Evaluation of Carotid Artery Stenosis by Power Doppler Imaging

Abstract

To the Editor: Steinke and coworkers1 recently reported on the possible advantages of power Doppler imaging (PDI) for quantification of stenoses of the internal carotid artery (ICA): similar to angiography, it should be possible to assess the degree of stenosis of the ICA as the percentage of the diameter reduction from the longitudinal image. We have tested this examination procedure by comparison with the usual, validated sonography criteria on 40 cases of ICA stenosis. Included in the observation period of the study were all consecutive stenosis findings for which color-coded duplex sonography (CCDS) fulfilled the following criteria: (1) detection of a local flow acceleration in the ICA, (2) peak flow velocity of ≥1 m/s (measurement of the jet flow at the stenosis maximum or, in cases of sound extinction there, directly distal from it), and (3) detection of flow disturbances. Quantification was achieved using the known Doppler criteria.2 In 22% of the cases an adequate evaluation by PDI was not possible: in 6 stenoses the residual lumen could not be demonstrated because of sound extinction; in an additional 3 stenoses, the vessel wall could not be imaged adequately for determination of the degree of stenosis. In the remaining cases the degree of stenosis was regularly underestimated in comparison with the Doppler criteria (Figure 1⇓). Figure 2⇓ illustrates this for the example of a high-grade stenosis of the ICA: the stenosis is very poorly demonstrated in the PDI (panel A). Angiography and conventional CCDS findings with determination of the peak systolic velocity were in agreement, and both revealed the high-grade stenosis (panels B and C). The problem of underestimation …