Power Doppler sonography in the assessment of synovial tissue of the knee joint in rheumatoid arthritis: a preliminary experience

Objective: To investigate the intra-articular vascularisation of the synovial pannus in the knee of patients with rheumatoid arthritis (RA) with power Doppler ultrasonography (PDS) and an echo contrast agent and correlate the area under the time-intensity curves with the clinical findings and laboratory measures of disease activity. Method: Forty two patients with RA (31 women, 11 men) with history and signs of knee arthritis, classified according to a modified index of synovitis activity (active, moderately active, and inactive), were studied. Clinical and functional assessment (number of swollen joints, intensity of pain, general health-visual analogue scale, disability index-Health Assessment Questionnaire, Ritchie articular index) and a laboratory evaluation were made on all patients. Disease activity was evaluated using the disease activity score (DAS) and the chronic arthritis systemic index (CASI) for each patient. All patients were examined with conventional ultrasonography and PDS before injection of intravenous ultrasound contrast agent (Levovist). The quantitative estimation of the vascularisation of the synovial membrane was performed with time-intensity curves and calculation of the area under the curves. Results: The mean (SD) value of the area underlying time-intensity curves was 216.2 (33.4) in patients with active synovitis, 186.8 (25.8) in patients with moderately active synovitis, and 169.6 (20.6) in those with inactive synovitis. The mean value of the areas differed significantly between the patients with active and those with inactive synovitis (p<0.01). The mean value of the area under the curve of the entire group was weakly correlated with the number of swollen joints (p=0.038), but a strong correlation was found with composite indexes of disease activity such as the DAS (p=0.006) and CASI (p=0.01). No correlation was found with age, disease duration, and other laboratory and clinical variables. Conclusion: PDS may be a valuable tool to detect fractional vascular volume and to assist clinicians in distinguishing between inflammatory and non-inflammatory pannus. The transit of microbubbles of ultrasound contrast across a tissue can be used to estimate haemodynamic alterations and may have a role in assessing synovial activity and the therapeutic response to treatment of synovitis of the knee joint.