##### Chapter 3 Transducers - Review

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1

A transducer converts one form of ______________ to another.

Energy

2

Ultrasound transducers convert ________________ energy into ____________ energy, and vise versa

Electric, ultrasounf

3

Ultrasound transducers operate on the ______________ principle.

Piezoelectric

4

Single-element transducers are in the form of ____________.

Disks

5

The ___________ of a transducer element changes when voltage is applied to its faces.

Thickness

6

The term transducer is used to refer to a transducer __________ or to a transducer ______________.

Element, assembly

7

A transducer _________________ is part of a transducer _________________.

Element, assembly

8

An electrical voltage pulse, when applied to a transducer, produces an ultrasound _____________ of a _____________ that is equal to that of the voltage pulse.

Pulse, frequency

9

The resonance frequency of an element is determined by by its ______________.

Thickness

10

Operating frequency ______________ as transducer element thickness is increased.

Decreases

11

The addition of damping material reduces the number of ___________ in the pulse, thus improving ___________ __________. It increases ______________.

Cycles, axial resolution, bandwidth

12

Damping material reduces the _____________ of the transducer and _______________ _______________. It increases _______________.

Efficiency, sensitivity

13

Ultrasound transducers typically generate pulses of ___________ or _____________ cycles.

Two, three

14

For a particular transducer element material, if a thickness of .4 mm yields an operating frequency of 5 MHz, the thickness required for an operating frequency of 10 MHz is ________________ mm.

.2 mm

.4 mm / 2= .2 mm

15

Which of the following transducer frequencies would have the thinnest element?

A) 2 MHz
B) 3 MHz
C) 5 MHz
D) 7 MHz
E) 10 MHz

E) 10 MHz

16

The matching layer on the transducer surface reduces _________ caused by _____________.

reflection

17

A coupling agent on the skin surface eliminates reflection caused by _______________.

air

18

True or False?

Damping lengthens the pulse.

False

19

True or False?

Damping increases efficiency.

False

20

The damping layer is in front or back of the element.

Back

21

The matching layer is in front or back of the element.

Front

22

The matching layer has ___________ impedance

intermediate

23

Elements in linear arrays are in the form of _____________.

rectangles

24

Transducer assemblies are also called ___________.

A) transducers
B) probes
C) scanheads
D) scan converters
E) skinheads
F) more than one of the above

F) more than one of the above

A) transducers
B) probes
C) scanheads

25

Operating frequency is also called ________.

resonance frequency

26

Mixtures of a piezoelectric ceramic and a non-piezoelectric polymer are called _______________.

composites

27

To operate a transducer at more than one frequency requires ______________ _____________.

broad bandwidth

28

It is practical to attempt to operate a 5-MHz transducer with a bandwidth of 1 MHz at 6 MHz?

No

these frequencies are outside the bandwidth (4.5 to 5.5 MHz)

29

It is practical to attempt to operate a 5-MHz transducer with a bandwidth of 2.5 at 3 and 7 MHz?

No

these frequencies are outside the 2.5-MHz bandwidth (3.75 to 6.25 MHz)

30

A beam is divided into two regions, called the _______ zone and the ____________ zone.

Near, far

31

The dividing point between the two regions is at a distance from the transducer equal to ___________ _______ length.

Near zone

32

Transducer size is also called _______________.

aperture

33

Near zone length increases with increasing source __________ and ______________.

aperture, frequency

34

Which transducer element has the longest near zone?

A) 6 mm, 5 MHz
B) 6 mm, 7 MHz
C) 8 mm, 7 MHz

C) 8 mm, 7 MHz

35

A higher frequency transducer produces a ____________ near-zone length.

longer

36

A smaller frequency transducer produces a ____________ near-zone length.

shorter

37

True or False?

A transducer with the near-zone length of 10 cm can be focused at 12 cm.

false

can focus only in the near zone

38

Which of the following transducers can focus at 6 cm?

