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PHYSICS > Chapter 3 Kremkau > Flashcards

Chapter 3 Kremkau Flashcards

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1
Q

size of a transducer element (for a single-element transducer) or a group of elements (for an array)

A

aperture

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2
Q

nonuniform driving of elements in an array to reduce grating lobes

A

apodization

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3
Q

a transducer assembly containing several piezoelectric elements

A

array

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4
Q

in the direction of the transducer axis

A

axial

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5
Q

the minimum reflector separation along the sound path that is required to produce separate echoes

A

axial resolution

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6
Q

region containing continuous wave sound; region through which a sound pulse propagates

A

beam

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7
Q

capactitative micromachined ultrasonic transducer that contains miniature elements that are comprised of two electrically conducting layers facing each other; one of which is fixed and the other of which is a flexible membrane

A

CMUT

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8
Q

combination of a piezoelectric ceramic and a nonpiezoelectric polymer

A

composite

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9
Q

curved linear array

A

convex array

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10
Q

element

A

crystal

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11
Q

temperature at which an element material loses its piezoelectric properties

A

curie point

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12
Q

material attached to the rear face of a transducer element to reduce pulse duration; the process of pulse duration reduction

A

damping

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13
Q

the ability to image fine detail and to distinguish closely spaced reflectors

A

detail resolution

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14
Q

a thin, flat, circular object

A

disk

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15
Q

aperture that increases with increasing focal length (to maintain constant focal width)

A

dynamic aperture

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16
Q

continuously variable reception focusing that follows the increasing depth of the transmitted pulse as it travels

A

dynamic focusing

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17
Q

the piezoelectric component of a transducer assembly

A

element

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18
Q

the detail resolution in the direction perpendicular to the scan plane. It is equal to the section thickness artifact.

A

elevational resolution

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19
Q

the region of a sound beam in which the beam diameter increases as the distance from the transducer increases; also called the far field

A

far zone

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20
Q

distance from a focused transducer to the center of a focal region or to the location of the spatial peak intensity

A

focal length

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21
Q

region of minimum beam diameter and area

A

focal region

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22
Q

length of the focal region

A

focal zone

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23
Q

the concentration of the sound beam into a smaller beam area than would exist otherwise

A

focus

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24
Q

additional weaker beams of sound traveling out in directions different from the primary beam as a result of the multielement structure of transducer arrays

A

grating lobes

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25
Q

perpendicular to the direction of sound travel

A

lateral

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26
Q

minimum reflector separation perpendicular to the sound path that is required to produce separate echoes

A

lateral resolution

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27
Q

a ceramic piezoelectric material

A

lead zirconate titanate

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28
Q

a curved material that focuses a sound or beam

A

lens

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29
Q

adjectival form of line

A

linear

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30
Q

array made of rectangular elements arranged in a straight line

A

linear array

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31
Q

linear array operated by applying voltage pulses to all elements, but with small time differences (phasing) to direct ultrasound pulses out in various directions

A

linear phased array

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32
Q

linear array operated by applying voltage pulses to groups of elements sequentially

A

linear sequenced array

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33
Q

material attached to the front face of a transducer element to reduce the reflections at the transducer surface

A

matching layer

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34
Q

the narrowing of a sound beam that occurs with an unfocused flat transducer element

A

natural focus

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35
Q

the region of a sound beam in which the beam diameter decreases as the distance from the transducer increases; also called near field

A

near zone

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36
Q

preferred (maximum efficiency) frequency of operation of a transducer

A

operating frequency

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37
Q

an array that steers and focuses the beam electronically (with short time delays)

A

phased array

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38
Q

linear sequenced array with phased focusing added; linear sequenced array with phased steering of pulses to produce a parallelogram-shaped display

A

phased linear array

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39
Q

conversion of pressure to electric voltage

A

piezoelectricity

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40
Q

transducer assembly

A

probe

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41
Q

the ability to distinguish echoes in terms of space, time, or strength (called detail, temporal, and contrast resolutions

