Fully automated system for the quantification of human osteoarthritic knee joint effusion volume using magnetic resonance imaging

MRI examinations consisted of two axial sequences: a T2-weighted true fast imaging with steady-state precession and a T1-weighted gradient echo. An automated joint effusion volume quantification system using MRI was developed and validated (a) with calibrated phantoms (cylinder and sphere) and effusion from knee OA patients; (b) with assessment by manual quantification; and (c) by direct aspiration. Twenty-five knee OA patients with joint effusion were included in the study.The automated joint effusion volume quantification was developed as a four stage sequencing process: bone segmentation, filtering of unrelated structures, segmentation of joint effusion, and subvoxel volume calculation. Validation experiments revealed excellent coefficients of variation with the calibrated cylinder (1.4%) and sphere (0.8%) phantoms. Comparison of the OA knee joint effusion volume assessed by the developed automated system and by manual quantification was also excellent (r = 0.98; P < 0.0001), as was the comparison with direct aspiration (r = 0.88; P = 0.0008).The newly developed fully automated MRI-based system provided precise quantification of OA knee joint effusion volume with excellent correlation with data from phantoms, a manual system, and joint aspiration. Such an automated system will be instrumental in improving the reproducibility/reliability of the evaluation of this marker in clinical application.Joint effusion is frequently associated with articular disorders. In osteoarthritis (OA), the effusion is an important marker of the disease flare-up, and its quantification could be helpful as a treatment outcome measure. The most common means used to quantify joint effusion volume is arthrocentesis. A major drawback of this method, however, in addition to being invasive and somewhat painful, is that it often fails to estimate the total joint effusion volume accurately [1]. Several methods for the calculation of the "true" joint effusion volume have been described, and thes