Differential washout of FDG activity in two different inflammatory lesions: implications for delayed imaging

We describe the changes of FDG uptake in different inflammatory lesions on multiple time point FDG PET/CT. FDG uptake in granulomatous lesions was more intense and focal, with higher intensity on delayed images. In contrast, FDG uptake in chronic arthritic joint inflammation was diffuse and mild, without significant change over time, while FDG uptake in nonarthritic joints was at near-background level with decreased activity on delayed images. The retention index was significantly higher in patients with granulomatous lesions than that in other groups. Our finding indicates differential FDG uptake and clearance in active granulomas versus chronic inflammation.