Pulsed Ultrasound Flashcards
pulse duration (what/equation)
time it takes for one pulse to occur (doesn’t include down time)
PD= TxRD
ring down means
cycles in a pulse
spacial pulse length (what/equation)
length of the pulse
SPL= λxRD
Does decreasing SPL improve or worsen image resolution
improves
increasing f decreases λ which _____ SPL
decreases
decreasing the number of cycles in a pulse will ______ SPL
decrease
for PRF what unit should we use
meters and m/s
what is the limiting factor to PRF
depth (deeper takes longer)
pulse repetition period (what/equation)
time from the beginning of one pulse to beginning of the next
PRP=d/C, PRP=1/PRF
PRP is another way of expressing
the go return time calculated by the range equation
Duty factor (what/equation)
is the fraction of time that the pulsed ultrasound is on
DF=PD/PRP x 100
what two factors determine acoustic velocity
density and compressibility
if everything else remains the same, an increase in density will cause a _______ in acoustic velocity
decrease
If everything else remains the same, an increase in compressibility will cause a _______ in acoustic velocity
decrease
bulk modulus
is the reciprocal of compressibility
AKA stiffness
as bulk modulus increases, compressibility ______ and velocity _____
decreases
increases
what is the dominant factor, compressibility or density
compressibility
as temp increases, acoustic velocity ______
increases
How does the pulse repetition frequency relate to the operating frequency of the probe?
Although both of these variables are frequencies, they are not related. The operating frequency represents the number of cycles within the pulse of sound emitted from the probe. The pulse repetition frequency is the number of pulses emitted per second.
The pulse repetition period (PRP) is related to the pulse repletion frequency and the duty factor. List the other equation that this variable can be expressed in.
The PRP is also the go-return time and is therefore, can be expressed in the range equation.
Would the pulse repetition frequency (PRF) be higher when scanning a liver at a depth of 15 cm or a gall bladder at a depth of 7 cm
The PRF is determined by depth and is higher when the sound has a shorter distance to travel. Therefore, the PRF is higher scanning the GB. (less listening time)
Would the duty factor be higher when scanning a liver at a depth of 15 cm or a gall bladder at a depth of 7 cm?
The depth is less scanning the GB as opposed to the liver emaning the pulses return to the probe faster. This results in more pulses/second, therefore, the probe is ringing more so the duty factor is higher scanning th GB
