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123 Cards in this Set
- Front
- Back
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Select the sequence that appears in increasing order.
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C. Centi means "one-hundreth", deci means "one-tenth", deca means "ten", and hecto means "hundred." Thus, this sequence is increasing, starting from the smallest and ending with the largest |
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Which term is the reciprocal of mega?
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D. Mega means million, the reciprocal of million is millionth. Micro means millionth. |
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What term is used to describe the effects of an ultrasound wave on living tissues?
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C. The effects of ultrasound on the tissues are called biological effects or bioeffects. There have been no confirmed bioeffects on humans with acoustic intensities typical of those used in diagnostic imaging.
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As a sound travels through a medium, what term describes the effects of the medium on the sound wave?
A. toxic effects B. acoustic propagation properties C. bioeffects D. transmission properties |
B. Acoustic propagation properties describes the effects of the medium on the wave traveling through it. Acoustic means "sound." Propagation means "to travel."
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Which of the following is true of all waves?
A. they travel through a medium B. all carry energy from one site to another C. their amplitudes do not change D. they travel in a straight line |
B. Waves carry energy from one place to another. A is incorrect because some waves, such as light, can travel through a vacuum. C is incorrect because many waves get weaker as they travel. Certain waves do not travel in a straight line, so D is also incorrect.
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Which of the following describes the characteristics of a sound wave?
A. longitudinal, non-mechanical B. mechanical, transverse C. transverse, acoustic D. mechanical, longitudinal |
D. Sound is mechanical, longitudinal wave. A mechanical wave, such as sound, actually imparts energy to the molecules of the medium through which it travels. The molecules of the medium vibrate, striking their neighbors, which in turn vibrate. This chain reaction results in the acoustic energy traveling through the medium.
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Sound is best described as _______________.
A. a series of compressions and rarefactions B. a transverse wave C. a wave that humans can hear D. an oblique displacement of acoustic energy |
A. Sound is composed of a series of compression and rarefactions. Molecules in the medium are alternately squeezed together (compressed) and stretched apart (rarefied).
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All of the following are true about sound waves except ____________.
A. they are mechanical B. they are transverse C. they carry energy from place to place D. they generally travel in a straight line |
B. Sound waves are not transverse, they are longitudinal.
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Sound can be characterized as:
A. energy flowing through a vacuum B. a variable C. cyclical oscillations in certain variables D. a principle of acoustics |
C. Sound is a wave. A wave is the rhythmical variation throughout time.
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A longitudinal wave propagates from eat to west at a speed of 2 miles per hour. What is the direction of motion of the particles within the wave?
A. from east to west only B. alternately from east to west and then from west to east C. from north to south only D. alternately from south to north and then from north to south |
B. A longitudinal wave is defined as a wave whose particles vibrate back and forth in the same direction that the wave is propagating. Since the wave is traveling from east to west, the particles in this wave will move alternately from east to west and then from west to east.
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The direction of motion of a particle in a wave is perpendicular to the direction of propagation of the wave. What type of wave is this?
A. longitudinal B. acoustic C. mechanical D. transverse |
D. A characteristic of transverse waves is that the direction of propagation is perpendicular to the direction of particle motion in the wave. Sound waves are not traverse, but rather longitudinal.
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Waves that exist at the same location and time will combine. What is this called?
A. inference B. rarefaction C. interference D. longitudinal interaction |
C. The combination of many waves into a single wave is called interference
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Two waves arrive at the same location and interfere. The resultant sound wave is smaller than either of the two original waves. What is this called?
A. constructive interference B. angular interaction C. destructive interference D. in-phase waves |
C. Destructive interference results when a pair of out-of-phase waves interfere with each other. The sum of the two out-of-phase waves has a smaller amplitude than at least one of the original waves.
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A pair of waves are in phase. What occurs when these waves interfere?
A. reflection B. constructive interference C. refraction D. destructive interference |
B. Waves that are in phase constructively interfere with each other. The single wave that results from the combination of the two in-phase waves will always have a higher amplitude than either of the original waves.
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With standard ultrasonic imaging, what happens to the period of a wave as it propagates?
A. increases B. decreases C. remains the same |
C. Certain parameters of a wave change as the wave travels through the body. However the period and the frequency of a wave typically remain constant as a sound wave propagates.
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What determines the period of an ultrasound wave?
A. the transducer B. the medium through which the sound wave travels C. both A and B D. neither choice A nor B |
A. The sound source (the transducer) that produces an acoustic signal determines the period of a wave. The wave's period is unrelated to the medium through which the sound travels, and will not change as the wave moves through one medium to another.
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Which of the following units are appropriate to describe the period of an acoustic wave? (more than one answer may be correct.)
A. minutes B. microseconds C. meters D. mm/μs E. cubic centimeters |
A and B.
