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DSM PHY > SPI > Flashcards

SPI Flashcards

1
Q

billion

A

10^9
giga
G

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2
Q

million

A

10^6
mega
M

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3
Q

thousand

A

10^3
kilo
k

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4
Q

hundred

A

10^2
hecto
h

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5
Q

ten

A

10^1
deca
da

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6
Q

tenth

A

10^-1
deci
d

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7
Q

hundreth

A

10^-2
centi
c

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8
Q

thousandth

A

10^-3
milli
m

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9
Q

millionth

A

10^-6

micro

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10
Q

billionth

A

10^-9
nano
n

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11
Q

Sound is a ______, ________ wave.

A

mechanical, longitudinal

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12
Q

Sound carries _____ from place to place.

A

Energy.

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13
Q

What are the acoustic variables?

A

Pressure, Density, Distance.

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14
Q

Define Pressure.

A

Concentration of force within an area.
(force/area)
units:Pascals (Pa)

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15
Q

Define Density.

A

Concentration of mass within a volume.

units: kg/cm^3

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16
Q

Define Distance.

A

Measure of particle motion

units: cm, ft, miles

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17
Q

With a transverse wave, particles travel in which direction?

A

Travel in a perpendicular direction, perpendicular to the wave.

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18
Q

With a longitudinal wave, particles travel in which direction?

A

Particles move in the same direction as the wave.

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19
Q

Acoustic Variables vs. Acoustic Parameters

A

Acoustic Variables inform us of which waves are sound waves while Acoustic Parameters describe the features of a particular sound wave.

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20
Q

7 parameters of continuous waves.

A 
Period
Frequency
Amplitude
Power
Intensity
Wavelength
Propagation Speed
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21
Q

Period

A

Time required to complete a single cycle.
Determined by: source
units: microseconds
nonadjustable

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22
Q

Frequency

A

Number of certain events that occur in a particular time duration.
Determined by: source
units:hz
nonadjustable

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23
Q

Amplitude

A

Difference between the average value and the maximum value of an acoustic variable.
Determined by: source (initially)
units:pascals, cm
adjustable

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24
Q

Power

A 
The rate that work is performed or rate of energy transfer.
Determined by: source (initially)
units:Watts
adjustable
Power=Amplitude^2
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25
Q

Intensity

A

Concentration on energy in a sound beam.
Determined by: source (initially)
units:watts/cm^2
adjustable

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26
Q

Wavelength

A

The length or distance of a single cycle.
Determined by: Both
units: meters, mm
nonadjustable

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27
Q

Propagation Speed

A

Rate that sound travels through a medium.
Determined by: Medium
units:m/s
nonadjustable

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28
Q

Equation for wavelength

A

wavelength = propagation speed (mm/microsec) / frequency (MHz)

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29
Q

Intensity is _________ related to power.

A

directly

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30
Q

Equation for intensity.

A

intensity = power(watts) / beam area(cm^2)

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31
Q

How to determine the wavelength in soft tissue.

A

divide 1.54 (mm/us) by the frequency (Mhz)

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32
Q

Density vs. Stiffness

A

increase in stiffness=increase in speed.

increase in density=decrease in speed.

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33
Q

Parameters of pulsed sound

A 
Pulse Duration
Pulse Repetition Frequency
Pulse Repetition Period
Duty Factor 
Spatial Pulse Length
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34
Q

Pulse Duration

A 
The time from the start of a pulse to the end of that pulse.
Determined by: source
units: microsec
Nonadjustable
PD= # of cycles in pulse x period
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35
Q

Spatial Pulse Length

A 
The length or distance that an entire pulse occupies in space.
Determined by: Both
units:mm
Nonadjustable
SPL=# of cycles x wavelength (mm)
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36
Q

Pulse Repetition Period

A

the time from the start of one pulse to the start of the next pulse; 1 pulse duration + 1 listening time.
Determined by: source
units:msec
Adjustable

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37
Q

Pulse Repetition Frequency

A

number of pulses created by the system in one second.
determined by: source
units:Hz
Adjustable

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38
Q

Duty Factor

A

% or fraction of time that the system transmits sound.
Determined by: source
unitless
adjustable

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39
Q

Duty factor is _____ related to depth.

A

Inversely; with shallower depth there is a higher duty factor, with more depth there is lower duty factor.

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40
Q

PRF is ____ related to depth.

A

Inversely; shallower image = higher PRF

deeper image = lower PRF

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41
Q

PRP is ____ related to depth.

A

Directly.

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42
Q

How are PRP and PRF related?

A

They are reciprocals.

