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Flashcards in Physics Chapter 8 & 9 Deck (40)
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1

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

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

2

What are the characteristics of non-imaging transducers?

- 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

3

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

The crystals piezoelectric properties are destroyed

4

Reverse Piezoelectric Effect

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

5

PZT is also known as _____?

Active element, crystal, or ceramic

6

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

- backing material
- dampening element

7

How is the Q-factor calculated?

Quality factor = main frequency / band width

8

What type of crystal will have a lower frequency?

A thicker PZT crystal

9

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

PZT > matching layer > gel > skin

10

What type of resolution does the dampening material improve?

Axial resolution

11

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

Continuous wave transducers (non-imaging)

12

How many rayls are in an active element transducer?

2 Mrayls

13

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

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

14

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

Case

15

What insulates the patient from electrical shock?

Case

16

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

Electrical shield

17

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

Acoustic insulator

18

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

Acoustic insulator

19

What size wave length is PZT?

1/2 wave length thick

20

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

Active element

21

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

Active element

22

Provides an electrical connection between the PZT and the ultrasound system

Wire

23

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

Matching layer

24

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

Matching layer

25

What size wave length is the matching layer?

1/4 wave length thick

26

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

Backing material or dampening element

27

What is commonly made of epoxy resin impregnated with tungsten filaments

Backing material or dampening element

28

What would create a beam with a deeper focus?

- a larger diameter of PZT
- a higher frequency

29

What would create a beam with a shallower focus?

- a smaller diameter of PZT
- a lower frequency

30

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

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