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BUSHBERG PHYSICS > Chapter 14: Ultrasound > Flashcards

Chapter 14: Ultrasound Flashcards

1
Q

A modality that uses Ultrasound Energy and the Acoustic properties of the body to produce an image from stationary and moving tissues.

A

Medical Diagnostic Ultrasound

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2
Q

The type of energy delivered to the tissues of the body when performing Ultrasound.

A

Short Pulse of Mechanical Energy

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3
Q

Discuss the propagation of Sound in Ultrasound.

A

Sound is a mechanical energy that propagates through a CONTINUOUS, elastic medium by COMPRESSION and RAREFRACTION of particles comprising it.

Note:

Rarefraction occurs following Compression event.

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4
Q

Type of wave where energy propagation occurs as a wave front in the direction energy travel:

A

LONGITUDINAL WAVE

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5
Q

This is the distance between compressions or rarefractions, or between any two points that repeat on the sinusoidal wave of pressure amplitude.

A

WAVELENGTH of Ultrasound Energy

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6
Q

This refers to the number of times the wave oscillates through one cycle each second.

A

FREQUENCY

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7
Q

Frequency Sound waves of INFRASOUND

A

Less than 15 cycles per second (Hz)

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8
Q

Range of sound waves comprising the AUDIBLE ACOUSTIC SPECTRUM

A

15Hz to 20 kHz

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9
Q

The frequency range of sound waves for Ultrasound

A

Above 20kHz

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10
Q

This refers to the time duration of one wave cycle.

A

PERIOD

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11
Q

This refers to the distance traveled by the wave per unit time.

=wavelength/period

A

SPEED OF SOUND

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12
Q

Average speed of sound of soft tissues:

A

1540 m/s

154,000cm/s or 1.5mm/us

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13
Q

Average speed of sound of fatty tissues:

A

1450 m/s

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14
Q

Average speed of sound of air:

A

330 m/s

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15
Q

What is the speed of sound utilized in the medical ultrasound machine in determining the localization of reflectors and creating the acoustic image?

A

1540 m/s

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16
Q

Ultrasound frequencies needed for body parts requiring greater travel distance of sound waves (ABDOMEN):

A

Lower Frequency Ultrasound of 3.5 to 5.0 MHz

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17
Q

Ultrasound frequencies needed for small body parts or organ closed to skin surface (THYROID and BREAST):

A

Higher Frequency Ultrasound of 7.5 to 10 MHz

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18
Q

What is the ultrasound frequency range of most Medical Imaging Applications?

A

2 to 10 MHz

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19
Q

This is defined as the peak maximum or peak minimum value from the average pressure on the medium in the absence of a sound wave.

A

PRESSURE AMPLITUDE

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20
Q

What is the SI unit of Pressure?

A

Pascal (Pa) = Newton/m2

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21
Q

This refers to the Amount of power per unit area (energy per unit).

This is proportional to the square of the pressure amplitude.

A

INTENSITY (I)

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22
Q

What is the unit of Intensity?

The amount of energy per unit time per unit area.

A

Milliwatts/cm2

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23
Q

The relative intensity and pressure levels are described as a logarithmic ratio:

A

DECIBEL (dB)

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24
Q

Discuss the relation of Intensity ratio with the decibels.

A

Intensity ratio > 1.0 = dB values are positive

Intensity ratio < 1.0 = dB values are negative

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25
Q

This occurs between 2 tissue boundaries where there is a difference in the acoustic impedance of adjacent materials.

A

REFLECTION

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26
Q

A conduit of tissue that allows ultrasound transmission through structures such as the lung.

A

ACOUSTIC WINDOW

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27
Q

This gives rise to the differences in transmission and reflection of ultrasound energy.

which is the means of producing image using pulse echo techniques.

A

ACOUSTIC IMPEDANCE

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28
Q

What is the SI unit of Acoustic Impedance?

A

rayl

1 rayl = kg/(m2s)

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29
Q

This described the change in the direction of the transmitted ultrasound energy with nonperpendicular incidence or the beam is not perpendicular to the boundary.

A

REFRACTION

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30
Q

This occurs by reflection or refraction, causes the beam to diffuse in many directions, and gives rise to the characteristic texture and grayscale in the acoustic image.

