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RAD1418 > Unit 5 > Flashcards

Unit 5 Flashcards

1
Q

3 definition of spatial resolution:

A
  1. the smallest structures that may be seen in an image measured in LP/mm.
  2. the ability to image adjacent objects as being separate.
  3. refers to the distinctness or sharpness of structural lines that represent an image.
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2
Q

What is spatial resolution expressed/measured in?

A

LP/mm

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3
Q

The ____ the number of LP/mm, the _____ the object that can be imaged, and the ____ the spatial resolution.

A

The higher the number of LP/mm, the smaller the object that can be imaged, and the better the spatial resolution.

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4
Q

What does LP/mm represent?

A

The smallest size object that the imaging system is capable of representing.

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5
Q

Penumbra:

A

term that describes the areas of unsharpness around the periphery of the radiographic image

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6
Q

Umbra:

A

term that describes a lack of unsharpness around the periphery of a radiographic image.

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7
Q

Factors that Affect Spatial Resolution: 8

A
  1. OID
  2. SID
  3. Filament Size
  4. Anode Angle Size
  5. Pt. Motion
  6. Shape distortion
  7. Size distortion
  8. Imaging System/Display
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8
Q

OID:

A

the distance from the IR to the object being imaged

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9
Q

Increasing OID results in the object being ____

A

magnified

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10
Q

Decreasing OID =

A

less mag

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11
Q

What has the largest impact on object mag?

A

OID

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12
Q

To double the size of a body part (2x mag), move the part 1/2 way between the ______ and the _____

A

IR and Source

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13
Q

SID:

A

the distance from the IR to the anode target

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14
Q

When you increase SID, mag ___

A

decreases

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15
Q

When you decrease SID, Mag _____

A

increases

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16
Q

Size distortion only alters ___ not shape

A

size

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17
Q

Size distortion is influenced by ___, ____, and ___.

A

SID, OID, and SOD

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18
Q

Longer SID = ____ size distortion

A

less

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19
Q

Shorter SID = ___ size distortion

A

more

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20
Q

more mag = ___ SR

A

less

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21
Q

less mag = ___ SR

A

more

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22
Q

SOD:

A

source to object distance

distance between the anode target and the object

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23
Q

the source of x-rays:

A

the target

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24
Q

Actual Focal Spot:

A

the area of the anode target struck by electrons from the cathode

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25
Q

AFS size is determined by

A
  1. Filament size
  2. Anode Target Angle
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26
Q

The larger the AFS, the ___ the SR

A

less

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27
Q

The smaller the AFS, the ____ the SR

A

better

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28
Q

Larger filament size = ____ AFS

A

larger

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29
Q

Smaller filament size = _____ AFS

A

smaller

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30
Q

Larger filament size = ____ SR

A

less

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31
Q

Smaller filament size = ____ SR

A

better

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32
Q

Smaller the filament = ___ EFS = ___ SR

A

smaller EFS = better SR

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33
Q

larger the filament = ____ EFS = ____ SR

A

larger EFS = less SR

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34
Q

smaller AA = ____ EFS= ___ SR

A

Smaller EFS = better SR

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35
Q

An increase in kVP results in which of the following?
1) Increased photon quantity
2) Increased photon quality
3) increased percentage of photoelectric effect

A

1 and 2

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36
Q

An increase in kVp will increase photon quality and quantity, but will ____ the percentage of the photoelectric effect.

A

An increase in kVp will increase photon quality and quantity, but will REDUCE the percentage of the photoelectric effect.

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37
Q

A 15% increase in kVp will double exposure to the ____

A

IR

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38
Q

A high contrast radiographic image has few shades of gray. It is also known as an image with an ____

A

Short gray scale

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39
Q

In order to maintain IR exposure, which of the following would be done if kVp was reduced by 15%?

A

Increase mAs by 100%.

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40
Q

While performing a portable abdominal radiograph, the technologist is satisfied with the IR exposure but would like to increase the subject contrast. What adjustments should be made to their exposure technique in order to improve subject contrast and maintain image receptor exposure?