The period of a wave is defined as the time that elapses as a wave oscillates through a single cycle. The units for period must be a measure of time, such as minutes or seconds. A and B are units of time. The incorrect selections C, D, and E are units of distance, speed, and volume, respectively. |
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True or False. The sonographer has the ability to alter the period of an ultrasound wave that is produced by a basic transducer.
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False. The monographer cannot adjust the period (or frequency) of a wave produced by a basic transducer. Think of striking a key on a piano. The frequency of a sound created by striking a single key is constant.
If the sound beam's frequency and period are not suited for the particular type of imaging, the sonographer must select a new transducer with a different frequency. |
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What term describes the number of cycles that an acoustic variable completes in a second?
A. period B. frequency C. pulse repetition period D. variable rate |
B. This is the definition of the term frequency. Frequency can also be thought of as the number of regularly occurring events in a specific time.
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Which of the following cannot be considered a unit of frequency?
A. per day B. cycles/sec C. Hz D. hertz E. cycles |
E. The term cycles informs us of the number of events, but does not inform us of the duration of time required for those events to occur.
Choice E is incomplete, and is not a unit of frequency. All the other choices reveal that a number of events took place in a specific time span. |
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What establishes the frequency of an ultrasound wave?
A. the transducer B. the medium through which the sound travels C. both A and B D. neither choice A nor B |
A. When created by a transducer, an ultrasound wave has a specific frequency. The frequency is not determined by the medium through which the sound travels. Only the sound source (the transducer) establishes the wave's frequency.
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When a sonographer increases the maximum imaging depth during an exam, what happens to the frequency?
A. frequency increases B. frequency decreases C. remains unchanged |
C. Imaging depth and frequency are unrelated. When the depth of view is increased, the frequency of sound remains the same.
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Ultrasound is defined as a sound with a frequency of ___________.
A. greater than 20,000 kHz B. less than 1 kHz C. greater than 10 MHz D. greater than 0.02 MHz |
D. Ultrasound is defined as an acoustic wave with a frequency so high that it is not audible to humans. Ultrasound is an inaudible wave with a frequency of at least 20,000 Hz, 20 kHz or 0.02 MHz
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Infrasound is defined as a sound with a frequency of ______.
A. greater than 20,000 kHz B. less than 20 Hz C. greater than 10 MHz D. less than 0.02 MHz |
B. Infrasound is defined as an acoustic wave with a frequency so low that it is not audible to humans. Infrasound is an inaudible wave with a frequency of less than 20 Hz.
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What is the characteristic of acoustic waves with frequencies exceeding 20,000 Hz when compared with waves having frequencies of less than 20,000 Hz?
A. they travel more effectively in soft tissue B. they travel more rapidly C. they attenuate less when traveling in soft tissue D. humans can't hear them |
D. Waves with frequencies exceeding 20 kHz are inaudible to humans and are called ultrasonic. They travel at the same speed as waves with lower frequencies and attenuate at a faster rate than waves with lower frequencies.
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The frequency of a continuous acoustic wave is 5 MHz. The wave is then pulsed with a duty factor of 0.1. What is the new frequency?
A. 0.5 B. 0.5 MHz C. 5 MHz D. 10 MHz |
C. Frequency is the reciprocal of the period. The fact that a wave is pulsed rather than continuous does not alter the frequency of the signal. The new and old frequencies are the same, 5 million/second.
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True or False. If the periods of two waves are the same, then the frequencies of the waves must also be the same.
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True. Frequency and period are reciprocals. When the periods of two waves are identical, the frequencies of the waves must also be identical.
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Compare two sound waves, A and B. The frequency of wave A is one-third that of wave B. How does the period of wave A compare with the period of wave B?
A. A is one-third as long as B B. A is the same as wave B C. A is three times as long as B D. cannot be determined |
C. Frequency and period are reciprocals. If the frequency of one wave is one-third as large as another, then the period of the wave will be three times longer than the other.
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_____________ is the reciprocal of period.
A. inverse period B. pulse repetition period C. frequency D. propagation period |
C. Frequency is the reciprocal of period. Reciprocals are related in two ways: As one increases, the other decreases. & When they are multiplied together, the result is unity.
For example, a wave with a period of one-hundreth of a second has frequency of 100 per second or 100 Hz. |
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What determines the initial amplitude of an ultrasound wave?
A. the transducer B. the medium through which sound travels C. both A and B D. neither choices A nor B |
A. The initial or amplitude of a sound wave is determined by the vibration of the piezoelectric crystal in the transducer. The greater the vibration of the crystal, the larger the amplitude of the ultrasound wave.
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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. The monographer can adjust the strength of the ultrasound signal that a transducer creates. 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 and, in turn, a stronger ultrasound wave.
