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Physics Vocabulary > Physics 111 Chapter 3 Transducers > Flashcards

Physics 111 Chapter 3 Transducers Flashcards

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1
Q

Thinner elements operate at __________ frequencies

A

Higher

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2
Q

The beam diameter is ___________ the diameter of the transducer element at a distance of two near zone lengths

A

Equal to

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3
Q

Linear phased array transducer, the elements measure the width of about

A

One quarter the wavelength

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4
Q

Focusing of the sound beam is achieved within

A

The fresnel zone

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5
Q

Utilizing multiple focal zone simultaneously increases image detail resolution and degrades

A

Temporal resolution

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6
Q

What happens to the near zone length if the aperture decreases

A

Decreases

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7
Q

In the linear array transducer the pulses travel in

A

straight lines

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8
Q

What is the impedance of the matching layer

A

an intermediate value between the transducer element and tissue

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9
Q

The ability to display moving structures in real time is termed

A

Temporal resolution

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10
Q

What is the material of the transducer that reduces the number of cycles produced in a pulse

A

Backing or damping material

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11
Q

If the sector width is increased by a factor of 2, what happens to the frame rate?

A

Decreases by a factor of 2

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12
Q

The sonographer is most likely to miss something changing quickly in time when

A

Using five focal zones

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13
Q

What are the three aspects of imaging resolution?

A

Detail
Contrast
Temporal

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14
Q

What is the cause of poor elevation resolution?

A

Too large of a beam width in the elevation plane

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15
Q

Where should the focal zone be located for the best lateral resolution?

A

At or just deep to the reflectors to be resolved

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16
Q

What is elevation resolution?

A

The ability to accurately differentiate between two structures in the slice-thickness plane

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17
Q

How can radial resolution of a transducer be maximized?

A

By using the thickest possible damping layer during transducer contruction

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18
Q

What is the best angular resolution

A

At the natural focus

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19
Q

What are the major limiting factors of temporal resolution?

A

Depth
Sweep angle
Line density
Pulse repetition frequency

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20
Q

What is the main disadvantage of continuous (Pedof) transducers?

A

Depth ambiguity

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21
Q

What does the term phased excitation mean

A

The electrical impulse to each element in the crystal array is excited at a slightly different time, resulting in a summated wave that has a wave front with varied direction and focal depth

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22
Q

____________ transducers do not utilize electronic steering

A

Mechanical sector

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23
Q

What is the shape of the footprint produced by a curved sequential array transducer?

A

Smaller convex near field and larger convex far field

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24
Q

In a linear array transducer, what function utilizes electronic steering

A

Color doppler

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25
Q

Which type transducer can produce a vector or trapezoid shaped image

A

Linear array

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26
Q

How does a linear sequential array transducer produce its characteristic image shape?

A

By sequencing

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27
Q

What is the effect of increasing the thickness of the damping material in transducer design?

A

It acts to decrease the spatial pulse length, increasing bandwidth, resulting in better axial resolution

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28
Q

What is considered a disadvantage of the damping material in a pulsed wave transducer?

A

Decreased sensitivity

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29
Q

What is the purpose of damping material in a pulsed wave transducer?

A

It decreases the spatial pulse length of the pulse, leading to improved axial resolution

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30
Q

What are two things that contribute to the efficient transmission of sound from the transducer into the patient

A

Matching layer
Gel

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31
Q

What part of the transducer provides protection from electric shock and reduces the effects of electrical interference

A

Transducer housing

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32
Q

What is the formula for the quality factor

A

operating frequency/bandwidth

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33
Q

What is constructive interference?

A

It occurs when in phase waves meet; the amplitude of the two waves are added to form one large wave

34
Q

What happens to the signal strength of an ultrasound wave during constructive interference?

A

It increases

35
Q

What type of interference pattern will result in the resultant wave having an amplitude of 0?

A

Out of phase, destructive interference

36
Q

How is the piezoelectric property instilled in a man-made crystal material?

