A carotid duplex scan, also called a carotid ultrasound, carotid artery Doppler sonography or a carotid Doppler, is a non-invasive (the skin is not pierced) type of vascular ultrasound study done to assess the blood flow of the arteries that supply blood from the heart through the neck to the brain. It also studies the vertebral arteries that take blood to the back of the brain. It looks for blockages in these blood vessels that may cause symptoms or changes in your physical examination that can be heard by your physician (called a “bruit,” pronounced “BROO-ee”)