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As an ultrasound wave travels through the body, its amplitude usually:
A. decreases B. increases C. remains the same D. cannot be determined |
A. As a sound wave 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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The power of an ultrasound wave can be reported with which of the following units? (more than one answer may be correct)
A. watts/square centimeter B. dB/cm C. watts D. kg/cm² |
C. 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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Typically, as an ultrasound wave travels through soft tissue the power of the wave:
A. decreases B. increases C. remains the same |
A. As a sound wave travels through 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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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. A sonographer can alter the power of an 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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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 |
D. Changes in the power of a wave are proportional to changes in the wave's amplitude squared. One-half squared equals one-quarter (1/2 x 1/2 = 1/4). When one-half of the wave's original amplitude remains, the only one-fourth of the original power remains.
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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 |
A. Alterations in 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 equals 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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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 |
C. 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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As sound travels in the body, what typically happens to the intensity of the wave?
A. increases B. decreases C. remains the same |
B. The intensity of a sound beam decreases as it travels through the body because of attenuate. Amplitude, power, and intensity are three different way to measure the strength of an ultrasound beam. They all decrease as sound propagates.
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What are the units of intensity?
A. watts B. watts/cm C. watts/cm² D. dB |
C. 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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True or False. With diagnostic ultrasonic imaging instruments, the operator can alter the intensity of an ultrasound beam produced by a transducer.
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True. Although operators cannot change all the characteristics of an ultrasound beam produced by an individual transducer, they can change the initial power. As the operator increases the output power of a transducer, the initial intensity increases.
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What determines the initial 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 A nor B |
A. 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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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 A nor B |
C. The source of the medium both ultimately determine the residual intensity of an ultrasound beam after it passes throughout the body. Sound waves attenuate as they propagate. The initial intensity of a sound beam is established by the source of the 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 lunch have a greater attenuation rate than soft tissue. In contrast, water has a lower attenuation rate than soft tissue.
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What happens when the power in an ultrasound beam is unchanged, and at the same time, the beam area doubles?
A. doubles B. is halved C. is quartered D. remains the same |
B. 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 area 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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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 |
B and C.
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 an acoustic variable oscillates though one complete cycle. Frequency and period are not related to amplitude, and remain unaltered when the amplitude changes. |
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A sonographer adjusts the output power of the wave emitted by the transducer. Which of the following also changes? (more than one answer may be correct)
A. pulse repetition period B. PRF C. propagation speed D. intensity |
D. As a sonographer adjusts the output power, the intensity will change.
The PRF and pulse repetition period will change only when the maximum imaging depth (also called depth of view) changes. The sound's propagation speed will change only if the medium changes. |
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The wavelength of a cycle in an ultrasound wave can be reported with which units?
A. units of time (sec, min, etc.) B. units of distance (feet, etc.) C. units of area (m², etc.) D. mm only |
B. Wavelength is the distance from the beginning to the end of one cycle. It has units of distance. In soft tissue, and with high frequencies typical of diagnostic imaging, wavelengths range from 0.15 to 0.75mm. Although it may be impractical to record wavelengths in miles or meters, it can be done since they are distances.
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The wavelength of an ultrasonic wave is determined by:
A. the sound source B. the medium through which the wave travels C. both A and B D. neither A nor B |
C. Wavelength is determined by both the sound source and the medium through which it travels. Wavelength is determined, in part, by the wave's frequency (which is established by the sound source). Wavelength is also affected by the speed of the sound wave, which is established by the medium.
In a particular medium, higher frequency waves have shorter wavelengths. With a particular frequency, faster propagation speeds create longer wavelengths. |
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What is the wavelength of 2 MHz sound in soft tissue?
A. 0.77 mm B. cannot be determined C. 1.54 mm D. 2 mm |
A. The wavelength of sound in soft tissue is defined by the following relationship:
wavelength (mm) = 1.54 / frequency (MHz) For 2 MHz sound, the wavelength is 1.54/2 or 0.77 MHz |
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Which of the following terms best describes the relationship between frequency and wavelength for sound traveling in soft tissue?
A. reciprocal B. direct C. related D. inverse |
D. The relationship between frequency and wavelength is inverse. Higher frequency waves are related to shorter wavelengths. Lower frequency waves are related to longer wavelengths.
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Two sound pulses travel through the same medium. One wave's frequency is 2 MHz and the other is 10 MHz. Which sound wave has a longer period?
A. the 10 MHz pulse B. the 2 MHz pulse C. neither pulse D. cannot be determined |
B. Frequency and period are reciprocals. The wave with a higher frequency has a shorter period. Lower frequencies have longer periods. The 2 MHz wave has a period five time longer than the 10 MHz wave.
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Two sound pulses travel through the same medium. One wave's frequency is 2 MHz and the other is 10 MHz. Which pulse has a longer wavelength?
