Exam 2 Flashcards
What is the range of period commonly found in waves produced by ultrasound systems?
.06- .5us
With standard ultrasonic imaging, what happens to the period of a wave as it propagates?
Remains the same
What determines the period of an ultrasound wave?
The transducer
Which of the following units are appropriate to describe the period of an acoustic wave?
Minutes Meters Microseconds Mm/us Cubic centimeters
Minutes
Microseconds
True or false? The sonographer has the ability to alter the period of an ultrasound wave that is produced by a basic transducer.
False
What term describes the number of cycles that an acoustic variable completes in a second?
Frequency
Which of the following cannot be considered a unit of frequency?
Per day Cycles/sec Hz Hertz Cycles
Cycles- informs us of the number of events but not of the duration of time
What is the range of frequencies emitted by transducers used in ultrasonic imaging?
1 to 3 MHz
1 to 1,000 kHz
-10,000 to +10,000Hz
2,000,000 to 15,000,000 Hz
2,000,000 to 15,000,000 Hz
What establishes the frequency of an ultrasound wave?
The transducer
True or false?
With standard ultrasound pulses, the frequency of the ultrasound changes significantly as the wave propagates through the body.
False
When a sonographer increases the maximum imaging depth during an exam, what happens to the frequency?
Remains unchanged
-imaging depth and frequency are unrelated
Ultrasound is defined as a sound with a frequency of ___.
Greater than .02MHz
Infrasound is defined as a sound with a frequency of ___.
Less than 20 Hz
True or false?
Waves in the ultrasound range behave in the same general manner as sound waves that are audible.
True
-primary diff btw audible waves and ultrasonic waves is that humans can hear audible waves
What is characteristic of acoustic waves with frequencies exceeding 20,000 Hz when compared with waves having frequencies of less than 20,000 Hz?
Humans can’t hear them
What is characteristic of acoustic waves with frequencies of less than 20 Hz when compared with waves having frequencies of more than 20 Hz?
Humans can’t hear them
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?
Frequency is the reciprocal of the period.
5MHz
True or false?
The period of an ultrasound wave is related to the frequency and is the same, regardless of whether the wave is pulsed or continuous.
True
True or false?
If the periods of the two waves are the same, then the frequencies of the waves must also be the same.
True
Compare two sound waves A and B. The frequency of wave A is 1/3 that of wave B. How does the period of wave A compare with the period of wave B?
A is 3x as long as B
Frequency and period are reciprocals
____ is the reciprocal of period.
Frequency
As one increases, the other decreases
When multiplied, the result is unity
A wave with a period of 1/100th of a second has a frequency of ___ per second.
100 per second or 100Hz
What determines the initial amplitude of an ultrasound wave?
The transducer
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.
True
As an ultrasound wave travels through the body, it’s amplitude usually:
Decreases
Which of the following are acceptable units for the amplitude of an acoustic wave?
Watts
Cm
Pascals
Gauss
Cm
Pascals
The maximum value of the density of an acoustic wave is 60 lb/in^2 while the minimum density is 20 lb/in^2. What is the amplitude of the wave?
Amplitude = max value of acoustic wave- min value and then divide the number in half.
60-20= 40 lb/in^2
40/2= 20 lb/in^2
The power of an ultrasound wave can be reported with which units?
Power = watts
Watts of a lightbulb, stereo system, etc
Typically an ultrasound wave travels through soft tissue, the power of the wave:
Decreases
Increases
Stays the same
Decreases
-as a sound travels through the body the power diminishes. This is called attenuation
True or false
A sonographer can routinely change the power of a wave emitted by a transducer used in diagnostic ultrasonic imaging
True
Power and amplitude are related
When amplitude increases, power increases
Mathematically, when a number is squared, the number is multiplied by ___.
Itself
The final amplitude of an acoustic wave is reduced to one-half of its original value. The final power is ___ the original power.
The same as
One- half
Double
None of the above
None of the above
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, then only one-fourth of the original power remains.
