Assessment of synovitis in the osteoarthritic knee: Comparison between manual segmentation, semiautomated segmentation, and semiquantitative assessment using contrast-enhanced fat-suppressed T1-weighted MRI.

Osteoarthritic joints regularly exhibit synovitis, which is ideally assessed on contrast-enhanced MRI. Manual segmentation is the reference standard for volumetric analysis but is labor intensive. The aim was to evaluate alternative semiautomated approaches of targeted thresholding and gaussian deconvolution. Volumetric and semiquantitative synovitis assessment was compared in addition. Thirty-two knees with osteoarthritis were scanned on a 1.5-T system. Synovitis volumes were plotted against each other and distributions fit with linear functions. The relationship between semiquantitative scores and synovitis volumes was assessed using Spearman's correlation coefficient. Semiautomated volume measurement was more time efficient than manual segmentation and showed a high correlation with manual analysis (R(2) = 0.88 and 0.82). Manual segmentation was correlated with summed and with maximum semiquantitative synovitis scores (rho = 0.71 and 0.47). In conclusion, semiautomated analysis provides comparable quantitative results when compared to manual segmentation but is approximately five times more time efficient. Semiquantitative assessment adds anatomic information on synovitis distribution.