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Ultrasound Physics > Transducers Ch 8 > Flashcards

Transducers Ch 8 Flashcards

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1
Q

A device that converts one form of energy into another

A

Transducer

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2
Q

When is electrical energy from the system converted into sound?

A

During transmission

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3
Q

When is the reflected sound pulse converted into electricity?

A

Durning reception

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4
Q

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

A

The piezoelectric effect

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5
Q

Piezoelectic materials change shape when a voltage is applied to them.

A

Reverse piezoelectric effect

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6
Q

Materials which convert sound into electricity are called

A

piezoelectric or ferroelectric

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7
Q

Lead zirconate titanate

A

PZT

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8
Q

Ceramic, active element, or crystal are other names for

A

PZT

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9
Q

The cylindrical tube, constructed of metal or plastic that protects the internal components of the transducer from damage and insulates the patient form electrical shock.

A

Case

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10
Q

A thin metallic barrier lining the inside of the case. The shield prevents spurious electrical signals in the air from entering the transducer.

A

Electrical shield

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11
Q

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

A

Acoustic insulator

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12
Q

The piezoelectric crystal itself, the active element is shaped like a coin and is one half wavelength thick

A

PZT or active element

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13
Q

Provides an electrical connection between the PZT and the ultrasound system. The active element requires electrical contact so that during transmission the voltage from the ultrasound system can cause the crystal to vibrate and produce an ultrasonic wave.

A

Wire or channel

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14
Q

Positioned in front of the PZT at the face of the transducer. Increases the efficiency of sound energy trasfer between the active element and the body and protects the active element is one quarter wavelength thick

A

Matching layer

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15
Q

Bonded to the back of the active element, it reduces the ringing of the PZT.commonly made of epoxy resin with tungsten fillaments. The emitted sound pulse is dampened thus its short in duration and length. It enhances axial resolution

A

Backing material or dampening element

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16
Q

1/2 wavelength

A

Active element

17
Q

1/4 wavelength

A

Matching Layer

18
Q

PZT>matching layer>gel>skin

A

Decreasing order of impedence

19
Q

Characteristics of damping material

A

High degree of sound absorption and acoustic impedence similar to PZT

20
Q

3 consequences of the use of backing material

A

Decreased sensitivity, wide bandwidth, and low quality factor.

21
Q

Single frequency that vibrates for a long time

A

resonant frequency

22
Q

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

A

Bandwidth

23
Q

Long duration events have what size bandwidths?

A

Narrow

24
Q

Short duration events have what size bandwidths?

A

Wide

25
Q

How are quality factor and bandwidth related?

A

Inversely

26
Q

How are Q factor and bandwidth related?

A

Directly

27
Q

The process of exposing a material to a strong electrical field while being heated to a substantial temp.

A

Polarization

28
Q

The temp at which PZT is polarized

A

Curie Temp or Currie point

29
Q

The loss of piezoelectric properties

A

Depolarization

30
Q

The destruction of all microorganisms by exposure to extreme heat, chemical agents, or radiation.

A

Sterilization

31
Q

The application of a chemical agent to reduce or eliminate infectious organisms on an object.

A

Disinfection

32
Q

Electrical frequency= acoustic frequency

A

true

33
Q

What characteristics determine the frequency of a pulsed wave transducer?

A

Speed of sound in the PZT and thickness of the PZT.

34
Q

How are the speed of sound in PZT and the frequency of sound related?

A

Directly

35
Q

How are PZT thickness and frequency related?

A

Inversely

Ultrasound Physics (6 decks)

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