A carotid doppler tests for diseases of the carotid arteries, aneurism, and infection. It uses reflected sound waves to evaluate blood as it flows through a blood vessel. It can show blocked or reduced blood flow through narrowing in the major arteries of the neck that could cause a stroke.
During a carotid doppler, a handheld instrument is passed over the skin above a blood vessel. The instrument, a transducer, sends and receives sound waves that are amplified through a microphone. The sound waves bounce off solid objects, including blood cells. This movement of blood cells causes a change in the pitch of the reflected sound waves (called the Doppler effect). If there is no blood flow through the vessel, the pitch does not change.
Information from the reflected sound waves is then processed by a computer and used to create graphs or pictures that represent the flow of blood through the blood vessels, which are further reviewed for evaluation.