Term
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Definition
| In diagnostic imaging, short pulses of acoustic energy are used to create anatomic images. |
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Term
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Definition
| A pulse is a collection of cycles that travel together. |
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Term
| What are five parameters of Pulsed Sound? |
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Definition
Pulse Duration
Pulse Repetition Period
PRF
Duty Factor
Spatial Pulse Length |
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Term
| What are two components of pulsed ultrasound? |
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Definition
1. The cycles "on or transmit time"
2. The dead time "off or receive time" |
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Term
Define:
Pulse Duration
What are the typical units?
Can the sonographer change the value?
What are the typical values in clinical imaging?
How do you determine PD?
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Definition
PD: The time from the start of a pulse to the end of that pulse; the actual time that the pulse is ON
μsec -- or any unit of time
No, PD is a characteristic of each transducer and does not change when depth is altered.
PD ranges from 0.5 to 3 μs and is comprised of 2-4 cycles
PD=#cycles•P
(PD=#cycles in pulse X period) |
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Term
Define:
Spatial Pulse Length
What are the typical units?
Can it be changed by the sonographer?
What are the typical values?
What is SPL determined by and what is the equation? |
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Definition
SPL: The length or distance that an entire pulse occupies in space. The distance from the start to the end of one pulse.
[For SPL, think of a train (the pulse), made up of cars (individual cycles). The overall length of our train from the front of the locomotive to the end of the caboose.]
mm -- any unit of distance
No
0.1 - 1mm
SPL is determined by both the source and the medium. [SPL determines axial resolution (image quality). Shorter pulses create higher quality images.]
SPL(mm)=#cycles•λ(mm) |
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Term
Define:
Pulse Repetition Period (PRP)
What are the typical units?
Can the sonographer change the value?
What are the typical values in clinical imaging?
How do you determine PRP? |
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Definition
PRP is the TIME from the start of one pulse to the start to the next pulse. It includes one PD and one "listening time."
msec--or any unit of time
Yes, can be changed by the sonographer. (only changes listening time when adjusting depth of view. PD never changes.
100 μs to 1 ms
Sound source (depth of view) |
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Term
Define:
Pulse Repetition Frequency (PRF)
What are the typical units?
Can the sonographer change the value?
What are the typical values in clinical imaging?
How do you determine PRF? |
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Definition
PRF is the number of pulses that occur in one second.
Hertz, Hz, per second
Yes
1-10 kHz
Sound source |
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Term
Define:
Duty Factor
What are the typical units?
Can the sonographer change the value?
What are the typical values in clinical imaging?
How do you determine DF? |
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Definition
The percentage of fraction of time that the system transmits sound.
Unitless! It's a percentage
Yes
PW 0.1% - 1%, CW 100%
Sound source
DF=PD/PRP |
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