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15 Cards in this Set
- Front
- Back
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What portion of sound spectrum is ultrasound?
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greater than 20,000 cycles per second (20 KHz)
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What are disadvantages of US
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attenuated in gaseous medium, especially at high frequencies
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What are the components of longitudinal ultrasound waves
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compression and rarefaction
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Compression
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Part of longitudinal wave with more densely packed particles
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Rarefaction
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component of longitudinal wave with less densely packed particles.
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What type of interfaces leads to greatest ultrasound reflection?
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Solid/gas interfaces and dense media. Causes poor penetration.
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Why does bone reflect?
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Because it has so many interfaces.
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Which tissues allow greatest penetration?
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Soft tissues and blood.
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Define an ultrasound wave cycle.
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One compression plus one rarefaction.
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What is wavelength?
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Distance between two similar points along the wave.
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What are the wavelengths used in diagnostic ultrasound?
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0.15 mm to 1.5 mm
Inversely related to frequency |
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What is the frequency of the sound wave?
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Number of cycles per second (expressed as Hertz or Hz. Inversely related to wavelength.
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What is absorption?
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Transfer of ultrasound energy to tissue during propagation.
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What is acoustic impedence?
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The product of the density of the medium and the velocity of sound: The differences in AI between two medium determine the ratio of transmitted versus reflected sound at the interface.
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What is amplitude
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Magnitude of presure change along a wave. Strength of the wave in decibels.
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