Applications of Doppler Ultrasound

Abstract

Traveling sound waves are characterized by minute fluctuations in pressure within the conducting medium. Waves with frequencies above 20 000 Hz are above the audible range of sound for the human ear and are classified as ultrasound. Advances in technology have allowed construction of transducers which can generate sound at frequencies well into the ultrasonic range and with enough power to penetrate tissue, experience reflection and scattering, and return with enough energy to be processed by the receiving apparatus of a transducer. Well understood properties of the ultrasound waves facilitate construction of images and calculation of blood cell velocities. It is the purpose of this chapter to describe the basic principles of physics which govern the manipulation of ultrasound to produce vascular images and measurements of blood flow, and the basic technology which remains relatively constant in the face of rapid updates in modalities and options. It will conclude with a discussion of three relatively new ultrasound approaches: color Doppler energy, three-dimensional imaging, and contrast sonography.