Term
How did ultrasound get its name?
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Definition
| Sound is classified based on the ability of humans to hear it. Sound with frequencies so high that humans cannot hear it is called ultrasonic or ultrasound. |
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Term
Why is frequency important in diagnostic sonography? |
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Definition
It affects penetration & image quality.
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Term
What is the relationship between frequency & period?
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Definition
Inversely related.
↑ F = ↓ P & ↑ P = ↓ F |
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Term
What is the difference between amplitude & peak-to-peak amplitude?
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Definition
Amplitude is measured from the midline to the max or min of the wavelength.
Peak-to-peak is measured from the top of the wavelength to the bottom. It is twice the value of the amplitude.
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Term
How are amplitude & power related? |
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Definition
Directly related.
↑ Power = ↑ Amplitude.
Both are parameters that describe the size or magnitude of a wave.
Power is ȣ to Amplitude2.
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Term
How is intensity related to power & amplitude?
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Definition
Intensity ȣ Power ȣ Amplitude 2.
They are all proportional to each other. |
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Term
What is the difference between wavelength & period? |
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Definition
Both are a single cycle in a sound wave, but a period is the time it takes to complete a single cycle & a wavelength is the length of a single cycle.
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Term
| What is the relationship between wavelength and frequency? |
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Definition
Inversely related.
↓ F = ↑ λ
The lower the frequency the longer the wavelength.
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Term
What is the wavelength of 1 MHz sound in soft tissue?
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Definition
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Term
What is the wavelength of other frequency sound waves in soft tissue?
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Definition
Sound with a frequency of 2 MHz has a wavelength of 0.77mm in soft tissue.
1.54mm = 0.77mm
2
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Term
What is the rule that defines the relationship btween frequency & wavelength of sound in soft tissue?
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Definition
Divide 1.54mm by the frequency in MHz.
λ (mm) = 1.54mm/us
F (MHz)
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Term
Why is wavelength important in diagnostic ultrasound? |
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Definition
Short wave = high frequency = better picture. |
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Term
What is the speed of sound in soft tissue? |
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Definition
1,540 m/s (or 1.54 mm/us)
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Term
What is the speed of sound in biologic tissues other than soft tissue?
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Definition
Lung = 500 m/s
Fat = 1,450 m/s
Liver = 1,560 m/s
Blood = 1,560 m/s
Muscle = 1,600 m/s
Tendon = 1,700 m/s
Bone = 3,500 m/s
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Term
What is the speed of sound in other media? |
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Definition
Air = 330 m/s
Water = 1,480 m/s
Metals = 2,000 – 7,000 m/s
C (m/s) = F (Hz) x λ (m)
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Term
What characteristics of a medium determine the speed of sound in that medium?
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Definition
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Term
How does stiffness affect speed? |
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Definition
Directly related.
↑ Stiffness = ↑ Speed
The stiffer the media, the faster the sound.
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Term
How does density affect speed? |
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Definition
Inversely related.
↑ Density = ↓ Speed
The denser the media, the slower the sound. If 2 media are equally stiff, the denser medium will have a lower speed.
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Term
What other terms describe stiffness? |
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Definition
Elasticity & Compressibility
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Term
| Which has the greater influence on speed, density or stiffness? |
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Definition
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