Dynamic MRI differentiates rheumatoid from psoriatic arthritis

Dynamic gadolinium-enhanced MR imaging can discriminate between patients with rheumatoid arthritis and psoriatic arthritis during the acute phase of the disease, according to research presented Friday at the ECR.

Dr. Simone Banderali and colleagues from the department of experimental medicine at the University of Genoa, Italy, imaged 40 consecutive outpatients with rheumatoid arthritis (RA) and 13 outpatients with psoriatic arthritis (PA), using a 0.18T extremity-dedicated machine. Patients had different degrees of disease activity.

After gadolinium injection, 20 consecutive fast spin-echo T1-weighted sequences of three slices of the wrist were obtained every 18 seconds. Enhancement curves were calculated using a region of interest in the synovial membrane in proximity to the radiocarpal joint relative to a garlic T1-hyperintense fiducial marker and to a sequence obtained before the injection of contrast medium.

The relative enhancement was 125 in RA and 83.1 in PA (p = 0.002). The rate of early enhancement was 1.6 in RA and 1 in PA (p = 0.02).

The researchers concluded that the test's short duration and safety make it ideal for routine use. They suggested that the discrimination is based on different vascularization of the synovial membrane in the two diseases.

Dr. Masataka Uetani and colleagues from Nagasaki University School of Medicine in Japan used dynamic MRI to determine the relationship of synovitis and bone marrow edema in early RA. They found that synovitis, bone marrow edema, and bone erosion was more frequently seen in RA patients than in non-RA patients. Additionally, bone marrow edema was always associated with synovitis.

The investigators acquired dynamic MR images (fast SPGR sequences at four-second intervals for 100 seconds) of both hands simultaneously in 57 patients with RA and 19 with non-RA. There was no significant difference between the two groups in age, duration of symptoms, and CRP. The rheumatoid factor was present in 67.2% of the RA group and in 16.7% of the non-RA group.

Uetani and colleagues evaluated 15 joints and the corresponding periarticular regions in each hand for the presence or absence of synovitis and bone marrow edema. A total of 2235 joints were analyzed.

Synovitis was seen in 94.6% of the RA group and 52.6% of the non-RA group. Bone marrow edema was seen in 57.9% and 52.6%, and erosion in 50.9% and 10.5%, respectively. The differences were significant in all three findings, but more so in bone marrow edema and erosion, Uetani said.

In the joints with synovitis, bone marrow edema was seen in 23% in RA and 1.7% in non-RA patients. The joints with synovitis and bone marrow edema showed significantly higher variance of enhancement rates than those without bone marrow edema.

As enhancement rate is already known to be an indicator of active synovitis, this study suggests that bone marrow edema is closely related to active synovitis in early RA, Uetani said.

"Bone marrow edema is easily evaluated without the use of contrast enhancement and could be used as a measure of disease activity without the added cost of contrast medium," he said.