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43
Q

Factors involved with deep imaging…

A

low PRF
low duty factor
long PRP

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44
Q

Factors involved with shallow imaging….

A

high PRF
high duty factor
short PRP

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45
Q

Definition of Intensity

A

The concentration of power in the beam

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46
Q

5 Key Words of Intensity

A 
Peak- max value
Average- mean value 
Spatial- refers to distance or space
Temporal- refers to all time
Pulsed- refers to transmit time only
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47
Q

The greatest intensity…

A

SPTP

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48
Q

The lowest intensity…

A

SATA

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49
Q

The intensity related to tissue heating…

A

SPTA

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50
Q

What is attenuation?

A

The decrease in intensity, power and amplitude of a sound wave as it travels.
units: dB

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51
Q

What are the three components of attenuation?

A

Absorption
Scattering
Reflection

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52
Q

With lower frequency and shorter path length there is ….

A

less attenuation

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53
Q

With higher frequency and longer path length there is….

A

more attenuation

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54
Q

Reflection occurs when…

A

propagating sound energy strikes a boundary between two media and some returns to the transducer

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55
Q

Specular reflection arises from a…

A

smooth reflector (they return in one direction)

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56
Q

Diffuse reflection or backscatter arises from…

A

rough boundary (sound is redirected in many directions)

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57
Q

When are specular reflections best seen?

A

When sound strikes the boundary at 90 degrees.

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58
Q

When does Rayleigh scattering occur?

A

When the reflector is much smaller than the wavelength of sound; sound is then uniformly distributed in all directions

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59
Q

Rayleigh scattering is related to…

A

Frequency^4

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60
Q

Higher frequency sound undergoes more…

A

Rayleigh scattering

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61
Q

What is the attenuation coefficient?

A

The amount of attenuation per centimeter.

units:dB

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62
Q

In soft tissue the attenuation coefficient is approx…

A

1/2 the frequency

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63
Q

Total attenuation equals…

A

path length(cm) x attenuation coefficient (dB/cm)

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64
Q

A mathematical expression that means ‘half the transducer frequency’ is…

A

0.5 dB/cm/MHz

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65
Q

Reflection of an ultrasound waves depends upon different

A

impedances

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66
Q

What is the equation for impedance?

A

impedance (rayls)= density (kg/m^3) x prop speed (m/s)

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67
Q

PORNN (normal incidence)

A

perpendicular
orthogonal
right angle
ninety degrees

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68
Q

Oblique incidence means…

A

not at right angles, anything other than 90 degrees.

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69
Q

What are the other names for Round Trip?

A

Time of flight

Go return time

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70
Q

What is the definition for time of flight?

A

The time needed for a pulse to travel to and from the transducer and the reflector

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71
Q

What is the average speed in soft tissue?

A

1.54 km/sec

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72
Q

In the 13 sec rule, what would the reflector depth and total distance traveled at 26 sec?

A

Reflector: 2cm
Total: 4cm

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73
Q

What is the relationship between time of flight and distance?

A

Directly related

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74
Q

What does speed equal?

A

Speed= distance/time

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75
Q

What is the definition of a transducers?

A

Any device that converts one form of energy into another

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76
Q

What is the Piezoelectric Effect?

A

Property of certain materials to create a voltage when pressure is applied or when material is mechanically deformed.

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77
Q

What are all of the Piezoelectric materials?

A

PZT
Ceramic
Active element
Crystal

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78
Q

What happens to the crystal when is exceeds the Curie Point?

A

Depolarizes

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79
Q

What is Sterilization?

A

Complete destructs of all living microorganisms by means of exposure to heat, chemical agents, or radiation

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80
Q

What is disinfection?

A

Application of chemical agent to reduce or eliminate infectious organisms on an object

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81
Q

What requires Sterilization?

A

Items that Penetrate skin or mucous membranes

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82
Q

What requires disinfection?

A

Things that come in contact with mucous membranes

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83
Q

What are transducers disinfected with?

A

Cider

Gluteradehyde

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84
Q

On the transducer, what does the case do?

A

Protects the internal components from damage and insulates the patient from electrical shock

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85
Q

Why don’t we use transducers with a cracked case or frayed wire?

A

Potential electric shock to patient

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86
Q

The matching layer is ___________ wavelength thick.

A

1/4

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87
Q

What are the impedances of the matching layer?

A

PZT>matching layer> gel> skin

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88
Q

What reduced the transducers ringing?

A

Damping element or Backing material

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89
Q

What is the “rule” for the backing material?

A

Short pulses create better images

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90
Q

What is the backing material made out of?

A

Epoxy resin impregnated with tungsten

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91
Q

With the damping material, what are the imaging transducer characteristics?