A. the 10 MHz pulse B. the 2 MHz pulse C. neither pulse D. cannot be determined |
B. In any specific medium, the wave with the lower frequency ha the longer wavelength. The 2 MHz sound's wavelength is five times longer than the 10 MHz wave.
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Two sound pulses travel through the same medium. One wave's frequency is 2 MHz and the other is 10 MHz. Which pulse has the lowest power?
A. the 10 MHz pulse B. the 2 MHz pulse C. neither pulse D. cannot be determined |
D. The power of a wave is not related to its frequency. The power relates to the strength of the wave, and in this case, no information is provided about the power. Therefore, we cannot answer this question based on the information provided.
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Two sound pulses travel through the same medium. One wave's frequency is 2 MHz and the other is 10 MHz. Which pulse has the lower propagation speed?
A. the 10 MHz pulse B. the 2 MHz pulse C. neither pulse D. cannot be determined |
C. The propagation speeds of all sound waves are identical while traveling in a specific medium
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Two sound pulses travel through the same medium. One wave's frequency is 2 MHz and the other is 10 MHz. Which pulse has a longer spatial pulse length?
A. the 10 MHz pulse B. the 2 MHz pulse C. neither pulse D. cannot be determined |
D. The spatial pulse length is equal to the wavelength multiplied by the number of cycles in the pulse. We know that 2 MHz sound has a longer wavelength than 10 MHz ultrasound. However, the number of cycles that comprise each pulse is unknown. The information provided is insufficient to answer the question.
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True or False. Lower frequency sound creates higher quality images with greater detail.
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False. Frequency plays a very important role in image quality. Higher frequency sound usually produces higher quality images with greater detail.
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What is the wavelength of 10 MHz sound in soft tissue?
A. 0.77 mm B. 0.15 mm C. 1.54 mm D. 10 mm |
B. The wavelength of sound in soft tissue is defined by the following relationship:
wavelength (mm) = 1.54 / frequency (MHz) For 2 MHz sound, the wavelength is 1.54/10 or 0.15mm |
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Propagation speed can be correctly recorded with which of the following units? (more than one may be correct)
A. miles per hour B. mm/msec C. km/sec D. inches per year |
All of the above.
Speed is recorded as a distance per unit of time, such as miles per hour, or feet/sec. Any relationship of distance per time is an acceptable answer |
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The propagation speed of continuous wave ultrasound is 1.8 kilometers per second. The wave is then pulsed with a duty factor of 50%. What is the new propagation speed?
A. 0.5 km/sec B. 0.9 km/sec C. 1.8 kim/sec D. 3.6 kim/sec E. cannot be determined |
C. The speed of sound in a medium is determined only by the medium. There is no difference in sound's speed whether the wave is continuous or pulsed Thus, the new and old speeds will be identical, 1.8 km/sec.
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True or False. Shorter wavelength sound creates higher quality images with greater detail.
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True. Wavelength plays a very important role in image quality. Shorter wavelength (higher frequency sound) produces high quality images with greater detail.
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The speed of sound traveling through bone is ________ soft tissue.
A. higher than B. lower than C. equal to D. cannot be determined |
A. The propagation speed of sound in bone is higher than in soft tissue. Sound travels at a speed of 2 to 5 km/sec in bone. This is two to three times fast than soft tissue.
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Compared to soft tissue, the speed of an acoustic wave through lung tissue is ____________.
A. faster B. slower C. equal D. cannot be determined |
B. The speed of sound in lung tissue is slower than in soft tissue. Sound travels at speeds in the range of 0.5 to 1.0 km/sec in lung tissue.
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As a general rule, which of the following lists media in increasing order of propagation speeds?
A. gas, solid, liquid B. liquid, solid, gas C. solid, liquid, gas D. gas, liquid, solid |
D. Generally, sound travels slowest in gases, faster in liquids, and fastest in solids
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What is the speed of sound in air?
A. 1,540 m/s B. 330 m/s C. 100 m/s D. 3,010 m/s |
B. The speed of sound in air is 330 m/s, substantially lower than the speed of sound in soft tissue.
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True or false. Soft tissue is an imaginary construct that actually does not exist.
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True. Soft tissue is an imaginary structure with characteristics that represent an "average" of body tissues, including muscle, blood, kidney, and spleen. It is used as an approximation.
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If sound travels at exactly 1,540 m/sec in a particular medium, then the medium __________.
A. must be soft tissue B. may be soft tissue C. cannot be soft tissue |
B. Sound waves travel exactly 1,540 m/sec in soft tissue. However, other media have the same propagation speed as that of soft tissue. The medium in question could be soft tissue, or it could be something else.
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If sound doesn't travel at 1,540 m/sec in a medium, then the medium ______.