A

SCATTERING

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31
Q

A smooth boundary between 2 media, where the dimensions of the boundary are much larger than the wavelength of the incident ultrasound energy.

A

SPECULAR REFLECTOR

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32
Q

Discuss echogenicity in relation ro scatter amplitude.

A

HYPERECHOIC - higher scatter amplitude

HYPOECHOIC - lower scatter amplitude

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33
Q

This refers to the loss of acoustic energy with distance traveled or loss of intensity of the ultrasound beam caused by tissue absorption and scattering in the beam or medium.

A

ATTENUATION

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34
Q

The process whereby the acoustic energy is converted to heat energy.

A

ABSORPTION

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35
Q

This refers to the relative intensity loss per centimeter of travel for a given medium.

A

ATTENUATION COEFFICIENT

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36
Q

What is the unit of Attenuation Coefficient?

A

dB/cm

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37
Q

What is the Half Value Layer or Thickness of the Ultrasound?

A

3dB reduction in intensity

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38
Q

This material comprised of one or more ceramic elements with electrochemical properties and peripheral components used to produce and detect Ultrasound.

A

TRANSDUCER

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39
Q

What are the major components of Ultrasound Transducer? (STAMP-BIT)

A 
Sensor Electrodes
Tuning Coil
Acoustic Absorber
Matching Layer
Piezoelectric Material

Backing Block
Insulating Cover
Transducer Housing

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40
Q

This is the functional component of the transducer that converts the electrical energy into mechanical energy.

A

PIEZOELECTRIC MATERIALS

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41
Q

A synthetic piezoelectric ceramic with a compound structure of molecular dipole most often used in Ultrasound Transducer for Medical Imaging Application.

A

Lead-Zirconate-Titanate (PZT)

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42
Q

This structure is layered on the back of the piezoelectric element, absorbs the backward directed ultrasound energy, and attenuates stray ultrasound signals from the housing.

A

DAMPING BLOCK

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43
Q

This provides the interface between the raw transducer element and the tissue.

This minimizes the acoustic impedance differences between the transducer and the patient.

A

MATCHING LAYER

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44
Q

Typically, 128-512 individual rectangular elements comprised of transducer assembly.

A

TRANSDUCER ARRAYS

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45
Q

This is the largest transducer assembly which typically contains 256-512 elements.

A

LINEAR ARRAY TRANSDUCER

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46
Q

This transducer assembly comprised of 64-128 individual elements in a smaller package.

A

PHASED ARRAY TRANSDUCER

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47
Q

This is another method of producing high frequency ultrasound which is made of silicon based electrostatic transducers. The basic element is a capacitor cell with a fixed electrode (backplate) and a free electrode (membrane).

A

CAPACITIVE MICROMACHINED ULTRASONIC TRANSDUCER (CMUT)

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48
Q

What is the principle of operation in CMUT?

A

ELECTROSTATIC TRANSDUCTION
- alternating voltage is applied between membrane and backplate, and the modulation of electrostatic force results in membrane vibration with generation of ultrasound.

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49
Q

What are the 2 distinct beam patterns of Ultrasound?

A
  1. Near Field

2. Far Field

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50
Q

A beam pattern which is adjacent to the transducer and has a slightly converging beam profile out to a distance determined by the geometry and frequency of transducers.

A

NEAR FIELD

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51
Q

Another term for Near Field.

A

FRESNEL ZONE

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52
Q

This describes a large transducer surface as an infinite number of point sources of sound energy where each point is characterized as a Radial Emitter.

A

HUYGENS’ PRINCIPLE

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53
Q

This type of beam pattern has a diverging beam beyond that point.
It is where the beam diverges.

A

FAR FIELD

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54
Q

Another term for Far Field?

A

FRAUNHOFER ZONE

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55
Q

The function of the transducer diameter, the center of operating frequency.

A

FOCAL DISTANCE

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56
Q

A method to rephrase the signals by dynamically introducing electronic delays as function of depth.

A

DYNAMIC RECEIVE FOCUSING

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57
Q

Increases the number of active receiving elements in the array with reflector depth, so that the lateral resolution does not degrade with the depth of propagation.

A

DYNAMIC APERTURE

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58
Q

Unwanted emissions of ultrasound energy directed away from the main pulse, caused by radial expansion and contraction of the transducer element.

