Signs of synovitis on ultrasonography and MRI in fourth proximal interphalangeal joint: early RA. Arrows indicate an area with synovitis. Ultrasonography in (a) the longitudinal plane from the dorsal aspect shows signs of synovitis (grade 4). Axial T1-weighted magnetic resonance images were obtained (b) before and (c) after contrast administration (grade 3 synovitis). MRI, magnetic resonance imaging; RA, rheumatoid arthritis.