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Breast Ultrasound Exam ARRT > Breast Ultrasound Physics > Flashcards

Breast Ultrasound Physics Flashcards

1
Q

Breast ultrasound systems require_____________ and ____________ for improved visualization

A

Spatial resolution

Contrast resolution

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2
Q

The linear array transducer contains ___________ ______________

A

Piezoelectric crystals

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3
Q

How does the linear array transducer activate piezoelectric crystals? What shape is the beam?

A

Crystals are activated in groups and sequenced to produce parallel scan lines to create a uniform image from near to far fields.

A rectangular image is created

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4
Q

Name 6 benefits of linear array transducer style for breast ultrasound

A

⏺Rectangular shape allows skin contact and even compression
⏺Beam is more perpendicular to the skin and chest wall
⏺Wide beam for near field structures
⏺Uniform image field
⏺Less beam divergence
⏺Narrow focusing improve needle visualization

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5
Q

Why is high frequency needed for breast imaging

A

To better visualize superficial structures of the breast

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6
Q

Key advantage of high frequency transducers

A

Improved axial resolution

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7
Q

Axial resolution

A

Ability to differentiate 2 closely spaced each interfaces lying in the direction of the sound beam (think of beam as an axis)

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8
Q

Most breast ultrasound systems use _______ MHz or higher

A

10

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9
Q

Disadvantage of using high frequency transducers

A

Reduced penetration due to rapid attenuation of the beam

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10
Q

A ___________ ___________ transducer produces a sound beam with more than 1 frequency

A

Pulsed-wave

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11
Q

Bandwidth and pulse length are _________ proportional

A

Inversely

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12
Q

Frequency and resolution are ________ related

A

Directly

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13
Q

Advantages of broad bandwidth transducers

A

Transducer can operate at different frequencies to optimize resolution and penetration

Can perform Doppler at a lower frequency when needed

Allows harmonic imaging with lower frequencies and reception of sound beam at higher frequency

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14
Q

The ultrasound beam of a transducer is ___ dimensional

A

3

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15
Q

A narrower sound beam improves

A

Resolution

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16
Q

A narrow sound beam intensifies sound energy at the

A

Focus

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17
Q

________ resolution is best where the sound beam is narrowest

A

Lateral resolution

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18
Q

Lateral resolution

A

The ability to resolve 2 closely spaced objects lying side-by-side in a direction perpendicular to the sound beam

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19
Q

6 Transducer features suitable for high resolution breast imaging

A 
Linear array format
High frequency
Broad bandwidth
Variable electronic focusing
Near-field focusing
Thin slice thickness
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20
Q

Variable electronic focusing

A

Focusing that occurs along the long axis of a linear array transducer

Focusing can be altered at various distances by altering or delaying the timing of excitation of the transducer elements

Multiple transmit foci create a narrow receive beam

Lateral resolution is improved

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21
Q

Fixed elevation focusing

A

Focusing along the short axis of the transducer

Fixed focal depth at 1.5cm

Corresponds to slice thickness

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22
Q

A shallow elevation focus of a linear array transducer with high frequency improves _________ and reduces ____________

A

Near-field resolution

Slice thickness

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23
Q

High-frequency, broad bandwidth transducers provide excellent _______________ and ______________

A

Spatial and contrast resolution

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24
Q

What is another word for spatial resolution. What is the definition?

A

Detail.

The ultrasound system’s ability to depict small anatomic structures at their correct location

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25
Q

___________ ___________is measured in 3 planes. What are they?

A

Spatial resolution

Axial plane
Lateral plane
Elevation plane

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26
Q

Define the 3 planes

A

Axial - along the direction of the sound beam (parallel to beam)

Lateral - perpendicular to the sound beam

Elevation - perpendicular to sound mean, also corresponds to slice thickness

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27
Q

Spatial resolution is affected by which transducer characteristics?

A

Frequency
Focusing
Scan lines

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28
Q

Axial resolution improves with ___________, ___________, __________

A

High frequency transducers Shorter pulse lengths

Broader bandwidth transducers

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29
Q

Contrast resolution

A

The ability of the ultrasound equipment to distinguish anatomic structures based on variations in echo brightness.