A

SIDE LOBES

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59
Q

Results when ultrasound energy is emitted far off axis by multielement arrays.

A

GRATING LOBES

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60
Q

Major factor that limits the spatial resolution and visibility of detail.

A

Volume of Acoustic Pulse

61
Q

3 Components of Spatial Resolution that determines the minimal volume element.

A
  1. Axial Dimension
  2. Lateral Dimension
  3. Elevational (size thickness) Dimension
62
Q

This refers to the ability to discern 2 closely spaced objects in the DIRECTION of the beam.

Equal to 1/2 SPL - Spatial Pulse Length

A

AXIAL RESOLUTION

63
Q

This refers to the number of cycles emitted per pulse by the transducer multiplied by the wavength.

A

Spatial Pulse Length (SPL)

64
Q

Refers to the ability to discern as a separate 2 closely objects PERPENDICULAR to the beam direction.

A

LATERAL RESOLUTION.

65
Q

Another term for Lateral Resolution.

A

AZIMUTHAL RESOLUTION

66
Q

A component of spatial resolution that is perpendicular to the image plane and is dependent on the transducer element width.

A

ELEVATIONAL RESOLUTION

67
Q

Another term for Elevational Resolution.

A

Slice Thickness Dimension

68
Q

This is the weakest measure of resolution for array transducers.

A

SLICE THICKNESS

69
Q

What are the components of the Pulse Echo Approach for Image Information? (BP-RADS)

A

Beam Former
Pulser

Receiver
Amplifier
Display System
Scan Converter/Image Memory

70
Q

Responsible for generating the electronic delays for individual transducer elements.

A

BEAM FORMER

71
Q

This controls the application-specific integrated circuits that provide transmit/receive switches.

A

DIGITAL BEAM FORMER

72
Q

This provides the electrical voltage for exciting the piezoelectric transducer elements and control the output transmit power.

A

PULSER (aka Transmitter)

73
Q

This is synchronized with the Pulser, isolates the high voltage associated with pulsing from the sensitive amplification stages during receive mode.

A

TRANSMIT/RECEIVE SWITCH.

74
Q

The ultrasound pulse created with a short voltage waveform provided by the pulser of the ultrasound system.
This is also known as tye “MAIN BANG”

A

PULSE ECHO OPERATION

75
Q

This refers to the number of times the transducer is pulsed per second.

A

PULSE REPETITION FREQUENCY (PRF)

76
Q

This refers to the time between pulses which is equal to the inverse of PRF

A

PULSE REPETITION PERIOD (PRP)

77
Q

This is determined from the product of the speed of sound and the PRP divided by 2.

A

MAXIMAL RANGE

78
Q

Refers to the ratio of the number of cycles in the pulse to the transducer frequency and is equal to the instantaneous “on” time.

A

PULSE DURATION

79
Q

This accepts the data from the beam former during the PRP, which represents echo information as a function of time (depth)

80
Q

The sequence of the Sequential Signal Processing:

A
  1. Gain Adjustment and Dynamic Frequency Tuning
  2. Dynamic Range (Logarithmic) Compression
  3. Rectification, Demodulation, and Envelope Detection
  4. Rejection
  5. Processed Images
81
Q

This defines the effective operational range of an electronic device from the threshold signal level to the saturation level.

A

DYNAMIC RANGE

82
Q

This inverts the negative amplitude signals of the echo to positive values.

A

RECTIFICATION

83
Q

Converts the rectified amplitudes of the echo into smoothed, single pulse.

A

DEMODULATION and ENVELOPE DETECTION

84
Q

This removes a significant amount of undesirable low-level noise and clutter generated from scattered sound or by the electronics.

85
Q

These are optimized for gray scale range and viewing of the limited dynamic range monitors.

A

PROCESSED IMAGES

86
Q

This is the display of processed information from the receiver versus time.

A

A-Mode (A for Amplitude)

87
Q

Earliest use of Ultrasound in Medicine

88
Q

This type of echo display mode is used in Ophthalmology.

A
  1. A-Mode

2. A Line information

89
Q

This is electronic conversion of the A-Mode and A-Line information into brightness modulated dots along the A-Line trajectory.

A

B-Mode (B for Brightness)

90
Q

This type of display mode is used for M-Mode and 2D Grayscale imaging.

