Module1.4 Flashcards
What is attenuation?
Energy removed from the incident beam that does not continue in this initial incident beam direction.
Ultrasound beam transports energy along the beam direction. How is the energy is quantified?
By intensity (I)
What is the unit of intensity?
J/second/cm^2 OR Watt/cm^2
What is an absorption?
The process whereby the ultrasound beam gives up energy to the tissue(medium) it is traveling in. Tissue energy content goes up and beam energy(intensity) goes down
What happens if the energy is absorbed to the patients body?
Tissue molecules vibrate and tissue heats up
What are the two essential ingredients that are responsible for energy absorption?
Ultrasound frequency and relaxation time
How does absorption and attenuation are normally expressed?
In the way the intensity or the amplitude changes as a function of distance through a material
What is the average value of ultrasound beam intensity changes (attenuation)?
0.7 dB /cm/MHz
Maximum depth in m or cm?
Cm since the attenuation rate is in cm