A) 5 MHz, near-zone length of 5 cm
B) 4 MHz, near-zone length of 6 cm
C) 4 MHz, near-zone length of 10 cm
D) B and C
E) none of the above

C) 4 MHz, near-zone length of 10 cm

39

Sound may be focused by using a ____________.

A) curved element
B) lens
C) phased array
D) more than one of the above.

D) more than one of the above.

A) curved element
B) lens
C) phased array

40

True or False?

Focusing reduces the beam diameter at all distances from the transducer

False

41

The distance from a transducer to the location of the narrowest beam width produced by a focused transducer is called ______________.

focal length

42

Transducer arrays are transducer assemblies with several transducer _______________.

elements

43

Linear arrays scan beams by _____________ element groups.

sequencing

44

A phased linear array with a single line of elements can focus in ________________ dimensions.

One

the lateral dimensions

45

Focusing in section thickness can be accomplished with _________ elements of a _______.

curved, lens

46

Electronic focusing in section thickness requires multiple rows of ___________.

elements

47

Match the following

A) Linear array
B) Phased array
C) Convex array

1) Voltage pulses are applied in succession to groups of elements across the face of a transducer

2) Voltage pulses are applied to most or all elements as a group, but with small time differences

A) Linear array - 1) Voltage pulses are applied in succession to groups of elements across the face of a transducer

B) Phased array- 2) Voltage pulses are applied to most or all elements as a group, but with small time differences

C) Convex array - 1) Voltage pulses are applied in succession to groups of elements across the face of a transducer

48

If the elements of a phased array are pulsed in rapid succession from right to left, the resulting beam is ___________.

A) steered right
B) steered left
C) focused

B) steered left

49

If the elements of a phased array are pulsed in rapid succession from outside in, the resulting beam is ___________.

A) steered right
B) steered left
C) focused

C) focused

50

_____________ and _______________ describe how arrays are constructed.

A) linear
B) phased
C) sequenced
D) vector
E) convex

A) linear
E) convex

51

____________, ___________, and ____________ describe how arrays are operated.

A) linear
B) phased
C) sequenced
D) vector
E) convex

B) phased
C) sequenced
D) vector

52

Shorter time delays between elements fired from outside in results in ____________ curvature in the emitted pulse and a _____________ focus.

A) no, weak
B) less, shallower
C) less, deeper
D) greater, shallower
E) greater, deeper

C) less, deeper

53

A rectangular image is a result of linear scanning of the beam. This means that pulses travel in ___________ _______________ direction from _____________ starting points across the transducer face.

The same, different

54

A sector image is a result of sector steering of the beam. This means that pulses travel in ___________ directions from a common _____________ at the transducer face.

different, origin

55

In ______________ and ____________ arrays, pulses travel out in different directions from different starting points on the transducer face.

convex, vector

56

Axial resolution is the minimum reflector separation required along the direction of the ___________ ___________ to produce separate ________________.

sound travel, echoes

57

Axial resolution depends directly on ___________ __________ ____________.

spatial pulse length

58

True or False?

Smaller axial resolution is better.

True

59

If there are three cycles of a 1 -mm wavelength in a pulse, the axial resolution is ___________ mm.

1.5 mm

SPL = 1 mm * 3 cycles = 3 mm
3 mm / 2 = 1.5 mm

60

For Pulse traveling through soft tissue in which the frequency is 3 MHz and there are four cycles per pulse, the axial resolution is ___________mm.

1 mm

Λ = 1.540 / 3 = .531 mm
SPL = .531 * 4 = 2.05
RL = 2.05 / 2 = 1.02

61

If there are two cycles per pulse, the axial resolution is equal to the ____________. At 5 MHz in soft tissue, this is _____________mm.

wavelength, .3 mm

Λ = 1.540 / 5 = .308 mm
SPL = .308 * 2 = .616
RL = .616 / 2 = .308

62

Doubling the frequency causes axial resolution to be ________.

halved

63

Doubling the number of cycles per pulse causes axial resolution to be ________________.

