Lesson 1 Flashcards
What is the formula for frequency?
f = 1/T
What is the formula for period?
T = 1/f
What is the formula for wavelength?
lambda = c/f
What is the formula for pulse duration?
PD = T x n
What is the formula for pulse repetition frequency?
PRF = 1/PRP
What is the formula for pulse repetition period?
PRP = 1/PRF
What is the formula for intensity?
I = P/A
What is the relationship between intensity and amplitude?
I = Amp ^2
Doppler effect
Change in frequency caused by the motion of a source, reflector or receiver
Doppler shift
Quantification of the change in frequency
What happens to the frequency as you get closer?
It increases
What happens to the frequency as you get farther?
It decreases
What kind of doppler shift do you get if you move closer?
Positive shift
What kind of doppler shift do you get if you move farther?
Negative shift
What do we do in doppler? (3)
- Fire a particular frequency
- Measure the frequency that returns
- Figure out the Doppler shift
What can we calculate with doppler?
How fast an object is moving
What is the formula for doppler shift?
Fd = Fr - Ft
What is the formula for velocity with doppler shift?
V(cc/s) = 77(cm/ms) x Fd (kHz)/ f (MHz)
Doppler angle
The angle of incident beam to the blood flow
What happens if you increase you doppler angle?
Decrease your Doppler shift
What happens if you decrease you doppler angle?
Increase your Doppler shift
What does a higher doppler angle mean?
Our velocity will be calculated too low
Where must angle correct be kept at?
60 deg
- to the vessel
What does doppler show? (5)
- Presence
- Direction
- Speed
- Character
- Quantification
What are the colour doppler controls? (6)
- Box
- Map
- Invert
- Baseline
- Gain
- Wall filter
What are the spectral doppler controls? (5)
- Gate size/sample volume
- Gain
- Spectral invert
- Baseline
- Wall filter
What does PRF affect?
Scale
Where can you only change PRF?
In doppler
- there is no pulses in grey scale
What happens when you decrease PRF?
Your scale decreases
What does decreasing your PRF allow to show?
Slower flow speeds
What happens if you decrease the PRF too much?
It will cause aliasing
- wrap around
What does increasing PRF allow?
Increase in scale
What does increase PRF try and show?
Faster flow speeds
What does increasing the PRF too much do?
Doesnt show slow speeds well
What does phasing allow?
Steering
