✅Chapter 6 Flashcards
What is the speed of sound in soft tissue
1540 m/s
Define attenuation
Weakening of sound waves as they travel through tissue
To determine the log of a number count the zeroes. So the long of 100 would be
2 logs
Frequency and distance are ______ related to attenuation
Directly
The more decibels, the ______ amplification
More
As decibels decrease, the attenuation _____
Increases
What are the three things that contribute to attenuation
Reflection, scattering, absorption
What are the two types of reflections
Specular and diffuse
Diffuse reflection is also known as
Backscatter
What is scattering
When the sound hits a smaller structure and it reflects everyway irregularly
Absorption and scattering are ______ related to frequency
Directly
Rayleigh scattering is when the sound is spread in ____ directions after hitting a red blood cell
Equal
When some structures absorb energy, it converts it to ______
Heat
What is the main cause of attenuation
Absorption
The attenuation coefficient is measured in what
dB per cm
The attenuation coefficient is constant and is always going to be ____ the frequency
Half
If we have a 7MHz transducer the attenuation coefficient is going to be ____dB/cm
3.5
Blood attenuates similar to _______
Soft tissue
From low to high attenuation organize the following
Muscle
Bone and lung
Soft tissue
Fat
Air
Biological fluids
Water
Water
Biological fluids
Fat
Soft tissue
Muscle
Bone and lung
Air
Half value layer thickness is also known as
Penetration depth or half boundary layer
Describe the half value layer thickness concept
This describes how far sound needs to travel to decrease by HALF his original value and it depends on the medium and frequency
In media with HIGH attenuation, half value layer is
Thin
(Takes less time to attenuate and decrease to 1/2 its value)
In media with low attenuation, half value layer is
Thick. Takes longer for it to attenuate to half of its original value
Impedance is also known as
Characteristic impedance
What is impedance
The resistance of sound traveling through a medium
What is refraction
Think about the pencil in the cup
Transmission with a CHANGE in direction, only happens during oblique incidence and 2 different media
Define sine
Unitless number with a value from 0 to 1