A 
Damping is effective
Short pulse and duration
Low sensitivity*
Wide bandwidth*
Low Q
Decreased output power
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92
Q

How come Therapeutic and Continuous wave transducers don’t use damping element?

A

They don’t create images

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93
Q

What does bandwidth mean?

A

Range of frequencies between the highest and the lowest frequency emitted from the transducer

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94
Q

What is another name for wide bandwidth?

A

Broadband

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95
Q

What are all the names of the main frequency emitted by the transducer?

A

Center
Resonant
Primary
Natural frequency

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96
Q

What is Quality factor?

A

Unitless number representing the extent of damping

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97
Q

What are the two characteristics that determine frequency in a pulsed transducer?

A
  1. Thickness

2. Propagation Speed

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98
Q

In pulsed transducers, what will have a high frequency?

A

Thin crystal and fast PZT

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99
Q

In pulsed transducers, what would have a low frequency?

A

Thick crystal

Slow PZT

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100
Q

When a PZT crystal is _____ as thick, the sounds frequency is ______ as high.

A

Half

Twice

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101
Q

Chart in book….

A

Component Thickness

  • PZT crystal= 1/2 wavelength thick
  • Matching layer= 1/4 wavelength thick

Pg. 57 cheater book

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102
Q

What creates better images?

A

Narrow beams

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103
Q

What is the focal point (focus)?

A

Location where the beam reaches its minimum diameter

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104
Q

What is the focal depth?

A

Distance from the transducer face to the focus.

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105
Q

What are the other names for focal depth?

A

Focal length

Near zone length

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106
Q

What is the near zone length?

A

Region or zone in between the transducer and the focus

Sound beams converge

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107
Q

What is another name for near zone?

A

Fresnel zone

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108
Q

What is the far zone?

A

Region or zone deeper than the focus, beyond the near field

Sound beams diverge

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109
Q

What is the focal zone?

A

Region surrounding the focus where the bean is “sort of narrow” and the image is good

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110
Q

What is focal depth determined by?

A

Transducer diameter (aperture)

Frequency

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111
Q

What is sound beam divergence determined by?

A

Transducer diameter

Frequency

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112
Q

What kind of sound wave does a large diameter crystal with a high frequency produce?

A

Less divergence in far field

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113
Q

What kind of divergence would a smaller diameter crystals with a lower frequency produce?

A

Large divergence in far zone

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114
Q

What is a continuous wave frequency determined by?

A

Electronic frequency

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115
Q

What is a pulsed frequency determined by?

A

Thickness of ceramic

Speed of sound

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116
Q

What is focal length determined by?

A

Diameter of ceramic

Frequency

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117
Q

What is divergence determined by?

A

Diameter of ceramic

Frequency

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118
Q

What is another name for V shaped wave?

A

Huygens wavelet

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119
Q

What produces the Huygens wavelet?

A

When produced by a tiny source, with a size near the wavelength of the sound waves will diverge in this shape as they propagate

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120
Q

What is the Huygens Principle?

A

Hourglass shape of an imaging transducers sound beam

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121
Q

The overall hourglass shape of a sound beam is the result of the ____________________ of many sound wavelets emitted from these numerous sound sources.

A

Constructive and destructive interference

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122
Q

What is Resolution?

A

Ability to image accurately

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123
Q

What is Axial Resolution?

A

Ability to distinguish two structures that are close to each other front to back, parallel to, or along beams axis

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124
Q

What is the synonym for Axial Resolution?

A

LARRD

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125
Q

What does LARRD stand for?

A 
LARRD:
Longitudinal
Axial
Range
Radial
Depth
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126
Q

What is the equation for Axial Resolution?

A

LARRD Resolution= Spatial Pulse Length/2

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127
Q

What does LARRD resolution improve with?

A

Less ringing

Higher frequency

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128
Q

When is Axial Resolution at its best?

A

Using transducers with the highest frequency and the fewest number per cycle

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129
Q

What is Lateral Resolution?

A

Minimum distance that two structures are separated by side-to-side or perpendicular to the sound beam that produces two distinct echoes

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130
Q

What is the synonym for Lateral Resolution?

A

LATA

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131
Q

What is the incident intensity?

A

intensity of the sound wave prior to striking a boundary.

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132
Q

What is the reflected intensity?

A

Portion of the incident intensity that, after striking a boundary, changes direction and returns back from where it came.

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133
Q

What is the transmitted intensity?

A

Portion of the incident intensity that, after striking a boundary, continues on in the same general direction that is was originally traveling.

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134
Q

What is the equation of incident intensity?

