Chapter 4- Pulsed Waves Flashcards
Define Pulse Duration
Pulse duration is the measure of time from the start of a pulse to the end of that same pulse.
What is Pulse Duration determined by? Is it adjustable?
It is determined by the source and is not adjustable.
Define Spacial Pulse Length
Spacial Pulse Length is the measure of distance from the start of a pulse to the end of that pulse.
What is Spacial Pulse Length determined by? Is it adjustable?
Spacial pulse length is determined by the source AND the medium. It is not adjustable
Define Pulse Repetition Period
Pulse repetition period is the measure of time from the start of one pulse to the start of the next pulse. This equals one pulse plus listening time.
What is Pulse Repetition Period determined by? Is it adjustable?
It is determined by the source and the imaging depth. It is adjustable.
Define Pulse Repetition Frequency
Pulse repetition frequency is the number of pulses per second.
What is Pulse Repetition Frequency determined by? Is it adjustable?
Pulse repetition frequency is determined by the source and also by the maximum depth. It is adjustable.
Define Duty Factor
Duty factor is the percentage or fraction of time that the pulse is being transmitted.
What is Duty Factor determined by? Is it adjustable?
Duty factor is determined by the source and is adjustable.
Why is spacial pulse length determined by both the source and medium?
SPL is equal to the number of cycles per pulse x wavelength. Since wavelength is determined by both source and medium, so is SPL.
What are the pulse duration equations?
PD= number of cycles times period
PD= number of cycles divided by frequency
What kind of pulse duration is used for diagnostic imaging? Why?
Shorter duration pulses. They create more accurate images.
What is the equation for spacial pulse length?
SPL= number of cycles times wavelength
How are pulse repetition period and depth of view related?
They are directly related
Why can a sonographer not adjust pulse duration when they can adjust the pulse repetition period?
They cannot change PD because it has a fixed value. But they can change the listening time since it changes with depth. Deeper image = longer listening time and therefore longer Pulse Rep Period
How are pulse repetition frequency and depth of view related? Why is this the case?
They are inversely related. When the depth is shorter, there is a shorter listening time before transmitting a new pulse. This means pulses will be transmitted more frequently so the Pulse Rep Frequency is higher.
Does duty factor relate to depth? How?
Yes. As there is a greater depth, there will be a longer lsitening time. As the listening time increases, the percent of time the beam is transmitting a pulse (duty factor) will decrease.
What is the duty factor equation?
Duty factor = Pulse duration / Pulse Rep Period
