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23 Cards in this Set
- Front
- Back
- 3rd side (hint)
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69. What determination the initial amplitude of an ultrasound wave? |
Answer; A
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The initial strength of amplitude of a sound wave is determined by the vibration of the piezoelectric crystal in the transducer. The greater the vibration of the crystal tyyg
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70. True or False? With standard diagnostic imaging instrumentation, the sonographer has the ability to vary the amplitude of a sound wave produced by the transducer.
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True
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The sonograher can adjust the strength of the ultrasound signal created by a transducer. When a sonographer increases the output power, the electrical voltage sent to the transducer is increased. This produces a more violent vibration of the piezoelectric crystal within the transducer piezoelectric crystal within the transducer and, in turn, a stronger ultrasound wave.
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71. As an ultrasound wave travels through the body, its amplitude usually.
A. decreases B. increases C. remains the same D. cannot be determined |
Answer; A
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As a sound wav travels in the body, its strength or amplitude diminishes. This process is called attenuation. We experience attenuation when walking away from a person who is speaking. The further away we are from a speaker, the weaker that person's voice becomes.
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72. Which of the following are acceptable units for the amplitude of an acoustic wave? (More than one answer may be correct)
A. cm B. atmospheres C. gauss D. watts |
Answer; A and B
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This acoustic variable are pressure density, and particle motion. The units of acoustic wave amplitude are cm for particle motion, and atmospheres for pressure.
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73. The maximum value of the density of an acoustic wave is 60 lb/in2 while the minimum density is 20 lb/in2. What is the amplitude of the wave?
A. 20 lb/in2 B. 40 lb/in2 C. 60 lb/in2 D. none of the above |
Answer; A
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The amplitude of a wave may be calculated by substracting the minimum value of the acoustic variable from its maximum and then dividing that number in half. In the case, the maximum minus the minimum is
60 -20 = 40 lb/in2 Half of 40 is 20/ lb/in2 |
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74. The power of an ultrasound wave can be reported with which of the following units? (More the one answer may be correct.)
A. watts/square centimeter B. dB/cm C. watts D. kg/cm2 |
Answer; C
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The units of power are watts. This is the same measure of power as for light bulbs, stereo systems, and curling irons.
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75. Typically, as an ultrasound wave travels through soft tissue, the power of the wave.
A. decreases B. increases C. remains the same |
Answer; A
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As a sound wave travel the body, its power diminishes. This process is called attenuation. Amplitude and power are both measure of the strength of an acoustic wave, and tend to decrease as sound travels.
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76. True or False? A sonographer can routinely change the power of a wave emitted by a transducer used in diagnostic ultrasonic imaging.
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True
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A sonographer can alter the power of an ultrasound wave by adjusting a control on the ultrasound wave by adjusting a control on the ultrasound system. Power and amplitude are related; if the amplitude is increased; then so is the power. When the amplitude decreases, the power also decreases.
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77. Mathematically, when a number is squared, the number is multiplied by
A. 2 b. 0.5 C. itself D. 1.5 |
Answer; C
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To square a number means to multiply the number by itself. Hence, the term "five square" means 5 times 5, or 25. Ten squared is 10 times 10, or 100
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78. The final amplitude of an acoustic wave is reduced to one-half of its original value. The final power is ____ the original power.
A. the same as B. one - half C. double D. none of the above |
Answer; D
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Changes in the power of a wave are proportional to change in the wave's amplitude squared. One-half squared equals one-quarter (one-half times one-half equals one quarter). When one-half of the waves's original amplitude remains, then only one-fourth of the original power remains.
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79. The amplitude of an acoustic wave decreases from 27 pascals to 9 pascals. If the initial power in the wave was 27 watts, what is the wave's final power?
A. 3 watts B. 9 watts C. 1 watt D. none of the above |
Answer; A
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Alteration in a wave's power are proportional to changes in its amplitude squared. The power is reduced to one-third of its previous value (from 27 to 9 pascals)
One-third squared equal one-ninth. Thus only one-ninth of the wave's original power remains. The initial power in the wave was 27 watts, one-ninth of that is 27/9 or 3 watts |
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80. The intensity of an ultrasound beam is defined as the _______ in a beam ________ by the ________ of the beam.
A. power, multiplied, diameter B. amplitude, divided, area C. power, divided area D. amplitude, multiplied, circumference |
Answer; B
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The intensity of an ultrasound beam is the concentration of the power within the beam area. It is calculated by dividing the power in a beam by its area. The units of intensity are watts per centimeter squared, w/cm2
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81. As sound travels in the body, what typically happens to intensity of the wave?
