doppler

Purpose:  Medical instrument which uses reflected sound waves (i.e. ultrasound) to evaluate blood as it flows through a blood vessel. 

How Works:  A transducer is passed lightly over the skin above a blood vessel which sends and receives sound waves that are amplified through a microphone. The sound waves bounce off solid objects, including blood cells.  The movement of blood cells causes a change in pitch of the reflected sound waves. Information from the reflected sound waves can be processed by a computer to provide graphs or pictures that represent the flow of blood through the blood vessels.