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Ultrasound Physics Review > Part 3: Ultrasound Transducers > Flashcards

Part 3: Ultrasound Transducers Flashcards

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1
Q

You are using a 5 MHz, 40 mm linear array transducer to image a structure. What is the width of the image?

A

40 mm

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2
Q

You have selected a wide-bandwidth transducer with multiple transmit frequencies to perform a sonographic examination. Which transmit frequency should you select for maximum penetration?
a. 3.0 MHz
b. 3.5 MHz
c. 4.0 MHz
d. 5.0 MHz
e. Penetration is not affected by frequency

A

a

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3
Q

Which probe would provide the best axial resolution to measure the thickness of a small structure?
a. 5 MHz linear array
b. 7 MHz linear array
c. 10 MHz linear array
d. 5 MHz curved array
e. 5 MHz phased array

A

c

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4
Q

You are performing a sonographic exam with a wide-bandwidth transducer. The advantage you obtain with this transducer compared to a narrow-band transducer is:

A

improved axial resolution

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5
Q

Which transducer would provide the longest near-zone length?
a. 10 MHz, 6 mm diameter aperture
b. 10 MHz, 5 mm diameter aperture
c. 10 MHz, 4 mm diameter aperture
d. 10 MHz, 3 mm diameter aperture
e. 10 MHz, 2 mm diameter aperature

A

a

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6
Q

The location where the sound beam reaches its narrowest diameter is known as the:

A

focal zone

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7
Q

Which of the following transducers creates a rectangular image shape?
a. linear array
b. phased array
c. annular array
d. curved array
e. b and c only

A

a

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8
Q

The term for a transducer that has an array of rectangular elements arranged in a straight line is:

A

linear array

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9
Q

For a linear array transducer consisting of a single row of elements, what method is most used to focus the beam in the elevational direction?

A

mechanical focusing

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10
Q

What type of transducer could you choose to produce a beam that is symmetric about the beam axis?

A

annular array

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11
Q

The ultrasound system in your lab has a transducer with a small footprint. This kind of transducer has the following disadvantage:
a. it cannot be focused in the elevational direction
b. the field of view in the far field is only one-quarter the diameter of the transducer
c. The near-field lateral resolution is poor
d. The Q value is very high
e. Resolution is degraded at large distances

A

e

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12
Q

Which of the following will NOT improve axial resolution?
a. increased damping
b. increased transducer frequency
c. increased bandwidth
d. decreased pulse length
e. increased focusing

A

e

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13
Q

You are reviewing an ultrasound image that has a sector display format that narrows to a point at the transducer surface. What kind of transducer was most likely used to acquire this image?

A

phased array

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14
Q

What is the point of maximum intensity in a sound beam?

A

focal point

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15
Q

What is the main advantage of using a 1.5D or multirow array transducer?
a. narrow slice thickness over a large part of the scanned volume
b. increased penetration
c. improved axial resolution
d. faster frame rates
e. smaller footprint

A

a

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16
Q

What benefit would you obtain by choosing a transducer having a large diameter compared to one having a small diameter?
a. it can focus at greater depths
b. it increases the frequency
c. It increases the beam diameter
d. A and c
e. all of the above

A

a

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17
Q

You are using a linear array transducer with four transmit focal zones. How many pulses are required on each scan line to create the image?

A

four

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18
Q

What type of transducer has the same measurement for elevational and lateral resolution?

A

annular array

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19
Q

With a 1D linear array, where in the out-of-plane dimension is the dimension of the sound beam the narrowest?
a. it is at the point of mechanical focusing
b. it is at the point of electronic focusing
c. The beam is the same width throughout the image
d. it is in the far field
e. it is always located at a depth equal to one-half of the transducer aperture

A

a

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20
Q

Another name for axial resolution is:

A

range resolution

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21
Q

Dynamic apodization is a method employed to:

A

reduce side lobes

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22
Q

What statement is most accurate regarding resolution with a standard one-dimensional linear array transducer?
a. Axial resolution is the worst measure of resolution with this type of transducer
b. lateral resolution is the worst measure of resolution with this type of transducer
c. elevational resolution is the worst measure of resolution with this type of transducer
d. isotropic spatial resolution is achieved
e. temporal resolution is the worst measure of resolution with this type of transducer

A

c

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23
Q

During the course of a sonographic exam, you notice lateral splaying of the echoes in the far field. What can you do to improve the image?
a. use the maximum acoustic power
b. Use the lowest line density setting
c. increase the number of transmit focal zones and optimize their location
d. decrease the scanning depth
e. .decrease the scan line density

A

c

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24
Q

You suspect that a bright spot on the B-mode image is a calcification, but a posterior acoustic shadow is not present. How can you best optimize your system to demonstrate a shadow distal to the calcification?

