of Crohn’s disease may provide new clinical applications of these biomarkers in the management of inflammatory disorders.