A. must be soft tissue B. may be soft tissue C. cannot be soft tissue |
C. Sound waves travel exactly 1,540 m/sec in soft tissue. since the propagation speed of sound in this medium is not 1,540 m/sec the medium cannot be soft tissue.
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The propagation speed of ultrasound waves in muscle, liver, kidney, and blood are ______.
A. exactly the same B. very similar to each other C. vastly different |
B. The speed of sound in these media are less than 5% different from each other. The characteristics of muscle, kidney, liver, and blood that determine the wave's speed in the media are quite similar.
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The speed at which a wave travels through a medium is determined by:
A. the sound wave's properties only B. the medium's properties only C. properties of both wave and medium D. none of the above |
B. Speed is determined by the characteristics of the medium only. The characteristics of the wave do not affect its speed. All sound waves of any frequency, period, intensity, and power travel at the same speed in a particular medium.
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What two properties establish sound's propagation speed in a given medium?
A. elasticity and stiffness B. stiffness and impedance C. conductance and density D. density and stiffness |
D. The two properties of the medium that affect sound's propagation speed are density and stiffness.
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Two sound waves with frequencies of 5 and 3 MHz travel to a depth of 8 cm in a medium and then reflect back to the surface of the body. Which acoustic wave arrives first at the surface of the body?
A. the 5 MHz wave B. the 3 MHz wave C. neither D. cannot be determined |
C. They both travel at the same speed and reach the surface of the body at exactly the same time. All sour waves, regardless of their features, travel at the same speed in a specific medium. The fact that these waves have different frequencies is irrelevant.
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What are the units of pulse duration?
A. units of frequency (Hz, etc.) B. msec only C. units of time (sec, years, etc.) D. units of distance (feet, etc.) |
C. The pulse duration is the actual time that a transducer is creating one pulse. Hence, it has units of time. The typical range of pulse durations found in diagnostic imaging equipment is 0.3 to 2 μsec, but it is valid to report pulse duration in any unit of time.
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What determines the pulse duration?
A. the source of the wave B. the medium in which the pulse travels C. both A and B D. neither A nor B |
A. The pulse duration is the actual time that a transducer is creating one sound pulse and is determined by the ultrasound system. Pulse duration does not include the listening time.
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The pulse duration is expressed in the same units as the _________.
A. period B. PRF C. wavelength D. density |
A. The pulse duration and the period are measured in units of time, such as seconds, minutes, or hours.
PRF has units of hertz. Wavelength has units of distance. Density has units of mass per volume. |
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True or False. A sonographer can adjust the duration of an acoustic pulse since it depends upon the pulse's propagation speed.
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False. a sonographer cannot change the pulse duration. It is a fixed feature of the transducer and ultrasound system. It does not depend upon propagation speed.
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True or False. A sonographer can adjust the duration of an acoustic pulse since it depends upon the maximum imaging depth.
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False. A sonographer cannot change the pulse duration. It has a constant value, and is not dependent on imaging depth.
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What is the pulse duration equal to?
A. frequency multiplied by period B. period multiplied by wavelength C. the number of cycles in the pulse divided by the wavelength D. period multiplied by the number of cycles in the pulse |
D. The pulse duration is the total time that the transducer is producing a pulse. The pulse duration is equal to the time to make a single cycle (the period) multiplied by the number of cycles that make up the pulse. For example, if there are 6 cycles in a pulse, each with a period of 0.2 μsec, then the pulse duration is 6 x 0.2 = 1.2 μsec.
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What happens to the pulse duration when a sonographer decreases the maximum imaging depth in an ultrasound scan?
A. increases B. decreases C. remains the same D. cannot be determined |
C. The time that a transducer is "pulsing" does not change with alterations in depth of view.
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The spatial pulse length describes certain characteristics of an ultrasound pulse. What are its units?
A. time B. hertz C. meters D. none; it is unitless |
C. Spatial pulse length is the distance that a pulse occupies in space. It's length is measured from the beginning to the end of the pulse. It can be reported in any unit of distance.
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In diagnostic imaging, what determines the spatial pulse length?
A. the ultrasound system B. the medium through which the pulse travels C. both A and B D. neither A nor B |
C. The spatial pulse length is the distance, or length, of a pulse. It depends, in part, upon the wavelength of each cycle in the pulse. Wavelength depends upon both the source of the sound and the medium through which the sound travels. The length of the entire pulse also depends upon both the source and the medium.
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Which of the following best describes the spatial pulse length?
A. frequency multiplied by wavelength B. PRF multiplied by wavelength C. wavelength multiplied by the number of cycles in the pulse D. duty factor multiplied by the wavelength |
C. The total length of a pulse equals the length of each cycle in the pulse multiplied by the number of cycles in the pulse.