A

resolution

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42
Q

operating frequency

A

resonance frequency

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43
Q

transducer assembly

A

scanhead

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44
Q

a geometric figure bounded by two radii and the arc of the circle included between them

A

sector

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45
Q

ability of an imaging system to detect weak echoes

A

sensitivity

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46
Q

weaker beams of sound traveling out from a single element in directions different from those of the primary beam

A

side lobes

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47
Q

the region of a medium that contains virtually all of the sound produced by a transducer

A

sound beam

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48
Q

an emitter of ultrasound; transducer

A

source

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49
Q

a device that converts energy from one form to another

A

transducer

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50
Q

transducer elements with damping and matching materials assembled in a case

A

transducer assembly

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51
Q

a device that converts electric energy to ultrasound energy, and vice versa

A

ultrasound transducer

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52
Q

linear sequenced array that emits pulses from different starting points and (by phasing) in different directions

A

vector array

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53
Q

Composites have lower impedance and improved _______, ________, _________.

A

bandwidth
sensitivity
resolution

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54
Q

sonographic imaging produces a __-__ cycle ultrasound pulse

A

2-3

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55
Q

Doppler ultrasound is typically __-__ cycles

A

5-30

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56
Q

typical thickness of diagnostic ultrasound elements

A

.2-1mm thick

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57
Q

Fo = c / 2 x thickness

A

operating frequency

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58
Q

provides electronic control of location of focus

A

phasing

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59
Q

______, ________, and ______ determine the beam width at the focus.

A

aperture, focal length, wavelength

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60
Q

imaging resolution has three aspects:

A

detail, contrast, temporal

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61
Q

AR = 1/2SPL

A

axial resolution

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62
Q

decrease in wavelength = _______ frequency

A

increased

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63
Q

increase in frequency, _______ penetration

A

reduces

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64
Q

attenuation increases while frequency ________.

A

increases

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65
Q

Lateral resolution is equal to

A

beam width

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66
Q

Beam width can be reduced by focusing to improve _______.

A

lateral resolution

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67
Q

Types of array construction

A

linear and covex

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68
Q

types of array scanning operations

A

sequenced, phased, vector

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69
Q

thinner elements operate at ____ frequencies

A

higher

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70
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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71
Q

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

A

one quarter the wavelength

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72
Q

Focusing of the sound beam is achieved within

A

the freesnel zone

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73
Q

utilizing multiple focal zone simultaneously increases image detail resolution and degrades

A

temporal resolution

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74
Q

What happens to the near zone length if the aperture decreases?

A

decreases

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75
Q

In the linear array transducer the pulses travel in

A

straight lines

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76
Q

What is the impendance of the matching layer

A

an intermediate value between the transducer element and tissue

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77
Q

The ability to display moving structures in real time is termed

A

temportal resolution

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78
Q

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

A

backing or damping material

79
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

80
Q

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

A

using five focal zones

81
Q

What are the three aspects of imaging resolution?

A

detail
contrast
temporal

82
Q

What is the cause of poor elevation resolution?

A

too large of a beam width in the elevation plane

83
Q

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

A

at or just deep to the reflectors to be resolved

84
Q

What is elevational resolution?

A

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

85
Q

How can radial resolution of a transducer be maximized?

A

By using the thickest possible damping layer during transducer construction

86
Q

what is the best angular resolution

A

at the natural focus

87
Q

What are the major limiting factors of temporal resolution?

A

depth
sweep angle
line density
pulse repetition frequency

88
Q

what is the main disadvantage of continuous (pedoff) transducers?

A

depth ambiguity

89
Q

What does the term phased excitation mean

A

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

90
Q

____ transducers do not utilitize electronic steering

A

mechanical sector

91
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

92
Q

In a linear array transducer, what function utilizes electronic steering

A

color Doppler

93
Q

Which type of transducer can produce a vector or trapezoid shaped image

A

linear array

94
Q

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

A

by sequencing

95
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

96
Q

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

A

decreased sensitivity

97
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

98
Q

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

A

matching layer
gel

99
Q

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

A

transducer housing

100
Q

What is the formula for the quality factor?

