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LMC Ultrasound > Physics Chapter 8 & 9 > Flashcards

Physics Chapter 8 & 9 Flashcards

1
Q

If you have 2 types of crystals made of the same material, the thicker crystal will do what?

A

Thicker active elements create pulses with lower frequency, longer wavelength cycles

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2
Q

What are the characteristics of non-imaging transducers?

A
  • creates continuous waves or pulses with long duration and length
  • no backing material
  • increased sensitivity
  • narrow band width
  • higher Q-factor
  • cannot create an image
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3
Q

If PZT is heated to the curie point, what happens to it?

A

The crystals piezoelectric properties are destroyed

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4
Q

Reverse Piezoelectric Effect

A

The process of piezoelectric materials changing shape when a voltage is applied to them

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5
Q

PZT is also known as _____?

A

Active element, crystal, or ceramic

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6
Q

What is the active element that reduces the ringing of the PZT?

A
  • backing material

- dampening element

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7
Q

How is the Q-factor calculated?

A

Quality factor = main frequency / band width

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8
Q

What type of crystal will have a lower frequency?

A

A thicker PZT crystal

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9
Q

What is the impedance difference between the crystal, skin, matching layer, and gel?

A

PZT > matching layer > gel > skin

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10
Q

What type of resolution does the dampening material improve?

A

Axial resolution

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11
Q

The frequency of sound emitted is equal to to the frequency of the electrical signal in what type of transducer?

A

Continuous wave transducers (non-imaging)

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12
Q

How many rayls are in an active element transducer?

A

2 Mrayls

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13
Q

What is the impedance level of PZT, matching layer, gel, and skin?

A

PZT = 2 Mrayls
Matching layer = 1.6 Mrayls
Gel = 1 Mrayls
Skin = 0.8 Mrayls

*values on p121 question 1. don’t know if these are really the values or not. know she mentioned something about it

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14
Q

Cylinderical tube constructed of metal or plastic that protects the internal components of the transducer from damage

A

Case

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15
Q

What insulates the patient from electrical shock?

A

Case

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16
Q

A thin metallic barrier lining the inside of the case that helps prevent electrical noise from contaminating the clinically important electric signals used to create diagnostic images

A

Electrical shield

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17
Q

A thin barrier of cork or rubber that isolates the internal components of the transducer from the case

A

Acoustic insulator

18
Q

What prevents vibrations in the case from inducing an electrical voltage in the PZT of the transducer?

A

Acoustic insulator

19
Q

What size wave length is PZT?

A

1/2 wave length thick

20
Q

In a simple probe, the characteristics of the sound beam emitted by the transducer are related to the dimensions of _____?

A

Active element

21
Q

In a simple probe, the characteristics of the sound beam emitted by the transducer are related to the dimensions of _____?

A

Active element

22
Q

Provides an electrical connection between the PZT and the ultrasound system

A

Wire

23
Q

What lies in front of the PZT at the face of the transducer?

A

Matching layer

24
Q

Helps increase the efficiency of sound energy transfer between the active element and the body and protects the active element

A

Matching layer

25
Q

What size wave length is the matching layer?

A

1/4 wave length thick

26
Q

Bonded to the back of the active element, it reduces the ringing of the PZT

A

Backing material or dampening element

27
Q

What is commonly made of epoxy resin impregnated with tungsten filaments

A

Backing material or dampening element

28
Q

What would create a beam with a deeper focus?

A
  • a larger diameter of PZT

- a higher frequency

29
Q

What would create a beam with a shallower focus?

A
  • a smaller diameter of PZT

- a lower frequency

30
Q

A probe with a smaller diameter and a lower frequency will diverge more or less?

A

More

31
Q

What probe creates a beam with the least divergence?

A

A larger diameter and higher frequency

32
Q

The frequency of a transducer does not change. If the diameter of the new piezoelectric crystal increases, what happens to the wavelength?

A

no change

33
Q

At the transducer, the beam diameter is greater than, equals, or less than the transducer diameter?

A

equals

34
Q

At the focus, the beam diameter is 1/2, 1/4, or the same as the transducer diameter?

A

1/2

35
Q

At 2 near zone lengths, the beam diameter is..

A

equal to the transducer diameter

36
Q

Deeper than 2 near zone lengths, the beam diameter is

A

wider than transducer diameter

37
Q

The frequency of a transducer does not change. If the diameter of the new PZT crystal increases, what happens to the near zone length?

A

Increases

38
Q

The frequency of a transducer does not change. If the diameter of the new PZT crystal increases, what happens to the beam diameter in the far zone?

A

Decreases

39
Q

What characteristics of the active element determine the frequency of sound created by a pulsed wave transducer?

A
  • speed of sound in the PZT

- thickness of the PZT

40
Q

What determines the depth of the focus?

A

the characteristics of the active element

fixed focus transducer:

  • transducer diamter
  • frequency of sound

LMC Ultrasound (32 decks)

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