Figure 10b. Rheumatoid arthritis in a 71-year-old woman with pain at the first MTP joint. (a) Axial T1-weighted MR image shows marginal erosions at the first metatarsal head (short arrows), low-signal-intensity synovial thickening (long arrows), and joint space narrowing. Note also the erosive changes at the interphalangeal joint of the great toe. (b) Coronal gadolinium-enhanced fat-suppressed T1-weighted MR image shows contrast enhancement of the synovium (long arrow) and subchondral bone (short arrow). The signal intensity changes in both a and b are nonspecific; however, a previously established diagnosis of rheumatoid arthritis in the hands, a lack of clinical indicators of infection, a normal serum urate level, and a positive response to steroids supported the diagnosis of rheumatoid arthritis at the first MTP and interphalangeal joints.