91
Q

Uses a B-mode information to display the echoes from a moving organ, such as Myocardium and Valve Leaflets, from a fixed transducer position and beam direction into the patient.

A

M-Mode (M for Motion)

92
Q

This provide excellent temporal resolution of motion patterns, allowing the evaluation of the function of heart valves and other cardiac anatomy. (2D echo, Doppler, Color Imaging Display)

93
Q

This creates a 2D images from echo information from distinct beam directions, and to perform scan conversion to enable image data to be viewed kn video display monitors.

A

SCAN CONVERTER

94
Q

This image is acquired by sweeping a pulsed ultrasound beam over the volume of interest and displaying echo signals using B-mode conversion of the A-mode signals.

A

2D Ultrasound Image

95
Q

These were mare with a single element transducer mounted in an articulating arm with angular position encoders to determine the location of the ultralsound beam path.

A

Early B-Mode Scanners

96
Q

Transducer that produces Rectangular Image

A

Linear Array Transducer

97
Q

Transducer that produces Trapezoidal Images

A

Curvilinear Array Transducer

98
Q

Transducers that are typically comprised of a tightly grouped array of 64, 128, or 256 transducer elements in a 3 to 5 cm wide enclosure.

A

PHASED ARRAY TRANSDUCER

99
Q

Is a metjod in which ultrasound information is obtained from several different angles of insonation and combined to produce a single image.

A

SPATIAL COMPOUNDING

100
Q

Describe the image storage of Ultrasound.

A

Ultrasound Images are typically composed of 640 x 480 OR 512 x 512 pixels. Each pixel has a depth of 8 bits (1 byte) of digital data, providing up to 256 levels of gray scale.

101
Q

Ultrasound that is based on the shift of FREQUENCY in an ultrasound wave caused by the moving reflector, such as blood cells in the vasculature.

A

DOPPLER ULTRASOUND

102
Q

It is the difference between the incident frequency and reflected frequency.

A

DOPPLER (FREQUENCY) SHIFT

103
Q

The angle between the direction of the blood flow and the direction of the sound.

A

DOPPLER ANGLE

104
Q

What is the preferred Doppler Angle?

A

30-60 degrees

105
Q

The simplest and least expensive device for measuring blood velocity.

A

CONTINUOUS WAVE DOPPLER SYSTEM

106
Q

Advantages of Continuous Wave Dopple System.

A
  1. High Accuracy of Doppler Shift measurement

2. No Aliasing

107
Q

This measures the magnitude of the Dopple Shift but does not reveal the direction of the Doppler shift.

A

QUADRATURE DETECTION

108
Q

This combines the velocity determination of continuous wave Doppler systems and the range of discrimination of pulse echo imaging.

A

PULSED DOPPLER OPERATION

109
Q

Refers to the combination of 2D B mode imaging and pulsed Doppler data acquisition.

A

DUPLEX SCANNING

110
Q

This providew 2D visual display of moving blood in the vasculature, superimposed upon the conventional grayscale image.

A

COLOR FLOW IMAGING

111
Q

A technique to measure the similarity of one scan line measurement to another when the maximum correlation occurs.

A

PHASED-SHIFT AUTO CORRELATIO

112
Q

An alternate method for Color Flow Imaging which is based upon the measurement that a reflector has moved over a time.

A

TIME-DOMAIN CORRELATION

113
Q

Interpretation of frequency shifts and direction of blood flow accompanied with fast Fourier Transform, analyzes detected signals and generate amplitude versus frequency distribution profile known as Doppler Spectrum

A

Doppler Spectral Interpretation

114
Q

Error caused by insufficient sampling rate (PRF) relative to high frequency doppler signals generated by fast moving blood.

A

VELOCITY ALIASING

115
Q

A signal processing method that relies on the total strength of Dopple signal and ignores directional info.

A

POWER DOPPLER

116
Q

Integral multiples of frequencies contained in an ultrasound pulse.

A

HARMONIC FREQUENCIES

117
Q

This enhances contrast agent imaging using a low frequency incident pulse and turning the receiver to a higher frequency harmonics.

A

HARMONIC IMAGING

118
Q

Acquires a 2D tomographic image data in a series of individual B-scans of a volume tissue.

