CT, MRI, US and radiography of a RA patient's 2nd to 5th MCP joints. CT of the 2nd to 5th MCP joints, in (a) coronal and (b, c) axial planes. Erosions in the 3rd and 5th metacarpal heads are marked with arrows. T1-weighted magnetic resonance images of the 2nd to 5th MCP joints, in the (d, e) coronal and (f) axial planes reveal the same erosions in the 3rd and 5th metacarpal heads as marked on the CT images. US at the ulnar aspect of the 5th metacarpal head, in (g) longitudinal and (h) transversal planes. An erosion (white arrow) at the same site as detected by CT and MRI (white arrows in panels a, c, d and f) is documented in both planes. (i) Radiography reveals no erosions at the corresponding sites. CT, computed tomography; MCP, metacarpophalangeal; MRI, magneticresonance imaging; RA, rheumatoid arthritis; US, ultrasonography.