Ch. 8 Transducers

Question 1

During ______ electrical energy from the system is converted into sound.

Answer 1

During transmission electrical energy from the system is converted into sound.

Question 2

During ______ the reflected sound pulse is converted into electricity.

Answer 2

During reception the reflected sound pulse is converted into electricity.

Question 3

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

Answer 3

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

Question 4

PZT in ultrasound transducer is also known as the ________________, _______________________, or ___________________.

Answer 4

PZT in ultrasound transducer is also known as the ceramic, active element, or crystal

Question 5

The ______________ is the cylindrical tube, constructed of metal or plastic, that protects the internal components of the transducer from damage.

Answer 5

The case is the cylindrical tube, constructed of metal or plastic, that protects the internal components of the transducer from damage.

Question 6

The ________________________ is a thin metallic barrier lining the inside of the case. This helps prevent electrical noise from contaminating the clinically important electrical signals used to create diagnostic images.

Answer 6

The electrical shield is a thin metallic barrier lining the inside of the case. This helps prevent electrically noise from contaminating the clinically important electrical signals used to create diagnostic images.

Question 7

The ___________________________ is a thin barrier of cork or rubber that isolated or “uncouples” the internal components of the transducer from the case. Also, prevents vibrations in the case from inducing an electrical voltage in the PZT of the transducer.

Answer 7

The acoustic insulator is a thin barrier of cork or rubber that isolated or “uncouples” the internal components of the transducer from the case. Also, prevents vibrations in the case from inducing an electrical voltage in the PZT of the transducer.

Question 8

The ______________ or _____________________ is the piezoelectric crystal itself. The characteristics of the sound beam emitted by the transducer are related to the deminsions of the active element.

Answer 8

The PZT or active crystal is the piezoelectric crystal itself. The characteristics of the sound beam emitted by the transducer are related to the deminsions of the active element.

Question 9

The ______________ provides an electrical connection between the PZT and the ultrasound system.

Answer 9

The wire provides an electrical connection between the PZT and the ultrasound system.

Question 10

The __________________________ is positioned in front of the PZT at the face of the transducer. The matching layer:
- increasing the efficiency of sound energy transfer between the active element and the body
- protects the active element

Answer 10

The Matching Layer is positioned in front of the PZT at the face of the transducer. The matching layer:

• increasing the efficiency of sound energy transfer between the active element and the body
• protects the active element

Question 11

The ______________________________ is bonded to the back of the active element, it reduces the “ringing” of the PZT.

Answer 11

The Backing Material is bonded to the back of the active element, it reduces the “ringing” of the PZT (enhancing axial resolution)

Question 12

Gel, Matching Layer, Skin, and PZT… list in discreasing order of impedance:

Answer 12

1. PZT
2. matching layer
3. gel
4. skin

Question 13

The thickness of the _________________________ is ________________________ of the wavelength of sound in the matching layer

Answer 13

The thickness of the matching layer is one-quarter of the wavelength of sound in the matching layer.

Question 14

The thickness of the _________________________ is __________________________ of the wavelength of sound in the active element

Answer 14

The thickness of the active element is one-half of the wavelength of sound in the active element

Question 15

What are the three consequences of using backing material?

Answer 15

1. decreased sensitivity
2. wide bandwidth
3. low quality factor

Question 16

_______________________________ means that during reception, transducers with damping material are less able to convert low-level sound reflections into meaningful electrical signals

Answer 16

Decreased Sensitivity means that during reception, transducers with damping material are less able to convert low-level sound reflections into meaningful electrical signals

Question 17

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

Answer 17

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

Question 18

_____________________________ is a unitless number that is inversely related to bandwidth.

Answer 18

Quality Factor is a unitless number that is inversely related to bandwidth

Question 19

Quality Factor formula:

Answer 19

QF = main frequency/bandwidth

Question 20

A shorter, dampened pulse has a _______ Q-factor.

Answer 20

lower

Question 21

A longer, undampened pulse has a ___________ Q-factor.

Answer 21

higher

Question 22

The temperature at which the PZT is polarized is called the ___________________________________ or ___________________________________

Answer 22

The temperature at which the PZT is polarized is called the Curie temperature or Curie Point

Question 23

_____________________________ is the destruction of all microorganisms by exposure to extreme heat, chemical agents, or radiation.

Answer 23

Sterilization is the destruction of all microorganisms by exposure to extreme heat, chemical agents, or radiation

Question 24

_____________________________ is the application of a chemical agent to reduce or eliminate infectious organisms on an object.

Answer 24

Disinfection is the application of a chemical agent to reduce or eliminate infectious organisms on an object

Question 25

Pulse length is [directly or inversely] related to pulse duration.

Answer 25

directly

Question 26

Q-factor is [directly or inversely] related to bandwidth

Answer 26

inversely

Question 27

Pulse Duration is [directly or inversely] related to bandwidth

Answer 27

inversely

Question 28

The sensitivity of transducers that create short duration pulses is likely to be [greater than, less than, or equal to] that of transducers that create long pulses

Answer 28

less than

Question 29

With continuous wave electrical frequency =

Answer 29

Acoustic frequency

Question 30

with a pulsed wave transducer, two characteristics of the active element combine to determine the frequency of sound:

Answer 30

1. speed of sound in the PZT 2. thickness of the PZT Average speed of sound in most PZT material ranges from 4 to 6 mm/us(about 4 times greater than the speed of sound in soft tissue) Thickness of PZT crystals in diagnostic imaging transducers range from 0.2 to 1mm

Question 31

High Frequency Pulsed Wave Imaging Transducers have _________________________ PZT crystals, and PZT with _____________________ speeds.

Answer 31

High Frequency Pulsed Wave Imaging Transducers have *thinner* PZT crystals, and PZT with *higher* speeds

Question 32

Low Frequency Pulsed Wave Imaging Transducers have ____________________ PZT crystals, and PZT with __________________ speeds

Answer 32

Low Frequency Pulsed Wave Imaging Transducers have *thicker* PZT crystals, and PZT with *lower* speeds

Question 33

frequency of pulsed wave imaging transducers equation:

Answer 33

frequency(MHz)= sound's speed in PZT(mm/us) / 2 x thickness(mm)