Sonographic assessment of carotid artery stenosis - Comparison of power Doppler imaging and color Doppler flow imaging

Background and Purpose Power Doppler imaging (PDI) is a new ultrasound technique that, in contrast to color Doppler flow imaging (CDFI), generates intravascular color signals from the reflected echo amplitude depending mainly on the density of red blood cells. We evaluated the diagnostic significance of PDI compared with CDFI for the measurement of carotid stenosis and characterization of plaque surface. Methods In 25 internal carotid artery stenoses, reduction of the intrastenotic lumen contrasted by blood density signals and color Doppler signals on longitudinal and transverse views was assessed for correlative evaluation. In addition, the peak systolic flow velocity of the Doppler spectrum was correlated with PDI and CDFI measurements. Results PDI provided good visualization of the residual lumen in all stenoses, whereas displays on CDFI were inadequate in two calcified plaques. PDI revealed two ulcerative stenoses classified as smooth on CDFI. The correlation between PDI and CDFI was high for measurement of area stenosis (r=.93) and moderate for diameter stenosis (r=.73). Similarly, cross-sectional reduction on both imaging methods correlated more significantly with peak systolic flow velocity than diameter reduction. Conclusions This pilot study suggests that PDI provides additional information for luminal measurement and characterization of plaque surface in complicated high-grade carotid stenosis. Because of the absent visualization of hemodynamics, PDI should be used in combination with CDFI.