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32 Cards in this Set
- Front
- Back
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can you hear ultrasound waves
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hell no, they are higher than what we can hear
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how many cycles per second is a megahertz
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1,000,000 cycles per second
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how many cycles per second is a hertz
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one cycle per second
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what is the highest kHz that a human can hear?
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20 kHz
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how many mHz do U/S use?
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2 to 10 mHz
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define frequency
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number of waves (cycles) per second
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define wavelength
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distance that a wave travels during one cycle
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define speed
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frequency x wavelength
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if you have a shorter wavelength what happens to the frequency?
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you increase the frequency
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what happens to the resolution if you increase the frequency?
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better resolution
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so if you increase the frequency what happens to the wavelength, penetration, and resolution?
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inc. freq
dec. WL dec. penetration inc. resolution |
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how should you select a transducer?
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always choose the highest frequency (resolution) that will penetrate to the depth needed for a particular examination
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what does the probe do?
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emits sound and listens for an echo
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what is the relationship between how many echo's return and what color they will appear on the U/S screen?
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the greater the amount of echo's the more white the image will appear
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what happens to ultrasound waves in fluid?
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sound goes all the way through, no echo's return to the probe, this will appear black- Anechoic
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what happens with ultrasound and bone or something solid?
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all the sound echo's back to the probe will appear hyper echoic
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what happens with ultrasound and gas?
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same as bone, all the sound echo's bounce back and will appear hyper echoic
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what happens with ultrasound and tissue?
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will be part/part and will appear grey
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what is really cool about ultrasound compared to xrays?
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you can see mets on organs that you wouldn't be able to pick up with rads
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which organ should be more hypo echoic, the liver or the spleen?
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the liver
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what is acoustic shadowing?
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if something is below a hyperchoic object, no sound will get to it then this area will appear black (anechoic)
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will there be acoustic shadowing with a blood clot?
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nope, its not a solid object like bone or calculi
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what is acoustic enhancement?
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as sound goes through a fluid, that energy goes to the next object and will cause it to look more hyper echoic than it actually should be
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what is edge shadowing?
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when the sound gets bounced of a tissue and goes into a different direction. The probe HAS to pick up the echo in the same direction as it sent the sound out, if not, then it appears anechoic because no echo's came back.
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what is a mirror image artifact?
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when ultrasound waves change direction. This is really confusing but you can just move the probe around to see its not real.
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are ultrasound waves produced constantly or in pulses?
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in pulses
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why do ultrasounds have to be in pulses?
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because if they keep making noise and you don't stop to listen you won't create an image
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so how much of the time does the probe emit sound and how much time does it spend listening?
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1 % emitting sound
99% listening for echo's |
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with the settings on the ultrasound, how do you adjust the power?
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you really don't, leave it very low and just don't bother with it
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what does power on the ultrasound machine regulate?
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the intensity of the sound input
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why would you modify gain on an ultrasound machine?
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this is the amplication, you will modify this a lot
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what is time-gain compensation
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so we expect objects far away to have less energy than those closer to we use this to fix it. this will allow you to amplify more for farther objects and less for closer objects
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