Clinical applications of advanced magnetic resonance imaging techniques for arthritis evaluation

Figure 5 Synovial fluid evaluation with diffusion-weighted imaging. In a 42-year-old woman with RA and knee swelling. A: Axial post contrast fat-suppressed TSE T1-weighted sequence shows articular fluid and synovial enhancement; B, C: DWI with a b value of 900 s/mm² and corresponding ADC map confirm the presence of an effusion without significant restriction of free water motion (ADC: 2, 8 × 10^-3 mm²/s) consistent with transudate due to rheumatoid arthritis, as confirmed by arthrocentesis. In this case, DWI helps to exclude infection. Note the presence of a prominent chondral erosion near to patellar apex (asterisk on A). DWI: Diffusion-weighted imaging; RA: Rheumatoid arthritis; ADC: Apparent diffusion coefficient.