Term
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Definition
| A collection of cycles that travel together. |
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Term
What characteristics distinguish pulses with long duration from those with short duration? |
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Definition
Long duration: Many cycles in the pulse, or individual cycles with long periods.
Short duration: Few cycles in the pulse, or individual cycles with short pulses.
In clinical imaging, a pulse typically contains 2-4 cycles.
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Term
Which type of pulse is more desirable in diagnostic imaging, and why?
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Definition
Shorter pulse durations.
They create images of greater accuracy.
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Term
What is the difference between pulse duration & spatial pulse length? |
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Definition
Pulse Duration: The time that a pulse is “on”. Measured in microseconds (us).
PD (us) = # cycles x P (us) OR PD (us) = # cycles
F
Spatial Pulse Length: The distance of the pulse end to end. Measured in millimeters (mm).
SPL (mm) = # cycles x λ (mm)
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Term
Which characteristics distinguish pulses with long pulse length from those with short length? |
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Definition
Long: 1. Many cycles in the pulse. 2. Cycles with longer wavelengths.
Short: 1. Fewer cycles in the pulse. 2. Cycles with shorter wavelengths.
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Term
Which type of pulse is more desirable in diagnostic imaging, and why?
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Definition
Short. They create better pictures.
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Term
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Definition
The maximum distance into the body that an ultrasound system is imaging. (Controlled by the sonographer.)
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Term
How are pulse repetition period and depth of view related?
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Definition
Directly related.
↑ Depth = ↑ PRP
Depth (mm) ȣ PRP (us)
PRF (MHz)
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Term
What are the 2 components of PRP? Which one can the sonographer change? |
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Definition
Transmit time (aka: Pulse Duration) & receive time.
The sonographer can alter the receiving time by adjusting the imaging depth.
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Term
How are PRF (transmit time) and depth of view related? |
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Definition
Inversely related.
↑ Depth = ↓ PRF
The deeper (increase) the depth, the fewer (decrease) pulses transmit into the body.
Depth (mm) ȣ PRP (us)
PRF (MHz)
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Term
How is Duty Factor calculated?
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Definition
DF (%) = PD (us) x 100
PRP (us)
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Term
What are the maximum & minimum values for duty factor? |
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Definition
Maximum: 100% or 1.0. Only with continuous waves.
Minimum: 0% (off time)
Typical Value: 0.2% with anatomic imaging.
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Term
How does the sonographer change duty factor? |
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Definition
By changing the imaging depth. |
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Term
Of the 4 temporal (time-related) intensity measurements, which has the highest value? |
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Definition
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Term
Rank the 5 intensities from largest to smallest. |
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Definition
1. SPTP 2. Im 3. SPPA 4. SPTA 5. SATA |
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