Chapter 4 Physics review questions

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

Pulse duration

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

Pulse repetition period

Pulse repetition frequency is the reciprocal of ______.

Pulse repetition period (A longer pulse repetition period results in a lower pulse repetition frequency and a shorter pulse repetition period results in a higher pulse repetition frequency).

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

0.001, or 10^-3. 10^-6 divided by 10^-3 = 10^-3 or 0.001.

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

20 kHz (shortest pulse repetition period, highest frequency).

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

The duty factor is 0.001

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

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

True or false. Two waves can have identitcal PRFs, even if their frequencies are different.

True. Frequency and pulse repetition frequency are unrelated.

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

True. Period and pulse repetition frequency are unrelated. Note: it only said period not pulse repetition period.

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

True. This is a very important concept.

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 micro secs C. 8000 ns D. 800 ms

A. 8 s (the longest pulse repetition period has the lowest pulse repetition frequency)

A sonographer is using a 3 MHz transducer & changes to a 6 MHz transducer. The imaging depth remains the same. What will happen to each of the following parameters? (Increase, decrease, unchanged) A. Period B. Frequency C. Wavelength D. Speed E. Intensity (initial) F. PRF G. Pulse repetition period

A. decreases B. increases C. decreases D. remains the same E. remains the same F. remains the same G. remains the same

A sonographer is using a 3 MHz transducer & increases the output power in order to visualize structures that are positioned deeper in the patient. No other controls are adjusted. What will happen to each of the following parameters? (Increase, decrease, unchanged) A. Period B. Frequency C. Wavelength D. Speed E. Power (initial) F. Intensity (initial) G. pulse duration H. PRF I. duty factor J. spatial pulse length K. pulse repetition period

A. remains the same B. remains the same C. remains the same D. remains the same E. increases F. increases G. remains the same H. remains the same I. remains the same J. remains the same K. remains the same

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 stay the same. A. period B. frequency C. wavelength D. speed E. amplitude F. pulse duration G. PRF H. duty factor I. spatial pulse length J. pulse repetition period

A. remains the same B. remains the same C. remains the same D. remains the same E. remains the same F. remains the same G. decreases H. decreases I. remains the same J. increases

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

B. shallow imaging (Shallow imaging does not belong. The other three choices are all associated with deep imaging).

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

C. 5ms (because the pulse with the shortest pulse duration will have the highest pulse repetition period).

Which of these four values for pulse repetition frequency would have the longest pulse repetition period? A. 2 kHz B. 4,000 Hz C. 6 Hz D. 1 kHz

C. 6Hz (because the longest pulse repetition has the lowest frequency).

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

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

What is the duty factor if the pulse duration is 1 micro sec and the pulse repetition period is 1 ms.

D. 0.001 (duty factor % = pulse duration/ pulse rep. period x 100.)

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?

Decreases. Longer pulse duration. Lower duty factor.

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

Decreases. Lower imaging depth, lower duty factor.

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

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

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

Increases. Higher frequency, increased duty factor