Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Phys 254 > Module 1: Transducer Design > Flashcards

Module 1: Transducer Design Flashcards

1
Q

What does a transducer do in terms of energy?

A

Converts energy from one form to another

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the transducer in terms of singals? What causes it to do it?

A
  1. Piezoelectric crystal or element
  2. Signal conversion device
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a crystal in terms of the ultrasound probe?

A

Piezoelectric material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the element in the U/S probe

A

Another name for piezoelectric crystal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the scan head in the ultrasound probe?

A

Another name for transducer (or the sonography)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the probe?

A

Another name for transducer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the transducer assembly?

A

The housing and internal circuitry

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

A single element in the ultrasound probe can be used to do what?

A

Send and receive sound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Some of the more common parts of the U/S probe is what?

A
  1. Housing
  2. Backing material
  3. Crystal
  4. Matching layer
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does the housing do in the ultrasound probe?

A

Contains all probe components

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the backing material in the ultrasound probe made of?

A

Mixture of metal, plastic, or epoxy bonded to the back of the crystal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the crystal in the ultrasound probe?

A

A ceramic element that has piezoelectric properties

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the matching layer in the ultrasound probe used for?

A

Used to reduce sound reflection from the skin and enhance sound transmission

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

The three main parts of the ultrasound probe?

A
  1. Crystal
  2. Backing material
  3. Matching layer
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Who discovered the piezoelectric principle?

A

Jacques and Pierre curie

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What does the piezoelectric principle explain?

A

How some materials can convert electric energy to mechanical and vice versa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Which natural materials have piezoelectric properties (and used in early days)?

A

Quartz, lithium sulphate, Rochelle salt, and tourmaline

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What crystals are used in modern day equipment?

A

Man made ceramics like
1. Lead zirconate
2. Lead titanate
3. Barium titanite
4. Lead zirconate titanate (PZT)*
5. Polyvinylidene fluoride (PVFD)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the piezoelectric (direct) effect?

A

When a mechanical pressure deforms the crystal which changes the orientation of the electric dipoles producing a small electric voltage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the reverse (indirect) effect?

A

Where an electric voltage changes the orientation of the dipoles causing the crystal to expand and contract

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are electric dipoles?

A

Essentially the molecules within the crystal and the have a positive charge at one end and a negative charge at the other end

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What else can electric dipoles be influenced by?

A

Electrical or magnetic fields

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Normally the dipoles are in what kind of alignment?

A

Random alignment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What does the random alignment of dipoles do for ultrasound?

A

They make the crystal inefficient for vibration when an electrical current is applied

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

If the dipoles are in alignment then what happens?

A

The vibration of the crystal will be much improved

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

When the crystal vibrates we must consider what?

A

The different modes of vibration that may occur

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

In early probes the crystal was what? This accounted for what:

A

Disc shaped and could vibrate in a thickeness mode or a radial mode

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What are the three modes of vibration for modern day probes?

A
  1. Thickness
  2. Length
  3. Width
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

For modern probes what are the most desirable mode?

A

Thickness

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Synthetic materials are used in the production of what? This does what?

A

Synthetic materials are used in the production of the crystal so that more pure product can be develop

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

How do we make substance align properly to enhance the piezoelectric properties for ultrasound production?

A

Currie temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What happens when we heat something above the Currie temperature?

A

The bonds between the molecule weaken

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What is the Currie temperature for PZT?

A

350 degrees

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What is the Currie temperature process?

A
  1. Heat above the Currie temp to weaken bonds
  2. Substance is subjected to an electrical field then the dipoles will align accordingly
  3. The substance is then cooled and the bonds strengthen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Heat can polarize what?

A

The dipoles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Reheating can do what?

A

Potential depolarize as well

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

In terms of frequencies the crystal determines what?

A

Frequencies a probe can emit

38
Q

What are the different kinds frequencies a crystal can emit?

A
  1. Resonant frequency
  2. Driving frequency
  3. Operating frequency
  4. Harmonic frequency
39
Q

What is resonant frequency? How is it determined?

A

The one at which the crystal likes to ring at. It is determined by the crystal material and thickness and is also called the fundamental frequency

40
Q

What is driving frequency?

A

It is determined by the AC voltage sent to the crystal. If the voltage is altered then the crystal can be forced to ring at a different frequency then the fundamental

41
Q

What is operating frequency?

A

The one that you are using to scan

42
Q

What is 2nd harmonic frequency?

A

Two times the resonant frequency

43
Q

The frequency of the crystal relates to what?

A

The propagation speed of sound and the thickness of sound

44
Q

The thickness of crystal which determines its resonance frequency is equal to what?

A

1/2 wavelength

45
Q

To build a 4 MHZ probe we do what?

A

We find the wavelength for 4 MHz and divide it by 2

46
Q

If we double the thickness of the crystal what do we do to frequency?

A

It will half the frequency

47
Q

When calculating the crystal thickness it is important to use what as the constant?

