Lesson 17 (Part 1)

Question 1

Linear phased array

Answer 1

Straight line of elements

Question 2

How are linear phased array elements fired?

Answer 2

Voltage applied with a small difference

Question 3

Phasing

Answer 3

Firing with a small time difference

Question 4

How much time is delayed between firing of each element?

Answer 4

< 1 us

Question 5

When is the delay bigger?

Answer 5

When the beam has a larger angle

Question 6

What happens when the delay is straight with the beam?

Answer 6

There is no delay

Question 7

Wavefront

Answer 7

Angled line that is created by the different phasing arrays

Question 8

How does a wave always travel?

Answer 8

Perpendicular to its wavefront

Question 9

What does the new wavelength created by secondary wavelets happen according to?

Answer 9

Huygen’s principle

Question 10

Huygen’s principle

Answer 10

Every point on a wave-front may be considered a source of secondary spherical wavelets which spread out in the forward direction at the speed of light

Question 11

How do we steer the beam when scanning the patient?

Answer 11

By phasing

Question 12

If you want to steer the beam to the right how is phasing organized?

Answer 12

On a left slope

Question 13

If you want to steer the beam to the left how is phasing organized?

Answer 13

On a right slope

Question 14

Why do we change our focus?

Answer 14

To get a better resolution

Question 15

What can we change at a particular spot?

Answer 15

Intensity

Question 16

When is beam width smallest?

Answer 16

At the focus

Question 17

Electronic focusing

Answer 17

Using phased array to focus the beam

Question 18

What happens in electronic focusing when you have a greater curvature?

Answer 18

It places the focus closer to the transducer

Question 19

What happens in electronic focusing when you have a lesser curvature?

Answer 19

It places the focus deeper

- farther away from them transducer

Question 20

How can electronic focusing move?

Answer 20

Based on time delayed

Question 21

What does increase delay of beams lead to?

Answer 21

Greater curvature

- focus is closer to the surface

Question 22

How do we achieve curvature? (2)

Answer 22

1. Fire outside crystals first and so on
   - 1 and 8, 2 and 7…
2. Fire the middle ones last

Question 23

What does decrease in delay of beams lead to?

Answer 23

Lesser curvature

- farther focus

Question 24

What does an unfocused sound beam have?

Answer 24

A natural focus

Question 25

What is a focused sound beam the same as?

Answer 25

Electronic focusing

Question 26

What does multiple foci require?

Answer 26

Multiple pulses

- each focused at a different depth

Question 27

Montage

Answer 27

Overlaid images

Question 28

What does montage lead to?

Answer 28

Better resolution at each depth

Question 29

What happens when the frame rate decreases?

Answer 29

It lags