Rheumatoid arthritis bone erosion volumes on CT and MRI: reliability and correlations with erosion scores on CT, MRI and radiography

Objectives: To investigate intramodality and intermodality agreements of CT and MRI erosion volumes in metacarpophalangeal (MCP) joints in rheumatoid arthritis ( RA), and to compare the volumes with erosion scores for CT, MRI and radiography. Methods: In total, 17 patients with RA and four healthy controls underwent unilateral CT, MRI and radiography of second to fifth MCP joints in one hand. Erosion volumes ( using OSIRIS software) and scores were determined from CT, MRI and radiography ( scores only). Results: CT, MRI and radiography detected 77, 62 and 12 erosions, respectively. On CT, the mean erosion volume was 26 mm(3) ( median 10; range 0 to 248) and 30 mm3 ( 18; 1 to 163) on MRI. Total erosion volumes ( per patient/control) were 97 mm3 ( 29; 0 to 485) on CT and 90 mm3 ( 46; 0 to 389) on MRI. For volumes, Spearman correlation coefficients were 0.96 to 0.99 ( CT vs CT), 0.95 to 0.98 ( MRI vs MRI) and 0.64 to 0.89 ( CT vs MRI), all p, 0.01. MRI erosion volumes correlated with the Outcome Measures in Rheumatology Clinical Trials/Rheumatoid Arthritis Magnetic Resonance Imaging Score (OMERACT RAMRIS) erosion scores (0.91 to 0.99; p, 0.01) and the Sharp/van der Heijde erosion score (0.49 to 0.63; p, 0.01). Conclusion: Very high intramodality and high intermodality agreements of CT and MRI erosion volumes were found, encouraging further testing in longitudinal studies. A close correlation with CT and MRI erosion volumes supports the OMERACT RAMRIS erosion score as a valid measure of joint destruction in RA.