Week 4 - Lesson 1

Question 1

Doppler shift

Answer 1

A change in frequency due to the Doppler effect

Question 2

What is the formula for doppler shift? (without velocity)

Answer 2

Fd = Ft - Fr

• Fd = doppler shift
• Ft = transmitted frequency
• Fr = returning frequency

Question 3

Which parameter profoundly affects the Doppler equation?

Answer 3

Angle of insonation

- cosine

Question 4

What is the cosine of 0 deg?

Answer 4

1

Question 5

What is the cosine of 30 deg?

Answer 5

0.8

Question 6

What is the cosine of 60 deg?

Answer 6

0.5

Question 7

What is the cosine of 90 deg?

Answer 7

0

Question 8

What is the formula for doppler shift? (with velocity)

Answer 8

Fd = 2 x f x V x cos / c

• Fd = doppler shift
• f = frequency
• V = velocity
• cos = cosine
• c = speed of sound (1540 m/sec)

Question 9

What are the 4 types of doppler?

Answer 9

1. Continuous wave doppler
2. Spectral doppler
   - duplex
3. Spectral and colour doppler
   - triplex
4. Power doppler

Question 10

What does the angle correct need to be in spectral doppler? (2)

Answer 10

1. 60 deg

2. Parallel to the walls of the vessel

Question 11

Where do you want the waveform to be situated on the US?

Answer 11

2 fingers or 1/3rd width from the bottom and not cutting it off at the top

Question 12

How does the angle affect the flow?

Answer 12

The direction of blood flow in relation to the transducer

- toward or away

Question 13

When does 0 deg to the vessel only work?

Answer 13

With straight vessels

Question 14

What happens if you alter angle correct?

Answer 14

You alter velocities

Question 15

How does 60 deg or less help measure a vessel?

Answer 15

It helps to minimize errors

Question 16

What is the ideal angle?

Answer 16

0

- but usually not possible

Question 17

What happens if you use an angle greater than 60?

Answer 17

Great error in velocity

Question 18

What happens if you use an angle greater than 90?

Answer 18

You will get a complete loss of flow

Question 19

What does signal above the baseline indicate?

Answer 19

Flow towards the transducer

Question 20

What does signal below the baseline indicate?

Answer 20

Flow away from the transducer

Question 21

What should the sample volume size be?

Answer 21

As small as possible when in arterial flow

Question 22

Why dont you want a larger sample volume?

Answer 22

Because a larger sample volume will depict an unclean signal
- lots of velocities

Question 23

What adjusts the scale?

Answer 23

PRF

Question 24

Doppler gain

Answer 24

Brightness of the signal

Question 25

What happens if the spectral wall filter is too low?

Answer 25

Wall thump from arterial systole

Question 26

What happens if the spectral wall filter is too high?

Answer 26

Eliminates the echoes within the waveform

- resulting in altered waveform

Question 27

What causes aliasing?

Answer 27

If PRF is too low

- causes wrap around

Question 28

How do you fix aliasing?

Answer 28

Increase the velocity

Question 29

What happens if the colour flow is too low?

Answer 29

Only higher flow will be depicted

Question 30

What happens if the colour flow is too high?

Answer 30

Only lower velocities will be depicted

Question 31

Doppler characteristics (7)

Answer 31

1. Baseline
2. Sample volume
   - gate
3. Scale
4. Doppler gain
5. Spectral wall filter
6. Spectral aliasing
7. Colour map