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Ultrasound Physics Review > Pulsed Ultrasound > Flashcards

Pulsed Ultrasound Flashcards

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1
Q

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.)

A

c. units of time (sec, years, etc.)

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2
Q

What determines the pulse duration?

a. the source of the wave
b. the medium of which the pulse travels
c. both a. & b.
d. neither a. nor b.

A

a. the source of the wave

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3
Q

True or False?

The pulse duration of an ultrasound and transducer system does not change significantly as long as the system components remain unchanged.

A

True

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4
Q

The pulse duration is expressed in the same units as the ____.

a. period
b. PRF
c. wavelength
d. density

A

a. period

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5
Q

True or False, is this regarding pulse duration?

A sonographer can adjust the duration of an acoustic pulse since it depends upon the pulse’s propagation speed.

A

False

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6
Q

True or False, is this regarding pulse duration?

A sonographer can adjust the duration of an acoustic pulse since it depends upon the maximum imaging depth.

A

False

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7
Q

True or False, is this regarding pulse duration?

The sonographer cannot change the duration of a sound pulse unless the transducers are switched.

A

True

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8
Q

True or False, is this regarding pulse duration?

The pulse duration cannot be changed under any circumstances or by any action of the sonographer.

A

False

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9
Q

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

A

d. period multiplied by the number of cycles in the pulse

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10
Q

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

A

c. remains the same

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11
Q

The spatial pulse length describes certain characteristics of an ultrasound pulse. What are its units?

a. time
b. hertz
c. meters
d. non; it is unitless

A

c. meters

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12
Q

In diagnostic imaging, what determines the spatial pulse length?

a. the ultrasound system
b. the medium through which the pulse travels
c. both a. & b.
d. neither a. nor b.

A

c. both a. & b.

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13
Q

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

A

c. wavelength multiplied by the number of cycles in the pulse

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14
Q

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

A

b. the 4 MHz pulse

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15
Q

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

A

c. remains the same

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16
Q

True or False?

While imaging soft tissue, the spatial pulse length does not change as long as the components of the ultrasound system.

A

True

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17
Q

On what does the pulse repetition period depend?

a. the source of the sound wave
b. the medium through which the pulse travels
c. both a. & b.
d. neither a. nor b.

A

a. the source of the sound wave

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18
Q

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

a. pulse repetition period

c. pulse repetition frequency

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19
Q

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

A

c. the sum of the pulse’s “on” time and the listening “off” time

20
Q

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

A

b. decreases

21
Q

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.

True or False?

The period of the 3 MHz sound is greater than the period of the 6 MHz sound.

A

True

22
Q

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.

True or False?

The wavelength of the 3 MHz ultrasound is greater than the 6 MHz sound.

A

True

23
Q

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.

True or False?

The pulses produced by both systems travel at the speed in the patient.

A

True

24
Q

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.

True or False?

The PRF of the 6 MHz transducer is greater than the PRF of the 3 MHz transducer.

A

False

25
Q

The maximum imaging depth during an exam is unchanged. A new transducer with a longer pulse duration is used.

True or False?

The pulse repetition period is increased.

A

False

26
Q

The maximum imaging depth during an exam is unchanged. A new transducer with a longer pulse duration is used.

True or False?

The pulse repetition frequency is increased.

A

False

27
Q

The maximum imaging depth during an exam is unchanged. A new transducer with a longer pulse duration is used.

True or False?

The duty factor is increased

A

True

28
Q

The maximum imaging depth during an exam is unchanged. A new transducer with a longer pulse duration is used.

True or False?

The frequency is increased.

A

False

29
Q

What are the units of pulse repetition frequency (PRF)?

a. seconds
b. 1/seconds
c. mm/us
d. seconds^-2

A

b. 1/seconds

30
Q

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

a. can be changed by the sonographer

31
Q

In diagnostic imaging, what established the pulse repetition frequency?

a. the source of the sound
b. the medium through which the sound travels
c. both a. & b.
d. neither a. nor b.

A

a. the source of the sound

32
Q

When a sonographer increases the maximum imaging depth during an exam, what happens to the PRF?

a. PRF increases
b. PRF decreases
c. remains the same

A

b. PRF decreases

33
Q

True or False?

The pulse repetition frequency and the frequency are unrelated.

A

True

34
Q

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

A

d. reciprocal of pulse repetition period

35
Q

What is a typical value for the duty factor (also called the duty cycle) of pulsed sound waves used in diagnostic imaging?

a. 0.001 msec
b. 0.001 kg/cm^3
c. 0.75
d. 0.001

A

d. 0.001

36
Q

What is the value of the duty factor for continuous wave ultrasound?

a. 100
b. 1%
c. 1000%
d. none of the above

A

d. none of the above

37
Q

In the case of pulsed ultrasound, what is the maximum value of the duty factor?

a. 100%
b. 1
c. less than 100%
d. none of the above

A

c. less than 100%

38
Q

While using a particular imaging system, what happens to the duty factor when the depth of view increases?

a. increases
b. decreases
c. unchanged

A

b. decreases

39
Q

True or False?

The sonographer alters the duty factor when adjusting the maximum imaging depth of a scan.

A

True

40
Q

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.

A

False

41
Q

While using the same ultrasound machine and transducer, which of the following can a sonographer alter? (more than one answer may be correct).

a. pulse repetition period
b. PRF
c. frequency
d. duty factor
e. pulse duration

A

a. pulse repetition period

b. PRF

d. duty factor

42
Q

Which of the following terms does not belong with the others?

a. increased depth of view
b. increased duty factor
c. increased pulse repetition period
d. decreased pulse repetition frequency

A

b. increased duty factor

43
Q

Which of the following terms does not belong with the others?

a. increased depth of view
b. decreased duty factor
c. increased pulse repetition period
d. decreased spatial pulse length

A

d. decreased spatial pulse length

44
Q

What is the importance of describing sound beam intensities in a variety of ways with regard to space and time?

a. it allows better transducer design
b. it’s important when studying bioeffects
c. it optimizes image quality
d. harmonics can be measured

A

b. it’s important when studying bio effects

45
Q

Which intensity is most closely correlated to tissue heating?

a. SPTP
b. SATP
c. SPTA
d. SATA

A

c. SPTA

Ultrasound Physics Review (30 decks)

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