Lesson 22 (Part 1)

Question 1

What is the speed of blood flow?

Answer 1

110cm/s

Question 2

What are characters of blood flow? (2)

Answer 2

1. Laminar

2. Turbulent

Question 3

What are 3 types of Doppler displays?

Answer 3

1. Colour
2. Spectral
3. Audible

Question 4

What does colour doppler demonstrate for blood flow?

Answer 4

1. Presence
2. Speed
3. Character
4. Direction

Question 5

What is a benefit for colour doppler compared to spectral doppler?

Answer 5

It asses a very large area at a time

Question 6

What is another name for colour doppler?

Answer 6

Duplex scanning

Question 7

Why is duplex scanning also another name for colour doppler?

Answer 7

Because the colour portion is on top of a grey scale

- 2 parts

Question 8

How is colour doppler steered?

Answer 8

Through phasing

Question 9

What is the end goal of phasing? (2)

Answer 9

1. To get closer to 0 deg
2. To avoid 90 deg
   - if vessels are parallel to the surface

Question 10

What is the formula for doppler shift?

Answer 10

fD = fR- fT
fD = doppler shift 
fR = frequency received 
fT = frequency transmitted

Question 11

When does doppler shift occur?

Answer 11

If the returning echoes have a different frequency than from the emitted ones

Question 12

What does a positive doppler shift indicate?

Answer 12

Flow is going towards the transducer

Question 13

What does a negative doppler shift indicate?

Answer 13

Flow is going away from the transducer

Question 14

What kind of pulses are sent out during colour doppler?

Answer 14

Multiple pulses are sent out per scan line

Question 15

What does a signal processor detect for colour doppler? (4)

Answer 15

1. Direction
2. Mean velocity
3. Variance
4. Power

Question 16

How is colour doppler created? (4)

Answer 16

1. Bean former
2. Signal processor
3. Image processor
4. Display

Question 17

What does direction do for colour doppler?

Answer 17

Tells us if it flowing towards the transducer (+) or away from the transducer (-)

Question 18

What does the mean velocity tell us with colour doppler?

Answer 18

The average velocity of the blood in an area is calculated and displayed

Question 19

What does the variance tell us with colour doppler?

Answer 19

The ‘variety’ within the blood flow / standard deviation

Question 20

What is power related to in colour doppler?

Answer 20

Amplitude

- strength/intensity of the echo

Question 21

What does power depend on?

Answer 21

1. Reflectors
   - specular vs scattering
2. Impedance
3. Concentration of RBCs

Question 22

What does it mean in colour doppler if you have a higher impedance mismatch?

Answer 22

There is more reflection

Question 23

What does it mean in colour doppler if the concentration of RBCs is high?

Answer 23

More reflection

Question 24

How many pulses are sent out per scan line in colour doppler?

Answer 24

3-32

- usually 10-20

Question 25

Ensemble length

Answer 25

Is the number of pulses per scan line

Question 26

Are more pulses per scan line good or bad?

Answer 26

Good

Question 27

Why are more pulses per scan line good?

Answer 27

1. Accuracy for speed calculation
2. Better sensitivity
   - can detect weaker echoes better

Question 28

What happens to temporal resolution with increasing pulses for scan line?

Answer 28

It gets worse

- the most functions the machine has to do the worse the temporal resolution gets