A modification of the Omeract RA MRI score for erosions for use with an extremity MRI system with reduced field of view

Objectives: To develop and test the reliability of a modified version of the OMERACT rheumatoid arthritis magnetic resonance imaging score ( RAMRIS) for erosions using extremity MRI ( eMRI) with reduced field of view ( RAMRIS-RV). Methods: Using a MagneVu 0.2 T machine, the preliminary RAMRIS-RV assessed erosions in metacarpophalangeal ( MCP) joints 2-3, bases of metacarpal ( MC) 2-5, and all wrist bones excluding base MC 1, pisiform and trapezium. T1 weighted images of >= 500 MCP and wrist bony sites from a mixed severity RA and control cohort were evaluated. An inter-reader reliability study evaluating 300 wrist and 160 MCP bony sites was then performed. Results: Mean per cent exact ( and close) agreement results were as follows: MCP proximal sites 83.5 ( 96.2), MCP distal 54.4 ( 77.2), bases MC 2-4 85.2 ( 96.7), carpal bones 79.0 ( 92.1), distal radius/ulna 66.4 ( 87.8). The base of MCP 5 was visualised in <= 50% cases ( 13/25) and was removed from the final RAMRIS-RV. Conclusions: The RAMRIS-RV is a practical tool that can be used with eMRI with a reduced field of view. This study shows excellent inter-reader reliability for erosion assessment, albeit in a reduced number of bony sites.