Physics Chapter 8 & 9

Question 1

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

Answer 1

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

Question 2

What are the characteristics of non-imaging transducers?

Answer 2

• 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

Question 3

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

Answer 3

The crystals piezoelectric properties are destroyed

Question 4

Reverse Piezoelectric Effect

Answer 4

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

Question 5

PZT is also known as _____?

Answer 5

Active element, crystal, or ceramic

Question 6

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

Answer 6

• backing material

- dampening element

Question 7

How is the Q-factor calculated?

Answer 7

Quality factor = main frequency / band width

Question 8

What type of crystal will have a lower frequency?

Answer 8

A thicker PZT crystal

Question 9

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

Answer 9

PZT > matching layer > gel > skin

Question 10

What type of resolution does the dampening material improve?

Answer 10

Axial resolution

Question 11

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

Answer 11

Continuous wave transducers (non-imaging)

Question 12

How many rayls are in an active element transducer?

Answer 12

2 Mrayls

Question 13

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

Answer 13

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

Question 14

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

Answer 14

Case

Question 15

What insulates the patient from electrical shock?

Answer 15

Case

Question 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

Answer 16

Electrical shield

Question 17

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

Answer 17

Acoustic insulator

Question 18

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

Answer 18

Acoustic insulator

Question 19

What size wave length is PZT?

Answer 19

1/2 wave length thick

Question 20

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

Answer 20

Active element

Question 21

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

Answer 21

Active element

Question 22

Provides an electrical connection between the PZT and the ultrasound system

Answer 22

Wire

Question 23

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

Answer 23

Matching layer

Question 24

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

Answer 24

Matching layer

Question 25

What size wave length is the matching layer?

Answer 25

1/4 wave length thick

Question 26

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

Answer 26

Backing material or dampening element

Question 27

What is commonly made of epoxy resin impregnated with tungsten filaments

Answer 27

Backing material or dampening element

Question 28

What would create a beam with a deeper focus?

Answer 28

- a larger diameter of PZT | - a higher frequency

Question 29

What would create a beam with a shallower focus?

Answer 29

- a smaller diameter of PZT | - a lower frequency

Question 30

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

Answer 30

More

Question 31

What probe creates a beam with the least divergence?

Answer 31

A larger diameter and higher frequency

Question 32

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

Answer 32

no change

Question 33

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

Answer 33

equals

Question 34

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

Answer 34

1/2

Question 35

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

Answer 35

equal to the transducer diameter

Question 36

Deeper than 2 near zone lengths, the beam diameter is

Answer 36

wider than transducer diameter

Question 37

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

Answer 37

Increases

Question 38

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?

Answer 38

Decreases

Question 39

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

Answer 39

- speed of sound in the PZT | - thickness of the PZT

Question 40

What determines the depth of the focus?

Answer 40

the characteristics of the active element fixed focus transducer: - transducer diamter - frequency of sound