Lesson 18 (Part 1) Flashcards Preview

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Flashcards in Lesson 18 (Part 1) Deck (28)
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1

Resolution (2)

1. To create a better picture
2. Being able to separate distinct echoes

2

What are 3 examples imaging resolution?

1. Detail/spatial
- transducer
2. Contrast
- instrument
3. Temporal
- instrument

3

What kind of resolution is better?

Smaller
- tinier details can be discerned

4

What happens if 2 reflectors are not separated sufficiently?

They produce overlapping echoes
- smear

5

What is axial resolution also known as? (4)

1. Longitudinal
2. Radial
3. Depth
4. Range

6

Axial resolution

Minimum reflector separation along scan lines to produce separate echoes

7

What happens to the image when distance between the structures is greater than the axial resolution?

It will appear as a single structure
- smear

8

What happens to the image when the distance between the structures is lower than the axial resolution?

You will get separate structures

9

What is the formula for axial resolution?

AR = SPL/2
- AR = axial resolution
- SPL - spatial pulse length

10

How do you get the best axial resolution?

Smaller SPL

11

What is the unit for axial resolution?

mm

12

How do we reduce SPL? (3)

1. Reducing the number of cycles
2. Reducing the wavelength
3. Increase frequency

13

How do you reduce the number of cycles?

Applying damping

14

What does increasing frequency affect?

Penetration

15

What is lateral resolution also known as? (3)

1. Angular
2. Transverse
3. Azimuthal

16

Lateral resolution

Minimum reflector separation perpendicular to scan line to produce separate echoes
- horizontal line

17

What is the formula for lateral resolution?

LR = Wb
- LR = lateral resolution
- Wb = width of beam

18

What is the unit for lateral resolution?

mm

19

What happens in lateral resolution of the resolution is too high?

You get a smearing effect

20

What happens if the beam is narrower than reflector separation in lateral resolution?

You get 2 distinct structures

21

What is the lateral resolution at the focus?

Same as what is the beam width at the focus

22

What is the formula for beam width?

1/2 of the aperture

23

What is the best lateral resolution?

The smaller the better

24

How is lateral resolution improved?

By reducing beam width

25

How can you reduce the beam width in lateral resolution?

By adjusting the focus
- making it more narrower

26

Where can you move the focus?

Near zone length
- NZL

27

Where cant you move the focus?

Far zone length

28

What can you change in the FZL?

Aperture size