Sound travels in waves. Ultrasound is sound that travels at a frequency that is beyond the hearing capacity of man. Using a handheld transducer placed on the skin, ultrasound waves penetrate the tissues and are reflected off the internal structures. The echoes produced are then captured by the transducer and a 2D image is projected upon a screen. Doppler ultrasound utilizes the same principles in order to image blood flow.
Continuous Wave Doppler Ultrasound allows your physician to listen to the sound of blood flowing through your vessels. A change in pitch can then provide an estimate of the degree of narrowing in the blood vessel.
Color Doppler Ultrasound utilizes two technologies simultaneously. In addition to the standard images that are obtained, Doppler sounds are converted into colors that are superimposed upon the image of the blood vessel representing the speed (velocity) of blood flow through the vessel under study.
Duplex Doppler Ultrasound also utilizes two technologies simultaneously. With standard techniques, an image of the blood vessels and neighbouring organs is produced. Additionally, the Doppler sounds are converted into a graph that records the speed and direction of flow in the blood vessel under study.