ARDMS SPI STUDY GUIDE 2023
In soft tissue, if the frequency of a wave is increased the Propagation Speed (PS) will... Ans- Remain the
Same because stiffness and density affect Propagation Speed.
What is the audible range? Ans- 20-20,000Hz
>20,000Hz=Ultrasound
Frequency is measured in Ans- ...
ARDMS SPI STUDY GUIDE 2023
In soft tissue, if the frequency of a wave is increased the Propagation Speed (PS) will... Ans- Remain the
Same because stiffness and density affect Propagation Speed.
What is the audible range? Ans- 20-20,000Hz
>20,000Hz=Ultrasound
Frequency is measured in Ans- Hertz (Hz)
is
Cycles per Second
Not affected by sonographer
Increase Frequency; Decrease Depth
A period is the length of time it takes for Ans- one complete wavelength to pass a fixed point
PRP is determined by Ans- Transmit time and receive time.
Period is measured in Ans- Time (μs)
When the sonographer changes the imaging depth what parameters are changed? Ans- PRP, PRF, Duty
Factor
What is duty factor? Ans- The percentage or fraction of time that the system is transmitting a pulse
(Time Sound is ON or ON-Time).
Propagation Speed in SOFT TISSUE Ans- 1.54 mm/μs
,(1540 m/sec)
Unit of measurement for Pulse Duration, Duty Factor, PRP, and Period Ans- Time, (μs)
Pulse duration is determined by Ans- Sound Source Only
Pulse Duration is controlled by Ans- the ultrasound system and transducer
Pulse Duration Formula Ans- pulse duration (μs) = # cycles in pulse/frequency(MHz)
PD= Number of cycles in Pulse/ Frequency(Hz)
Spatial Pulse Length (SPL) (measurement) Ans- The distance that a pulse occupies in space from the start
to the end of a pulse.
(mm)
Typical values for spatial pulse length in soft tissue. Ans- 0.1 to 1.0 mm
Spatial pulse length is determined by Ans- sound source and medium
Spatial Pulse Length is directly proportional to Ans- the Number of Cycles in the Pulse
and
the Wavelength
(Directly Proportional means that increased SPL will increase both the number of cycles in the pulse and
the wavelength if increased).
Spatial pulse length is inversely proportional to Ans- Frequency (MHz)
, (Inversely Proportional means that increased SPL will lower frequency. This is because axial resolution is
better with lower frequency)
Pulse Duration (PD) Ans- The actual time from the start of a pulse to the end of that pulse; a single
transmit, talking, or "on" time.
Time the pulse is on typically measured in (ms).
Pulse Length Ans- The distance of the pulse start to end or the
duration or length of a single pulse
Pulse Length is typically measured in (mm).
the ability of an object to resist compression and relates to the hardness of a medium? Ans- Stiffness.
Think:
↑ Stiffness ↑ Speed
↓ Density ↑ Speed
An increase in pulse repetition frequency would lead to: Ans- Increasing pulse repetition frequency,
increases duty factor.
↑ PRF ↑ Duty Factor
Which of the following would have the highest propagation speed? Ans- Bone has the highest
propagation speed, at 2000-4000 m/s.
What has the lowest propagation speed? Ans- air technically has the lowest propagation speed at 300
m/s
Which has the Slowest Propagation Speed?
Water
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