Doubled

64

True or False?

When studying an obese subject, a higher frequency likely will required

False

65

True or False?

If better resolution is desired, a lower frequency will help.

False

66

If frequencies less than __________ MHz are used, axial resolution is not sufficient.

2 Mhz

67

If frequencies higher than __________ MHz are used, penetration is not sufficient.

15 Mhz

68

Increasing frequency improves resolution because ___________ is reduced, thus reducing ____________ ___________ ___________.

wavelength, Spatial pulse length

69

Increasing frequency decreases penetration because _________ is increased.

attenuation

70

Lateral resolution is the minimum ___________ between two reflectors at the same depth such that when a beam is scanned across them, two separate __________ are produced.

separation, echoes

71

Lateral resolution is equal to __________ ____________ in the scan plane.

beam width

72

Lateral resolution does not depend on _____________.

A) frequency
B) aperture
C) phasing
D) depth
E) dampening

E) dampening

73

True or False?

For an aperture of a given size, increasing frequency improves lateral resolution.

True

74

True or False?

Lateral resolution varies with distance from the transducer.

True

75

True or False?

For a given frequency, a smaller aperture always yields improved lateral resolution.

False

in general - only true near transducer

76

Lateral resolution is determined by:

A) dampening
B) frequency
C) aperture
D) number of cycles in the pulse
E) distance from the transducer
F) focusing

B) frequency
C) aperture
E) distance from the transducer
F) focusing

77

Match the following transducer assembly parts with the functions:

A) Cable
B) Dampening material
C) Piezoelectric element
D) Matching layer

1) Reduces reflection at transducer surface
2) Converts voltage pulses to sound pulses
3) Reduce pulse duration
4) Converts voltage pulses

A) Cable - 4) Converts voltage pulses

B) Dampening material - 3) Reduce pulse duration

C) Piezoelectric element - 2) Converts voltage pulses to sound pulses

D) Matching layer - 1) Reduces reflection at transducer surface

78

Which of the following improve sound transmission from the transducer element into the tissue?

A) Matching layer
B) Doppler effect
C) dampening material
D) coupling medium
E) refraction

A) Matching layer
D) coupling medium

79

A 5 -MHz unfocused transducer with an element thickness of .4 mm, an element width of 13 mm, and a near-zone length of 14 cm produces two-cycle pulses. Determine the following

A) Operating frequency if thickness is reduced to .2 mm: ___________ MHz

B) Axial resolution in the case of a: __________ mm

C) Depth at which lateral resolution is best: ________ cm

D) Lateral resolution at 14 cm: _________ mm

E) Lateral resolution at 28 cm: _________ mm

F) This transducer can be focused at depths less than __________ cm.

A) 10
B) .15
C) 14
D) 6.5
E) 13
F) 14

A) If thick halved, fo is doubled 2 * 5 MHz = 10 MHz

B) SPL = nc/f
(2 * 1540 m/s) / 10 MHz
3080 m/s / 10 MHz = .308
Axial = ½ * SPL = .5 * .308 = .154

D) RL = beam width = Focus width
½ e.width
.5 * 13 = 6.5

80

Lateral resolution is improved by _____________.

A) dampening
B) pulsing
C) focusing
D) matching
E) absorbing

C) focusing

81

For an unfocused transducer, the best lateral resolution (minimum beam width) is ____________ the transducer width. This value of lateral resolution is found at a distance from the transducer face that is equal to the _________________ ______________ length.

half, near-zone

82

For a focused transducer, the best lateral resolution (minimum beam width) is found in the __________ region.

focal

83

An unfocused 3.5-MHz, 13-mm transducer will yield a minimum beam width (best lateral resolution) of ________ mm.