A

increase the transducer frequency

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25
Q

When an electric signal is applied to a piezoelectric element, what happens to the element?

A

it expands and contracts

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26
Q

Which statement is NOT true regarding lateral resolution?
a. It is equal to beam width
b. it is improved by focusing
c. It is defined as the minimum separation required to resolve two structures perpendicular to the beam axis
d. it is also known as azimuthal resolution
e. It remains constant throughout scanning depth

A

e

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26
Q

You are scanning a phantom containing multiple rows of identical 5 mm spherical fluid-filled structures embedded in a tissue-mimicking material. What type of resolution is best evaluated with this phantom?

A

elevational

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27
Q

Which type of transducer should you select to produce the narrowest slice thickness throughout the image plane?
a. a 1.5D multirow array
b. A phased array with a small footprint
c. A tightly curved curvilinear array
d. a mechanical sector
e. a mechanically rocked 3D transducer

A

a

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28
Q

The matching layer between the piezoelectric element and the tissue is designed to:
a. insulate the patient from the hot element
b. reduce the vibration of the transducer
c. reduce the acoustic impedance mismatch between the element and tissue
d. increase the reflection coefficient at the transducer-skin interface
e. decrease spatial pulse length

A

c

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29
Q

If you choose a lower frequency transducer to image a highly attenuating structure, what tradeoff are you making?

A

decreased spatial resolution for improved penetration

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30
Q

You have been asked to perform an ultrasound study of a structure located about 3 cm below the skin surface. Which transducer frequency range would be most appropriate for this study?
a. 2-5 MHz
b. 4-8 MHz
c. 8-10 MHz
d. 10-12 MHz
e. 5 MHz

A

d

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31
Q

Dynamic receive focusing uses:
a. mechanical means to focus the beam
b. time delays to excite array elements
c. variable number of elements to form the transmitted beam
d. Time delays before echo signals from array elements are combined
e. all of the above

A

d

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32
Q

Varying the excitation voltage to each element in the group used to form the ultrasound pulse is called:

A

apodization

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33
Q

Which of the following describes a phased array transducer?
a. electronically focused in two dimensions and mechanically steered
b. electronically focused along the length of the array, mechanically focused along the elevational dimension (width), and electronically steered
c. Electronically focused along the elevational dimension of the array, mechanically focused along the length of the array, and unsteered
d. mechanically focused in two dimensions and mechanically steered
e. electronically focused along the width of the array, mechanically focused along the length of the array, and mechanically steered

A

b

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34
Q

Resolution of two structures at different depths along the path of the sound beam is termed:

A

axial resolution

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35
Q

Which transducer has the same distance between the scan lines in both the near and far fields?

A

linear array

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36
Q

Which of the following minimizes the degree to which beam width varies with depth?
a. apodization
b. dynamic aperture
c. coprocessing
d. rectification
e. frame averaging (persistence)

A

b

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37
Q

The sound beam can be focused by all of the following EXCEPT:
a. acoustic mirror
b. acoustic lens
c. curved crystal
d. matching layer
e. electronic phasing

A

d

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38
Q

What type of focusing decreases the frame rate?

A

multiple transmit focusing

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39
Q

For a single transducer to offer multiple frequency selections for scanning, it must have:

A

wide bandwidth

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40
Q

The ability to distinguish between adjacent structures that produce echoes of similar amplitude is termed:

A

contrast resolution

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41
Q

When you increase the scan line density in the B-mode image, you improve:

A

lateral resolution

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42
Q

The conversion of an incident pressure wave to an electric signal is the:

A

piezoelectric effect

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43
Q

Electronic focusing in the transmit mode is accomplished using:

A

time delays to excite transducer elements

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44
Q

What is the purpose of subdicing?

A

to reduce grating lobes

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45
Q

What transducer component is designed to control ringing of the piezoelectric element?

A

backing material

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46
Q

The transducer you are using is an array assembly. What is an advantage of this type of transducer?

A

transducer arrays enable electronic focusing and steering

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47
Q

What is an advantage of single-crystal or pure-wave crystal transducers?
a. wide bandwidth
b. lower frequencies at higher resolution
c. absence of aliasing with pulsed Doppler
d. Higher frame rates
e. Greater steering angles

A

a

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48
Q

Increasing the number of transmit focal zones to improve spatial resolution involves the following tradeoff:
a. lateral resolution vs. axial resolution
b. lateral resolution vs. temporal resolution
c. spatial resolution vs. contrast resolution
d. contrast resolution vs. frame rate
e. elevational resolution vs. frame rate

A

b

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49
Q

Which of the following is NOT associated with a low-Q transducer?
a. wide bandwidth
b. multifrequency selection
c. long pulse length
d. diagnostic pulsed-wave ultrasound
e. loss of most energy in first few vibrations

A

c

50
Q

The ability to distinguish similar structures with varying gray scales is termed:

A

contrast resolution

51
Q

If the number of cycles in the transmitted pulse is increased:
a. axial resolution is degraded
b. lateral resolution is degraded
c. spatial pulse length becomes shorter
d. rate of attenuation is increased
e. penetration is decreased

A

a

52
Q

If the frame rate is too slow for adequate temporal resolution, what action could you take to improve frame rate?
a. reduce the number of transmit focal zones
b. increase the scan line density
c. increase the scanning depth
d. decrease the dynamic range
e. reduce the transmit frequency

A

a

53
Q

You have been requested to image a superficial mass and to adjust your equipment to optimize spatial resolution. Spatial resolution consists of:
a. contrast and temporal resolution
b. temporal and axial resolution
c. axial and contrast resolution
d. contrast and lateral resolution
e. lateral and axial resolution

A

e

54
Q

What is the purpose of the radiofrequency shield that is placed around the crystal and backing material of the ultrasound probe?

A

it reduces electromagnetic interference

55
Q

What type of resolution is affected most by pulse duration?

A

axial resolution

56
Q

With a standard one-dimensional linear array transducer, what type of resolution is affected most by electronic focusing and dynamic aperture?

A

lateral resolution

57
Q

What type of resolution is most affected by the mechanical focus on a linear array transducer?

A

elevational resolution

58
Q

The spectrum of frequencies emitted by a pulsed-wave transducer is known as the:

A

bandwidth

59
Q

What is the optimal thickness for the matching layer?

A

one-fourth of a wavelength

60
Q

A method for improving frame rates with multizone focusing is:

A

parallel processing

61
Q

Which of the following best describes the f-number?
a. focal length divided by the aperture
b. aperture multiplied by the number of elements in the transducer
c. number of transducer elements divided by the Fraunhofer zone
d. beam width 1 cm from the transducer surface
e. focal length multiplied by the number of elements in the transducer

A

a

62
Q

If you wish to use an array transducer that allows you to control transmit focal depth, what type would you select?
a. linear array
b. convex array
c. phased array
d. annular array
e. any of the above

A

e

63
Q

If you wish to acquire a sonogram with the largest possible field of view both in the near field and at depth, what type of transducer would be most preferable?

A

curved array

64
Q

A commonly used material in modern transducer elements is:

A

lead zirconate titanate

65
Q

You are using a linear array transducer to evaluate the thyroid gland. For standard B-mode imaging, this transducer most likely produces pulses of how many cycles?

A

1-3

66
Q

What is the purpose of applying multiple matching layers to the transducer face?

A

Multiple matching layers result in increased transducer bandwidth

67
Q

For a nonfocused transducer, the region between the transducer element and the point at which the sound beam is narrowest is called the:

A

Near-zone length

68
Q

Axial resolution is determined chiefly by:

A

pulse duration

69
Q

What is the main advantage of using an intracavitary probe compared to a standard transducer?
a. The intracavitary probe has superior focusing capabilities because of the increased radius of the curved probe face
b. The intracavitary probe uses a lower frequency that provides superior penetration and closer inspection of the pelvic structures
c. The intracavitary probe does not demonstrate side lobes or grating lobes because of the close spacing and curvature of the elements
d. since the intracavitary probe is closer to the area of interest, a higher-frequency transducer can be used, resulting in superior spatial resolution
e. Bioeffects are greatly reduced with the intracavitary probe because of its frequency range and power output

A

d

70
Q

What defines the best axial resolution that can be obtained with a given transducer?

A

spatial pulse length divided by 2

71
Q

What term describes the ability of an imaging device to separate closely spaced objects?

A

resolution

72
Q

What happens when pressure is applied to a piezoelectric crystal?

A

it emits an electric signal

73
Q

The interpreting physician has asked you to use a standoff pad to evaluate a superficial mass. What is the main advantage the standoff pad provides to improve the image?
a. the standoff pad has an acoustic impedance closer to that of the crystal, which results in improved transmission of sound into the body
b. the standoff pad has a propagation speed equal to twice that of soft tissue, which decreases the wavelength of the sound beam
c. the standoff pad increases the distance between the transducer and the mass, making it more likely that the mass will be located close to the elevational focus of the sound beam
d. the standoff pad creates a soft interference between the crystal and tissue, increasing constructive interference and reducing scattering
e. The standoff pad eliminates artifacts associated with reverberation, side lobes, and grating lobes

A

c

74
Q

What array transducer fires all of the elements for each acoustic scan line, using small time delays to steer the beam?

A

phased array

75
Q

If you are using a transducer with poor elevational resolution, which of the following problems are you most likely to encounter?
a. inability to resolve two structures that lie close together and parallel to the path of the beam
b. inability to resolve two structures that lie close together, perpendicular to the path of the beam, and parallel to the long axis of the transducer
c. inability to penetrate through dense tissue
d. inability to clearly demonstrate small cystic structures
e. inability to demonstrate rapidly moving structures accurately

A

d

76
Q

What can you do to achieve a higher frame rate?
a. decrease the number of focal zones
b. decrease the line density
c. decrease the sector width
d. all of the above
e. none of the above

A

d

77
Q

What can you do to improve contrast resolution in the ultrasound image?
a. increase the sector width
b. decrease the number of focal zones
c. use a 2D or matrix array transducer
d. use a phased array transducer
e. use a curved array transducer

A

c

78
Q

increasing which of the following will result in improved axial resolution?
a. pulse duration
b. pulse length
c. frequency
d. period
e. focusing

A

c

79
Q

Which represents the best measure of resolution for modern-day ultrasound scanners?
a. contrast
b. axial
c. elevational
d. temporal
e. lateral

A

b

80
Q

Which of the following transducers produces side lobes or grating lobes?
a. mechanical sector
b. linear sequential array
c. phased array
d. convex array
e. all of the above

A

e

81
Q

Which transducer type is best suited to vascular imaging?

A

linear array

82
Q

Which of the following transducer types is best suited to cardiac imaging?
a. mechanical sector
b. linear array
c. phased array
d. convex array
e. annular array

A

c

83
Q

Which of the following can NOT be evaluated with a tissue-equivalent phantom?
a. axial resolution
b. lateral resolution
c. contrast resolution
d. slice thickness
e. temporal resolution

A

e

84
Q

Increasing the frequency on a multifrequency transducer from 3.5 MHz to 5.0 MHz will:
a. increase the sound propagation speed
b. increase the pulse length
c. increase penetration
d. decrease the pulse repetition frequency
e. decrease the wavelength

A

e

85
Q

You notice a loss of detail in the lateral dimension of the ultrasound image. What can you do to improve this?

A

increase the scan line density

86
Q

You are performing an exam on a patient with highly attenuating tissue. Which of the following solutions would be most likely to improve penetration through the tissue?
a. decrease dynamic range
b. decrease near field TGC
c. choose a lower-frequency transducer
d. increase the scan line density
e. change the gray-scale map

A

c

87
Q

you can reduce beam width to improve spatial resolution in the image by which of the following?
a. focusing
b. decreasing aperture
c. decreasing transducer diameter
d. decreasing transducer width
e. increasing backing material

A

a

88
Q

Which transducer frequency would have the thinnest crystal?
a. one with a 15 MHz center frequency
b. one with a 10 MHz center frequency
c. One with a 7 MHz center frequency
d. One with a 5 MHz center frequency
e. all would have the same crystal thickness

A

a

89
Q

What component of a pulsed-wave transducer helps to reduce the spatial pulse length and improve axial resolution?

A

backing material

90
Q

Which transducer would have a lower line density in the far field compared to the near field?
a. linear array
b. curved array
c. tightly curved array
d. phased array
e. b, c, and d

A

e

91
Q

What transducer component reduces reflection at the transducer/skin interface?

A

matching layer

92
Q

Axial resolution is improved with:
a. increased bandwidth
b. shorter pulse length
c. shorter wavelength
d. b and c
e. all of the above

A

e

93
Q

What is a side lobe?

A

sound beam emitted from the transducer that travels in a different direction from the main beam

94
Q

What is the purpose of curving the transducer elements or applying a lens over the elements?

A

to provide focusing in the out-of-plane (elevational) direction

95
Q

What best describes the difference between the ultrasound frequencies used for Doppler and for B-mode imaging with a given transducer?
a. The frequency for Doppler is usually lower than for imaging
b. The frequency for Doppler is usually higher than for imaging
c. The transmit pulse for Doppler has a greater bandwidth compared to the bandwidth for imaging
d. The frequency for Doppler and for B-mode imaging must be identical for a given transducer
e. The frequency for Doppler is usually double that for B-mode imaging.

A

a

96
Q

In order to focus a sound beam relatively far away from the transducer, it is advantageous to:
a. increase the thickness of the element
b. increase the diameter of the element
c. decrease the width of the element
d. decrease the frequency of the element
e. increase the curvature of the element

A

b

97
Q

Which factor LEAST influences axial resolution?
a. damping
b. beam width
c. frequency
d. pulse duration
e. pulse frequency

A

b

98
Q

Spatial pulse length is equal to:

A

the wavelength times the number of cycles in the pulse

99
Q

What is the disadvantage of using multiple transmit focal zones?
a. decreased lateral resolution
b. decreased temporal resolution
c. decreased elevational resolution
d. decreased axial resolution
e. all of the above

A

b

100
Q

What is the advantage of using multiple transmit focal zones?
a. increased lateral resolution
b. increased temporal resolution
c. increased elevational resolution
d. increased axial resolution
e. all of the above

A

a

101
Q

What factor LEAST influences lateral resolution?
a. frequency
b. focus depth
c. beam width
d. transducer diameter
e. damping

A

e

102
Q

Which transducer will exhibit the LEAST amount of volume averaging?
a. mechanical single element
b. 1.5D or multirow array
c. linear array
d. phased array
e. convex array

A

b

103
Q

The ability to differentiate between two regions at different different depths having similar echogenicitiy

A

contrast resolution

104
Q

Imaging frame rate decreases when you:
a. decrease frequency
b. increase dynamic range
c. increase frame averaging (persistence)
d. Increase sector width
e. decrease the number of transmit focal zones

A

d

105
Q

The optimal transducer technology for cardiac scanning is:

A

phased array

106
Q

Axial resolution improves with increasing ______.

A

frequency

107
Q

Axial resolution is improved with _______ transducers.

A

wide-bandwidth

108
Q

The near zone length increases with increasing _____.

A

aperture

109
Q

The size of the source of the sound

A

aperture

110
Q

the z-axis is also known as the:

A

out-of-plane dimension

111
Q

the axis that runs across the width of the transducer

A

z-axis

112
Q

Focusing in the ____ is accomplished by mechanical means- either a lens or curvature of the element.

A

z-axis

113
Q

a round transducer in which the elements are arranged concentrically.

A

annular array

114
Q

this transducer creates a cone shaped beam that is symmetric in all dimensions.

A

annular array

115
Q

With small-footprint transducers, the beam diverges very rapidly in the far field, resulting in poor ______.

A

lateral resolution

116
Q

Focusing improves lateral resolution because it_

A

decreases beam width

117
Q

At the _____, the beam width is the narrowest.

A

focal point

118
Q

An ____ transducer produces a beam that is symmetric about the beam axis. Therefore, its lateral resolution is equal to its elevational resolution.

A

annular

119
Q

_______ with linear array transducers is determined by the point of mechanical focusing along the width of the array.

A

slice-thickness

120
Q

The out-of-plane dimension is ______ to the imaging plane.

A

perpendicular

121
Q

Variation in excitation strength to the array elements

A

apodization

122
Q

_______ is the poorest measure of resolution for array probes.

A

elevational resolution

123
Q
A

Ultrasound Physics Review (3 decks)

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