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SPI Review Flashcards

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1
Q

The thickness of the matching layer is ________ the wavelength

A

1/4

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2
Q

What do the piezoelectric crystals do?

A

Convert electrical signals to acoustic pulses

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3
Q

The thickness of the PE is ________ the wavelength

A

1/2

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4
Q

What does frequency depend on in the transducer?

A

element thickness

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5
Q

Thicker element = _______ frequency

A

lower

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6
Q

Wider element diameter = ___________ beam intensity

A

low

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7
Q

Higher frequency = ___________ axial/lateral resolution and ________ penetration

A

improved / less

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8
Q

What does the damping/backing layer do?

A

reduces the ringing

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9
Q

Damping _________ axial resolution and decreases the ________

A

improves / SPL

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10
Q

What is the footprint?

A

The portion of the transducer that touches the skin

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11
Q

When is a therapeutic ultrasound transducer used?

A

Usually with physical therapy

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12
Q

What are 1-D arrays?

A

Elements arranged side by side oriented with the long axis and fired along the parallel axis

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13
Q

What are 1.5-D arrays?

A

arranged side by side oriented with the long axis but are etched parallel to the long axis to create multiple elements in the short axis.

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14
Q

What are 2-D arrays?

A

Typically have a few thousand elements. Used in 3D imaging and with linear, sector, and curvilinear transducers.

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15
Q

What is propagation speed in soft tissue?

A

1.54 mm/ms

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16
Q

Detail resolution is _________ and _________

A

axial and lateral

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17
Q

Axial resolution is determined by

A

the length of the pulse (1/2 the SPL) and pulse duration

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18
Q

Axial resolution is for structures ____________ to the beam?

A

parallel

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19
Q

Lateral resolution is for structures _______ to the beam?

A

perpendicular

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20
Q

Lateral resolution has to do with _______________

A

beam width

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21
Q

Contrast resolution has to do with

A

number of shades of grey

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22
Q

Temporal resolution has to do with

A

frame rate. The number of focuses, the number of scan lines

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23
Q

Which resolution is controlled by depth?

A

temporal

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24
Q

Deeper = _______ PRF

A

longer

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25
Q

Spatial resolution = __________ resolution

A

detail

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26
Q

Other names for axial resolution

A

depth, longitudinal, radial, range, linear

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27
Q

If frequency increases, axial’s numbers ________, and indicates _________ axial resolution

A

decrease / better

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28
Q

Other names for lateral resolution

A

transverse, angular, azimuthal

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29
Q

What is temporal resolution?

A

the ability to accurately display moving structures over time

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30
Q

_______ has the best temporal resolution and _______ has the worst

A

M-mode / color Doppler

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31
Q

Temporal resolution increases with

A

shallow depth
single focal zone
decreased pulses per scan line
narrow sector angle
decreased line density
interpolation

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32
Q

What is frame time?

A

the amount of time required to produce a single frame

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33
Q

________ frame time leads to ________ frame rate and _______ resolution

A

increased / decreased / temporal

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34
Q

What is slice thickness resolution? (Elevational resolution)

A

A measure of the beam width perpendicular to the image plane. Set by the manufacturer

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35
Q

The ______ the element diameter, the _____ the near zone

A

wider / longer

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36
Q

The ________ the frequency of the beam, the _______ the near zone

A

higher / longer

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37
Q

Linear array have about how many elements?

A

about 200

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38
Q

Linear arrays use _______ focusing and beam steering

A

electronic

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39
Q

What specialties use linear arrays?

A

abdominal, OB, small parts, vascular, and musculoskeletal

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40
Q

About how many elements are in curvilinear arrays?

A

120-250

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41
Q

Curvilinear arrays have _________ focusing and beam steering?

A

electronic

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42
Q

Curvilinear arrays are used in what specialties?

A

abdominal, OB, gynecological, small parts

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43
Q

About how many elements are used in phased arrays?

A

100-200

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44
Q

Phased array has _______ steering and steered

A

electronic

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45
Q

Phased arrays are used in what specialties?

A

cardiac, abdominal, pelvic, vascular, transcranial, and neonatal brain imaging

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46
Q

Vector array is used in what specialties?

A

pelvic, echocardiography, abdominal, transcranial, neonatal brain imaging

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47
Q

What is laminar flow?

A

Concentric layers of flow each with a slight difference in velocity. (fastest in the center, slower at the edges due to friction)

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48
Q

What is plug flow?

A

When all layers of flow are moving at relatively the same velocity (like the aorta)

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49
Q

What is parabolic flow?

A

When there is more of a difference in the velocity between layers.

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50
Q

What is Poiseuille’s equation about?

A

The relationship between pressure, flow volume, and resistance

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51
Q

When is Poiseuille’s equation used?

A

to describe how much fluid (blood) moves through a pathway (artery)

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52
Q

Vessel length and viscosity are relatively _________. Increases in either one will cause __________ resistance

A

constant / increased

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53
Q

What is resistance?

A

the rate of flow in the arteries and is regulated by the arterioles

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54
Q

In a resting patient, the highest resistance in the arterial system is

A

the arterioles

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55
Q

Extremities/muscles have a much ________ resistance to blood flow than the organs

A

higher

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56
Q

increased viscosity and vessel length lead to ______ resistance

A

increased

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57
Q

increased vessel radius leads to _________ resistance

A

decreased

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58
Q

As resistance increases, blood flow __________ with ____________ in pressure

A

decreases / no change

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59
Q

Stenosis causes resistance to increase ___________ to a stenosis and decreases ________ to the stenosis

A

proximal / distal

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60
Q

Pressure is defined as

A

the concentration of force within an area

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61
Q

When does pressure increase?

A

systole

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62
Q

Average pressure in the veins is _______ and in the arteries _______

A

2 mmHg / 100 mmHg

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63
Q

Arterial stenosis leads to _________ pressure as the velocity __________ with stenosis

A

decreased / increases

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64
Q

Volumetric flow rate is always _________ to blood pressure

A

proportional

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65
Q

resistance and flow rate are _________ related

A

inversely

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66
Q

What is the Bernoulli effect?

A

The decrease in pressure at a stenosis due to increased velocity at the site

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67
Q

What is antegrade?

A

moving forward in the direction of blood flow

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68
Q

what is retrograde?

A

backward flow or filling, or against the normal direction of flow

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69
Q

what is turbulence?

A

disrupted flow cause by a stenosis, tortuosity, or bifurcation, appears at the exit point of a stenosis

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70
Q

what is bruit?

A

abnormal blood flow sound in a blood vessel, can be due to stenosis; also seen with vessel branching or tortuosity

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71
Q

what is thrill?

A

abnormal flow sensation in a blood vessel (vibration), can be due to stenosis; also seen with pseudo aneurysm and hemodialysis grafts

72
Q

What is pulsatility?

A

continuous throbbing or beating, flow in the arteries pulsates due to continuous cardiac contractions, venous flow is not pulsatile because it is not moved by cardiac contraction

73
Q

What is capacitance?

A

the ability of veins to store blood

74
Q

Why are veins considered the capacitive vessels?

A

because of their increased compliance and ability to store larger volumes of blood than arteries

75
Q

What is hydrostatic pressure?

A

weight of the column of blood inside the vessels

76
Q

What is transmural pressure?

A

pressure within the veins pushing outward. (normally low)

77
Q

______ and _____ are responsible for moving flow through the venous system

A

respiration / muscle contraction

78
Q

Which increases venous return to the heart from the upper body, inspiration or expiration?

A

inspiration

79
Q

What is the Doppler shift?

A

the mathematical difference between the transmitted and received frequencies, occurs when structures are moving towards or away form the listener

80
Q

Doppler shift is directly related to ____________, __________ of red blood cells being sampled, and the ___________ between the US beam and blood flow

A

transducer frequency / velocity / cosine of the angle

81
Q

The angle between the ________ and the ________ must be known to determine an accurate Doppler shift

A

US beam / blood flow

82
Q

Doppler shift is inversely related to the _________

A

speed of sound in the medium

83
Q

Doppler measures ______ not _________

A

velocity / speed

84
Q

A low pass filter does what?

A

Eliminates the signal from the blood and only shows color information representing wall motion (color Doppler)

85
Q

Larger packet size causes ___________ frame rates but produce more __________ flow velocity information

A

decreased / accurate

86
Q

Larger packet sizes are better able to identify ________ flow more accurately

A

low velocity

87
Q

What is autocorrelation?

A

automatically correlates data from multiple sampling sites. assesses the data from multiple sampling sites and produces a display representing mean flow velocities

88
Q

What is packet size?

A

the number of pulses per scan line within the color gate.

89
Q

Flow needs to be __________ to the beam. Never _________

A

parallel / 90 degrees

90
Q

What is power Doppler?

A

Doppler mode in which the signal is determined by the amplitude of the shift, not the shift itself. Amplitude is directly proportional to the number of red blood cells.

91
Q

How is power doppler imaging different than color doppler imaging?

A

Power doppler measures the energy variance not the frequency shift. It is not angle dependent

92
Q

Power doppler is very __________, it is ideal for ______________, but also makes it more susceptible to __________

A

sensitive / slow, small vessels / patient or organ motion

93
Q

For CD, PD, PW, and CW signals, ___________ are customarily used to eliminate the small doppler shift caused by movements of other tissues

A

high-pass wall filters

94
Q

What is spectral doppler?

