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27 terms

Chapter 4 key terms and definitions

The key terms and definitions from chapter 4
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What is pulsed sound?
A pulse of ultrasound is a collection of cycles that travel together.
What are the two components of pulsed ultrasound?
1. Transmit, talking or "on" time 2. Receive, listening or "off" time
Pulse Duration definition:
the actual time from the start of a pulse to the end of that pulse. ("on" time)
Pulse Duration is determined by:
Sound source only,
Is pulse duration adjustable?
No
Which type of pulse is more desirable in diagnostic imaging and why?
Shorter duration pulses are desirable because they create images of greater accuracy.
Spatial Pulse Length definition:
the distance that a pulse occupies in space from the start to the end of a pulse.
Spatial Pulse Length is determined by:
BOTH the source and the medium. (like wavelength)
Is spatial pulse length adjustable?
No
What is the difference between pulse duration and spatial pulse length?
Pulse duration is the TIME a pulse is "on". Spatial pulse length is the DISTANCE of the pulse end to end.
Which type of pulse is more desirable in diagnostic imaging and why?
Shorter pulses are desirable because they create more accurate images.
Pulse Repetition Period definition:
the time from the start of one pulse to the start of the next pulse.
Pulse Repetiton Period is determined by:
The sound source only.
Is pulse repetition period adjustable?
Yes the sonographer can change it by adjusting the imaging depth.
What is depth of view?
Depth of view describes the maximum distance into the body that an ultrasound system is imaging.
How are PRP and depth of view related?
Directly - as depth of view increases pulse repetition period increases.
How can a sonographer change PRP?
by changing listening time which alters the depth of the image
Pulse Repetition Frequency definition:
the number of pulses that an ultrasound system transmits into the body each second.
Pulse repetition frequency is determined by:
the sound source only
Is pulse repetition frequency adjustable?
Yes (by adjusting the depth of view)
How are pulse repeition frequency and depth of view related?
Inversely: as depth of view increases, PRF decreases.
How are PRF and PRP related?
Inversely and as reciprocals PRF x PRP = 1
Duty Factor definition:
the percentage or fraction of time that the system is transmitting a pulse.
Duty factor is determined by:
Sound source only.
Is the duty factor adjustable?
Yes, by changing the depth of view.
How are duty factor and depth of view related?
inversely
What three things can be changed by adjusting depth of view?
1. Pulse repetition period 2. Pulse repetition frequency 3. Duty factor