A

operating frequency/bandwidth

101
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

102
Q

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

A

It increases

103
Q

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

A

out of phase, destructive interference

104
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

105
Q

Coupling medium is applied to the transducer tissue boundary to

A

increase transmission of the sound wave

106
Q

Arrays are operated in two ways called

A

sequencing
phasing

107
Q

The transducer element converts ____ to ____ and vice versa

A

electricity; ultrasound

108
Q

The transducer has an impedance ____ times that of tissue

A

20

109
Q

The linear image consist of ____ scan lines

A

vertical

110
Q

Another name for the Fresnel zeon

A

the near zone

111
Q

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

A

side lobes

112
Q

Lateral resolution is equal to

A

Beam width

113
Q

The useful frequency range for most diagnostic applications is

A

2-20 MHz

114
Q

Factors that determine axial resolution

A

number of cycles in the pulse and wavelength

115
Q

What is the purpose of the matching layer?

A

Reduces reflection of ultrasound at the element

116
Q

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

A

Piezoelectric principle

117
Q

Electric ____ applied to the transducer are converted to ultrasound

A

voltages

118
Q

Sequenced, phased, and vector are types of

A

operations

119
Q

_____ resolution relates more directly to transducers

A

detail

120
Q

The critical temperature an ultrasound transducer cannot exceed is called

A

the curie point

121
Q

_____ is attached to the rear face of the transducer element

A

Damping

122
Q

Ultrasound transducers operating according to

A

the piezoelectric principle

123
Q

Shortening the pulses in diagnostic ultrasound

A

broadens the bandwidth

124
Q

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

A

vector

125
Q

Partial-volume artifact is also called

A

section thickness artifact

126
Q

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

A

operating frequency

127
Q

Intravascular imaging generally utilizes a frequency range

A

up to 50 MHz

128
Q

Linear and convex are types of ____ arrays

A

assembly

129
Q

Increasing the transducer frequency _____ the maximum imaging depth

A

decreases

130
Q

The purpose of the coupling medium is to

A

facilitate passage of ultrasound into human tissue

131
Q

Invasive transducers utilize ____ wavelengths

A

smaller

132
Q

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

A

80%

133
Q

In the curved array, the pulses travel

A

out in different directions

134
Q

Electronic scanning is performed by

A

array transducers

135
Q

phasing can

A

focus the beam
improve the image quality
steer the beam

136
Q

The dimension perpendicular to the scan plane is called the

A

section thickness

137
Q

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

A

grating lobes

138
Q

______ is a combination of linear and phased array operations

A

vector

139
Q

With phasing, the reception beam is _____ and dynamically _____

A

steered; focused

140
Q

If the aperture increases, the near zone length

A

increases

141
Q

What is axial resolution?

A

the minimum separation necessary to resolve reflectors along the scan line

142
Q

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

A

focal length

143
Q

What determines the beam width at the focus>

A

aperture, focal length, and wavelength

144
Q

What is achieved within the Fresnel zone?

A

Focusing of the sound beam

145
Q

Improvements in Principle 2 virtual beam forming include reduced section thickness, which improves ______

A

elevational resolution

146
Q

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

A

Higher efficiencies

147
Q

Axial resolution is often normally _____ that lateral resolution

A

better

148
Q

Focusing in the section thickness place reduces

A

section thickness artifact

149
Q

Various formulations of ______ are commonly used in modern day transducers

A

lead zirconate titanate

150
Q

Beam width can be reduced by focusing to improve

A

lateral resolution

151
Q

A transducer converts one form of _____ to another.

A

energy

152
Q

Ultrasound transducers convert _____ energy into ______ energy, and vice versa.

A

electric, ultrasound

153
Q

Ultrasound transducers operate on the _____ principle.

