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attenuation is proportional (directly related) to what 2 factors
path length and frequency
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with normal incidence the larger the impedance difference the
greater the reflection
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with orthogonal incidence the larger the propagation speed difference the
greater the scattering
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if the impedances of two media are the same what will happen to a sound beam with a perpendicular incidence as it goes from one media to the other
most is transmitted
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shadow comes from both sides of an image is due to
different propagation speed, oblique incidence, redirection, critical angle
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sound waves that are at 90 degrees to the interface or media are termed what
right, normal, 90 degrees, perpendicular
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all sound waves that are not 90 degrees are termed
oblique
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what does Snell's law describe
oblique incidence, different propagation speeds, transmission, direction of sound beam towards or away from the normal
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which has the most reflection
- gallstone/liver
- muscle/bone
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which has the most transmission
myocardium/endocardium
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what is the most attenuating
plaque on valve, gallstone, bone, metal
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what is the least attenuating
blood, bile, urine
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what does a great amount of attenuation cause
shawdowing
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what does a small amount of attenuation cause
enhancement
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increase in frequency will increase
medium
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which is the dominate form of attenuation
absorption
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what happens to the energy that is absorbed
changes to heat
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if there is reflection or echoes produced what did the sound wave encounter
medium with different propagation speed
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what is specular reflection
large and smooth
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what is scattering and what causes it
small and rough interface equals or smaller than wavelength
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what is Rayleigh scattering or what causes it
much smaller than wavelength RBC
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what is non-specular reflection
scatter
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for a large patient you chose to use low frequency transducer why
goes deeper not attenuated greater but you lose resolution
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a high frequency transducer will have a ___ attenuation
greater
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a lower frequency transducer will have a ____ resolution
less
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if refraction occurs what type of misregistration will appear
- laterally
- alway put air to side straw in water
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Considering different propagation speeds and oblique incidence, if medium 2 has a greater impedance than medium 1, what will the transmission wave do?
greater angle or transmission than angle of incidence
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what is impedance
resistance of sound beam to travel or propagate
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what is a type of great impedance to the ultrasound beam
fat
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what is a type of lesser impedance to the ultrasound beam
fluid, blood, urine, bile
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