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30
Q

Factors that affect contrast resolution

A 
Acoustic imprudence mismatch
Transducer frequency
Dynamic range
Signal-to-noise ratio
Artifacts
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31
Q

Example of what happens when a system has poor contrast resolution

A

2 closely spaced objects may appear as one

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32
Q

Temporal resolution

A

The ability of a system to distinguish moving objects (not affected I breast ultrasound because of limited depth of field)

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33
Q

_________ resolution is limited by the frame rate

A

Temporal

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34
Q

Equipment parameters that need to be optimized for a breast US exam

A 
Output power 
Overall gain
Time Gain Compensation (TGC)
Dynamic range
Focal zone placement
Frame rate
Image scale
Monitor brightness and contrast
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35
Q

Brightness is affected by

A

Output power
Overall gain
TGC
Dynamic range

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36
Q

Output power affects the ______

of the transmit voltage and the intensity of the __________ __________.

A

Amplitude

Transmitted beam

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37
Q

The output power controls the excitation voltage that drives the _________ ____________

A

Transducer crystals

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38
Q

How output power affects the quality of US exam

A 
⬆️Output power➡️
⬆️Voltage to crystals➡️
⬆️Oscillation of crystals➡️
⬆️Amplitude/intensity of sound beam➡️
⬆️Ultrasound energy to patient
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39
Q

A higher intensity sound beam produces a _______ ________ ___ _______ _________

A

Signal to noise ratio

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40
Q

The _______ ________ control provides uniform amplification of all echo signals returning to the transducer

A

Overall gain

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41
Q

Why is overall gain important?

A

Since returning echo signals are weakened due to attenuation, the returning signals need to be electronically amplified

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42
Q

Overall gain is the same as ______ _______

A

Receiver gain

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43
Q

⬆️overall/receiver gain ➡️

⬆️_________ and vice versa

A

Brightness

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44
Q

Gain and dynamic range settings should be set so that fat displays a _____ ________ ________ shade

A

Medium level gray

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45
Q

Excessive settings of the gain and dynamic range will introduce ______ _______ of breast tissues and cysts

A

False echoes

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46
Q

How would too low a setting of overall gain and dynamic range affect the appearance of solid masses

A

They would reduce the detection of real echoes with solid masses, making them appear cystic

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47
Q

The ________ control allows selective amp location of weaker signal from deep structures to compensate for attenuation loss

A

TGC (Time Gain Compensation)

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48
Q

TGC control makes the image more

A

Uniform

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49
Q

TGC should be adjusted so that echoes from similar structures are displayed with the same ________ or ________

A

Brightness

Amplitude

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50
Q

Dynamic range definition:

A

The ratio of the smallest to the largest strength level that a system can handle without distortion.

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51
Q

Increasing the dynamic range allows for a greater range of____________ to be displayed, thus increasing the __________.

A

Echoes

Grayscale

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52
Q

⬆️ dynamic range➡️

⬆️___________

A

Grayscale

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53
Q

Decreasing dynamic range leads to an image with greater _________, showing less differentiation of grayscale patterns

A

Contrast

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54
Q

Electronic focusing narrows the __________ along the ________ axis of the transducer.

A

Beam width

Long

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55
Q

A conventional linear array transducer does not allow manual adjustment of the _____ ______ _______

A

Fixed short axis plane

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56
Q

Incorrect focusing can cause ______ _______ from volume averaging

A

False echoes

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57
Q

How does using multiple focal zones affect breast ultrasound imaging? How many zones produce adequate focusing?

A

Multiple focal zones improve lesion clarity

3

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58
Q

Frame rate definition

A

The number of images displayed/second

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59
Q

Frame rate affects _______ resolution

A

Temporal

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60
Q

Which ultrasound functions or adjustments affects the frame rate

A

Changing

  1. Number of focal zones
  2. Image depth
  3. Frame size
  4. Doppler
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61
Q

Using multiple focal zones ⬆ or ⬇️ the frame rate

A

⬇️

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62
Q

How can a sonography the compensate for a slow frame rate?

A

Decrease depth

Decrease image size

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63
Q

Why would enlarging the field of view be helpful

A

To visualize margins and internal featured of a mass

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64
Q

What are the 3 Doppler modes used in breast imaging

A
  1. Pulsed-waved Spectral Doppler
  2. Color flow Doppler
  3. Power Doppler
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65
Q

Pulsed-waved Spectral Doppler

A

⏺Blood flow is sampled at a selected depth within a vessel segment
⏺Spectral waveform displays changes in flow velocity and direction of moving red blood cells
⏺Waveform differentiates arterial vs. venous flow
⏺Waveform differentiates turbulent vs. laminar (sliding)
⏺Measurement of peak, mean, and minimal velocities

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66
Q

Color Flow Dopplar

A

Superimposed display of blood flow over anatomic image
Identification of vessel blood flow
Demonstration of blood flow turbulence
Mosaic of colors with high velocities

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67
Q

Power Doppler

A

⏺Estimates total amplitude and intensity
⏺Less angle dependent
⏺Better sensitivity to low flow states
⏺Better demonstration of tortuous vessels
⏺No info on flow direction, velocity or turbulence
⏺More susceptible to motion artifacts

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68
Q

Which types of Doppler are more angle dependent? Which is not?

