[18F]fluoro-PEG-folate images and corresponding time-activity curves of arthritic and normal knees. (A) Example of [18F]fluoro-PEG-folate image of arthritic rat at the level of the knees (L = left contralateral knee, R = right arthritic knee). (B) corresponding time-activity curves (of ROI as indicated in 4A) of arthritic and contralateral knees. (C) Arthritic-to-contralateral knee ratio as function of time. Results are presented as mean ± SD of four arthritic rats.