A. increases B. decreases C. remains the same |
Answer; B
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The intensity of a sound beam decreases as it travels through the body because of attenuation. Amplitude, power and intensity are three different ways to measure the strength of an ultrasound beam. They all decrease as sound propagates.
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82. What are the units of intensity?
A. watts B. watts/cm C. watts/cm2 D. db |
Answer; C
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The intensity of a beam is the power in the beam divided by its cross-sectional area. Power has units of watts and beam area has units of square cm. Intensity has units of watts/cm2
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83. if the power in an ultrasound beam is unchanged, while at the same time, the beam area doubles, then the beam's intensity.
A. doubles B. is halved C. is quartered D. remains the same |
Answer; B
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Intensity is equal to power divided by beam area. In this case, the power is unchanged while the beam area is doubled. Therefore the beam's intensity is halved. For example. If the original power was 2 watts and the initial beam areas was 2 cm2, then the starting intensity was 2 watts divided by 2 cm2, or 1 watt/cm2. Now, beam area is doubled, from 2 to 4 cm2. The new intensity is 2 watts divided by 4 cm2 or 0.5 watts/cm2. The initial intensity was 1, and the final intensity is 0.5 watts/cm2, therefore, the intensity has been halved.
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85. True or False? With diagnostic ultrasound image instruments, the operator can alter the intensity of an ultrasound beam produced by a transducer.
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True
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Although the operator cannot change all of the characteristic of an ultrasound beam created by an individual transducer, he or she can change the initial power. As the operator increases the output power of a transducer, the initial intensity increases.
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86. When the power in an acoustic beam is doubled and the cross-sectional area of the beam is halved, then the intensity of the beam is;
A. doubled B. halved C. quartered D. four times larger |
Answer D
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The intensity rises to four times its original value. Intensity is equal to power divided by beam area. In this case, the power is doubled and the area is halve. For example, if the original power was 4 watts and the initial beam area was 4 cm2, then the starting intensity was 4 watts divided 4 cm2 or 1 watt/cm2. Now, the power is doubled form 4 to 8 watts and the beam area is halved from 4 to 2 cm2. The new intensity is 8 watts divided by 2 cm2, or 4 watts/cm2. The initial intensity was 1, and in the final intensity in 4 watts/cm2, therefore the intensity has increased fourfold.
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87. What determines the intensity of an ultrasound beam?
A. the source of the sound wave B. the medium through which the sound travels. C. both A and B D. neither choice A nor B |
Answer; A
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The source of the acoustic wave determines the initial intensity (as well as the wave's amplitude and power). At its point of origin, the strength of an acoustic wave will not be related to the medium that the sound is about to enter.
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88. What determines the intensity of an ultrasound beam after it has traveled through the body?
A. the sound wave's source B. the medium through which the sound travels C. both A and B D. neither choice A nor B |
Answer; C
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The combination of the source and the medium ultimately determine the residual intensity of an ultrasound beam following a passage through the body. Sound waves attenuate as they propagate.The initial intensity of a sound beam is established by the source of sound, the transducer. The frequency, which is also determined by the transducer, affects the rate of attenuation. In addition, the characteristics of the medium help to determine attenuation. For example, bone and lung has a greater attenuation rate than soft tissue. In contrast, water has a lower attenuation rate than soft tissue.
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89. What happens to the intensity of an ultrasound beam when the beam's cross-sectional area remains unchanged while the amplitude of the wave triples?
A. it triples B. increases ninefold C. remains the same D. none of the above |
Answer; B
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A change in the intensity of a wave is proportional to the change in the amplitude of the wave squared. When the amplitude of a wave is tripled, the intensity is increased ninefold (3x3 = 9)
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90. If the power of the beam is tripled while the cross-sectional area of the beam remains the same, the intensity ________
A. triples B. increases ninefold C. remains the same D. none of the above |
Answer A
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When the cross-sectional area of a beam remains unchanged (which is true in this question), the change in the intensity of a beam is proportional to the change in the power. The question sates that the power is tripled. If the power is tripled, then the intensity is also tripled.
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91. The amplitude of an acoustic wave is increased. Which of the following will most likely remain unchanged? (More than one answer may be correct)
A. power B. frequency C, period D. intensity |
Answer B and C
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Amplitude relates to the strength of a wave. The frequency of a wave describes the number of cycles in one second. A wave's period is the time as an acoustic variable oscillates though one complete cycle. Therefore, frequency and period are not related to amplitude, and remain unaltered when the amplitude changes.
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84. What happened to an acoustic beam's intensity when the power in the beam increases by 25% while the cross-sectional area of the beam remains the same?
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Answer A
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The intensity is equal to the power divided by the beam area. If the power increases by 25% while the beam's are is unchanged, than the intensity is also increased by 25%.
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