A

The speed of sound in the crystal as the constant

48
Q

What is another name for backing material?

A

Damping block

49
Q

What is the purpose of backing material?

A
  1. Reduce the SPL which will improve axial resolution.
  2. Reduce the amplitude of the wave and reducing sensitivity
  3. Absorbs sound so that reflections don’t occur from behind the crystal
50
Q

What is backing material usually made of?

A

Epoxy resin with metal powder (tungsten) that is stuck on back of the crystal

51
Q

As we increase the amount of damping material what will we do?

A

Shorten the length of the pulse.

52
Q

To absorb sound so that reflections don’t occur the z value of the damping material must be what?

A

Comparable to the element, typically around 2-3 cycles per pulse

53
Q

What is dynamic damping?

A

Electronic means to suppress the ringing of the crystal.

54
Q

How do we apply dynamic damping?

A

We use an inverse wave

55
Q

What is the matching layer? And why is it important?

A

Bridging the impedance mismatch between the crystal and the skin is quite large and without the matching layer much of the sound would return to the probe before entering the patient.

56
Q

The matching layer has a z value between the crystal and skin to do what?

A

Reduce the amount of the reflection

57
Q

What do we need to remember about cutting the matching layer?

A

To cut the thickness of the matching layer to 1/4 lambda

58
Q

1/4 lambda helps create destructive interference of waves that do what?

A

Reverberate between matching layers

59
Q

How many matching layers are there?

A

Typically more than one layer is used since there are multiple frequencies that come out of the probe

60
Q

Many matching layers will do what?

A

It will accommodate multiple frequencies thus improving the transmission and reception of a wide bandwidth of frequencies

61
Q

What is also considered a matching layer between the probe and the skin?

A

The gel we use.

62
Q

What is the Z value of gel?

A

Somewhere between the last matching layer of the probe and the skin

63
Q

What is probe excitation?

A

The way that the probe is excited with voltage helps determine the driving frequency

64
Q

What is spike voltage method?

A
  1. Older technology for probe excitation
  2. Uses a direct current (DC) to vibrate the crystal
65
Q

What is burst voltage method?

A

Newer technology for probe excitation

66
Q

How does Spike voltage work?

A

The current from the pulsed hits the crystal where one spike is equal to one pulse.

67
Q

In spike voltage method the driving/operating frequency is always equal to what?

A

The resonant frequency

68
Q

DC current is also called what?

A

“Saw tooth” voltage because of the appearance

69
Q

What is frequency bandwidth?

A

The range of frequencies that are produced by a pulse

70
Q

Normally when the crystal is stimulated it will ring at what?

A

Resonant frequency and there is a very small range of frequencies produced

71
Q

When we dampen the crystal to shorten the length of the pulse what happens?

A

A greater range of frequencies are emitted from the probe

72
Q

If we were to graph the bandwidth what would we see?

A

We would see the range of frequencies that are produced on the X axis with the resonant frequency having the highest amplitude (y axis)

73
Q

Why do we see a range of frequencies when we graph the bandwidth?

A

The crystal thickness and material helped determine the most efficient frequencies to ring at

74
Q

The shorter the pulse what happens to the bandwidth?

A

The wider the bandwidth
this is more desirable for better resolution

75
Q

Having a wider bandwidth means what?

A

We have more options for what driving frequency we can choose

This is on top of better resolution

76
Q

The frequencies that we can drive the probe are limited by what?

A

The size of the bandwidth and attenuation

77
Q

Any frequencies that have an amplitude of less than half of the resonant frequencies are what?

A

Too weak to be used by the system

78
Q

The usable bandwidth is referred to as what?

A

The 6dB bandwidth.

79
Q

What is 6dB equal to?

A

1/2 the amplitude or 1/4 intensity of the resonant frequency

80
Q

It is the damping material that effects the bandwidth just as it effects what?

A

The SPL

81
Q

If we increase the amount of damping then we should do what?

A

Shorten the pulse and increase the range of frequencies that are emitted
remember that the sensitivity is reduced

82
Q

What is fractional bandwidth?

A

A common way to express the bandwidth of the probe

83
Q

A probe with a Frequency bandwidth over 80% is considered to be what?

A

Broadband design

84
Q

What is the formula for frequency bandwidth?

A

FB = Bandwidth/ frequency

85
Q

What is quality factor or Q?

A

Another term for describing the bandwidth of a probe

86
Q

Q or quality factor is a reciprocal of what?

A

Frequency bandwidth

87
Q

It is desirable to have a low Q for what?

A

2D scanning and it gets higher as we use
1. Doppler
2. Pulsed doppler
3. CW doppler

88
Q

To optimize the 2D image we use more what?

A

Damping to shorten the pulse for better axial resolution

89
Q

Modes that require more sensitivity will benefit from what?

A

A narrower bandwidth or higher Q (CW doppler)

90
Q

How does an increase in bandwidth affect q factor?

A

A lower Q factor

Phys 254 (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions