Ch. 8 Transducers

Question 1

Define transducer

Answer 1

Any device that converts one form of energy into another.

Question 2

Ultrasound transducers two functions:

Answer 2

Transmission and reception

Question 3

Transmission

Answer 3

Electrical energy from the system is converted into sound.

Question 4

Reception

Answer 4

The reflected sound pulse is converted into electricity.

Question 5

Piezoelectric effect defined

Answer 5

Describes the property of certain materials to create a voltage when they are mechanically deformed or when pressure is applied to them.

Question 6

Reverse piezoelectric effect

Answer 6

When a voltage is applied to piezoelectric materials change shape.

Question 7

Piezoelectric or ferroelectric materials

Answer 7

Convert sound into electricity (and vice versa).

Question 8

Piezoelectric materials found in nature

Answer 8

Quartz and tourmaline

Question 9

Piezoelectric materials commonly used in clinical transducers

Answer 9

Lead zirconate titanate or PZT, are synthetic or man-made.

Question 10

Synonyms for PZT

Answer 10

Ceramic, active element, or crystal.

Question 11

The thickness of the matching layer

Answer 11

One-quarter of the wavelength of sound.

Question 12

The thickness of the active element

Answer 12

One=half of the wavelength of sound.

Question 13

Backing material

Answer 13

Plays an essential role in optimizing the pulses created by imaging transducers.

Question 14

The three consequences of using backing material are:

Answer 14

1. Decreased sensitivity
2. Wide bandwidth
3. Low quality factor

Question 15

The characteristics of damping material include:

Answer 15

High degree of sound absorption.

Acoustic impedance similar to PZT.

Question 16

Bandwidth

Answer 16

The range of frequencies in the pulse. It is the difference between the highest and lowest frequencies.

Question 17

Imaging probes produce pulses that are identified as

Answer 17

Wide bandwidth or broadband

Question 18

As a general rule, long duration events are ____ bandwidth, whereas short duration events are ___ bandwidth (broadband).

Answer 18

Narrow, wide.

Question 19

Average transducer thickness

Answer 19

0.2 1 mm

Question 20

Quality factor defined

Answer 20

A unitless number that is inversely related to bandwidth.

Question 21

What probes have a low Q-factor?

Answer 21

Wide bandwidth probes

Question 22

Which probes have a high Q-factor?

Answer 22

Narrow bandwidth probes.

Question 23

Because imaging probes use backing material and have a wide bandwidth they are referred to as ____.

Answer 23

Low-Q.

Question 24

Transducers used in therapeutic ultrasound and have continuous wave doppler do not contain backing material. They have a narrow bandwidth and ____.

Answer 24

High- Q

Question 25

PZT is created by

Answer 25

Exposing the material to a strong electrical field while being heated to a substantial temperature. Polarization.

Question 26

The temperature at which PZT is polarized is called

Answer 26

Curie temperature or curie point.

Question 27

How can piezoelectric properties be destroyed?

Answer 27

Exposure to high temperature.

Question 28

Depolarization

Answer 28

The loss of piezoelectric properties when crystals are heated above the curie temperature.