A

The crystal is heated to 328 to 365 degrees C in the presence of a magnetic field and then cooled

37
Q

Coupling medium is applied to the transducer-tissue boundary to

A

Increase transmission of the sound wave

38
Q

Arrays are operated in two ways, called

A

Sequencing
Phasing

39
Q

The transducer element converts _________to ________ and vice versa

A

electricity; ultrasound

40
Q

The transducer has an impedance ______ times that of tissue

A

20

41
Q

The linear image consist of _________ scan lines

A

verticle

42
Q

Another name for the Fresnel Zone is

A

The near zone

43
Q

In a single-element transducer, additional beams not included in the ultrasound beam are called

A

side lobes

44
Q

Lateral resolution is equal to

A

Beam width

45
Q

The useful frequency range for most diagnostic applications is

A

2-20 MHz

46
Q

Factors that determine axial resolution

A

number of cycles in the pulse and wavelength

47
Q

What is the purpose of the matching layer?

A

Reduces reflection of ultrasound at the element

48
Q

What principle states that some materials produce a voltage when deformed by an applied pressure

A

Piezoelectric principle

49
Q

Electric ___________ applied to the transducer are converted to ultrasound

A

voltages

50
Q

Sequenced, phased, and vector are types of

A

Operations

51
Q

_____________ resolution relates more directly to transducers

A

Detail

52
Q

The critical temperature an ultrasound transducer cannot exceed is called

A

the curie point

53
Q

______________ is attached to the rear face of the transducer element

A

Damping

54
Q

Ultrasound transducers operate according to

A

The piezoelectric principle

55
Q

Shortening the pulses in diagnostic ultrasound broadens the

A

bandwidth

56
Q

Which image format would be similar to that of convex array except that the footprint is smaller?

A

Vector

57
Q

Partial - volume artifact is also called

A

section thickness artifact

58
Q

The near zone length is determined by the size and the ____________ ___________ of the element

A

operating frequency

59
Q

Intravascular imaging generally utilizes a frequency range

A

up to 50 MHz

60
Q

Linear and convex are types of ___________ arrays

A

assembly

61
Q

Increasing the transducer frequency _______________ the maximum imaging depth

A

decreases

62
Q

The purpose of the coupling medium is to

A

facilitate passage of ultrasound into human tissue

63
Q

Invasive transducers utilize ___________ wavelengths

A

smaller

64
Q

Without compensation the ultrasound transducer would cause about __________ of the emitted intensity to be reflected at the skin boundary

A

80%

65
Q

In the curved array, the pulses travel

A

out in different directions

66
Q

Electronic scanning is performed by

A

array transducers

67
Q

Phasing can

A

focus the beam
improve the image quality
steer the beam

68
Q

The dimension perpendicular to the scan plane is called the

A

section thickness

69
Q

Arrays have additional beams resulting from their multi-element structure called

A

Grating lobes

70
Q

___________ is a combination of linear and phased array operations

A

Vector

71
Q

With phasing, the reception beam is _________________ and dynamically ___________

A

steered; focused

72
Q

If the aperture increases, the near zone length

A

increases

73
Q

What is axial resolution

A

the minimum separation necessary to resolve reflectors along the scan line

74
Q

The distance from the transducer to the center of the focal region is called the

A

focal length

75
Q

What determines the beam width at the focus

A

Aperture, focal length, and wavelength

76
Q

What is achieved within the Fresnel zone?

A

Focusing of the sound beam

77
Q

Improvements in Principle 2 virtual beam forming include reduced section thickness, which improves_________________ ______________.

A

Elevational resolution

78
Q

Continuous wave transducers have ____________ ___________ because energy is not lost to damping material

A

Higher efficiencies

79
Q

Axial resolution is often normally __________________ than lateral resolution

A

better

80
Q

Focusing in the section thickness plane reduces

A

section thickness artifact

81
Q

Various formulations of ____________ ____________ ____________ are commonly used in modern day transducers

A

lead zirconate titanate

82
Q

Beam width can be reduced by focusing to improve

A

lateral resolution

Physics Vocabulary (6 decks)

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