A

incident intensity = reflected intensity + transmitted intensity

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135
Q

What is the Intensity Reflection Coefficient?

A

The percentage of the US intensity that bounces back when the sound strikes a boundary.

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136
Q

What is the Intensity Transmission Coefficient?

A

The percentage of the incident intensity that after striking a boundary continues on in the same general direction that it was originally traveling.

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137
Q

Where does conservation of energy exists?

A

at a boundary.

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138
Q

IRC + ITC = ?

A

100%

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139
Q

When the reflected and transmitted intensities are added, what is the result?

A

The incident intensity

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140
Q

With greater impedance differences between the two media, the IRC ______, and the amount of reflection ____.

A

increases, increases

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141
Q

Whatever is not transmitted, must be ____.

A

reflected

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142
Q

What do we know about oblique incidence?

A

Nothing!

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143
Q

What is refraction?

A

Transmission with a bend.

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144
Q

Refraction requires what?

A
  1. ) oblique incidence

2. ) different speeds

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145
Q

Refraction cannot occur with…

A

Normal incidence and the same speeds.

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146
Q

Snell’s Law describes..

A

The physics of refraction

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147
Q

How are period and frequency related?

A

They’re reciprocals.

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148
Q

Narrower sound beams create better____________

A

Images

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149
Q

What is another name for transducer diameter?

A

Aperture

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150
Q

What is the focus (focal point)?

A

Location where the beam reaches its minimum diameter

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151
Q

What is focal depth?

A

Distance from the transducer face to the focus.

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152
Q

What is another name for focal depth?

A

Focal length

Near zone length

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153
Q

What is the near zone?

A

Region or zone in between the transducer and the focus. Sound beams converge!

154
Q

What is another name for the near zone?

A

Fresnel zone

155
Q

What is the far zone?

A

Region or zone deeper than the focus, beyond the near field. Sound beams diverge

156
Q

What is another name for the far zone?

A

Fraunhofer zone

157
Q

What is the focal zone?

A

Region surrounding the focus where the beam is “sort of narrow” and picture is relatively good

158
Q

What is focal depth determined by?

A

Transducer diameter (aperture)

Frequency

159
Q

Hint….

A

Compared to beams with a shallow focus, beams with a deep focus have a lower intensity at the focus

160
Q

What will cause a shallow focus?

A

Small diameter

Low frequency

161
Q

What will cause a deep focus?

A

Large diameter

High frequency

162
Q

Define sound beam divergence.

A

Spread of the sound beam in the deep far zone

163
Q

What factors affect sound beam divergence?

A

Transducer diameter (aperture)

Frequency

164
Q

What kind of transducer would produce the best lateral resolution?

A

Beam narrower in far field

Large diameter

High frequency

165
Q

Transducer that would produce the worst lateral resolution?

A

Far field diameter is wide.

Small diameter with low frequency

166
Q

What is continuous wave frequency determined by?

A

Electronic frequency

167
Q

What is Pulsed wave frequency determined by?

A

Thickness of ceramic

Speed of sound

168
Q

What is focal length determined by?

A

Aperture of ceramic

Frequency

169
Q

What is divergence determined by?

A

Aperture of ceramic

Frequency

170
Q

What is another name for diffraction pattern?

A

Huygens wavelet

171
Q

What is the shape of the waves produced by diffraction pattern?

A

V shaped wave

172
Q

What is the Huygens Principle?

A

Hourglass shape of an imaging transducers sound beam

173
Q

The overall hourglass shape of a sound beam is the result of the ______________________ interference of the many sound wavelets emitted from these numerous sound sources.

A

Constructive and destructive interference

174
Q

What is resolution?

A

Ability to image accurately

175
Q

What is Axial resolution?

A

Ability to distinguish two structures that are close to each other

Front to back

Parallel to

Along the beams main axis.

176
Q

What is the synonym for Axial resolution?

A

LARRD:

Longitudinal
Axial
Range
Radial
Depth
177
Q

What creates better axial resolution?

A

Shorter pulses

  • short pulse means short spatial length or short pulse duration
178
Q

What are the units for Axial resolution?

A

Mm, cm - units of distance

179
Q

Equation:

A

LARRD= Spatial Pulse Length/2

180
Q

What does LARRD improve with?

A

Less ringing

Higher frequency

181
Q

Note….

A

As frequency increases, the numerical value of LARRD resolution decreases. This means high frequency transducers have improved LARRD resolution and create more accurate images.

182
Q

What is Axial Resolution best with?

A

Highest frequency

fewest number of cycles per pulse

183
Q

Define Lateral Resolution

A

Minimum distance that two structures are separated by

Side by side

Or perpendicular to sound beam that produces two distinct echoes

184
Q

What is the synonym for Lateral resolution?

