chpt 4 " describing pulsed waves"

Which of these four values for pulse repetition frequency would have the longest pulse repetition period?

• 2 kHz

• 4,000 HZ

• 6 Hz

• 1 kHz

Answer explanation

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.

pulse duration is directly proportional to _______

(could be more than one)

• # cycles in the pulse

• frequency

• period

• all of these

• - actual time from the start of a pulse to the end of that pulse

• - talking, or "on" time

• - units of time, such as microseconds (us).

• - typical value : 0.3-2.0(us)

• - determined by sound source only , NOT adjustable

• pulse duration

• spatial pulse length

• pulse repetition period

• pulse repetition frequency

• duty factor

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?

Groups:

(a) remains the same

,

(b) increase

,

(c) decrease

• frequency

• speed

• period

• intensity

• wavelength

• PRF

• PRP

Which of the following describes line E?

• frequency

• pulse rep. period

• period

• pulse duration

• none of the above

Answer explanation

Line E represents only the listening time.

Which type of pulse is more desirable in diagnostic imaging ?

• Shorter duration pulses are desirable for imaging because they create images of greater accuracy.

• longer duration pulses are desirable for imaging because they create images of greater accuracy.

• thinner duration pulses are desirable for imaging because they create images of greater accuracy.

• thicker duration pulses are desirable for imaging because they create images of greater accuracy.

Which of the following describes line A?

• frequency

• pulse repetition period

• pulse duration

• period

• duty factor

Answer explanation

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

1. Which two of the patterns in Fig. 4.13

2. identify an ultrasound system that cannot perform anatomic imaging?

• A

• B

• C

• D

Answer explanation

1. 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.

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

• true

• false

pulse duration

• • - actual time from the start of a pulse to the end of that pulse

  • - talking, or "on" time

  • - units of time, such as microseconds (us).

  • - typical value : 0.3-2.0(us)

  • - determined by source only , NOT adjustable

• • - distance that a pulse occupies in space from start to end of pulse

  • - units of distance such as mm

  • - typical value : 0.1 - 1.0mm

  • - determined by source & medium , NOT adjustable

• • - time from the start of one pulse to the start of the next pulse (1pulse duration, 1 off time)

  • - units of time, such as ms

  • - typical value: 100 microseconds(us) - 1millisecond(ms)

  • - determined by source & depth , Adjustable

• • - # of pulses that an ultrasound system transmits into the body each second

  • - units of hertz(Hz) or per second

  • - typical value: 1,000 - 10,000hertz

  • - determined by: source only , adjustable

• • - percentage or fraction of time system transmits a pulse

  • - unitless, or percentage

  • - typical value : 0.002-0.005%, 0.2%-0.5%

  • - determined by: source only, adjustable