Ch. 4 Physics: Describing Pulsed Waves Flashcards
What are short bursts of energy that repeat?
Pulsed sound or pulsed energy
True or false
Continuous sound produces images
Fasle
only pulse can produce images
True or false
A pulse can have any number of cycles
True
True or false
Every pulse has a beginning and an end with “off time” before the next pulse.
True
What are the two important characteristics that pulsed sound uses to create diagnostic images?
Transmitting -“talking” or “on” time
Receiving -“listening” or “off” time
What are the 5 parameters for pulsed waves?
Pulse duration
Spatial pulse length
Pulse repetition period (PRP)
Pulse repetition frequency (PRF)
Duty factor
The actual time of the pulse from start to end is called what?
Pulse Duration
_______ is equal to the number of cycles in each pulse multiplied by the period of each cycle.
Pulse Duration
Pulse duration is ________ ________ to period
Directly proportional
PD= # cycles x period
Pulse duration is _______ ________ to frequency
Inversely proportional
PD= # cycles / frequency
What is the meausred units for pulsed duration?
Time
ms
microsec
What is the value range of pulsed duration?
0.3- 2.0microsec
Pulse is determined by….
The source
True or false
The sonographer can alter the pulse
Fasle
Not adjustable
Many cycles grouped together in a pulse or individual cycles with long periods.
Long pulse duration
Fewer cycles in a pulse or individual cycles with short periods.
Short pulse duration
Which pulse duration is better for imaging in diagnostic ultrasound?
Shorter pulses
The distance pulse occupies in space from the start of the pulse to its end.
Spatial Pulse length
What is the measurement unit for spatial pulse length
mm
What is the typical length range in soft tissue?
0.1- 1.0mm
What determines the spatial pulse length?
The source and medium
True or false
The sonographer cannot alter spatial pulse length
True
Spatial pulse length is ______ _______ to the number of cycles in each pulse and the wavelength of each cycle.
Directly proportional
Spatial pulse length is _______ ________ to the frequency of the cycle
Inversely proportional
True or false
Pulses that are short in time are also short in distance
True
This pulse length has many cycles in a pulse and causes the quality of the image to decrease.
Long pulse
This pulse length has fewer cycles in a pulse and causes the quality of images to increase.
Short pulse
As spatital pulse length ________, image quality _________.
increases, decreases
The time from the start of one pulse to the start of the next pulse is….
Pulse Repetition period (PRP)
PRP includes both…..
Talking time and listening time
PRP is a funcetion of depth and is ______ to period
unrelated
PRP is the time from the start of pulse to the start of…
another pulse
PRP is ________ related to depth of view
Directly
What is PRP measured in?
time, ms, secs
What is the time ranges for PRP?
100microsec to 1 ms
Is PRP adjustable or not adjustable by the sonographer?
Adjustable
What is the PRP determined by?
Sound source
The number of pulses transmits into a medium per second is…
Pulse repetition frequency (PRF)
PRF is ________ to frequency
unrelated
What is PRF related to?
DOV (depth of view)
What is the relationship between PRF and DOV?
Inversely related
What is the measurement of PRF?
Hertz (HZ)
What is the value range for PRF?
1-10kHz
What determined the PRF?
sound source
Is the PRF adjustable or not adjustable by the sonographer?
Adjustable
As DOV decreases, the PRF_____
increases
As the DOV increases, the PRF______
Decreases
PRP and PRF are ________ related
inversely
When PRF increases, PRP_______
decreases
When PRF decreases, PRP_______
increases
PRF and PRP share a reciprocal relationship: when they are multiplied together, they equal _____.
One
In deep imaging, what is higher, the PRP or the PRF?
PRP
In shallow imaging, what is higher, the PRP or the PRF?
PRF
Which of the following pulse repetition periods listed below would have the highest pulse repetition frequency?
4 s
300 ks
75 ms
6 ms
6 ms
True or false
PRP and PRF are both determined by depth.
True
The percentage of time in the system is transmitting a pulse, or the time it is “on” is called what?
Duty Factor
What is the measure of unit for Duty factor?
It is unitless
What are the typical ranges for duty factor?
0.002 to 0.005 or 0.2% to 0.5%
What is the duty factor of a continuous wave?
100% or 1.0
True or false
Continuous waves creates images
False
What kind of waves are used for imaging?
Pulsed waves
True or false
Ultrasound imaging systems spend more time “listening” than “talking”.
True
Duty factor is ________ related to DOV
inversely
What determines duty factor?
system source
Is duty factor adjustable or not adjustable by the sonographer?
adjustable
If DOV decreases, duty factor ________.
increases
What 3 parameters change when a sonographer changes depth?
PRP, PRF, Duty Factor
What happens to the duty factor when the PRP is increased?
Decreases
