Fig. 3

Corresponding transverse cross-section of DWI b = 800 s/mm² (a, d, g, j), ADC map (b, e, h, k), contrast-enhanced T1w imaging (c, f, i, l) in four different patients, rated as not having synovitis (category 1, a-c), showing mild synovial irritation (category 2, d-f), active synovitis with joint effusion (category 3, g-i) and synovitis aggravated by synovial thickening (category 4, j-l) on contrast enhanced MRI as the diagnostic standard. The fourth patient (j-l) was rated as category 3 on DWI, since the synovial layer appears less prominent and since the ADC map nicely delineates synovium from joint effusion (arrow heads) and periarticular oedematous signal increase. Contrast-enhanced MRI may overestimate the extent of synovial proliferation in the presence of perisynovial inflammation and oedema in this patient