The purpose of this study was to compare the relative results from conventional high-field-strength 1.5-T MRI, 0.2-T low-field-strength dedicated extremity MRI, and radiography to detect and grade bone erosions, joint-space narrowing, and synovitis in the hands and wrists of patients with rheumatoid arthritis.
Eighteen patients with rheumatoid arthritis underwent conventional high-field-strength MRI, low-field-strength dedicated extremity MRI, and conventional radiography of both hands and wrists. Two independent reviewers searched for the presence and extent of bone erosions, joint-space narrowing, and synovitis. Bone erosions (E scores) and joint-space narrowing (J scores) were evaluated at 14 and 13 sites, respectively, on conventional high-field-strength MRI, low-field-strength dedicated extremity MRI, and radiography, using the Sharp-Genant scoring system. Synovitis (S scores) were evaluated at 13 sites on conventional high-field-strength MRI and low-field-strength dedicated extremity MRI.
For the detection of bone erosions, we found no significant difference (p = 0.71) between conventional high-field-strength MRI (mean +/- SD E score, 27.5 +/- 9.8) and low-field-strength dedicated extremity MRI (28.8 +/- 10.0), but a significant difference (p < 0.001) appeared between MRI and radiography (13.1 +/- 8.3). J scores derived from MRI (conventional high-field-strength MRI, 15.2 +/- 8.3; low-field-strength dedicated extremity MRI, 14.5 +/- 10.4) were higher than those derived from radiography (12.7 +/- 9.6), although the difference was not significant (p = 0.70). Conventional high-field-strength MRI (S score, 35.1 +/- 8.6) and low-field-strength dedicated extremity MRI (30.8 +/- 10.2) were equivalent (p = 0.14) for the evaluation of synovitis. The interobserver agreement for MRI scores was good to excellent (intraclass correlation coefficients, 0.83-0.94).
Conventional high-field-strength MRI and low-field-strength dedicated extremity MRI showed similar results in terms of cross-sectional grading of bone erosions, joint-space narrowing, and synovitis in the hands and wrists of patients with rheumatoid arthritis.