A

LATA:

Lateral
Angular
Transverse
Azimuthal

185
Q

Note….

A

Lateral resolution = beam diameter

186
Q

What is point spread artifact?

A

When two side by side structures are closer together than the beam width, only one wide reflection is seen on image

187
Q

What are the three ways focusing alters the sound beam?

A
  1. Narrower “waist” in US beam
  2. Shallower focus
  3. Smaller focus zone
188
Q

What are the general types of focusing?

A
  1. Fixed (conventional)(mechanical)

2. Adjustable (phased array)

189
Q

What are the three methods of focusing?

A
  1. Lens- external focusing
  2. Curved Pizeoelectric Crystal- internal focusing
  3. Electronic focusing- adjustable
190
Q

Note…

A

Single crystal transducers are always fixed focus

191
Q

What are 2D images referred to as?

A

B-scans or “B-mode”

192
Q

What is mechanical scanning?

A

Contains one disc, element

193
Q

What is the steering for mechanical scanning?

A

Mechanical

194
Q

What is the focusing for mechanical scanning?

A

Conventional or fixed

195
Q

What is the image shape for mechanical scanning?

A

Sector

196
Q

If the crystal is destroyed in mechanical scanning, what does the image look like?

A

No image.

197
Q

Switched arrays are also known as what?

A

Sequential

198
Q

What is the steering for linear switched?

A

No steering. Scan lines are parallel and remain equally spaced at depths

199
Q

What is the focusing for a linear switched?

A

Fixed focusing or curved crystal

200
Q

What is image shape for linear switched?

A

Rectangular

201
Q

There is a defective Crystal in a linear switched, what will image look like?

A

Dropout from superficial to deep

Top to bottom

202
Q

What does a phased array mean?

A

Adjustable focus or multi-focus

203
Q

What is the steering and focusing for a phased array?

A

Electronic

204
Q

What is the image shape for a phased array?

A

Sector shaped

205
Q

What is the time delay for a phased array?

A

10ns

206
Q

What is a beam former?

A

Created electronic patterns. Delays are 10ns

207
Q

Multidimensional arrays

A

2D create 3D or 4D images.

208
Q

What resolution does a 1 1/2 dimensional array improve?

A

Elevational

209
Q

Vector array, what is the image shape?

A

Trapezoidal imaging

210
Q

What is contrast resolution?

A

visualizing a variety of gray shades in an image.

211
Q

What is spatial resolution?

A

visualizing detail in an image.

212
Q

What is real-time imaging

A

“motion picture” A series of frames displayed in a rapid fashion to give the impression of constant motion.

213
Q

What is temporal resolution?

A

the ability to accurately locate moving structures at anyh particular instant in time.

214
Q

What is temporal resolution determined by?

A

Frame rate only

215
Q

What are the units of temporal resolution?

A

Hertz (20Hz-100Hz)

216
Q

What is frame rate determined by?

A

1) Imaging depth

2) # of pulses per image

217
Q

What is frame rate limited by?

A

1) speed of sound in the medium

2) imaging depth

218
Q

What is the fundamental limitation of temporal resolution?

A

Speed

219
Q

What 3 things change the number of pulses in an image?

That are under sonographer control

A

1) # of pulses per scan line (multi-foucus)
2) sector size
3) line density

220
Q

The 4th setting that the sonographer controls for temporal resolution, but dose not effect the number of pulses in an image?

A

maximum imaging depth

221
Q

Temporal resolution improves with…

A
  • shallower depth and fewer pulses
  • less time to create am image (higher frame rate)
  • more frames created each second
222
Q

Temporal resolution degrades with…

A
  • deeper and more pulses
  • more time to create an image (lower frame rate)
  • less frames created each second
223
Q

If the imaging depth is doubled the frame rate will be..

A

halved

224
Q

Improving image quality often degrades….

A

temporal resolution

225
Q

Multi focus improves ….

A

Lateral resolution

226
Q

Multi focus degrades..

A

temporal resolution

227
Q

A narrow sector is better for..

A

temporal resolution

228
Q

Line Density

A

the number of scan lines per degree of sector

229
Q

Low line density degrades..

A

spatial resolution

230
Q

With regard to line density, what will create a frame with fewer pulses?

A

Low Line density

231
Q

The time required to make a frame is called?

A

Tf

232
Q

Tf X FR=

A

1

233
Q

When one frame is created in 1/10th of a second then the frame rate will be….

A

10/second or 10 Hz

234
Q

What is an Ultrasound System?