A

Doppler shifts are detected along a single line and used to produce a graphic representation of the blood velocities

95
Q

How does PW Doppler work?

A

Using controlled time intervals between transmitted and received sounds to collect information using a single PZT element

96
Q

Aliasing is the biggest disadvantage of PW Doppler because…

A

it limits the velocities that can be evaluated

97
Q

Doppler shift is _______________ related to the transducer frequency

A

directly

98
Q

The best incident angle to produce the most accurate Doppler shift information is

A

0 degrees (or 180 degrees)

99
Q

The best obtainable incident angle that is most commonly used to provide Doppler shift information is

A

60 degrees

100
Q

A 90 degree Doppler incident angle will demonstrate ________

A

no flow in either direction

101
Q

An insonation angle less than 90 degrees will result in _________ shift

A

positive

102
Q

an insonation angle greater than 90 degrees will result in _______ shift

A

negative

103
Q

What does adjusting the color gain do?

A

adjusts the displayed amplitude of the reflected frequency shift from the flowing blood.

104
Q

Setting the macine to a proper color gain involves what?

A

increasing the gain until blossoming is noted and then decreasing to just below that level

105
Q

What is the optimum color angle sample between the sample box and the blood flow

A

0 degrees or parallel to flow

106
Q

What happens as the incident angle moves closer to 90 degrees?

A

color Doppler display will decrease until it is absent

107
Q

More _______ structures provide better color display with _____ frame rates and ______ temporal resolution

A

superficial / faster / improved

108
Q

What is the color packet size?

A

also known as the ensemble length. The packet size refers to the number of samples taken during evaluation

109
Q

What does the wall filter do?

A

Eliminates low frequency Doppler shifts from display. Used to reduce clutter/flash/ghosting artifacts. Will not eliminate aliasing

110
Q

What is color priority/threshold?

A

determines wheter color pixels should be displayed preferentially over grayscale pixels

111
Q

Lower threshold means _____
Higher threshold means _____

A

less color / more color

112
Q

What is persistence?

A

temporal compounding. color sensitivity. uses the average of previous frames to create the displayed image. improves signal to noise ratio on color image

113
Q

Higher persistence levels allow

A

prolonged display of color on the image. It is preferred for slow moving flow.

114
Q

Increased persistence and sensitivity levels can aid in

A

the evaluation of heavily calcified arteries

115
Q

For spectral Doppler, what is displayed on the graph?

A

Doppler shifts along a single line, used to produce a graphic representation of the blood velocities

116
Q

What does the horizontal axis on the spectral graph represent?

A

Time

117
Q

What does the vertical axis on the spectral graph represent?

A

Doppler shift/Velocity

118
Q

What degree of angle will flow velocity be miscalculated?

A

20 degrees off axis

119
Q

Usually a ________ cursor angle is necessary to obtain accurate Doppler information (especially in vascular)

A

60 degrees

120
Q

What is the average size of the sample volume for arterial evaluations?

A

1 - 1.5 mm

121
Q

What is the standard sweep speed setting for spectral Doppler display?

A

50 mm/s

122
Q

Anytime a monophasic waveform is seen in an _____ it is abnormal

A

extremity

123
Q

anytime a biphasic/triphasic waveform is seen in an _______ it is abnormal

A

organ

124
Q

What is resistive index?

A

Doppler measurment used to quantitate the resistiveness of the distal bed.

125
Q

When is resistive index used?

A

to evaluate arterial stenosis

126
Q

What is pulsatility index?

A

Doppler measurement used to determine how pulsatile a vessel is over time.

127
Q

How many planes/views are required to determine if it’s artifact or something more?

A

at least two

128
Q

What is range ambiguity?

A

Shallow reflectors reflect sound energy that arrives at the transducer before the rest of the original pulse finishes transmitting.

129
Q

What does noise/speckle degrade?

A

contrast and spatial resolution

130
Q

What is volume averaging artifact?

A

also known as slice thickness or beam width artifact. The echo information from the 3rd dimension is overlapped with the echoes from the center of the beam on the image. Happens the most in deep imaging where the beam is widest.

131
Q

How to correct for slice thickness artifact?

A

narrowing the thickness of the beam, short axis focusing, using a standoff pad, or repositioning the focal zone

132
Q

What is clutter (Doppler artifacts)

A

Also known as color flash, color bleeding, color ghosting. Unwanted Doppler display patterns typically caused by structure motion or breathing

133
Q

What is blooming or blossoming (Doppler artifact)?

A

Color obscures the gray scale display of soft plaque because the resolution of color Doppler is lower than the gray scale. Causes the pixel to be displayed as color instead of grey scale.

134
Q

What does the x and y axis represent in M-mode?

A

x = time / y = depth

135
Q

What does the x and z axis represent in B-mode?

