Lesson 22 (Part 2) Flashcards
Where does the data go for colour doppler once the instrument processes it?
On the display
What kind of parameters does colour doppler use? (3)
- Hue
- Saturation
- Luminance
Hue
What colour is being displayed
Saturation
The amount of colour being shown
Luminance
Echo intensity/power/brightness
How are stronger echoes demonstrated in colour doppler?
Brighter
- red or white
How are weaker echoes demonstrated in colour doppler?
Darker
- grey to black
What can be done to affect the effectiveness of the colour doppler examination? (9)
- Colour box/window
- size can be changed - Map
- Invert
- Baseline
- PRF
- Aliasing
- Gain
- Priority
- Wall filter
What does changing the shape of the colour box/window do? (3)
- Affects the frame rate
- Affects temporal resolution
- Changes the coverage
What does a colour map do?
Helps to interpret data
What does the colour map interpret? (3)
- Mean velocities
- Direction of flow/sign
- Variance
Variance
Change in colour from left to right
What is the most commonly used spectrum for colour doppler?
Red to blue
What does red represent on the colour map?
A positive shift
- usually
What does blue represent on the colour map?
A negative shift
- usually
What does invert do in colour doppler?
Flips the colour map
What does invert do?
Adjusts the representation
- doesnt change the direction of flow
What does baseline mean?
No doppler shift
- zero point
Why does baseline help?
IF you have all positive flow you can switch the baseline so there is less blue and more red showing a more detailed map of the flow
What does no doppler shift appear as?
Black
Can we control PRF in doppler and in 2D?
No, only in doppler
- not in 2D
What is the unit for our PRF?
kHz
What is the unit for our scale?
cm/s
How does changing PRF help in colour doppler?
Can pick up faster or slower speeds by increasing or decreasing the PRF
What happens to PRF if we decrease depth?
It increases
- more superficial
What happens to PRF if we increase depth?
It decreases
- deeper structures
What does PRF change?
Scale
What happens to the scale if PRF decreases?
It decreases
What happens to the scale if PRF increases?
It increases
What is very important about scale?
Having it set appropriately
What happens if the scale is too high?
Slower flows go undetected
What happens if the scale is too low?
You get artifacts
- alias (faster flows)
