Range Equation Flashcards
What must travel to a reflector and return to the transducer to create a dot on the image?
A pulse of sound.
What is the term that describes the time it takes to go and return from the reflector?
Time of Flight
What is another way to think of the Time of Flight? (go and return)
Round trip.
What is the comparison between the trip to and from deeper structures vs the trip to and from superficial structures.
The time of flight is clearly longer for deeper structures.
What is the total distance a beam and echo travels ?
The total distance is from the source to the reflector and back, or the total distance traveled is twice the depth of the relfector.
What is the total time?
The time it takes for the beam to travel to the reflector and back. (round trip)
How do you calculate depth?
Rate x Time= Distance
How do you find the reflector depth?
(Rate x Time)/ 2 =DIstance
What is the ultrasound rate in soft tissues?
1.54mm/µsec
If a round trip to a soft tissue reflector snf back is 13µsec, what is the reflector depth?
1.54 mm/µsec x 13µsec=10 mm →1 cm
A pulse of ultrasound is sent into the tissue. It stops to “hear” the echoes from the reflectors before it sends another pulse in. How long does it wait to send the next pulse in?
It depends on the depth setting. So when you set the depth, you set the timing of each pulse of ultrasound.
What is PRP?
Pulse Repetition Period.
It is the length of time to get between pulses (µsec)
What is the equation for PRP?
PRP (µsec)= image of death (cm) x 13 µsec/cm
What is the relationship between PRP and depth?
Directly proportional
What is PRF?
Pulse Repetition Frequency
PRF is the number of pulses sent per second (Hz)
What is the equation of PRF?
PRF (Hz)= 77,000 cm/sec /imaging depth (cm)
What is the relationship between PRF and Depth?
It is inversely related.
As depth inreases, frequency of pulse decreases since they need more time to travel.
Is a low PRF bad or good?
It is bad (fewer pulses in a second) because it means that we may have missed some things by sending fewer impulses, so less information is gained.
Is a high PRP bad or good?
It is bad (more time between pulses) because it means that the length of time for gathering per pulse means that less information is gained.
What kind of depth should be used when scanning?
The least depth necessary.
