Lesson 2 (Part 2)

Question 1

What does the instrument automatically achieve?

Answer 1

The highest PRF

Question 2

Pen

Answer 2

Penetration

Question 3

Why must pen x PRF not exceed 77cm/ms?

Answer 3

In order to avoid echo misplacement

- pen(cm) x PRF (kHz) < 77(cm/ms)

Question 4

What happens to PRF if frequency is reduced and pen increases?

Answer 4

It gets reduced

-avoiding echo misplacement

Question 5

What happens if you go over 77cm/ms?

Answer 5

You get an artifact

- range ambiguity

Question 6

What happens to PRF in 2D if the depth is increased by 4x?

Answer 6

It decreases by 4x

Question 7

What gets produced by a greater voltage amplitude? (2)

Answer 7

1. Greater amplitude pulse

2. Greater intensity pulse

Question 8

What does AMP(voltage) equal?

Answer 8

AMP(pulse)

Question 9

Amplitude

Answer 9

The power or strength of the beam entering the tissue

- closely related to intensity

Question 10

What do pulse delays do? (2)

Answer 10

1. Decided how many element/crystals are involved

2. Which ones are getting fired

Question 11

What is pulse delays involved with? (6)

Answer 11

1. Sequencing arrays
2. Phasing
3. Electronic focusing
4. Dynamic aperture control
5. Apodization
6. Code excitation

Question 12

Sequencing array

Answer 12

Multiple blocks of sound, each producing a scan line

Question 13

Phasing

Answer 13

Microsecond delays between each element firing

Question 14

What does phasing help with?

Answer 14

Steering

Question 15

Electronic focusing

Answer 15

Microsecond delays between firing elements on a curved delay patter in order to send the sound beam into a focal point

Question 16

What does adjusting the delays do in electronic focussing?

Answer 16

It puts the focus either closer to or farther away

Question 17

What does the dynamic aperture decide?

Answer 17

The width of the aperture

Question 18

What can the dynamic aperture affect? (2)

Answer 18

1. Our near zone length

2. Beam width

Question 19

How does the dynamic aperture affect our imaging?

Answer 19

Through lateral resolution

- LR = beam width

Question 20

What happens if you use a small aperture?

Answer 20

You will get a better picture

- higher resolution

Question 21

What does apodization do?

Answer 21

It decreases the strength to the outer elements

- reducting of grating lobes in arrays

Question 22

What does apodization only work for?

Answer 22

Arrays

- not side lobes

Question 23

What is the ensemble length?

Answer 23

1

Question 24

What is the doppler ensemble length?

Answer 24

3-30

- has some delays in between

Question 25

What does coded excitation involve?

Answer 25

A decoder in the beam former

Question 26

What does coded excitation not include?

Answer 26

Range ambiguity

Question 27

Why doesn’t coded excitation include range ambiguity?

Answer 27

Because the decoder knows how it is sent out

Question 28

What does coded excitation allow? (5)

Answer 28

1. Multiple foci
2. Spatial compounding
3. Increased penetration
4. Increased contrast resolution
5. B-flow imaging

Question 29

B-flow imaging

Answer 29

Multiple pulses are sent down the same scan line and the decoder stacks the received echos
- constructive interference

Question 30

What do you get with B-flow imaging?

Answer 30

Overall higher intensity echoes

Question 31

Is B-flow and B-mode the same thing?

Answer 31

No

Question 32

Channel

Answer 32

Is an independent signal path consisting of a transducer element, delay and possibly other electronic components

Question 33

Transmission channel

Answer 33

Each path TO each individual element is a channel

- pulse –> pulse delays –> element

Question 34

Reception channels

Answer 34

Each path FROM each individual element is a channel

- element –> amplifier/ADC –> echo delays/summer

Question 35

What does an increased number of channels allow?

Answer 35

More precise control of beam characteristics

Question 36

What do numbers of channels not exceed?

Answer 36

The number of elements in the transducer