A

Angle dependent

  1. Pulse-waved
  2. Color Doppler

Not angle dependent
1. Power Doppler

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69
Q

Doppler settings should be optimized for _________ flow states

A

Low flow

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70
Q

T or F

Intravenous contrast is commonly used in breast ultrasound.

A

F

FDA does not approve intravenous contrast agents for breast ultrasound

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71
Q

Panoramic views are also known as

A

Extended Field of View

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72
Q

How does harmonic imaging work

A

The US system transmits at a given frequency

73
Q

In general terms, how does ultrasound work

A

Conventional ultrasound imaging sends out a burst of sound and listens for that burst to echo off of structures in the body. The time it takes for the echo to return is proportional to the distance the sound wave traveled.

74
Q

What are the benefits of harmonic imaging

A

Harmonic imaging has a number of potential clinical benefits including

  1. improved spatial resolution to permit visualization of smaller objects
  2. improved contrast resolution to improve demonstration of increasingly subtle differences in grayscale.
75
Q

How does harmonic US imaging work as compared to conventional US?

A

With conventional imaging, the ultrasound system transmits and receives a sound pulse of a specific frequency The difference between the transmitted and returned signal is that the returned signal is less intense, losing strength as it passes through tissue.
With Harmonic Imaging, the signal returned by the tissue includes not only the transmitted frequency, but also signals of other
frequencies – most notably, the “harmonic” frequency, which is twice the
fundamental frequency. Once this combined fundamental/harmonic signal is received, the ultrasound system separates out the two components and then processes the harmonic signal alone.

76
Q

Harmonic imaging reduces _______. How?

A

Artifacts. False echoes are eliminated.

77
Q

Why is harmonics used?

A
  1. False echoes are eliminated in cysts and masses.

2. Margins better visualized

78
Q

What is spatial compound imaging

A

New type of transducer transmits multiple scan planes at different angles, producing a better, compounded image with more defined margins of masses, subareolar structures with reduced artifacts

79
Q

Other technologies

A

Convex Linear - transducer can electronically chafe to trapezoid shape for wider field of view

3D/4D Imaging/ Multiplanar/Multi slice - can be viewed in multiple planes showing enhanced images of speculation

Elasticity Imaging - shows stiffness

80
Q

What is a spectrum of frequencies?

A

Bandwidth

81
Q

Dopplar and harmonic imaging are performed using ⬆️or ⬇️ frequencies

A

⬇️

82
Q

Artifacts are caused by:

A
  1. Atypical sound interaction with body
  2. Equipment malfunction
  3. Interfering signals
  4. Image processing
  5. Operator error
  6. Patient motion
83
Q

Reverberation artifacts court when

A

The beam encounters 2 strong parallel reflectors

84
Q

Reverberation artifacts occur when the sound beam is _______ to the interface

A

Perpendicular

85
Q

a sound beam that reflects back and forth between an object and the transducer causes ________

A

Reverberation artifacts

86
Q

________ is a common cause of false echoes within a cystic structure

A

Reverberation

87
Q

If present, where does the reverberation artifact appear in a cystic structure

A

Anterior portion

88
Q

Similar to reverberation, this type of artifact appears as multiple small parallel echo bands.

A

Comet tail artifacts

89
Q

What can cause comet tail artifacts

A

Imaging of surgical clips and biopsy needles

90
Q

Another type of Reverberation artifact, produced by gas bubbles

A

Ring down artifact

91
Q

During which exam do ring down artifacts occur

A

Vacuum assisted biopsies

92
Q

What are 3 types of attenuation artifacts

A
  1. Enhancement (aka posterior enhancement
  2. Shadowing
  3. Edge shadowing
93
Q

What causes shadowing

A

Sound beam travels through weak reflectors such as a cyst. The beam travel easily through these structures and the is more sound energy left after exiting the structure to “sonify” distal structures. These will appear bright or “enhanced”

94
Q

What causes shadowing

A

Sound beam that travels through a strong reflector or absorber will be absorbed and sound beam intensity is decreased and shapes appear behind the structure

