Purpose: To compare the interobserver agreement in qualitative and quantitative two- (2D) and three-dimensional (3D) power Doppler ultrasonographic assessment of joint vascularity in wrist arthritis of patients with rheumatoid arthritis (RA) during anti-inflammatory therapy.
Materials and methods: Tender and swollen wrists of 15 patients with RA were examined by two independent ultrasound investigators before and at day 3, 7, 14 and 42 after the initiation of an anti-inflammatory therapy. Besides the assessment of clinical and laboratory disease activity parameters, a linear array transducer was used to produce grey-scale images of synovitis and effusion as well as 2D and 3D power Doppler sonographic images and movies of synovial vascularity. Interobserver agreement was evaluated with regard to the obtained qualitative information such as grading of synovitis and Doppler signal intensity and compared with the correlations of quantitative assessments such as measurement of synovial thickening, resistance index (RI), 3D blood vessel count, computerized pixel count and first described computerized voxel count.
Results: High interobserver agreement was found for the measurement of synovial thickening (r = 0.86), the computerized voxel count (r = 0.85) and the 3D blood vessel count (r = 0.83) in contrast to significantly lower levels of agreement for RI measurement, the computerized pixel count, the grading of synovitis and the 2D and 3D Doppler grading. A significant decrease of synovial perfusion could be demonstrated by means of 2D and 3D Doppler ultrasound under the anti-inflammatory treatment in accordance with an improvement in clinical and laboratory disease activity.
Conclusion: Quantification of 3D power Doppler images (voxel count) showed higher interobserver agreement compared with 2D quantitative analyses as well as with 2D and 3D semiquantitative grading, indicating this method as a reliable approach to measure synovial perfusion as sign of inflammatory activity in arthritis.