[Color Doppler sonography for investigation of peripheral joints and ligaments]

Doppler ultrasound is able to visualize blood flow by the change in frequency (Doppler shift) of sound waves which are reflected by moving blood cells inside the vessels (Doppler effect). As hyperemia caused by vasodilatation and angiogenesis is the earliest detectable pathologic change in the beginning of synovitis, Doppler ultrasonography can be used to assess inflammatory activity. Several studies could show a strong correlation between magnetic resonance imaging (MRI) as well as histological findings (blood vessel density) and Doppler sonographic determination of synovial perfusion. Equipment settings must be adapted to slow blood flow in very small blood vessels to reach an appropriate imaging quality. Color and power Doppler ultrasound can depict different grades of intra-articular and peritendinous blood flow, which allows an estimation of inflammatory activity and facilitates the differentiation and monitoring of rheumatic diseases during follow up.