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Two transducers send ultrasound pulses into soft tissue. One transducer emits sound with a 4 MHz frequency, and the other produces sound at a 6 MHz frequency. Each pulse contains 4 cycles. Which has a greater spatial pulse length?
A. the 6 MHz pulse B. the 4 MHz pulse C. they are the same D. cannot be determined |
B. Since both pulses have the same number of cycles, the pulse whose individual cycles have a longer wavelength will have the greater overall length. In a given medium, waves with lower frequencies have longer wavelengths. The 4 MHz wave has a longer wavelength than the 6 MHz wave and therefore will have a longer spatial pulse length.
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Using a specific transducer, what happens to the spatial pulse length as the sonographer increases the maximum imaging depth?
A. increases B. decreases C. remains the same D. cannot be determined |
C. The spatial pulse length is determined by the number of cycles in the pulse and the wavelength of each cycle. With the same system, these factors are unchanged, and the spatial pulse length remains the same.
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On what does the pulse repetition period depend?
A. the source of the sound wave B. the medium through which pulse travels C. both A and B D. neither A nor B |
A. Similar to the PRF, the pulse repetition period depends only on the ultrasound system. The pulse repetition period is the time from the start of one pulse to the start of the next pulse and includes the pulse duration and the receiving time. When the sonographer adjusts the depth of view, the pulse repetition period is altered. To be more exact, the listening time is lengthened with deeper imaging and shortened with shallower imaging
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A sonographer adjusts the maximum imaging depth of an ultrasound system. Which of the following also changes? (more than one answer may be correct)
A. pulse repetition period B. wavelength C. pulse repetition frequency D. frequency |
A and C.
As imaging depth is altered, the PRD and pulse repetition period change. The wavelength and frequency remain constant, as these terms describe the attributes of a single cycle within the pulse, and are not affected by alterations in imaging depth. |
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Which of the following correctly describes pulse repetition period?
A. the product of wavelength and propagation speed B. the reciprocal of the frequency C. the sum of the pulse's "on" time and the listening "off" time D. the time that the transducer is pulsing |
C. The pulse repetition period is the actual time from the start of one pulse to the start of the next pulse. It is equal to the time that the transducer is pulsing (the pulse duration) plus the time that the ultrasound system is listening for reflected echoes
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What happens to the pulse repetition period if the sonographer decreases the maximum imaging depth achieved in an ultrasound scan?
A. increases B. decreases C. remains the same D. cannot be determined |
B. As the maximum imaging depth, or depth of view, is decreased, the interval of time during which the ultrasound machine listens for returning echoes is diminished. As a result of this shorter listening time, the pulse repetition period is shortened. Simply stated, pulse repetition period and depth of view are directly related.
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What are the units of pulse repetition frequency (PRF)?
A. seconds B. 1/seconds C. mm/μs D. seconds⁻² |
B. Pulse repetition frequency is the number of pulses that are produced by the ultrasound system in one second. PRF has the same units as frequency, and these units are hertz, Hz, or per second.
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The pulse repetition frequency of ultrasound produced by a transducer typical of diagnostic imaging systems _________.
A. can be changed by the sonographer B. depends on the medium through which the sound travels C. is unchanged as long as the same ultrasound system is used D. has nothing to do with clinical imaging |
A. The pulse repetition frequency (PRF) is inversely related to the maximum imaging depth that is achieved during an exam. As the sonographer increases the maximum imaging depth, the PRF must decrease.
This occurs because the transducer must wait a longer time for echoes to return from deeper depths. Sonographers, therefore, alter the PRF when they adjust the maximum imaging depth. |
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In diagnostic imaging, what establishes the pulse repetition frequency?
A. the source of the sound B. the medium through which the sound travels C. both A and B D. neither A nor B |
A. The sole determinant of the pulse repetition frequency is the source of the acoustic wave, the ultrasound system. The medium through which the sound travels does not directly affect the pulse repetition frequency.
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When a sonographer increases the maximum imaging depth during an exam, what happens to the PRF?
A. PRF increases B. PRF decreases C. remains unchanged |
B. When the depth of view is increased, the system waits and listens a longer time for reflections. This reduces the system's ability to send out as many pulses per second. Hence, as imaging depth increases, the pulse repetition frequency decreases. Imaging depth and PRF are inversely related.
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The pulse repetition frequency is the ________.
A. product of the wavelength and propagation speed B. reciprocal of the period C. sum of pulse duration and listening time D. reciprocal of pulse repetition period |
D. The PRF and the pulse repetition period are reciprocals. For example, if the PRF is 100 per second, then the pulse repetition period is one-hundreth of a second. If the system creates five hundred pulses per second, then the pulse repetition period is 1/500 of a second.
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What is the value of the duty factor for continuous wave ultrasound?