A

a device that produces sound beams, retrieves the echoes and produces visual images and audio signals.

235
Q

What are the 6 components of an Ultrasound system?

A 
Master Synchronizer
Transducer
Pulser
Receiver
Display
Storage
236
Q

What communicates with all of the individual components, and organizes and times their functions so as to operate as
a single integrated system?

A

Master Synchronizer

237
Q

What converts electrical into acoustic energy during transmission and converts acoustic in to electrical energy during reception?

A

Transducer

238
Q

What controls the electrical signals sent to the active elements for sound pulse generation?

A

Pulser

239
Q

What determines the pulse repetition period and pulse amplitude?

A

Pulser

240
Q

What creates a firing pattern for phased array systems (beam former)?

A

Pulser

241
Q

What processes the electronic signal produced by the transducer during reception and producing a picture on a display device?

A

Receiver

242
Q

What is associated with the presentation of processed data for interpretation, monitor, speakers, paper record?

A

Display

243
Q

A device or media that are used to permanently archive the data…

A

Storage

244
Q

This increases the sound intensity created by the transducer and sent into the patient….

A

When the sonographer increases the output power.

245
Q

For a phased array system the pulser is also called the…

A

beam former

246
Q

Other words for Transducer Output

A 
output gain
acoustic power
pulser power
energy output
transmitter output
247
Q

What is determined by the excitation voltage from the pulser?

A

Transducer output

248
Q

The crystal vibrates with a magnitude related to the….

A

Transducer output

249
Q

What results from a transducer output change?

A

All reflections change..the brightness of the entire image changes.

250
Q

Signal

A

meaningful portion of the data

251
Q

noise

A

inaccurate part of the data. Degrades the quality of information.

252
Q

High signal to noise ratio

A

the meaningful part of data is stronger=high quality image

253
Q

Low signal to noise ratio

A

the inaccurate part of the data is stronger=poor quality image

254
Q

Receiver functions

A 
Amplification
Compensation
Compression
Demodulation
Rejection
255
Q

What increases the strength of all electrical signals in the receiver prior to further processing?

A

Amplification

256
Q

Amplification is also called…

A

receiver gain

257
Q

Amplification changes the brightness of…

A

the entire image..”uniform amplification”

258
Q

Preamplifier

A

alters the signal before it is amplified

259
Q

Compensation

A

makes all echoes from similar reflectors appear identical regardless of depth. “uniform brightness from top to bottom”

260
Q

What is used to create uniform brightness from top to bottom?

A

Compensation

261
Q

TGC is

A

compesation

262
Q

The more attenuation…

A

the more TGC must be used

263
Q

TCG curve

A 
near gain
delay
slope
knee
far gain
264
Q

What will you adjust if you cannot see reflectors in the near field?

A

TGC

265
Q

Compression

A

reduces the total range of signals, from smallest to the largest

266
Q

What keeps signals within the operating systems electronics and the gray scale within the range of what the human eye can see?

A

compression

267
Q

What decreases the dynamic range of the signals?

A

compression

268
Q

What allows us to see all gray shades?

A

compression

269
Q

What changes the gray scale mapping?

A

compression

270
Q

What changes the signals form to one more suitable for display?

A

Demodulation

271
Q

What part of demodulation changes all of the negative voltages in to positive ones?

A

rectification

272
Q

What part of demodulation puts and envelope around the “bumps” to even them out?

A

Enveloping or Smoothing

273
Q

What eliminates low-level noise in our images?

A

Rejection

274
Q

Does rejection effect bright echoes?

A

NO

275
Q

Output Power vs Receiver gain

A

When the term suggests outgoing function it is output power.

When the word indicates reception or incoming, the function is receiver gain

276
Q

Harmonics

A

creates scans from sound reflections at 2x the transmitted frequency.

277
Q

Where are harmonics created?

A

In the tissues

278
Q

A transducer creates a sound pulse with a fundamental frequency of 2MHz. In the harmonic mode, an image is created from ?MHz sound reflections is displayed?

A

4

279
Q

Non-linear behavior creates

A

harmonics

280
Q

Sound moves slightly faster in regions of…

A

compression

281
Q

Sound moves slightly slower in regions of

A

rarefaction (lower pressure)

282
Q

Pulse inversion Harmonic Imaging

A

positive and negative pulses are transmitted down each scan line.

283
Q

What is a disadvantage of pulse inversion imaging?

A

degrades temporal resolution, because the frame rate is half that of the fundamental imaging

284
Q

Brightness

A

related to the brilliance of the image

285
Q

contrast

A

determines the range of brilliancies that are displayed.