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?
3 watts
One third squared equals one ninety
Thus only one-nineth of the wave’s original power remains. The original power was 27 watts
27/1 x 1/9 = 3 watts
The intensity of an ultrasound beam is defined as the ___ in a beam ___ by the ___ of the beam.
Power, multiplied, diameter
Amplitude, divided, area
Power, divided, area
Amplitude, multiplied, circumference
Power, divided, area
As sound travels in the body, what typically happens to the intensity of the wave?
Decreases
What are the units of intensity?
Watts/cm^2
True or false?
With diagnostic ultrasonic imaging instruments, the operator can alter the intensity of an ultrasound beam produced by a transducer.
True
What determines the initial intensity of an ultrasound beam?
The source of the sound wave
What determines the intensity of an ultrasound beam after it has traveled through the body?
1) The sound wave’s source
2) The medium through which the sound travels
What are the units of the transmitted intensity of a sound wave?
W/cm^2
What happens when the power in an ultrasound beam is unchanged, and at the same time, the beam area doubles?
Is halved
What happens 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?
It increases by 25%
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:
Four times larger
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?
Increases ninefold
When the amplitude of a wave is tripled, the intensity is increased ninefold (3x3=9)
If the power of the beam is tripled while the cross sectional area of the beam remains the same, the intensity ____.
Triples
The amplitude of an acoustic wave ave is increased. Which of the following will most likely remain unchanged?
Power
Frequency
Period
Intensity
Frequency
Period
A sonographer adjusts the output power of the wave emitted by the transducer. Which of the following also changes?
Pulse repetition period
PRF
Propagation speed
Intensity
Intensity
The wavelength of a cycle in an ultrasound wave can be reported with which units?
Units of distance (feet, etc.)
The wavelength of an ultrasonic wave is determined by:
1) the sound source
2) the medium through which the wave travels
What is the wavelength of 2 MHz sound in soft tissue?
Wavelength (mm) = 1.54/ frequency (MHz)
For 2 MHz sound, the wavelength is 1.54/2 or .77MHz
Which of the following terms best describes the relationship btw frequency and wavelength for sound traveling in soft tissue?
Inverse
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?
The 2 MHz pulse has a period five times longer than the 10 MHz wave
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?
The 2 MHz pulse
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?
Cannot be determined
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?
Cannot be determined
True or false
Lower frequency sound creates higher quality images with greater detail.
False
What is the wavelength of 10MHz sound in soft tissue?
1.54/10 or .15mm
Wavelength = 1.54/ frequency
Two waves, a 5 MHz ultrasonic wave and a 5kHz audible wave, travel through soft tissue. Is the statement true or false?
The period of 5 MHz wave is less than the period of the audible wave.
True
Two waves, a 5 MHz ultrasonic wave and a 5kHz audible wave, travel through soft tissue. Is the statement true or false?
The wavelength of the 5MHz wave is greater than the wavelength of the 5kHz wave.
False
Two waves, a 5 MHz ultrasonic wave and a 5kHz audible wave, travel through soft tissue. Is the statement true or false?
The ultrasound wave travels much faster than the audible wave.
False
All sound waves travel the same speed regardless of frequency
In soft tissue, speed propagates at a peed of 1,540 m/sec
Two waves, a 5 MHz ultrasonic wave and a 5kHz audible wave, travel through soft tissue. Is the statement true or false?
Both the 5MHz and the 5 kHz waves travel at similar speeds through the medium.
True
An ultrasound pulse propagates from soft tissue through a mass. Sound’s propagation speed in the mass is 1,575 m/s. Is the following statement true or false?
The frequency of the wave increases as it travels through the mass.
False
An ultrasound pulse propagates from soft tissue through a mass. Sound’s propagation speed in the mass is 1,575 m/s. Is the following statement true or false?
The period of the sound wave decreases as it travels through the mass.
