Chapter 4 - Describing Pulsed Waves UUP

Pulse repetition period.

Pulse repetition frequency is the reciprocal of ____________.

The propagation speed for pulsed and continuous wave sound is the same; in this case, 1.8 km/sec. It depends only upon the medium through which the sound travels.

The speed of a 5 MHz continuous wave is 1.8 km/sec. The wave is then pulsed with a duty factor of 0.5. Calculate the new propagation speed.

True. This is a very important concept.

True or False. PRF and pulse repetition period are determined only by the imaging depth.

True. Frequency and pulse repetition frequency are unrelated.

True or False. Two waves can have identical PRFs, even if their frequencies are different.

True. Period and pulse repetition frequency are unrelated.

True or False. Two waves can have identical PRFs, even if their periods are different.

False. Two waves can never have identical PRFs if their pulse repetition periods are different.

True or False. Two waves can have identical pulse repetition frequencies, even if their pulse repetition periods are different.

The duty factors are as follows: - pattern A 100% - pattern B 33% - pattern C 0% - pattern D 50%

What are the duty factors of the 4 patterns that appear in Fig. 4.13? Hint: to determine a duty factor, use a single pair of complete pulse duration and Pulse Repetition Period (PRP) times.

a) period - remains the same b) frequency - remains the same c) wavelength - remains the same d) speed - remains the same e) amplitude (initial) - remains the same f) pulse duration - remains the same g) Pulse Repetition Frequency (PRF) - decreases h) duty factor - decreases i) spatial pulse length - remains the same j) pulse repetition period (PRP) - increases

A sonographer adjusts the depth of view of an ultrasound scan from 8 cm to 16 cm. Would each of the following parameters increase, decrease or remain the same? a) period b) frequency c) wavelength d) speed e) amplitude (initial) f) pulse duration g) Pulse Repetition Frequency (PRF) h) duty factor i) spatial pulse length j) pulse repetition period (PRP)

d) 0.001

What is the duty factor if the pulse duration is 1 microsecond and the pulse repetition period is 1 ms? a) 100% b) 0.1 c) 0.01 d) 0.001

The duty factor is 0.001, or 10 to the power of -3. 10 to the power of -6 divided by 10 to the -3 = 10 to the -3, or 0.001.

What is the duty factor if the pulse duration is 1 microsecond, and the pulse repetition period is 1 ms?

The duty factor is 0.001 or 0.1%, 0.001 divided by 1.0 = 0.001.

What is the duty factor if the pulse duration is 1 millisecond, and the pulse repetition period is 1 second?

d) A/C To determine the duty factor, divide pulse duration by pulse repetition period. This is choice D.

Which of the following best describes the duty factor? a) A x B b) A/E c) D/E d) A/C e) ExF f) (A + B)/C

d) pulse duration. If the units for line A are time, line A is a pulse duration.

Which of the following describes line A? a) frequency b) pulse rep. period (PRP) c) period d) pulse duration e) duty factor f) amplitude

d) spacial pulse length. If the units for line A are distance, line A is a spacial pulse length. Both spatial pulse length and pulse duration describe a pulse.

Which of the following describes line A? a) frequency b) pulse rep. period (PRP) c) period d) spacial pulse length e) duty factor f) amplitude

f) amplitude

Which of the following describes line B? a) frequency b) pulse rep. period (PRP) c) period d) pulse duration e) duty factor f) amplitude

b) pulse rep. period (PRP)

Which of the following describes line C? a) frequency b) pulse rep. period (PRP) c) period d) pulse duration e) duty factor f) amplitude

c) period. If the units for line D are time, line D is a period.

Which of the following describes line D? a) frequency b) pulse rep. period (PRP) c) period d) pulse duration e) duty factor f) amplitude

c) wavelength. If the units for line D are distance, line D is a wavelength. Both wavelength and period describe a single cycle.

Which of the following describes line D? a) frequency b) pulse rep. period (PRP) c) wavelength d) pulse duration e) duty factor f) amplitude

f) none of the above. Line E represents only the listening time.

Which of the following describes line E? a) frequency b) pulse rep. period (PRP) c) period d) pulse duration e) duty factor f) none of the above

e) peak-to-peak amplitude

Which of the following describes line F? a) frequency b) pulse rep. period (PRP) c) period d) pulse duration e) peak-to-peak amplitude

c) low PRF. This is associated with deep imaging. The other three choices are all associated with shallow imaging.

