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SPI 1 > Transducers and Sound Beams > Flashcards

Transducers and Sound Beams Flashcards

1
Q

How are time of flight and depth related?

A 
Directly
depth (mm) = (1.54 mm/us x go return time us)/2
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2
Q

What is the 13 microseconds rule?

A

states that for every 13 us of go return time, the object that creates the reflection is 1 cm deeper in the body

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3
Q

How are PRP and depth related?

A

Directly

PRP (us) = imaging depth (cm) x 13 us/cm

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4
Q

What is a transducer?

A

Any device that turns one form of energy into another

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5
Q

What is the piezoelectric effect?

A

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

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6
Q

What is another term for piezoelectric materials?

A

Ferroelectric

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7
Q

What happens to the ultrasound transducer during transmission?

A

the transducer converts electrical energy from the system into sound

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8
Q

What happens to the ultrasound transducer during reception?

A

the transducer converts the reflected sound pulse into electricity

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9
Q

What is PZT?

A

Lead zirconate titanate

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10
Q

What are the synonyms for PZT?

A

Ceramic
Active element
Crystal

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11
Q

What is the Curie Temperature?

A

the temperature at which PZT is polarized

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12
Q

What happens when PZT reaches the Curie point?

A

If it goes higher than the Curie point, the crystal’s piezoelectric properties are destroyed, called depolarization.

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13
Q

Should you heat sterilize or autoclave a transducer?

A

No, you should not sterilize a transducer with heat.

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14
Q

What is sterilization?

A

Destroying all microorganisms by exposing them to extreme heat, chemical agents, or radiation

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15
Q

What is disinfection?

A

Applying a chemical agent to an object to reduce or eliminate infectious organisms

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16
Q

What is the purpose of the case?

A

protects the internal components of the transducer and insulates the patient from electrical shock

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17
Q

Is it safe to use a transducer if the case is cracked?

A

No

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18
Q

How are the active element and wavelength related?

A

Active element is 1/2 wavelength thick

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19
Q

What is the purpose of the matching layer?

A

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

20
Q

How thick is the matching layer?

A

1/4 wavelength thick

21
Q

What is the purpose of the backing material?

A

to reduce the “ringing” of the PZT

22
Q

How does backing material affect pulse duration?

A

It produces short pulses and makes pulse duration shorter

23
Q

How does backing material affect transducer sensitivity?

A

It decreases the sensitivity - because it makes the transducer less able to convert low-level sound reflections into electrical signals

24
Q

What are the three consequences of using a backing material?

A

Decreased sensitivity
Wide bandwidth
Low quality factor

25
Q

Do continuous or pulsed wave transducers need backing material?

A

Pulsed wave

26
Q

What is bandwidth?

A

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

27
Q

Do long or short pulses have a wider bandwidth?

A

Short duration pulses have a wider bandwidth

28
Q

What are the synonyms for the main frequency produced by a transducer?

A

Center
Resonant
Primary
Natural frequency

29
Q

Does a short or long pulse have a higher quality factor?

A

A longer pulse has a higher q-factor

30
Q

For a CW transducer how are frequency of voltage and the sound frequency related?

A

The frequency of the voltage is equal to the sound frequency.
Electrical frequency = acoustic frequency

31
Q

What two characteristics of the active element determine transducer frequency?

A

The speed of sound in PZT and thickness of PZT

32
Q

How are speed of sound in PZT and frequency related?

A

Speed of sound in PZT and frequency are directly related.

When sound in PZT is faster, frequency is higher, and when sound in PZT is slower, frequency is lower.

33
Q

How are crystal thickness and frequency related?

A

Crystal thickness and frequency are inversely related.

Thinner PZT crystals produce higher frequency waves, and thicker crystals produce lower frequency waves.

34
Q

What is the focus or focal point?

A

The point at which the sound beam is the narrowest

35
Q

What is the focal depth?

A

The distance from the transducer to the focus

36
Q

What are synonyms for focal depth?

A

Focal length

Near zone length

37
Q

What is the near zone?

A

The region from the transducer to the focus

38
Q

What are synonyms for near zone?

A

Near field

Fresnel zone

39
Q

What is the far zone?

A

The region that starts at the focus and extends deeper

40
Q

What are synonyms for far zone?

A

Far field

Fraunhofer zone

41
Q

What is the focal zone?

A

The region around the focus that is relatively narrow

42
Q 
For an unfocused CW transducer, what is the beam diameter at:
transducer
end of near zone
2 near zone lengths
deeper than 2 near zone lengths
A

Transducer - beam dia = transducer dia
End of near zone - beam dia = 1/2 transducer dia
2 near zone lengths - beam dia = transducer dia
Deeper than 2 near zone lengths - beam diameter > transducer dia

43
Q

What factors determine sound beam divergence in the far zone?

A

Transducer diameter

Frequency of sound

44
Q

Do smaller or larger diameter crystals create beams that diverge more in the far field?

A

Smaller crystals produce beams that diverge more in the far field

45
Q

Do higher or lower frequency beams spread out more in the far field?

A

Lower frequency beams

46
Q

What is a Huygen’s Wavelet?

A

A V-shaped wave created when the source is about the size of the sound’s wavelength.

47
Q

What is Huygen’s Principle?

A

The inconsistency between large and small sound sources and their beams. It states that a large active element can be thought of as millions of tiny sound sources.

SPI 1 (13 decks)

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