[Color duplex sonography of extracranial brain-supplying arteries]

Ultrasound examination of extracranial blood-supplying arteries allows the simultaneous acquisition of morphologic and hemodynamic information with high spatial and temporal resolution. For detection and quantification of stenoses in the carotid and vertebral arteries, an intrastenotic peak systolic velocity of more than 120 cm/s is the threshold value for a diameter reduction of >50%. In addition there are further direct and indirect stenosis parameters (intrastenotic and poststenotic circulation disturbance, increased pulsatility in the prestenotic common carotid artery, intracranial or extracranial collateral pathways) which together with diameter and area reduction in the B-scan, lead to a high reliability of color duplex sonography for stenoses of the internal carotid artery (ICA). Sonographic and patho-anatomic comparative studies have shown a high agreement (r >0.9) by using a battery of several ultrasound criteria. Following stenting of the ICA the blood flow velocity in the stent is generally increased so that a > or =70% in-stent restenosis is present in case of a peak systolic velocity of 300-450 cm/s. For the description of arteriosclerotic plaques in the B-scan, ultrasound terminology but not histological terms should be used to describe the internal, surface and motion structure of plaques as well as the sonic shadow formation.