An ultrasound system and method are described for acquiring a sequence of ultrasound images of the carotid artery during the delivery of a contrast agent. Plaque in the images is identified and a time-intensity curve is calculated for pixels in the images. The intensity values before and after the arrival of contrast are compared to identify pixels or groups of pixels having perfusion. An anatomical image may be formed showing areas in an image of the plaque of the intensity and presence of perfusion, or the perfusion may be quantified by determining the percentage of pixels in the plaque image which exhibit perfusion. The extent and degree of perfusion is an indicator of the risk of plaque particulates in the blood stream which may lead to stroke-related symptoms.