A. 100 B. 1% C. 1000% D. none of the above |
D. The duty factor for continuous wave ultrasound is 1.0 or 100%. This means that the transducer is producing an acoustic signal at all times. None of the answers indicate this: 100 is not 100%, 1% means one-hundreth and is incorrect, and 1000% means 10 times and is also false.
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While using a particular imaging system, what happens to the duty factor when the depth of view increases?
A. increases B. decreases C. unchanged |
B. Duty factor is inversely related to depth of view. As the system images to a greater depth, the system requires more time to listen for reflections, and the duty factor decreases.
The duty factor is the fraction or percentage of time that an imaging system is transmitting. It is equal to the pulse duration divided by the pulse repetition period. Under normal operation, the pulse duration never changes. However, as depth of view increases, the pulse repetition period increases. |
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True or False. The sonographer alters the duty cycle when adjusting imaging depth of a scan.
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True. The duty cycle is the percentage of time that an ultrasound system is creating an acoustic wave. Duty factor is inversely related to depth of view. Duty factor decreases when'd depth of view increases.
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While using the same ultrasound machine and transducer, which of the following can the sonographer alter? (more than one answer may be correct)
A. pulse repetition period B. PRF C. frequency D. duty cycle E. pulse duration |
A, B, and D.
While adjusting the desired maximum imaging depth in an exam, the sonographer adjusts the pulse repetition period and the PRF. The duty factor is also altered. Unlike choices A, B and D, the frequency of the ultrasound and pulse duration are fixed once a transducer is selected. These parameters cannot be altered. |
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Which intensity is most closely related to tissue heating?
A. SPTP B. SATP C. SPTA D. SATA |
C. The SPTA intensity relates most closely to tissue temperature elevation.
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The logarithm of a numeral is defined as how many times _____ must be multiplied together to get that numeral.
A. 1 B. 2 C. 5 D. 10 |
D. The logarithm of a numeral is equal to the number of tens that are multiplied together to result in that number.
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What is a decibel?
A. the absolute value of a number B. a range of values C. a relationship between two numbers D. none of the above |
C. A decibel represents a relationship between two numbers. A decibel is a relative measure of intensity or power. The term "relative" indicates that we are not dealing with an absolute power, but rather with how the power is related to a reference level.
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Decibel notation is a ______ between two numbers.
A. difference B. sum C. product D. ratio |
D. Decibels are calculated by dividing the final strength of a signal by starting strength. Thus, decibel notation is ratio between two numbers
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The scale associated with decibel notation is ______.
A. linear B. discrete C. logarithmic D. additive |
C. Decibel notation is based on the mathematical relationship of logarithms
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What is the decibel notation for an acoustic signal that is attenuated?
A. positive B. negative C. equal to zero |
B. When a signal is attenuated, its magnitude decreases it becomes weaker. In decibel notation, a decrease in signal strength is described with negative decibels. Negative dB means "getting smaller."
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The power in a wave is increased to ten times its original value. How many decibels describe this change?
A. 3 B. 6 C. 10 D. 20 |
C. An increase of ten times the original power of a wave is reported as +10 dB
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The intensity of an ultrasound wave is changed by -6 dB. This means that the current intensity is _____ as much as its original level.
A. one-tenth B. four times C. one-fourth D. one-sixth |
C. A change in intensity of -6 dB indicates that only one-fourth of the initial intensity remains. the minus sign indicates a decrease in the signal magnitude. Each -3 dB change means that one-half the original intensity remains. Since there are two sets of -3 dB, one half multiplied by one-half indicates that there is only one-fourth remaining.
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What are units used to describe attenuation?
A. watts B. watts/cm² C. macro D. decibels |
D. Attenuation is measured in decibels. Attenuation is reported as a relative change in strength, not an absolute change.
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What does a 3 dB change in value intensity mean?
A. the value has doubled B. the value has tripled C. the value has increased 30% D. the value has increased ten times |
A. A 3 decibel change in the intensity indicates that the value has doubled
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As sound propagates through a medium, the total power in the wave decreases. What is this entire process called?
A. absorption B. scattering C. attenuation D. reflection |
C. As a wave propagates through a medium, its power diminishes. This is attenuation. Choices A, B, and D are all components or contributors to attenuation.
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Attenuation is determined by which of the following factors?
A. density and stiffness of the medium B. frequency of sound and propagation speed C. PRF of sound and path length D. path length and frequency of sound |
D. The factors that determine the degree to which a sound beam weakens are: 1. the distance that the sound travels, and 2. the frequency of the sound.
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An acoustic wave is traveling through soft tissue. Its intensity undergoes six decibels of attenuation. How does the final intensity of wave relate to the intensity of the wave when its started its journey?