A

Decrease kVp 15% and double mAs

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41
Q

Shorter OID = ___ MAG

A

less

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42
Q

Longer OID = ____ MAG

A

more

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43
Q

Larger AA = ____ EFS = ____ SR

A

greater EFS and less SR

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44
Q

EFS:

A

the area projected onto the pt.

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45
Q

Smaller filament = ___ SR

A

better

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46
Q

Focal spot blur:

A

blurred region of a radiograph that tech has little control over

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47
Q

Focal Spot Blur origin:

A

due to geometric quality of the beam

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48
Q

____ OID helps reduce effects of focal spot blur

A

reduced

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49
Q

Line Focus Principle:

A

states that by angling the face of the anode target, a large AFS can be maintained and a small EFS size can be created.

50
Q

On an angled anode with an angle that is _________, EFS is always smaller than FSS

A

<45 degrees

51
Q

a larger AA = ____ EFS size

A

larger AA = smaller EFS size

52
Q

Why do we want to make the AFS larger than the filament size?

A

Heat dissipation.
The larger the angle, the greater ability of the anode to dissipate heat.

53
Q

What is the line focus principle purpose?

A

to create a desired small EFS after creating a larger AFS

54
Q

____ target angles = sharper images

A

less

55
Q

____ AA = better heat disspiation

A

Greater

56
Q

____ AA = less heat dissipation

A

Less

57
Q

Larger filament = ____ AFS

A

larger

58
Q

Smaller filament = ___ AFS

A

smaller

59
Q

Greater EFS = ____ divergence = _____ SR

A

Greater EFS = more divergence = less SR

60
Q

Smaller EFS = _____ divergence = _____ SR

A

Smaller EFS = less divergence = more SR

61
Q

Pt. motion always ____ SR

A

Lowers

62
Q

Shape distortion:

A

distortion of object shape

63
Q

“True distortion”

A

Shape Distortion

64
Q

Types of shape distortion:

A

Foreshortening
Elongation

65
Q

Shape distortion results from ____

A

Anatomy, CR, and IR alignment

66
Q

Which shape distortion is worse, and why?

A

Foreshortening. Can superimpose anatomy, and miss pathology.

67
Q

Elongation cause:

A

Cr angled to anatomy.
- Angle of the CR will project the anatomy.
IR angled but CR and anatomy are perpendicular.

68
Q

Foreshortening cause:

A

Anatomy not parallel with the IR

69
Q

Examples of using shape distortion:

A

1) AP Axial Towne Skull
- better images occipital and parietal bones
2) PA Axial Projection (Tunnel View)
- elongation of intercondyloid fossa
3) PA Projection of OS Calcis
- elongation of calcaneous

70
Q

Image distortion types:

A

Size and Shape

71
Q

Size distortion causes:

A

Increased OID
Decreased SID
Increased Mag = more penumbra = less SR

72
Q

Shape distortion causes:

A

Elongation from angling CR or IR
Foreshortening from angling the anatomy

73
Q

3 primary geometric factors affecting image quality:

A

1) Magnification
2) Distortion (shape and size)
3) Focal spot blur: has to do w/ divergence

  • all cause blur
74
Q

Prime exposure factor and Pt. dose:

A

1) kVp
2) mA
3) Time
4) SID (distance)

75
Q

Increasing kVp increases the quality and penetrability of the beam.

The creation of a _____ # of photons is created at the target when kVp increases.

A

Greater

76
Q

X-ray quantity varies _______ w/ changes in kVp

A

Exponentially

77
Q

Changes in x-ray quantity is _____ to the square of the ratio of the kVp

A

Proportional

78
Q

When kVp is doubled, the beam quality increases by ______

A

a factor of 4

79
Q

kVp x2 = Quantity x

A

4

80
Q

Increasing kVp = increasing beam quantity along the entire spectrum of the x-ray beam = _____ pt. dose

A

increased

81
Q

Bigger beam = ____ dose

A

more

82
Q

There are more lower energy photons created that will be absorbed as dose, along with a greater number of higher energy photons that pass through the pt.

Increased dose = ____ transmission

A

increased

83
Q

There is a greater proportional increase in the # of high energy photons that will pass through the pt., therefore there is a ____ in image contrast

A

Decrease

84
Q

15% rule:

A

creates a 30% increase of photons hitting the pt.