286
Q

bistable

A

high contrast

287
Q

Analog

A

real world

a variable attains a continuum of values

288
Q

digital

A

computer world

a variable attains only discrete values

289
Q

Scan converter

A

changes the data format.

Gray scale not possible with out it

290
Q

Digital scan converter

A

converts the image into numbers . the numbers can be processed and translated for display as an image

291
Q

The smallest element of a digital picture

A

pixel

292
Q

pixel density

A

pixels per sq inch
low pixel density= poor spatial resolution
high pixel density= good spatial resoluion

293
Q

spatial resolution on a digital display is determined by…

A

pixel density

294
Q

spatial resolution is related to

A

the number of lines per frame

295
Q

the smallest number of digital storage is

A

Binary Digit

296
Q

a bit is

A

bistable, either 0 or 1

297
Q

a group of bits is assigned to

A

each pixel

298
Q

the more bits per pixel the

A

more shades of gray and the better the contrast resolution

299
Q

Byte

A

8 bits

300
Q

2 bytes

A

16 bits is a Word

301
Q

If you have 10 bits per pixel how many shades of gray can be represented per pixel?

A

2 to the 10th power = 1024 shades of gray

302
Q

How many bits are needed to represent 10 shades of gray?

A

4 . 4 bits can display up to 16 shades of gray.

2x2x2x2=16

303
Q

Preprocessing

A

manipulating the data before the storage. Can not be reversed.

304
Q

Post processing

A

manipulating the data after it has been stored. Performed on frozen images.

305
Q

Electrical signals created by the PZT are

A

analog

306
Q

Analog-Digital Conversion

A 
Analog signal from transducer
A to D converter
Digital scan converter
D to A converter
Analog Signal dislpay
307
Q

Read Magnification

A

number of pixels is unchanged and pixel size increases

308
Q

Write Magnification

A

the size of the pixels stays the same and the number of pixels increases

309
Q

Fill-In Interpolation

A

improves images by filling in the gaps between lines. Preprocessing.
Improves image detail (spatial resolution)

310
Q

What artifact causes a granular appearance in tissues that are really homogenous? Created by interference effects.

A

Speckle

311
Q

When are scan lines steered by the transducer in different directions or views, so structures are interrogated by multiple pulses from several different angles?

A

Spatial Compounding

312
Q

What type of transducers can use Spatial Compounding?

A

Phased array

313
Q

What provides a history of past frames that are overlaid or added on top of the current frame?

A

Temporal Compounding or Persistence

314
Q

What divides the reflection into sub-bands of smaller frequency ranges and creates images from each of theses sub-bands?

A

Frequency Compounding

315
Q

Dynamic Aperture

A

a from of electronic receive focusing

Uses a varying number of elements to receive a reflected signal.

316
Q

Edge enhancement

A

increases the contrast at a boundary

317
Q

What uses long sound pulses that contain a complex pattern of frequencies and cycles, called a code?

A

coded excitation

318
Q

coded excitation takes place in the …

A

pulser

319
Q

coded excitation improves…

A 
signal to noise ratio
penetration
axial resolution
spatial resolution
contrast resolution
320
Q

What technique produces images based on a change in shape when a force is applied to a tissue?

A

elsastography

321
Q

What is rendering?

A

creates images with shadow, color, texture and optical effects.

322
Q

dynamic range

A

the ratio of the largest to the smallest signal strength.

323
Q

PACS

A

Picture Archiving and Communications System

324
Q

DICOM

A

Digital Imaging and Communications in Medicine

325
Q

NAS

A

network storage device used in PACS

326
Q

What is flow?

A

the movement of a fluid from one location to another

327
Q

Steady flow

A

fluid movement at a constant speed or velocity.

328
Q

Pulsatile flow

A

arterial
cardiac contraction
high pressure

329
Q

Phasic flow

A

venous
respiration
low pressure

330
Q

What is Laminar flow?

A

streamlines are layered, may be “plug” or “parabloic”

Parallel and aligned

331
Q

What is Turbulent Flow?

A

chaotic flow in many directions and speeds.

332
Q

What is a swirling pattern of rotational flow?

A

vortex

333
Q

What are small regions of turbulent flow that have vastly different velocities?

A

Doppler spectral broadening

334
Q

When flow energy is lost, what does it convert to?

A

sound (murmurs, bruits)

vibration (thrill)

335
Q

What is Energy Gradient?

A

When the total fluid energy at one location differs from the total fluid energy at another location.

336
Q

What is another name for “motion energy”?

A

Kinetic Energy

337
Q

What is a form of potential or stored energy that has the ability to perform work?

