Summarizing Ultrasound

Summary

• The acoustic impedance is defined as:

  \(Z=\mathrm{\rho v},\)

  \(\rho \) is the density of a medium through which the sound travels and \(v\) is the speed of sound through that medium.
• The intensity reflection coefficient \(a\), a measure of the ratio of the intensity of the wave reflected off a boundary between two media relative to the intensity of the incident wave, is given by

  \(a=\cfrac{{({Z}_{2}-{Z}_{1})}^{2}}{{({Z}_{1}+{Z}_{2})}^{2}}.\)

• The intensity reflection coefficient is a unitless quantity.

Glossary

acoustic impedance

property of medium that makes the propagation of sound waves more difficult

intensity reflection coefficient

a measure of the ratio of the intensity of the wave reflected off a boundary between two media relative to the intensity of the incident wave

Doppler-shifted ultrasound

a medical technique to detect motion and determine velocity through the Doppler shift of an echo