Quiz 2 (study Guide Q’s) Flashcards
(30 cards)
What is Rayleigh scattering?
When the tissue dimensions are smaller than the beams wavelength
What happens to frequency when Rayleigh scattering increases?
Frequency increases
When frequency doubles, what happens to Rayleigh scattering?
Increases by 16 times
Is Rayleigh scattering organized or disorganized?
Organized sound in all directions
What are the 2 forms of reflection?
Diffuse (backscatter) and specular
What is reflection?
When sound hits a boundary, a portion of the waves energy is reflected back to the transducer
The weaker part of the wave continues going forward
Reflection occurs when the boundary is large
What is a specular reflection?
Smooth boundary
Reflected in 1 direction
Organized
What is diffuse reflection?
Not smooth
More than 1 direction
Disorganized
What is scattering?
Random redirection of sound in many different directions
Small tissue interface
How is scattering related to frequency?
Directly related to
How is distance and attenuation related?
Directly related to
How is frequency and attenuation related?
Directly related
More attenuation means ________ distances and __________ frequencies
Longer distances
Higher frequencies
What does attenuation decrease?
It decreases intensity, power and amplitude
What 3 things contribute to attenuation?
Reflection
Scattering
Absorption
How is absorption related to frequency?
Directly related
Higher frequencies increase what 3 things?
Absorption
Attenuation
Scattering
What is the formula for attenuation coefficient in soft tissue?
Attenuation coefficient (dB/cm)=frequency (MHz) divided by 2
Attenuation coefficient = 0.5dB/cm/MHz
What is refraction?
The bending of sound as it strikes the interface
Thin half value layer consists of?
High attenuation
High frequency
Thick half value layer consists of?
Low attenuation
Low frequency
Water has what kind of attenuation?
Extremely low
Blood, urine and fat have what kind of attenuation?
Low
Soft tissue has what kind of attenuation?
Intermediate