A

piezoelectric

154
Q

Single element transducers are in the form of ______

A

disks

155
Q

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

A

thickness

156
Q

The term transducer is used to refer to a transducer ______ or to a transducer _______.

A

element, assembly

157
Q

A transdcuer _______ is part of a transducer _______.

A

element, assembly

158
Q

An electric voltage pulse, when applied to a transducer, produces an ultrasound _____ of a(n) _______ that is equal to that of the voltage pulse.

A

pulse, frequency

159
Q

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

A

thickness

160
Q

Operating frequency _____ when transducer element thickness is increased

A

decreases

161
Q

The addition of damping material to a transducer reduces the number of _______ in the pulse, thus improving _______. It increases _______.

A

cycles, axial resolution, bandwidth

162
Q

Damping material reduces the ______ of the transducer and ______ of the diagnostic system.

A

efficiency, sensitivity

163
Q

Ultrasound transducers typically generate pulses of ______ or ______ cycles.

A

two, three

164
Q

For a particular transducer element material, if a thickness of 0.4 mm yields an operating frequency of 5 MHz, the thickness required for an operating frequency of 10 MHz is _____ mm.

A

0.2

165
Q

Which of the following transdcuer frequencies would have the thinnest elements?
a. 2 MHz
b. 3 MHz
c. 5 MHz
d. 7 MHz
e. 10 MHz

A

e

166
Q

The matching layer on the transducer surface reduces _____ caused by impedance differences.

A

reflection

167
Q

A coupling medium on the skin surface eliminates reflection caused by ______.

A

air

168
Q

Damping lengthens the pulse.

A

false

169
Q

Damping increases efficiency.

A

false

170
Q

The damping layer is in ____ of the element.

A

back

171
Q

The matching layer is in ____ of the element.

A

front

172
Q

The matching layer has _____ impedance.

A

intermediate

173
Q

Elements in linear arrays are in the form of _______.

A

rectangles

174
Q

Transducer assemblies are also called _____.
a. transducers
b. probes
c. scanheads
d. scan converters
e. more than one of the above

A

e

175
Q

Operating frequency is also called ____.

A

resonance frequency

176
Q

Mixtures of a piezoelectric ceramic and a nonpiezoelectric polymer are called _____.

A

composites

177
Q

To operate a transducer at more than one frequency requires ______.

A

broad bandwidth

178
Q

Is it practical to attempt to operate a 5 MHz transducer with a bandwidth of 1 MHz at 6 MHz.

A

No

179
Q

Is it practical to attempt to operate a 5 MHz transducer with a bandwidth of 2.5 at 3 and 7 MHz.

A

No

180
Q

A focused beam is divided into three regions, called the _______ zone, the _______ zone, and the _______ zone.

A

near, focal, far

181
Q

The region between the transducer and the focal region is the _____ length.

A

near zone

182
Q

Transducer size is also called ____.

A

aperture

183
Q

Near-zone length increases with increasing source _____ and _____.

A

aperture, frequency

184
Q

Which transducer element has the longest near zone?
a. 6mm, 5 MHz
b. 6mm, 7 MHz
c. 8mm, 7 MHz

A

c

185
Q

A higher-frequency transducer produces a ____ near-zone length

A

longer

186
Q

A smaller aperture produces a(n) near-zone length

A

shorter

187
Q

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

A

false

188
Q

Which of the following transducer(s) 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

A

c

189
Q

Sound may be focused by using a ______.
a. curved element
b. lens
c. phased array
d. more than one of the above

A

d

190
Q

Focusing reduces the beam diameter at all distances from the transducer.

A

false

191
Q

The distance from a transducer to the location of the narrowest beam width produced by a focused transducer called focal _____

A

length

192
Q

Transducer arrays are transducer assemblies with several transducer _____

A

elements

193
Q

Linear arrays scan beams by ______ element groups.

A

sequencing

PHYSICS (26 decks)

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