[Velocity variance function: additional information in color-coded Doppler sonography of the carotids].

A new software, called the velocity variance programme, by which flow disturbances are additionally colour-coded, was systematically applied with colour Doppler sonography in 59 patients with stenotic atheromatous lesions of different grades in the carotid bifurcation. A direct comparison with and without using this programme was made. In group 1 (n = 23) with stenosis of the internal carotid artery of more than 50% it could be demonstrated that flow disturbances were maximally in the region immediately downstream of the stenosis and complete dissipation of these effects occurred within 8-10 vessel diameters downstream. Moreover, a direct correlation between the size of the region of disturbed flow and the irregularity of the stenotic plaque surface within the stenosis could be demonstrated. Distal to the stenosis there was an inverse relationship between the extension of disturbed flow and the length of the stenosis and a direct relationship to the grade of the stenosis and the irregularity of the plaque surface. In patient group 2 (n = 36) with less than 50% diameter reduction, a local flow disturbance near the atheromatous plaque was shown in 27 patients. In eighteen of these patients the region of disturbed flow could be revealed only by using the velocity variance programme. The importance of this non-invasive in-vivo visualisation of flow disturbances in the carotid bifurcation is discussed.