Ch. 4 - Pulsed Sound Flashcards
In diagnostic imaging, short _____ of _____ _____ are used to create anatomic images.
pulses of acoustic energy
T or F? Continuous wave sound can create anatomic images.
False
What is the term for a collection of cycles that travel together?
pulse
A pulse must have a _____ and a(n) _____, otherwise the sound is a continuous wave.
beginning
end
What are the 2 components of pulsed ultrasound?
cycles ("on" or "transmit" time)
dead time ("off" or "receive" time)What are 5 additional parameters of pulsed sound?
Pulse Duration (PD) Pulse Repetition Period (PRP) Pulse Repetition Frequency (PRF) Duty Factor (DF) Spatial Pulse Length(SPL)
The time from the start of a pulse to the end of that pulse, the actual time that pulse is “on”.
Pulse Duration
What is the unit for pulse duration?
microsecond (or any unit of time)
Is the pulse duration determined by the sound source or the medium?
sound source
Pulse duration is determined by multiplying the number of _____ in the pulse and the _____ of each cycle.
cycles
period
Can the pulse duration be changed by the sonographer?
No (it is characteristic of each transducer, it does not change when altering the image depth)
The typical values of Pulse Duration are
0.5 - 3 microseconds
A Pulse is comprised of how many cycles?
2 - 4 cycles
The equation for Pulse Duration is
cycles in pulse
X period
————————-
Pulse Duration
The length or distance that an entire pulse occupies in space. The distance from the start to the end of one pulse.
Spatial Pulse Length
The unit for Spatial Pulse Length is
mm (or any unit of distance)
Can Spatial Pulse Length be changed by the sonographer?
No
The typical values of Spatial Pulse Length are
0.1 - 1mm
Spatial Pulse Length determines _____ _____.
axial resolution (image quality)
Shorter pulses create _____ (lower/higher) image quality.
higher
The equation for Spatial Pulse Length is
# of cycles X wavelength (mm) ----------------------------- Spatial Pulse Length (mm)
The time from the start of one pulse to the start of the next pulse. It includes one pulse duration and one “listening time”.
Pulse Repetition Period
The units for Pulse Repetition Period are
microseconds (or any unit of time)
The Pulse Repetition Period is determined by the
sound source
Can the Pulse Repetition Period be changed by the sonographer?
Yes (when adjusting the depth of view, this changes the “listening time”)
Typical values for Pulse Repetition Period are
100 microseconds to - 1 ms
In reality, the _____ time is hundreds of times longer than the _____ time (pulse duration).
listening
talking
As imaging depth increases, PR Period _____ (increases/decreases).
increases
As imaging depth decreases, PR Period _____ (increases/decreases).
decreases
_____ is the number of pulses that occur in 1 second.
Pulse Repetition Frequency
Units for Pulse Repetition Frequency are
Hertz (Hz)
Pulse Repetition Frequency is determind by the
sound source
Can the Pulse Repetition Frequency be changed by the sonographer?
Yes
The typical values for Pulse Repetition Frequency are
1,000 - 10,000 Hz (1-10 kHz)
T or F? The Pulse Repetition Frequency is determined by the imaging depth.
True
As imaging depth increases, Pulse Repetition Frequency _____ (increases/decreases).
decreases
Imaging depth and Pulse Repetition Frequency have a(n) _____ (inverse/direct) relationship.
inverse
Since the depth of view is changed by the sonographer, the sonographer changes the Pulse Repetition Frequency. The operator actually adjusts the _____ _____ ____, thereby changing the Pulse Repetition Frequency.
pulse repetition period
Pulse Repetition Period and PRF are _____ (relationship).
Reciprocals
Since Pulse Repetition Period and PRF are reciprocals, the Pulse Repetition Period also depends on _____ _____ (since Pulse Repetition Frequency does too).
imaging depth
The equation for Pulse Repetition Frequency is
Pulse Repetition Period
X Pulse Repetition Frequency (Hz)
————————————————–
1
Pulse Repetition Frequency is determined only by imaging depth. Pulse Repetition Frequency _____ (is/is not) related to frequency.
is not
The percentage or fraction of time that the system transmits sound is
Duty Factor
The units for Duty Factor are
NONE (unitless)
Max = 1 or 100%, continuous wave Min = 0 or 0%, the system is off
Duty Factor is determined by the
sound source
Can Duty Factor be changed by the sonographer?
Yes
The typical values for Duty Factor are
from 0.1% to 1% or 0.001 to 0.01
little talking, lots of listening
T or F? Duty Factor always has a small value.
True
With Duty Factor, with deeper imaging, the Duty Factor is _____ (smaller/bigger).
smaller
Shallow imaging has the same meaning as
deep imaging
High Pulse Repetition Frequency (PRF) has the same meaning as
Low Pulse Repetition Frequency (PRF)
High Duty Factor has the same meaning as
Low Duty Factor
Short Pulse Repetition Period has the same meaning as
Long Pulse Repetition Period
By adjusting the imaging depth, the operator changes these 3 things as well
Pulse Repetition Period
PRF
Duty Factor
Parameters for sound describe the
features of sound
Typical Duty Factor for anatomical imaging is
0.2%
Listening Time is usually ____ times longer than ____ Time in anatomical imaging.
500
Talking Time
