Week 4 - Lesson 3

Question 1

What happens if colour gain is too high?

Answer 1

Flaring

- saturation

Question 2

What happens if colour gain is too low?

Answer 2

No flow will show up

Question 3

How should colour gain be set?

Answer 3

As high as possible without displaying random colour speckles

Question 4

What does bleeding outside of the vessel in colour doppler cause?

Answer 4

False echoes to appear

Question 5

What happens if the colour filter is set too high?

Answer 5

The low velocity flow close to the walls wii not appear

Question 6

What kind of impression do we get if the colour filter is too high?

Answer 6

False impression of wall thickening

Question 7

What are the guidelines for optimizing doppler? (6)

Answer 7

1. Adjust gain and filter
2. Adjust velocity scale and baseline
3. Doppler angle < 60 by steering and probe position
4. Colour box as small and superficial as possible
5. Sample volume size
   - 2/3rd of the vessel width in the center
6. Avoid transducer motion

Question 8

What are the advantages of power doppler? (5)

Answer 8

1. No aliasing
2. Angle independent
3. Increased sensitivity to detect low velocity flow
4. Useful in imaging tortuous vessels
5. Increase accuracy of grading stenosis

Question 9

When do you use power doppler?

Answer 9

High grade stenosis

• eg. narrow flow channels in ICA
• string sign/trickle flow

Question 10

What are the disadvantages of power doppler? (3)

Answer 10

1. Does not provide velocity of flow
2. Does not provide direction of flow
3. Very motion sensitive
   - poor temporary resolution
   - less suitable for rapid scanning along vessels