A

3D ULTRASOUND IMAGING

119
Q

Volume Sampling can be achieved in several ways with the following transducer arrays:

A
  1. Linear Translation
  2. Freedom Motion with External Localizers
  3. Rocking Motion
  4. Rotation of Scan
120
Q

Measure of Ultrasound Image Quality includes the following: (4)

A
  1. Spatial Resolution
  2. Contrast Resolution
  3. Image Uniformity
  4. Noise Characteristic
121
Q

This arises from the incorrect display of anatomy or noise during imaging which may be due to Machine or Operator related.

122
Q

Change in the transmitted ultrasound pulse direction at a boundary with nonperpendicular incidence, when 2 tissues support a different speed of sound.
- Misplaced anatomy ofter occurs

A

REFRACTION

123
Q

Hypointense signal area distal to the object or interface caused by objects with high attenuation or reflection without return of echoes.

124
Q

Occurs distal to the objects having very low ultrasound attenuation.

A

ENHANCEMENT

125
Q

Arise from multiple echoes generated between 2 closely spaced interfaces reflecting ultrasound energy back and forth during acquisition of signal and before the next pulse.
- Caused by reflection between a highly reflective interface and transducer

A

REVERBERATION

  • manifested as Multiple equally spaced boundaries with decreasing amplitude along a straight line from transducer.
  • Comet tail artifact is a form of reverberation
126
Q

Caused by variability of speed of sound in different tissues

A

SPEED DISPLACEMENT

127
Q

Nearly highly reflective surfaces, multiple beam reflections, and refractions can find their way back to the transducer.
- Anatomy involved is misplaced on beam axis

A

MULTIPATH REFLECTION and MIRROR IMAGE

128
Q

Created when high PRF limits the amount of time spent listening for echoes during the PRP.

129
Q

Represented as rapidly changing mixture of colors in doppler, typically seen distal to a strong reflector
- due to echoes from strong reflector with frequency changes

A

TWINKING ARTIFACT

130
Q

This is determined by the beam width of transducer array perpendicular to the image plane and is greater than the beam width in image plane.
- Mostly significant at distances close and far from transducers.

A

SLICE THICKNESS

131
Q

Rate of energy production, absorption, flow.

132
Q

SI unit of power

A

Watt (W) = 1 joule or energy/sec

133
Q

Rate at which the sound energy flows through a unit area

A

ACOUSTIC INTENSITY

134
Q

Measures ultrasound pressure amplitude with in a beam

- A device containing a small piezoelectric element coupled to external conductors and mounted in a protective housing

A

HYDROPHONE

135
Q

Highest instantaneous intensity in the beam

A

TEMPORAL PEAK

136
Q

The time average intensity over the PRP

A

TEMPORAL AVERAGE

137
Q

The average intensity of pulse

A

PULSE AVERAGE

138
Q

Highest intensity spatially in the beam

A

SPATIAL PEAK

139
Q

Average intensity over the beam area, usually taken to the area of the transducer

A

SPATIAL AVERAGE

140
Q

Good indicator of thermal ultrasound effects

A

SPATIAL-PEAK-TEMPORAL AVERAGE INTENSITY

141
Q

An indicator of potential mechanical bioeffects and cavitation

A

SPATIAL-PEAK PULSE AVERAGE INTENSITY

142
Q

The ratio of acoustic power produced by transducer to power required to raise tissue in the beam area by 1 degree C

A

THERMAL INDEX (TI)

143
Q

A value that estimates the likelihood of cavitation by ultrasound beam

A

MECHANICAL INDEX (MI)

144
Q

A consequence of negative pressure that induce bubble formation from the extraction of dissolved gases in the medium

A

CAVITATION

145
Q

Assumed attenuation for the logarithm that estimates MI

A

0.3 (dB/cm)/MHz

146
Q

Best indicator for heat deposition

- Measure of intensity and calculated TI value

A

SPATIAL PEAK TEMPORAL AVERAGE INTENSITY

147
Q

Defined as sonically generated activity of highly compressible border composed of gas and / or vapor

A

CAVITATION

148
Q

Refers to the pulsation of persistent bubbles in tissue that occue at low and intermediate ultrasound intensities

A

STABLE CAVITATION

149
Q

Whereby the bubbles respond nonlinearly to the driving force, causing collapse approaching the speed of sound

A

TRANSIENT CAVITATION

BUSHBERG PHYSICS (2 decks)

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