Hyperaemia caused by vasodilatation is one of the earliest detectable pathological changes at the start of synovitis, and angiogenesis is an important feature of pannus formation, which has a crucial role in the maintenance of synovitis. Thus imaging of synovial perfusion and vasculature at the microvascular level by contrast enhanced magnetic resonance imaging (MRI) and power Doppler ultrasonography (PDUS) are promising methods of assessing and monitoring arthritic activity.¹ Several studies have shown a high correlation between MRI and PDUS determination of synovial perfusion.^2,3 A high correlation has also been found between MRI and PDUS imaging, on the one hand, and the histologically determined blood vessel density, on the other.^4,5

Because measurement of synovial perfusion by PDUS is still difficult, most investigators use semiquantitative four step grading: 0 = no flow, 1 = mild flow, …