6.5 mm

½ * 13 mm

84

An unfocused 3.5-MHz, 13-mm transducer produces three-cycle pulses. The axial resolution in soft tissue is ___________ mm.

.7 mm

SPL = nc/f
(3 * 1.540) / 3.5
4.62 / 3.5 = 1.320
½ SPL = 1.320 * .5 = .66

85

True or False?

An unfocused 3.5-MHz, 13-mm transducer produces three-cycle pulses, will yield a minimum beam width (best lateral resolution) of 6.5 mm. The axial resolution in soft tissue is .7 mm.

Axial resolution is better than lateral resolution.

True

86

True or False?

Axial resolution is often not as good as lateral resolution in diagnostic ultrasound.

False

87

The two resolutions may be comparable in the ____________ region of a strongly focused beam.

Focal

88

True or False?

Beam diameter may be reduced in the near zone by focusing

True

89

True or False?

Beam diameter may be reduced in the far zone by focusing.

False

90

Match each transducer characteristic with the sound beam characteristic it determines

A) Element thickness
B) Element width
C) Element shape
D) damping

1) Axial resolution
2) lateral resolution
3) operating frequency

A) Element thickness - 1) Axial resolution, 2) lateral resolution, 3) operating frequency

B) Element width - 2) lateral resolution

C) Element shape - 2) lateral resolution

D) Damping - 1) Axial resolution

91

The principle on which ultrasound transducers operate is the _______________.

A) Doppler effect
B) Acousto-optic effect
C) Acousto-electric effect
D) cause and effect
E) piezoelectric effect

E) piezoelectric effect

92

Which of the following is not decreased by damping

A) refraction
B) pulse duration
C) spatial pulse length
D) efficiency
E) sensitivity

A) refraction

93

Which three things determine beam diameter for a disk transducer?

A) pulse duration
B) frequency
C) aperture
D) distance from disk face
E) efficiency

B) frequency
C) aperture
D) distance from disk face

94

True or False?

A two-cycle pulse of 5-MHz ultrasound produces separate echoes from reflectors in soft tissue separated by 1 mm.

True

axial resolution .3 mm

SPL = (nc)/f
(2 * 1540) / 5
3080 / 5 = .616
½ SPL = .5 * .616 = .308 mm
1 mm > .3 mm

95

The lower and upper limits of the frequency range useful in diagnostic ultrasound are determined by ___________ and ___________ requirements respectively.

resolution, penetration

96

The range of frequencies useful for most applications of diagnostic ultrasound is ____________ to __________ MHz

2, 15

97

Because diagnostic ultrasound is usually two or three cycles long, axial resolution is usually equal to ___________ to __________ wavelength

1, 1.5

98

What is the axial resolution A-B?

A - An image of a set of six rods in a test obeject. They are separated by 5, 4, 3, 2, and 1 mm from top to bottom. This scan was made using a transducer that produces 3.5-MHz ultrasound. The first three rods have been separated, whereas the images of the last three rods have merged. This image also shows small reverberation echoes behind each rod.

B - The same rods image with a 5-MHz transducer. Higher-frequency transducer produce shorter pulse lengths and therefore provide improved axial resolution.

3 mm, 2 mm

99

At what depth is the best lateral resolution C?

Beam diameter for 6-mm, 5-MHz transducer

C - A focused beam. This is an ultrasound image of a beam profile test object containing a thin vertical scattering layer down the center. Scanning this object generates a picture of the beam (pulse width at all depths) In this case, the focus occurs at a depth of about 4 cm ( this image has a total depth of 15 cm) Depth markers (in 1-cm increments) are indicated on the left edge

4 cm

100

Match the transducer type with the display formats

A) Linear array - 1
B) convex array - 4
C) phased array - 3
D) vector array - 5
E) phased linear array - 2

A) Linear array - 1
B) convex array - 4
C) phased array - 3
D) vector array - 5
E) phased linear array - 2

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