A

x = reflector depth / z = reflector brightness (amplitude)

136
Q

What does the beam former do?

A

Controls the timing of the signals sent to the individual elements for steering and focusing the beam

137
Q

What are grating lobes?

A

artifacts caused by extraneous sound that lies outside of the primary path of the beam

138
Q

What is apodization?

A

controlled by the beam former by decreasing the strength of the voltage pulse sent to the outermost elements.

139
Q

What is the pulser?

A

part of the beam former that controls the strength, or amplitude, of the electricity striking the elements, as well as the PRF and PRP.

140
Q

What does the pulser control?

A

The amount of power entering the patient.

141
Q

What other terms mean power?

A

output, output gain, output power, acoustic power…

142
Q

The _______ the output power, the ______ the return echo

A

higher / stronger

143
Q

What are the benefits of increased power output?

A

1) higher amplitude return echoes for a better signal-to-noise ratio.
2) improved depth penetration

144
Q

How can the sonographer adjust the output power?

A

adjust the control stating output, power, or transmit.

145
Q

What is frequency compounding?

A

Soft tissue is imaged at various frequencies and averaged. The displayed image is the result of all the frequencies and is another way to produce the image with improved contrast resolution and reduction in noise and acoustic speckle.

146
Q

What is the master synchronizer?

A

The part of the machine responsible for controlling the timing of the echoes. It tells the pulser to send out a pulse and pays attention to when the echoes come back to determine their range.

147
Q

What is harmonics?

A

harmonic signal produced by the patient’s tissue that is a multiple of the fundamental frequency. Harmonics are only generated as the beam travels deeper. (2F is used)

148
Q

If a 2 MHz beam is sent into the patient, with harmonic imaging, what signal is sent back?

A

4 MHz

149
Q

What type of resolution is improved with harmonic imaging?

A

lateral resolution

150
Q

What is the receiver?

A

Where the return signal is processed. (preampfication, amplification, compensation, compression, demodulation, and rejection)

151
Q

What is amplification?

A

overall gain. increases or decreases the strength of all the returning echoes equally

152
Q

What is compensation?

A

time-gain compensation. compensates for the fact that attenuation occurs, and the more distant echoes are increased in brightness to achieve a uniform level of brightness.

153
Q

What is compression?

A

the function of the receiver that decreases the range of signal amplitudes present within the machines receiver.

154
Q

What is dynamic range?

A

The series of echo amplitudes present within the signal. Inversely related to compression.

155
Q

What is demodulation?

A

processes the signal to make it easier for the machine to handle. (Rectification and smoothing)

156
Q

What is rectification?

A

Turning negative voltages into positive voltages

157
Q

What is smoothing?

A

wrapping an envelope around the signal to make it less bumpy or remove the humps.

158
Q

What is rejection?

A

discards signal amplitudes below a certain threshold to reduce image noise

159
Q

What is the transmit/receive switch?

A

Ensures the electrical signals travel in the correct direction. It ensures the pulser voltages go to the transducer, and the received voltages from the transducer go to the signal processor (receiver)

160
Q

What is the scan converter?

A

part of the machine that makes grayscale imaging possible and is responsible for storage of the image data.

161
Q

Signals travel from the receiver to the __________ and then to the scan converter/image memory, and then to the _______

A

analog to digital converter / digital to analog converter

162
Q

What is preprocessing?

A

where incoming signals are assigned shades of gray based on their amplitudes. Happens before the scan converter. Images are still live at this point.

163
Q

A ______ is the smallest amount of computer memory possible.

A

Bit

164
Q

_____ bits make 1 ______

A

8 / byte

165
Q

The more pixels on display, the better the ______ resolution

A

spatial

166
Q

What is write zoom?

A

a pre-processing function, enlarges the image by redrawing it. High quality zoomed image

167
Q

What is read zoom?

A

a post-processing function, enlarges the image by magnifying the pixels. Offers a coarser, less optimal type of zoom.

168
Q

What is spatial compounding?

A

Eliminates edge shadowing because the object is imaged at different angles.

169
Q

What does spatial compounding reduce?

A

speckle artifact and reverberation

170
Q

What is the purpose of the damping material?

A

to shorten the length of the pulse by decreasing the number of cycles in the pulse

171
Q

What is sensitivity of the transducer?

A

the ability of the system to display low-level or weak echoes.

172
Q

What is bandwidth?

A

the range of frequencies present within the beam

173
Q

The more damping there is, the _______ the pulse, the ______ the bandwidth, the _____ the QF

A

shorter / wider / lower

174
Q

What is the quality factor?

A

the measure of the beam purity. the operating frequency of the transducer divided by the bandwidth

175
Q

What is elevational resolution?

A

the resolution in the third dimension of the beam. the slice-thickness plane

Ultrasound Physics - me (1 decks)

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