A

Pressure energy

338
Q

What is the conversion of other forms of energy into heat?

A

Friciton

339
Q

Viscosity

A

describes the thickness of a fluid (poise)

340
Q

What increases the viscosity of blood?

A

Increased hematocrit or hemoglobin

341
Q

What is a narrowing or irregularity in a lumen?

A

Stenosis

342
Q

Units of resistance?

A

Ohms

343
Q

What are the resistance vessels in circulation?

A

Arterioles

344
Q

What is Bernoulli’s Principle?

A

In a stenosis, the highest velocity, lowest pressure and kinetic energy is highest at the maximum narrowing.

345
Q

During Inspiration

A 
Diaphragm desends
pressure in the abd  increases
venous flow to legs decreases
pressure in the thorax decreases
venous return to heart increases
346
Q

During Exhalation

A 
Diaphragm ascends
pressure in the abd decreases
venous flow to legs increases
pressure in the thorax increases
venous return to heart decreases
347
Q

What is the valsalva maneuver?

A

a bearing down or forceful attempt at expiration, when nose and mouth are closed. It increases pressure in the thorax and reduces all venous flow.

348
Q

What is a doppler shift?

A

a change or variation in the frequency of the sound as a result of motion between the sound source and the receiver. or difference between received and transmitted frequencies.

349
Q

positive doppler shift

A

when source and receiver are approaching each other, so the reflected frequency is higher than the transmitted.

350
Q

negative doppler shift

A

when the source and receiver are moving apart, so the reflected frequency is lower than the transmitted.

351
Q

Does doppler measure frequency or amplitude?

A

frequency

352
Q

if emitted frequency is FE and reflected frequency is FR then…

A

FD (doppler frequency)=FR-FE

353
Q

doppler shift is directly related to…

A

blood cell speed
frequency of the transducer
cosine of the angle

354
Q

doppler shift is inversely related to…

A

speed of sound in the medium

355
Q

doppler shift =

A

2x reflector speed x incident frequency x cos (angle) / propagation speed

356
Q

What requires magnitude and direction?

A

velocity

357
Q

How many crystals are in a continuous wave doppler?

A

2
1 always transmitting
1 always receiving

358
Q

What is the advantage to continuous wave doppler?

A

high velocities are accurately measured

359
Q

What are the disadvantages to continuous wave doppler?

A

range ambiguity

360
Q

How many crystals are in a pulsed wave doppler?

A

1

361
Q

What is the advantage to pulsed wave doppler?

A

since we have a gate we know where the flow is being measured, this is called range resolution or specificity

362
Q

Aliasing is an disadvantage of what?

A

pulsed wave doppler

363
Q

What is it called when you are imaging and using doppler at the same time?

A

duplex

364
Q

What does x axis represent for doppler?

A

time

365
Q

What does y axis represent for doppler?

A

velocity

366
Q

What is it called when high velocities appear negative on doppler?

A

aliasing

367
Q

Nyquist limit=

A

PRF/2

368
Q

What king of doppler does not create aliasing?

A

continuous wave

369
Q

Ways to reduce aliasing are…

A 
use continuous wave
use a lower frequency
select a new view with a shallower sample volume
increase the scale
baseline shift
370
Q

Do smaller or larger sample volumes (gates) produce a doppler spectra with a cleaner window?

A

smaller

371
Q

What are gray shade on a doppler spectrum related to?

A

amplitude of the reflected signal

number of red blood cells creating the reflection

372
Q

What doses color doppler report?

A

average velocities

373
Q

When using color doppler in velocity mode what does the color on the top represent?

A

blood cells flowing towards the transducer

therefore bottom color represents flow away from transducer

374
Q

When using color doppler in variance mode, what does the appearance of colors on the right side of the color bar mean?

A

turbulent flow

therefore left side represents laminar flow

375
Q

What are multiple ultrasound pulses needed to accurately determine red blood cell velocities by Doppler called?

A

doppler packets

can be large or small

376
Q

what are the advantages to large doppler packets?

A

greater accuracy

sensitivity to low flow

377
Q

What are the disadvantages to large doppler packets?

A

more time required

frame rate and temporal resolution are reduced

378
Q

What are the limitations of color power doppler?

A

no measurement of velocity or direction
lower frame rates
flash artifact

379
Q

What are the advantages of color power doppler?

A

increase sensitivity to low flows
not affected by angle , except 90 degrees
no aliasing

380
Q

When is spectral analysis used?

A

to identify the individual frequencies making up the complex signal

381
Q

What are the current methods of spectral analysis?

A

fast fourier transform (FFT)

autocorrelation (less accurate but faster)

DSM PHY (14 decks)

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