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RTE 1418 > Exam 1 > Flashcards

Exam 1 Flashcards

0
Q

ability to img small objects that have high subject contrast

A

spatial resolution

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1
Q

the random fluctuation in the OD of the img

A

noise

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2
Q

2 other terms for spatial resolution

A

detail, recorded detail

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3
Q

what factors affect the visibility of detail

A

img contrast and OD

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4
Q

what is quantum mottle? how does it appear on the img?

A

the random nature by which XRs interacts w/ IR. If produced w fewer XRs, quantum mottle increases; causes grainy appearance

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5
Q

how do you minimize quantum mottle?

A

high mAs, low kVp, slow IR

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6
Q

what’s contrast resolution?

A

ability to img 2 separate objects and visually distinguish btw the 2

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7
Q

how does speed affect detail?

A

fast IRs = high noise, low spatial/contrast resolution slow IRs = low noise, high spatial/contrast resolution

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8
Q

what is sensitometry?

A

study of relationship btw intensity of exposure and blackness (density) on img

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9
Q

what is on the x and y axis on a sensitometric curve?

A

X-axis: LRE, y-axis: OD

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10
Q

3 parts of a characteristic curve?

A
  1. toe, 2. straight-line portion, 3. shoulder
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11
Q

what part of characteristic curve represents optimum contrast?

A

straight-line portion

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12
Q

what part of characteristic curve represents over exposure?

A

shoulder

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13
Q

what part of characteristic curve represents under exposure

A

toe

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14
Q

density can be measured using a

A

densitometer

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15
Q

formula for calculating OD?

A

OD=log(Lo/Lt); Lo - original light, Lt - light transmitted

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16
Q

what is the diagnostically useful density range for an XR?

A

0.25 - 2.5

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17
Q

what is the range for base plus fog density?

A

approx 0.1 - 0.3

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18
Q

radiographic contrast is the product of ______ and ______

A

IR contrast & subject contrast

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19
Q

film contrast is related to the ______ of the _______ part of the characteristic curve

A

slope & straight-line

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20
Q

how do you calculate the slope of a characteristic curve

A

calculate the avg gradient

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21
Q

what is the formula for calculating avg gradient?

A

avg gradient = (OD2 - OD1)/(LRE2 - LRE1); OD2 - OD of 2.0 + base and fog densities (LRE2 assoc w OD2); OD1 - OD of 0.25 + base and fog densities (LRE1 assoc w OD1)

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22
Q

how do you ID the faster characteristic curve?

A

faster films located to the L of slower films (on x-axis) (curve closest to y-axis)

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23
Q

how do you ID the characteristic curve that has more contrast?

A

steeper slope –> higher contrast

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24
Q

how do you ID the characteristic curve that has narrow latitude?

A

steeper slope –> less/narrow latitude

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25
Q

how do you ID the characteristic curve w short scale contrast?

A

steeper slope (narrow latitude = short scale contrast)

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26
Q

how do you ID the characteristic curve w long scale contrast?

A

(wider slope) wide latitude = long-scale contrast

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27
Q

how do you ID characteristic curve w less latitude?

A

narrow latitude = less latitude = steeper slope

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28
Q

latitude and contrast are ________ proportional

A

inversely

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29
Q

3 principal geometric factors that affect XR quality?

A

sharpness, recorded detail, distortion

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30
Q

2 formulas that can be used to calculate the magnification factor?

A

MF = Img Size/Object Size MF = SID/SOD

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31
Q

factors that affect magnification?

A

size, shape, SID & OID

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32
Q

how can you minimize magnification?

A

increase SID, decrease OID

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33
Q

what is shape distortion?

A

unequal magnification of different portions of the same object

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34
Q

what factors affect distortion?

A

object thickness, object position, object shape, SID/OID

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35
Q

will thicker/thinner object be most distorted?

A

thicker

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36
Q

will object in path of CR or away from CR be distorted the most?

A

away from CR

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37
Q

if img of an object is smaller than the object, the img is _________

A

foreshortened

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38
Q

if img of object is longer than the object, it is said to be _________

A

elongated

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39
Q

what is spatial distortion?

A

misrepresentation in the img of the actual spatial relationships among objects

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40
Q

focal spot blur is ______ on the anode side and ______ on the cathode side of the img

A

small (anode); large (cathode)

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41
Q

6 factors that affect subject contrast?

A

pt thickness, tissue mass density, effective atomic #, object shape, kVp, subject contrast

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42
Q

what is the most important influence on subject contrast?

A

kVp

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43
Q

low kVp produces ________ contrast

A

high subject/short scale contrast

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44
Q

high kVp produces __________ contrast

A

low subject/long scale contrast

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45
Q

motion blur will be more visible when using _________ SID

A

short

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46
Q

motion blur will be more visible when using _______ OID

A

long

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47
Q

3 factors that control the amount of scatter produced?