95
Q

The greater the attenuation, the _________ the shadowing

A

Greater

96
Q

____________ represents a change in direction of the sound beam as it passes from one medium to another.

A

Refraction

97
Q

What are 2 types of refraction

A
  1. Edge shadowing

2. Critical angle shadowing

98
Q

When does refraction occur

A
  1. When there’s significant difference in propagation speeds at an acoustic interface
  2. When sound beam is not perpendicular to the interface
99
Q

When does refractive edge shadowing occur

A

When sound beam bends and loss of energy occurs causing a shadow. Sound beam is refracted and loses energy when it transmits across the interface on lateral edges of structure

100
Q

When does critical edge shadowing occur

A

Oblique incidence with Cooper’s ligaments

101
Q

________ represents incorrect registration of the depth of a structure on the image when sound velocity through the structure is different from the assumed velocity of ________ for soft tissue

A

Propagation speed error

1540 m/s

102
Q

If propagation speed error occurs when imaging a cyst, what happens. Why? What happens with a solid mass?

A

The location of the cyst is registered more superficially because the sound beam travels thru cyst more quickly than thru soft tissue, thus the signal returning to the transducer is faster. This causes a time/distance error.

With a solid mass the system registers the location at a deeper level

103
Q

What is axial resolution artifacts and how do they appear

A

Failure to resolve 2 separate reflectors in the direction of the sound beam

2 objects appear as 1

104
Q

Transducer frequency and special pulse length is related to which type of artifact

A

Axial resolution artifact

105
Q

What is the type of artifact where there is a failure to resolve 2 separate reflectors perpendicular to the sound beam

A

Lateral resolution artifact

106
Q

Lateral resolution artifact is related to ______ and _____

A

Beam width and focusing

107
Q

What are side lobes and grating lobes

A

Side lobes are weaker sound beams emitted from a single element transducer directed to regions other than the main beam axis

Grating lobes are extra sound beams emitted from a multi element transducer

108
Q

How do side lobes and grating lobes artifacts occur

A

Reflections from these these beams in other areas than the main beam cause echoes that degrade the image

109
Q

Where do side lobes appear and with when are they the most obvious

A

In the near field.

When imaging cysts

110
Q

What is slice thickness artifact

A

Fill-in effect related to the fact that beam width is not razor thin

111
Q

What is speckle/noise and what causes it

A

Granular false echoes caused by scattered beams that produce weak echoes. Appears as bright or dark spots

112
Q

What system function is speckle/noise caused by

A

Excessive gain and electrical interference

113
Q

What image quality does speckle and noise have an effect on

A

Detail and contrast resolution

114
Q

What is B mode and M mode in ultrasound imaging

A

Brightness mode

Motion mode

115
Q

What system function can cause Doppler artifacts

A

Excessive gain and low filter settings

116
Q

A high filter setting will _____ detection of low velocity blood flow

A

Reduce

117
Q

What is PRF

A

The number of pulses (or send/listen cycles) sent out by the transducer

118
Q

________is an imaging error which occurs due to under-sampling. The ultrasound system is trying to image an event that is occurring ________ than the rate we are sampling it, and as a result the system is uncertain about the direction of the signal and displays this as heading in the opposite direction.

A

Aliasing

Faster

119
Q

How are filters used in Doppler imaging

A

All types of Doppler ultrasound equipment employ filters to cut out the high amplitude, low-frequency Doppler signals resulting from tissue movement, for instance due to vessel wall motion. Filter frequency can usually be altered by the user, for example, to exclude frequencies below 50, 100 or 200 Hz. This filter frequency limits the minimum flow velocities that can be measured.

120
Q

What will happen if Doppler angle is perpendicular to flow

A

No flow will be detected

121
Q

Too low a Doppler filter setting can cause ______

A

Aliasing

122
Q

Aliasing makes it look like blood flow is traveling _________

A

In the opposite direction

123
Q

How to reduce Cooper’s ligament shadowing

A

Increase transducer pressure

Angle transducer do that scan is more perpendicular to the ligaments

124
Q

What happens to PZT crystals when they are stimulated by electric current

A

Vibrate

125
Q

__________ __________ change size when stimulated by electrical current

A

Change size

126
Q

What is the unit used for measuring pressure

A

Pascals

127
Q

What is the definition of period

A

The time it takes to complete one cycle

128
Q

______ is the distance of one cycle

A

Wavelength

129
Q

________ is the number of cycles over a specific period of time

A

Frequency

130
Q

Ultrasound is measured in_____ ______ _________

A

Cycles per second

131
Q

Breast imaging is ______ to ________ MHz

A

10-17

132
Q

The speed of sound is _________

A

1540 m/s

133
Q

What type of ultrasound is it when crystals are pulsing and receiving

A

Pulse wave

134
Q

What does PRF stand for and what is it

A

Pulse Repetition Frequency

The PRF is the number of pulses (send and listen cycles) of ultrasound sent out by the transducer per second.

