Figure 5.

Diffusion-weighted imaging in a patient with gonarthritis and a popliteal cyst. Arthritis of the left knee in a 14-year-old boy with JIA. Post-contrast T1W (a) and DWI b = 1000 with inverted gray scale (b) both show synovial signal changes, layered signal of the parapatellar lateral recessus in the presence of effusion and reactive popliteal lymphadenopathy (arrow head). With 6 averages and 2 min 50 s scan time, DWI signal and image quality are substantially improved, as compared to Figure 4. A caudal cross-section of the same knee joint depics a Baker cyst in the medial popliteal fossa, also showing signs of synovitis (arrow) on both post-contrast T1W (c) and DWI (d). ADC measurement with three small circular regions of interest (ROI) is demonstrated in (b).