Lesson 22 (Part 1) Flashcards Preview

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Flashcards in Lesson 22 (Part 1) Deck (28)
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1

What is the speed of blood flow?

110cm/s

2

What are characters of blood flow? (2)

1. Laminar
2. Turbulent

3

What are 3 types of Doppler displays?

1. Colour
2. Spectral
3. Audible

4

What does colour doppler demonstrate for blood flow?

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

5

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

It asses a very large area at a time

6

What is another name for colour doppler?

Duplex scanning

7

Why is duplex scanning also another name for colour doppler?

Because the colour portion is on top of a grey scale
- 2 parts

8

How is colour doppler steered?

Through phasing

9

What is the end goal of phasing? (2)

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

10

What is the formula for doppler shift?

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

11

When does doppler shift occur?

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

12

What does a positive doppler shift indicate?

Flow is going towards the transducer

13

What does a negative doppler shift indicate?

Flow is going away from the transducer

14

What kind of pulses are sent out during colour doppler?

Multiple pulses are sent out per scan line

15

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

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

16

How is colour doppler created? (4)

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

17

What does direction do for colour doppler?

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

18

What does the mean velocity tell us with colour doppler?

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

19

What does the variance tell us with colour doppler?

The ‘variety’ within the blood flow / standard deviation

20

What is power related to in colour doppler?

Amplitude
- strength/intensity of the echo

21

What does power depend on?

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

22

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

There is more reflection

23

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

More reflection

24

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

3-32
- usually 10-20

25

Ensemble length

Is the number of pulses per scan line

26

Are more pulses per scan line good or bad?

Good

27

Why are more pulses per scan line good?

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

28

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

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