Physics 2 - The Ultrasonic Field Module 3

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230 Terms

1

Spreading out of a sound wave from a small source

What is divergence

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2

Small

Would a bigger or smaller source have more divergence

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3

Fire a group of elements together to create a wave front

How did Huygen's principle teach us to limit divergence

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4

Non-uniform

What kind of beam uniformity do near fields have

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5

Interference

What causes the beam uniformity to be non-uniform in near fields

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6

Uniform

What kind of beam uniformity do far fields have

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7

Low Q

What can also make the near field less uniform

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8

Intensity differences

What else can the non-uniformity of the near field be related to/represented

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9

Off axis beams

What are grating lobes

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10

Main beam

Do the grating lobes or main beam contain most of the energy

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11

True

T/F: the grating lobes are weaker than the main beam

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12

Main beam

What is 1

<p>What is 1</p>
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13

Grating lobes

What is 2

<p>What is 2</p>
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14

Side lobes

What are the grating lobes called in mechanical probes

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15

Cross talk from length and width vibration

What are the grating lobes a result of

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16

Radial mode vibration in the single disc probes

What are the side lobes a result of

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17

Fresnel

What is another name for the near field

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18

Fraunhofer

What is another name for the far field

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19

Nearly constant beam width

What is the near field characterized by

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20

Divergent beam width

What is the far field characterized by

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21

True

T/F: even with old flats disc there is a natural narrowing of the beam

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22

One near field length

Where does the natural narrowing of the beam occur in old flat disc probes

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23

Transition zone

What is the point called where there is a natural narrowing of the beam one near field length

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24

One half the crystal diameter

How big is the beam at the transition zone

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25

2 NZL

What is the measurement of 1

<p>What is the measurement of 1</p>
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26

1 NZL

What is the measurement of 2

<p>What is the measurement of 2</p>
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27

1/2 crystal diameter

What is the measurement of 3

<p>What is the measurement of 3</p>
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28

1 of crystal diameter

What is the measurement of 4

<p>What is the measurement of 4</p>
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29

Usable beam shape

What does the natural beam shape define

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30

2 NZL

What is the length of the beam equal to

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31

Reasonable lateral resolution

What does the length of the beam (2 NZL) provide

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32

NZL = D^2 / 4 x wavelength

What is the formula to calculate the near field

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33

NZL = D^2 x f / 6

How is the formula to calculate the near filed rewritten for soft tissue

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34

So does the NZL

In the NZL formula, as frequency or diameter of the crystal increases:

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35

Divergent part of the beam

The far field or the Fraunhofer zone is the:

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36

Sin 0 = 1.22 x wavelength / D

What is the formula used to calculate the amount of divergence

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37

Decrease the angle of divergence

What does increasing the frequency or diameter of the crystal do in the amount of divergence equation

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38

2

Which beam has a bigger diameter and a smaller angle of divergence

<p>Which beam has a bigger diameter and a smaller angle of divergence</p>
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39

2

Which beam most likely has a higher frequency

<p>Which beam most likely has a higher frequency</p>
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40

How many crystals that are going to fire in a group to manipulate the diameter

What is a simple description of aperture

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41

False, was only considering single disc probes

T/F: the previous diameter principles were considering BOTH single disc and array probes

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42

Aperture

What is diameter controlled by in the array probe

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43

Increases

What happens to aperture as the depth of focus increases

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44

To maintain relatively consistent beam width

Why does aperture increase as depth of focus increases

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45

3

Which has more aperture

<p>Which has more aperture</p>
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46

Improve lateral resolution

What is the prime reason for focusing

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47

Decreasing beam width

What are we doing to the beam when focusing

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48

Improves sensitivity

What else does decreases the beam width do while focusing

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49

Near field only

Can you focus the near field, far field, or both

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50

Mechanical and electronic

What are the two different types of focusing

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51

Internal and external

What are the two types of mechanical focusing

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52

Curve is applied to the crystal

When does internal focusing occur

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53

Curve in a pair of glasses

What is the curve of the crystal in internal focusing analogous to

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54

Acoustic lens or mirror

What are the two ways external focuses is accomplished

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55

Acoustic lens

What kind of external focusing is 1

<p>What kind of external focusing is 1</p>
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56

Mirror

What kind of external focusing is 2

<p>What kind of external focusing is 2</p>
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57

It is fixed

What is the nature of the focus in older single crystal probes

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58

Short, medium, long

What are the three categories that mechanical probes can be categorized into

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59

Focal lengths

What are the categories short, medium, and long based on

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60

1-4cm

What is the focal length range for the short category

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61

4-10cm

What is the focal length range for the medium category

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62

7-19cm

What is the focal length for the long category

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63

Array transducers

What probes is electronic focusing found in

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64

Transmit focusing

What should electronic focusing be referred to as

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65

It is variable and operator controlled

What is the nature of electronic focusing

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66

Flat single disc

How do the elements act is there are excited at the same time

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67

Focus

Applying delays to the crystal can steer and ______ the probe

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68

Increase

Increasing the delays will ______________ the focus

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69

Focal region

What do the wave fronts converge toward when time delays are used to excite a group of elements

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70

Lens or curved element

The wave fronts converging toward the focal region when excited using delays is similar to :

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71

Lateral resolution improves

What is the advantage of using focus

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72

Divergence in far field increases and NZL will decrease

What are the disadvantages of using focus

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73

Dynamic aperture and frequency

What can be used to overcome the disadvantages of focus

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74

Machine

Do we need to change the dynamic aperture or does the machine usually do this for us

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75

We have to change it

Do we need to change the frequency or does the machine does this for us automatically

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76

Use of both mechanical and electronic focusing

What is dual focusing

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77

3D

Is the beam 2D or 3D

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78

Z-axis

What is another axis that we usually don't consider

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79

Elevational plane

What is another name for the z-axis

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80

Mechanical focus

What focus is used on the z-axis

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81

False

T/F: the z-axis is a consistent thickness

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82

Natural z-axis focus

What does the natural converge and diverge of the z-axis result in

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83

May not be at the ideal spot

What is the negative of the natural z-axis focus

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84

Manipulates where the z-axis focus is

How does mechanical focus used on the elevational plane

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85

True

T/F: you can get artifacts from the elevational plane

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86

Cystic structure that is smaller than the beam gets echoes from behind/in front of it that looks like they are in the cyst

Explain how you get artifacts from the elevational planes

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87

Elevational

What thickness is 1

<p>What thickness is 1</p>
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88

Lateral

What thickness is 2

<p>What thickness is 2</p>
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89

Axial

What thickness is 3

<p>What thickness is 3</p>
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90

Thickness of beam

What is lateral related to

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91

SPL

What is axial related to

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92

True

T/F: it is possible to have more than one transmit focus on the image

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93

Better lateral resolution throughout image

What is the advantages of multiple focus

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94

Decreases frame rate

What is the disadvantage of multiple focus

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95

Because the transducer has to wait for all of the scan lines to return before getting an image

Why does multiple focus decrease frame rate

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96

Thyroid

When is it okay to have multiple focus

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97

Echo and OB

What are some examples of when it is never okay to have multiple focus

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98

Long fucs

What does expanding the focal regions of the transducer result in

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99

True

T/F: array transducers can also focus the received echo signals

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100

Time delays are applied to the received echoes to allow for constructive interference

How do array transducers focus the received echo signals

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