False
An ultrasound pulse propagates from soft tissue through a mass. Sound’s propagation speed in the mass is 1,575 m/s. Is the following statement true or false?
The wavelength increases while the wave travels through the mass.
True
An ultrasound pulse propagates from soft tissue through a mass. Sound’s propagation speed in the mass is 1,575 m/s. Is the following statement true or false?
The power in the wave increases as it travels through the mass.
False
Three sound waves with identical frequencies of 3 MHz have powers of 2 mW, 5mW, and 15 mW. They all travel through three media — wood, brick, and fat— with identical thickness of 5 cm. Is the following statement true or false?
The waves travel through all three media at the same speed since they have identical frequencies.
False
Three sound waves with identical frequencies of 3 MHz have powers of 2 mW, 5mW, and 15 mW. They all travel through three media — wood, brick, and fat— with identical thickness of 5 cm. Is the following statement true or false?
The sound waves travel through all three media at different speeds because the waves have different powers.
False
Three sound waves with identical frequencies of 3 MHz have powers of 2 mW, 5mW, and 15 mW. They all travel through three media — wood, brick, and fat— with identical thickness of 5 cm. Is the following statement true or false?
The waves travel through all three media at different speeds bc the waves have different powers.
False
Three sound waves with identical frequencies of 3 MHz have powers of 2 mW, 5mW, and 15 mW. They all travel through three media — wood, brick, and fat— with identical thickness of 5 cm. Is the following statement true or false?
The waves travel through all three media at different speeds bc the media are different.
True
Propagation speed can be correctly recorded with which of the following units?
Miles per hour
Mm/sec
Km/sec
Inches per year
All of the above
The propagation speed of continuous wave ultrasound is 1.8 kilometer per second. The wave is then pulsed with a duty factor of 50%. What is the new propagation speed?
- 8 km/sec
- there is no difference in sound’s speed whether the wave is continuous or pulsed. The new and old speeds will be identical
What is the best estimate of the distance that sound can travel in soft tissue in one second?
1,540 meters per second in soft tissue. This is approximately one mile per second.
True or false?
Shorter wavelength sound creates higher quality images with greater detail.
True
True or false?
The wavelength of an acoustic wave is shorter when it is pulsed rather than continuous.
False
Wavelength doesn’t change based on whether cycle is pulsed or continuous
The speed of sound traveling through bone is ___ soft tissue.
Lower than
Higher than
Equal to
Cannot be determined
Higher than
Compared to soft tissue, the speed of an acoustic wave through lung tissue is ___.
Slower
-speed of sound in lung tissue is slower than in soft tissue.
What is the best estimator the speed of sound in tendon?
1,000 m/s
1,540 m/s
1,754 m/s
5,400 m/s
1,754 m/s
Sound travels slightly faster in tendon than in soft tissue.
As a general rule, which of the following lists media in increasing order of propagation speeds?
Gas, solid, liquid
Liquid, solid, gas
Solid, liquid, gas
Gas, liquid, solid
Gas, liquid, solid
Generally sound travels slowest in gases, faster in liquids, and fastest in solids
What is the speed of sound in air?
330 m/s
True or false?
Soft tissue is an imaginary construct that actually does not exist.
True
Soft tissue is an imaginary structure with characteristics that represent an “avg” of body tissues such as muscle, blood, kidney, and spleen. It is used as an approximation.
What is the propagation speed of a 5 MHz (megahertz) sound wave in soft tissue?
1.54 mm/us
1,540 m/sec
1.54 km/sec
If sound doesn’t travel at 1,540 m/sec in a medium, then the medium ___.
Cannot be soft tissue
If sound travels at exactly 1,540 m/sec in a particular medium, then the medium ___.
May be soft tissue
The propagation speeds of ultrasound waves in muscle, liver, kidney, and blood are ___.
Very similar to each other
The speed at which a wave travels through a medium is determined by:
The characteristics of the medium only
What two properties establish sound’s propagation speed in a given medium
Density and stiffness
The characteristics of four media are described below. Which of the media has the slowest propagation speed?
High density and high elasticity
Compressibility describes a characteristic of a medium. Which two terms describe the same property as compressibility?
Stiffness and elasticity
When the elasticity of a medium is high, the ___ is high.
Compressibility
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?
Neither
Both travel at the same speed and reach body at the same time- frequency is irrelevant to speed
What are the units of pulse duration?
Units of time (sec, min, years, etc)
.3 to 2 usec
What determines the pulse duration?
The source of the wave
Pulse duration- 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.
True or false?
The pulse duration of an ultrasound and transducer system does not change significantly as long as the system components remain unchanged.
True
The pulse duration is expressed in the same units as ___.
Period
True or False?
A sonographer can adjust the duration of an acoustic pulse since it depends upon the pulse’s propagation speed.
False
True or False?
A sonographer can adjust the duration of an acoustic pulse since it depends upon the maximum imaging depth.
False
Pulse duration has a constant value and can’t be changed nor is it dependent on imaging depth
True or False?
The pulse duration cannot be changed under any circumstances or by any action of the sonographer.
False
It can be altered by switching to a different imaging transducer
True or False?
The sonographer cannot change the duration of a sound pulse unless the transducers are switched.
True
What is the pulse duration equal to?
Period multiplied by the number of cycles in the pulse
What happens to the pulse duration when a sonographer decreases the maximum imaging depth in an ultrasound scan?
Remains the same
The time that a transducer is “pulsing” does not change with alterations in depth of view
The spatial pulse length describes certain characteristics of an ultrasound pulse. What are its units?
Meters
In diagnostic imaging, what determines the spatial pulse length?
1) The ultrasound system
2) the medium through which the pulse travels
Which of the following best describes the spatial pulse length?
Frequency multiplied by wavelength
PRF multiplied by wavelength
Wavelength multiplied by the number of cycles in the pulse
Duty factor multiplied by the wavelength
Wavelength multiplied by the number of cycles in the pulse
Two transducers send ultrasound pulses into soft tissue. One transducer emits sound with a 4MHz frequency, and the other produces sound at 6MHz frequency. Each pulse contains 4 cycles. Which has a greater spatial pulse length?
The 4MHz pulse
4MHz wave has a longer wavelength than the 6MHz wave and therefore will have a longer spatial pulse length.
Using a specific transducer, what happens to the spatial pulse length as the sonographer increases the maximum imaging depth?
Remains the same
True or false?
While imaging soft tissue, the spatial pulse length does not change as long as the components of the ultrasound system are the same.
True
On what does the pulse repetition period depend?
The source of the sound wave
A sonographer adjusts the maximum imaging depth of an ultrasound system. Which of the following also changes?
Pulse repetition period
Pulse repetition frequency
Which of the following correctly describes pulse repetition period?
The sum of the pulse’s “on” time and the listening “off” time
What happens to the pulse repetition period if the sonographer decreases the maximum imaging depth achieved in an ultrasound scan?
Decreases
Two ultrasound systems, one producing sound with a frequency of 3 MHz and the other at 6 MHz, are used to image a patient. The maximum imaging depth of both exams is 8 cm. Is the following statement True or false?
The period of the 3MHz sound is greater than the period of the 6 MHz sound.
True
Two ultrasound systems, one producing sound with a frequency of 3 MHz and the other at 6 MHz, are used to image a patient. The maximum imaging depth of both exams is 8 cm. Is the following statement True or false?
The wavelength of the 3MHz ultrasound is greater than the 6MHz sound.
True
Two ultrasound systems, one producing sound with a frequency of 3 MHz and the other at 6 MHz, are used to image a patient. The maximum imaging depth of both exams is 8 cm. Is the following statement True or false?
The pulse produced by both systems travel at the same speed in the patient.
True
Two ultrasound systems, one producing sound with a frequency of 3 MHz and the other at 6 MHz, are used to image a patient. The maximum imaging depth of both exams is 8 cm. Is the following statement True or false?