135
Q

Increased depth increases/decreases PRF

A

Decrease

136
Q

Increased transducer frequency allows more/less depth and increased/decreased resolution

A

Less depth

Increased resolution

137
Q

Decreased transducer frequency allows more/less depth and increased/decreased resolution

A

More depth

Decreased resolution

138
Q

What is redirection of a portion of the beam back to the transducer called

A

Reflection

139
Q

What is the relationship between amplitude, power and intensity

A

Direct - as on increased the others increase

140
Q

What is the wave equation

A

The wave equation: product of wavelength (λ) and frequency (f) represents the velocity (c) of the sound wave.
Wavelength X frequency = velocity
c = λ f

141
Q

Triangle depiction of relationship between wavelength (λ), frequency (f), and velocity (c)

A

c

        λ                f

λ X f = c

142
Q

Speed of sound wave through different mediums

A 
Velocity (m/sec)
Air          330
Fat	       1450
Water	1480
Soft tissue	1540
Kidney	1560
Blood	1570
Muscle	1580
Bone	4080
143
Q

How are power and amplitude related

A

Power = amplitude squared

144
Q

Increased stiffness of medium allows increased/decreased speed

A

Increased

145
Q

What is the bending of the beam called

A

Refraction

146
Q

Edge shadowing is a type of

A

Refraction

147
Q

Attenuation is measured in ________

A

Decibels

148
Q

Sound waves strengthen/weaken as it propagates

A

Weaken

149
Q

The propagation of sound waves is called

A

Attenuation

150
Q

What does TCG stand for

A

Time gain compensation

151
Q

What does TCG compensate for

A

Attenuation

152
Q

What does gain adjust

A

Overall brightness

153
Q

The ultrasound system needs to set fat to

A

Medium gray

154
Q

The beam is narrowest at the

A

Focal point

155
Q

The beam is relatively narrow at the

A

Focal zone

156
Q

Where is the near zone

A

From the crystals to the focal point

157
Q

What is the far zone

A

The focus to the deeper tissue

158
Q

The ability to distinguish 2 structures that are parallel to the beam

A

Axial resolution

159
Q

The ability to distinguish 2 structures that are side by side

A

Lateral resolution

160
Q

What is doubling the fundamental frequency called

A

Harmonics

161
Q

Color Doppler detects

A

Direction

162
Q

Power Doppler detects

A

Flow

163
Q

What is the purpose of the backing layer of the transducer

A

Reduces ringing

164
Q

Where is the backing layer located

A

Behind the crystal

165
Q

How are the crystals positioned in a linear array transducer

A

In a straight line

166
Q

Where is the dead zone

A

Area close to transducer showing artifacts

167
Q

T/F - Never autoclave or sterilize with heat a transducer

A

T

168
Q

What is the problem when the screen shows a blacked out area fro top to bottom

A

Broken crystal

169
Q

What is a testing object that contains tissue mimicking material that simulates properties of tissue, such as solidity, cystic, axils and lateral resolution

A

Phantom

170
Q

A shorter pulse length results in wider/narrower bandwidth

A

Wider

171
Q

Optimal resolution and penetration results from a transducer that is able to operate at different _________

A

Frequencies

172
Q

The ability to resolve 2 closely spaced objects lying side-by-side in a direction perpendicular to the sound beam

A

Lateral resolution

173
Q

What type of focusing is used by a linear array transducer

A

Variable electronic focusing

174
Q

Focusing along the short axis of the transducer

A

Focusing along the short axis of the transducer

175
Q

Which transducer is rectangular shaped and allows skin contact and even compression

A

Linear array

176
Q

Which transducer produces less beam divergence

A

Linear array

177
Q

Which transducer has narrow focusing and improves needle visualization

A

Linear array

178
Q

Ability to differentiate 2 closely spaced each interfaces lying in the direction of the sound beam (think of beam as an axis)

A

Axial resolution

179
Q

The ability to resolve 2 closely spaced objects lying side-by-side in a direction perpendicular to the sound beam

A

Lateral resolution

Breast Ultrasound Exam ARRT (4 decks)

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