Measuring bone erosion and edema in rheumatoid arthritis: a comparison of manual segmentation and RAMRIS methods.

PURPOSE: To investigate the reliability, feasibility, and validity of a computer-assisted manual segmentation (outlining) technique for measuring magnetic resonance imaging (MRI) bone erosion and edema at the wrist in rheumatoid arthritis (RA).
MATERIALS AND METHODS: The 3T MRI scans were obtained in 22 RA patients (<2 years). Bone erosion and edema volumes were scored by two readers using outlining and were compared with RAMRIS scores.
RESULTS: Using outlining, intraobserver reliability for erosions and edema was high: intraclass correlation coefficients (ICCs) = 0.994 (0.991, 0.997) and 0.996 (0.994, 0.998), respectively (Reader 1). Interobserver reliability was high for bone erosion (ICC [90% confidence interval, CI] = 0.80 [0.64, 0.92]) and comparable to RAMRIS scoring (ICC 0.78 [0.64, 0.92]), but was only moderate for bone edema (0.46 [0.00, 0.96]), compared with RAMRIS (ICC = 0.84 [0.73, 0.94]). The methods were highly correlated for erosion scores, r = 0.90, 0.82 (Readers 1 and 2) and moderately correlated for edema, r = 0.57, 0.87.
CONCLUSION: Segmentation (outlining) can be used to measure the volume of MRI bone erosion and edema at the wrist in RA patients. When compared with RAMRIS scoring, outlining had similar reliability for quantifying erosions but reliability was lower for bone edema, possibly reflecting difficulty delineating the borders of affected bone.