The PRF of the 6 MHz transducer is greater than the PRF of the 3 MHz transducer.
False
The PRF changes only when imaging depth changes. Since the depth of view for both systems is the same, the PRFs are also the same.
The maximum imaging depth during an exam is unchanged. A new transducer with a longer pulse duration is used. Is the following statement true or false?
The pulse repetition period is increased.
False
The maximum imaging depth during an exam is unchanged. A new transducer with a longer pulse duration is used. Is the following statement true or false?
The pulse repetition frequency is increased.
False
The maximum imaging depth during an exam is unchanged. A new transducer with a longer pulse duration is used. Is the following statement true or false?
The duty factor is increased.
True
The maximum imaging depth during an exam is unchanged. A new transducer with a longer pulse duration is used. Is the following statement true or false?
The frequency is increased.
False
What are the units of pulse repetition frequency (PRF)?
1/seconds
PRF has the same units as frequency, and these units are Hz or per second
The pulse repetition frequency of ultrasound produced by a transducer typical of diagnostic imaging systems ___.
Can be changed by the changed by the sonographer
Sonographers alter PRF when they adjust imaging depth. As depth increases, PRF must decrease. This occurs bc transducer must wait a longer time for echoes to return from deeper depths.
I’m diagnostic imaging, what establishes the pulse repetition frequency?
The source of the sound/acoustic wave
Medium through which sound travels does not directly affect PRF
When a sonographer increases the maximum imaging depth during an exam, what happens to the PRF?
PRF decreases
True or False?
The PRF and frequency are unrelated.
True
- PRF is only determined by depth
- Frequency is determined by characteristics of transducer
The pulse repetition frequency is the ___.
Reciprocal of pulse repetition period
If PRF is 100 per second, then PRP is one-one hundredth of a second (.01)
What is the typical value for the duty factor/ duty cycle of pulsed sound waves used in diagnostic imaging?
.001
What is the value of the duty cycle for continuous wave ultrasound?
- 0 or 100%
- this means the transducer is producing an acoustic signal at all times
In the case of pulsed ultrasound, what is the maximum value of the duty factor?
Less than 100%
-this is bc at least a tiny bit of time must be spent listening rather than transmitting the wave. Therefore, the percentage of time transmitting must be less than 1 or less than 100%.
If the percentage equals 100%, then the system is a continuous wave.
While using a particular imaging system, what happens to the duty factor when the depth of view increases?
Decreases
Duty factor and depth are inversely related
True or False?
The sonographer alters the duty cycle when adjusting the maximum imaging depth of a scan.
True
Duty factor and depth are inversely related
-depth increases, duty factor decreases
True or false?
The duty factor is a characteristic of an ultrasound and transducer system and does not change as long as the system components remain unchanged.
False.
Duty cycle changes when depth changes during an exam
While using the same ultrasound machine and transducer, which of the following can a sonographer alter?
Pulse repetition period
Pulse repetition frequency
Frequency
Duty cycle
Pulse duration
PRP
PRF
Duty cycle
Which of the following terms does not belong with the others?
Increased depth of view
Increased duty factor
Increased pulse repetition period
Decreases pulsed repetition frequency
Increased duty factors are related to shallower imaging
The other three are consistent with deeper imaging
Which of the following terms does not belong with the others?
Increased depth of view
Decreases duty factor
Increased pulse repetition period
Decreased spatial pulse length
Decreased spatial pulse length is unrelated to alterations in depth of view imaging
The other three are all related to deeper imaging
What is the importance of describing sound beam intensities in a variety of ways with regard to space and time?
It’s important when studying bioeffects
Describing the intensity of a sound beam as they vary in time and space is important in the study of bioeffects
Which intensity is most closely correlated to tissue heating?
SPTP
SATP
SPTA
SATA
The SPTA intensity relates most closely to the tissue temperature elevation.