85
Q

Increasing kVp by 15% is equivalent to the mAs being ____

A

doubled

86
Q

a 15% increase in kVp does not double ______

A

X-ray intensity

87
Q

a 15% increase in kVp is equivalent to ______ ____ to the IR

A

doubling mAs

88
Q

Radiographically, only a 15% increase in kVp is necessary to double IR exposure for two reasons:

A

1) increased # of photons created
2) increased # of photons penetrating the pt. and reaching the IR (other 70%)

89
Q

Increasing kVp is better than increasing ____

A

Increasing mAs

90
Q

kVp increased 15% = _x photons hitting the IR = _x mAs

A

kVp increased by 15% = 2x photons hitting the IR = 2x mAs

91
Q

Decreasing kVp by 15% is equivalent to _____ the mAs

A

halving

92
Q

a 15% decrease of kVp does not half the ____ ____

A

x-ray intensity

93
Q

a 15% decrease in kVp is the equivalent to halving the ____ to the IR.

A

mAs

94
Q

Radiographically, only a 15% decrease in kVp is necessary to half IR exposure for two reasons:

A

1) decreased # of photons created
2) decreased # of photons penetrating the pt. and reaching the IR

95
Q

Quantum Noise

A

Umbrella term?

96
Q

Underexposed means:

A

kVp or mAs is insufficient

97
Q

If you increase kVp 15%, but don’t touch mAs = _x photons will strike the IR and fix the image

A

2x

98
Q

To increase the exposure to the IR, ____ kVp by 15%

A

increase

99
Q

To decrease the exposure to the IR, ____ kVp by 15%

A

decrease

100
Q

Decrease contrast and maintain exposure by ___ kVp 15% and ___ mAs

A

increase kVp 15% and 1/2 mAs

101
Q

Increase contrast and maintain exposure by ____ kVp 15% and ___ mAs

A

decrease kVp 15% and double mAs

102
Q

15% rule can ____ pt. dose

A

decrease

103
Q

Increasing kVp 15% and 1/2 mAs 50% = _____ less dose

A

20%

104
Q

Increasing kVp 15% without adjusting mAs will increase pt. dose by ____

A

30%

105
Q

mAs and dose relationship:

A

proportional

106
Q

As mA increases, so does the # ________ crossing the tube to reach the anode

A

Electrons

107
Q

2x mA = 2x electrons = 2x xrays emitted

A

1/2 mA = 1/2 electrons = 1/2 xrays emitted

108
Q

Time (S):

A

the amount of time that potential difference (voltage) is applied to the tube.

109
Q

Changes in the length of time a tube is energized will effect the total # of ____ flowing from C to A

A

electrons

110
Q

exposure time is directly proportional to the # of electrons crossing the tube, and is also directly proportional to the # of ____

A

x-rays generated

111
Q

2x time = 2x # of electrons = 2x xrays generated
2x time = 2x dose
1/2 time = 1/2 dose

A

2x time = 2x # of electrons = 2x xrays generated
2x time = 2x dose
1/2 time = 1/2 dose

112
Q

Beam Intensity:

A

the measurement of the concentration of photons in the primary beam measured at a single point.

113
Q

Factors affecting beam intensity:

A

1) mA
2) exposure time
3) kVp
4) distance:
5) target material
6) target angle
7) generator type
8) filtration

114
Q

Intensity of the beam and exposure to the IR varies greatly w/ changes in distance because:

A

the beam diverges as it travels from the anode target.

115
Q

X-ray intensity and exposure to the IR will decrease as distance ___

A

increases

116
Q

X-ray intensity and exposure to the IR will increase as distance ____

A

decrease

117
Q

What illustrates the relationship between distance and beam intensity?

A

Inverse Square Law

118
Q

If you double distance = Dose _____ x4

A

decreases

119
Q

If you half distance = dose ____ x4

A

increases

120
Q

A ____ SID requires mAs to increase to maintain exposure to the IR

A

Increased

121
Q

A _____ SID requires mAs to decrease to maintain exposure to the IR

A

decreased

RAD1418 (5 decks)

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