Objectives With contrast-enhanced MRI as the reference method, to explore to which extent synovitis in wrists and metacarpophalangeal (MCP) joints of patients with rheumatoid arthritis (RA) can be reliably assessed by unenhanced MRI. Furthermore, we explored the influence of different MRI field strengths, coil types and image resolutions.

Methods 41 RA patients and 12 healthy controls underwent 7 MRI examinations (Coronal short tau inversion recovery (STIR) and T1-weighted (T1w) sequences) on 4 MRI units (0.23 T, 0.6 T, 1.5 T, and 3.0 T, with different coils, see table for details) within 24 hours. Additional post-contrast T1w sequence was performed at the 1.5T unit (gold standard). Images were scored according to OMERACT RA MRI score (RAMRIS) (1) by an experienced reader blinded to participant’s details and MRI field strength. Gold standard images were scored on a different session. Intrareader reliability was evaluated on a subset of 18 patients and controls.

Results Fair to good correlation (ICC=0.38-0.72) was seen between different STIR protocols and the gold standard reference (Table 1). The highest correlation was found using the 1.5T unit with the smaller voxel size and extremity coil. Sensitivity for the presence or absence of synovitis was moderate-high in all units (per patient: 0.8-1.0, per joint: 0.63-0.85) whereas the exact agreement on scores was poorer (0.5-0.66).

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Conclusions Unenhanced MRI, using STIR sequences, is only moderately reliable for assessing synovitis in RA MCP and wrist joints, when contrast-enhanced MRI is considered the gold standard reference. 0.6 T and 1.5 MRI performed best.

1. Ostergaard M. et al. J Rheumatol 2003;30:1385-6.

Disclosure of Interest None Declared