To evaluate the effectiveness of power Doppler ultrasonography (PDUS) for assessing inflammatory activity in the metacarpophalangeal (MCP) joints of patients with rheumatoid arthritis (RA), using dynamic magnetic resonance imaging (MRI) as a reference method.
PDUS and dynamic MRI were performed on 54 MCP joints of 15 patients with active RA and on 12 MCP joints of 3 healthy controls. PDUS was performed with a LOGIQ 500 unit by means of a 7-13-MHz linear array transducer. Later the same day, MRI was performed with a 1.0T MR unit. A series of 24 coronal T1-weighted images of the second through the fifth MCP joints was obtained, with intravenous injection of gadolinium diethylenetriaminepentaacetic acid after the fourth image (dynamic MRI). From the MR images, the rate of early synovial enhancement (RESE; defined as the relative enhancement per second during the first 55 seconds postinjection) was calculated and compared with the flow signal on PDUS, which was scored as present or absent.
In RA patients, flow signal on PDUS was detected in 17 of 54 MCP joints examined. Postcontrast MR images revealed an RESE of > or = 1.0%/second in 18 of 54 RA MCP joints. PDUS showed no flow in 47 of 48 MCP joints with an RESE of <1.0%/second and revealed flow in 16 of 18 MCP joints with an RESE of > or = 1.0%/second. Using dynamic MRI as a reference, PDUS had a sensitivity of 88.8% and a specificity of 97.9%.
PDUS was reliable for assessing inflammatory activity in the MCP joints of RA patients, using dynamic MRI as the standard. PDUS and clinical assessment of joint swelling/tenderness were only weakly correlated.