Which of the following terms does not belong with the others? a) high duty factor b) shallow imaging c) low PRF d) short pulse repetition period

b) shallow imaging. This does not belong. The other three choices are all associated with deep imaging.

Which of the following terms does not belong with the others? a) low duty factor b) shallow imaging c) low PRF d) long pulse repetition period

Choice B has the deepest imaging depth because the pulse repetition period is the longest.

Which of the patterns in Fig. 4.13 indicates a system with a deep imaging depth?

Choice D has the shallowest imaging depth because the pulse repetition period is the shortest.

Which of the patterns in Fig. 4.13 indicates a system with a superficial imaging depth?

c) 20 kHz. Pulse repetition period is the reciprocal of pulse repetition frequency. This answer has the highest pulse repetition frequency and, thus, the shortest pulse repetition.

Which of these four pulses with PRFs listed below has the shortest pulse repetition period? a) 12 kHz b) 6,000 Hz c) 20 kHz d) 1 kHz

c) 6 Hz. Pulse repetition period is the reciprocal of pulse repetition frequency. This choice has the lowest pulse repetition frequency and, thus, the longest pulse repetition period.

Which of these four valves for pulse repetition frequency would have the longest pulse: a) 2 kHz b) 4,000 Hz c) 6 Hz d) 1 kHz

A and C. System A cannot perform anatomic imaging because it is continuous wave. Only pulsed sound creates imaging. Also, system C cannot perform imaging because it does not produce sound.

Which two of the patterns in Fig. 4.13 identify an ultrasound system that cannot perform anatomic imaging?

Pulse duration

___________ is the time from the start of a pulse to the end of that pulse.

Pulse repetition period

_____________ is the time from the start of a pulse to the start of the next pulse.

a) period - remains the same b) frequency - remains the same c) wavelength - remains the same d) speed - remains the same e) power (initial) - increases f) intensity (initial) - increases g) pulse duration - remains the same h) pulse repetition frequency (PRF) -remains the same i) duty factor - remains the same j) spatial pulse length - remains the same k) pulse repetition period - remains the same

A sonographer is using a 3 MHz tranducer and increases the output power to visualize structures that are positioned deeper in the patient. No other controls are adjusted. Would each of the following parameters increase, decrease, or remain the same? a) period b) frequency c) wavelength d) speed e) power (initial) f) intensity (initial) g) pulse duration h) pulse repetition frequency (PRF) i) duty factor j) spatial pulse length k) pulse repetition period

a) period - decreases b) frequency - increases c) wavelength - decreases d) speed - remains the same e) intensity (initial) - remains the same f) pulse repetition frequency (PRF) - remains the same g) pulse repetition period - remains the same

A sonographer is using a 3 MHz transducer and changes to a 6 MHz transducer. The imaging depth remains unchanged. Would each of the following parameters increase, decrease or remain the same? a) period b) frequency c) wavelength d) speed e) intensity (initial) f) pulse repetition frequency (PRF) g) pulse repetition period

a) pulse repetition frequency b) duty factor d) pulse repetition period

By changing the imaging depth, which of the following does the operator also change (more than 1 may be correct)? a) pulse repetition frequency b) duty factor c) propagation speed d) pulse repetition period e) amplitude f) spatial pulse length

c) 5 ms. The pulse with the shortest pulse duration will have the highest pulse repetition frequency.

Four pulses have pulse repetition periods as listed below. Which of the following four waves has the highest pulse repetition frequency? a) 8 s b) 80 ms c) 5 ms d) 400 ks

a) 8 s. The pulse with the longest pulse duration will have the lowest pulse repetition frequency.

Four waves have pulse repetition periods as listed below. Which of the following four waves has the lowest pulse repetition frequency? a) 8 s b) 80 microseconds c) 8000 ns d) 800 ms

decreases

If all other factors remain unchanged, what happens to the duty factor [increases, decreases, remains the same] when imaging depth increases?

increases

If all other factors remain unchanged, what happens to the duty factor [increases, decreases, remains the same] when the pulse repetition frequency increases?

decreases

If all other factors remain unchanged, what happens to the duty factor [increases, decreases, remains the same] when the pulse repetition period increases?

increases

If all other factors remain unchanged, what happens to the duty factor [increases, decreases, remains the same] when the sonographer uses a new transducer with a longer pulse duration?