ARDMS SPI STUDY GUIDE
Ultrasound Physics Certification T est Study Questions
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 T ransmit time and receive time.
Period is measured in - ANS T ime (
μ
s)
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 (T ime Sound is ON or ON-T ime).
Propagation Speed in SOFT TISSUE - ANS 1.54 mm/
μ
s
(1540 m/sec) Unit of measurement for Pulse Duration, Duty Factor , PRP , and Period - ANS
Time, (
μ
s)
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 (
μ
s) = # 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 W avelength
(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).
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