A. it is now four times larger B. it is now six times larger C. it is now one-fourth as large D. it is now one-then as large |
C. When a wave undergoes dB of attenuation, the intensity of the wave is decreased to one-fourth of its initial value. The term attenuation means "to weaken, or reduct." Attenuation always describes a reduction in the intensity of the wave. Six decibels of attenuation is made up of two groups of -3 dB. Each -3 dB indicates a halving of intensity. One-half multiplied by one-half means that only one-fourth of the original intensity remains.
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A sound wave reaches a rough or irregular border between two media. Under these explicit circumstances, which process is most likely to occur?
A. backscatter reflection B. specular reflection C. Rayleigh scattering D. refraction |
A. The smoothness or roughness of a boundary will help to determine what form of reflection takes place. Backscatter is likely to occur when the boundary has irregularities that are larger than the wavelength of the incident acoustic pulse. Diffuse reflection is another name for backscatter.
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Which of the following is true of diffuse reflections?
A. they're created by smooth boundaries B. they're created by large reflectors C. sound reflects in many directions D. they do not appear in soft tissue |
C. Diffuse reflections, also called backscatter, are dispersed in multiple directions.
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What is the uniform dispersion of a sound wave in many different directions after striking a very small particle?
A. microscattering B. backscattering C. Rayleigh scattering D. total absorption |
C. Rayleigh scattering is the redirection of an acoustic wave in many different direction as a result of striking a small particle. When Rayleigh scattering occurs, the dimension of the reflecting particle is usually less than the wavelength of the ultrasound wave. The amount of Rayleigh scattering also depends on the frequency of the ultrasound.
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Which of the following is considered a Rayleigh scatterer?
A. bone B. liver C. muscle D. blood cell |
D. A blood cell is a Rayleigh scatterer. A red blood cell is smaller than the wavelength of the typical acoustic wave used in diagnostic imaging. When an acoustic wave strikes a blood cell, the energy within the pulse is scattered in many directions.
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As a pulse passes through soft tissue, a certain amount of acoustic energy remains in the tissue as heat. What is this constituent of attenuation called?
A. scattering B. absorption C. refraction D. rarefaction |
B. The conversion of acoustic energy into heat is called absorption. This process deposits a portion of the energy from the beam into the soft tissues.
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What is the amount of attenuation per centimeter that a sounds ave undergoes called?
A. beam uniformity coefficient B. attenuation coefficient C. attenuation D. duty factor |
B. The attenuation coefficient reports a sound beam's decibels of attenuation per centimeter. This is a useful tool as its value remains constant, regardless of the actual path length.
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A sound beam travels 9 cm in soft tissue. The attenuation coefficient is 3db/cm. What is the total attenuation that the sound beam experienced?
A. 9 dB B. 3 dB C. 27 dB D. 18 dB |
C. To calculate total attenuation, multiply path length by attenuation coefficient. In this example, the overall attenuation is: 3 x 9 = 27 dB
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The attenuation of an acoustic wave traveling through bone is ____ its attenuation through soft tissue.
A. greater than B. less than C. equal to |
A. The attenuation of ultrasound in bone is greater than its attenuation in soft tissue
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Ultrasound waves traveling through lung tissue attenuate to a _________ extent than when traveling through soft tissue.
A. greater B. lesser C. nearly equal |
A. Ultrasound attenuates more than traveling through lung tissue than when traveling through soft tissue.
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Which of these lists indicates media with increasing attenuation of ultrasound?
A. water, lung, soft tissue, bone, air B. lung, air, soft tissue, bone C. lung, fat, muscle D. water, blood, fat, muscle, bone, air |
D. This list orders tissues with increasing attenuation rates of ultrasound
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True or False. Attenuation and propagation speed are unrelated.
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True. Attenuation and propagation speed are entirely unrelated. Attenuation is the weakening of a beam as it travels and has nothing to do with how fast it travels.
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Acoustic impedance is property of the ________ and has units of _________.
A. source and medium, lmps B. medium, dB C. medium, Rayls D. medium, Ohms |
C. Acoustic impedance is property of the medium through which sound travels. It is unaffected by the sound source or characteristics of the wave itself. The units of impedance are Rayls.
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To calculate the acoustic impedance of a medium, one should ______ the _______ by the _________.
A. divide, propagation speed, density B. multiply, density, propagation speed C. divide, density, propagation speed D. multiply, stiffness, density |
B. To obtain the value of acoustic impedance, multiply the density of a medium by its propagation speed.
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Which two attributes help establish the acoustic impedance of a medium?
A. density and temperature B. density and stiffness C. stiffness and elastance D. elasticity and compressibility |
B. To calculate the acoustic impedance, multiply the propagation speed of the medium by the density of the medium. A medium's propagation speed is determined by the density and the stiffness of the medium. Therefore, acoustic impedance is a property of both density and stiffness.
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