Lesson 17 (Part 2)

Question 1

Spatial compounding

Answer 1

Hitting the same object from different angles

Question 2

What is the benefit of spatial compounding? (3)

Answer 2

1. Clears out cysts
2. Sharpens borders
3. Smoother images

Question 3

What does spatial compounding have more of?

Answer 3

More pulses per image

Question 4

Sector image

Answer 4

Phasing of a very small group of elements

Question 5

What can sector imaging be used to assess?

Answer 5

Large areas through very small windows

Question 6

Vector array

Answer 6

Phasing can be applied to each element group in a linear sequenced array

Question 7

What do vector array’s do?

Answer 7

Steer pulses in various directions

Question 8

How does vector array initiate pulses?

Answer 8

At various starting points across the array

Question 9

What makes up a linear array? (2)

Answer 9

Linear array + phased array

Question 10

What does a vector array have?

Answer 10

A flat top

Question 11

What is vector array a combination of? (2)

Answer 11

1. Sequencing

2. Phasing

Question 12

What is another word for sector?

Answer 12

Widescreen

Question 13

What is a sector used to measure?

Answer 13

Larger organs

Question 14

What is vector array?

Answer 14

Phasing applied to a linear sequenced array

Question 15

What is kept the same for each group in vector array?

Answer 15

Delays

Question 16

How are beams sent out in vector array?

Answer 16

In an angled direction

Question 17

What kind of display is vector array?

Answer 17

Parallelogram shaped display

Question 18

When is vector array used?

Answer 18

In Doppler ultrasound

Question 19

Are all elements if a phased array used to generate all pulses?

Answer 19

No

Question 20

What are smaller groups of arrays used for?

Answer 20

Shorter focal lengths

Question 21

What are larger groups of array used for?

Answer 21

For foci located at increasing depths

Question 22

Side lobes

Answer 22

Usually represent unwanted radiation in undesired directions

Question 23

Grating lobes

Answer 23

Are the maxima of the main beam, as predicted by the pattern multiplication theorem

Question 24

What kind of interactions come from grating lobes?

Answer 24

Interelement interactions

Question 25

What can happen in grating lobes?

Answer 25

It can hit a strong reflector and produce strong echoes

Question 26

What are strong reflector examples the grated lobe can hit? (3)

Answer 26

1. Diaphragm
2. Gas
3. Fetal bone

Question 27

What do grating lobes show as?

Answer 27

Artifacts

Question 28

What do grating lobes look like?

Answer 28

Amniotic bands

Question 29

How do you fix grating lobes? (3)

Answer 29

1. Apodization
2. Subdicing
3. THI

Question 30

Apodization

Answer 30

Optical filtering technique

Question 31

Where do grating lobes come from?

Answer 31

The edges of all the elements

Question 32

What happens to the grating lobes if we reduce the amplitude of the voltage to the outside elements?

Answer 32

Less artifact

- weak beam is going out, so weaker echo is coming back

Question 33

Can side lobes be apodized?

Answer 33

No

Question 34

What does subdicing of each element into a small group of small crystals do?

Answer 34

Weakens grating lobes

Question 35

What does subdicing reduce?

Answer 35

Inter-element interactions

Question 36

What is subdicing only used for?

Answer 36

Grating lobe artifacts

Question 37

When do you use THI?

Answer 37

When grating lobes or side lobes are too weak to produce harmonic signals