A

kVp, field size, pt thickness

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48
Q

increasing kVp will produce _______ scatter

A

more

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49
Q

increasing collimation will produce ______ scatter

A

less

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50
Q

increasing the field size will produce ________ scatter

A

more

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51
Q

thicker pt will produce _____ scatter

A

more

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52
Q

using compression during a KUB will produce ______ scatter

A

less

53
Q

will a KUB have more contrast if pt in supine or prone pos?

A

prone

54
Q

will a cone or cylinder collimation device produce an XR w better contrast?

A

cone

55
Q

f(x) of the 1st stage entrance shutter?

A

to prevent off-focus rad

56
Q

f(x) of PBL?

A

to limit the field size to the IR size

57
Q

what does PBL stand for?

A

positive beam limiting device

58
Q

what devices can be used to minimize the amount of rad reaching the IR?

A

Grid and beam restrictors (*variable aperture collimator, cones, cylinders, aperture diaphragm)

59
Q

what is the grid ratio?

A

ratio of the height of pb strips to the D btw them

60
Q

how do you calculate grid ratio?

A

Grid Ratio = H/D

61
Q

what is grid frequency?

A

the # of pb strips per unit length (in/cm)

62
Q

principal f(x) of rad grid?

A

absorb scatter rad

63
Q

interspacing materials used in rad grids?

A

Al & plastic fiber

64
Q

types of grids used in rad

A

linear and crossed

65
Q

most common type of grid used

A

linear

66
Q

which grid type produces more contrast?

A

crossed

67
Q

which grid type has more pos latitude?

A

linear

68
Q

does a high or low ratio grid have more pos latitude?

A

low ratio grid

69
Q

main disadvantages of a parallel grid?

A

less contrast, removes less scatter

70
Q

main disadvantages of crossed grids?

A

less pos latitude, absorbs more primary beam (may need to increase mAs to replace beam, which is more pt dose)

71
Q

factors that control/affect detail?

A

screen blur, geometric blur, and motion blur

72
Q

as the speed of the IR increases, rad noise ______ and spatial res is _______

A

increases (rad noise); decreased (spatial res)

73
Q

what is the avg grid frequency used in rad depts?

A

25-45 lines/cm or 60-110 lines/in

74
Q

which grid ratio has more pos latitude?

A

low ratio grid

75
Q

what are the most important characteristics of img qual? (4)

A

spatial res., contrast res., noise & artifacts

76
Q

primary control of rad contrast?

A

kVp

77
Q

primary control of OD?

A

mAs

78
Q

film factors? (3)

A

characteristic curve, OD, film processing

79
Q

Geometric factors? 3(4)

A

magnification, distortion, focal spot blur, (heel effect)

80
Q

detail is controlled by what? influenced by?

A

focal spot size; SID/OID and motion

81
Q

factors that control/affect detail?

A

screen blur, geometric blur, & motion blur

82
Q

if the speed of the IR is doubled, what will you do to maintain the density?

A

reduce mAs by 1/2 new IR speed/old IR speed = old mAs/new mAs

83
Q

MATH: If 3600 light beams strike an XR and 36 light beams pass through it, what’s the OD?

A

3

84
Q

in a particular grid the length of the pb strips are 12 mm and are positioned 1 mm apart. what is the grid ratio?

A

12:1

85
Q

grids are required when?

A

anatomical part 10 cm or greater or more than 60 kVp needed

86
Q

which grid ratio will have better contrast?

A

high grid ratio (absorbs more scatter)

87
Q

a grid is made w pb strips that are 16 mm long and separated by an interspacing material of 2 mm wide. what is the grid ratio?

A

8:1

88
Q

how do you calculate D to grid cutoff?

A

D to cutoff = SID/grid ratio

89
Q

what happens to img contrast when grids are used?

A

img contrast approximately doubles

90
Q

Reverse:

noise

A

the random fluctuation in the OD of the img

91
Q

Reverse:

spatial resolution

A

ability to img small objects that have high subject contrast

92
Q

Reverse:

detail, recorded detail

A

2 other terms for spatial resolution

93
Q

Reverse:

img contrast and OD

A

what factors affect the visibility of detail

94
Q

Reverse:

the random nature by which XRs interacts w/ IR. If produced w fewer XRs, quantum mottle increases; causes grainy appearance

A

what is quantum mottle? how does it appear on the img?

95
Q

Reverse:

high mAs, low kVp, slow IR

A

how do you minimize quantum mottle?

96
Q

Reverse:

ability to img 2 separate objects and visually distinguish btw the 2

A

what’s contrast resolution?

97
Q

Reverse:

study of relationship btw intensity of exposure and blackness (density) on img

A

what is sensitometry?

98
Q

Reverse:

densitometer

A

density can be measured using a

99
Q

Reverse:

IR contrast & subject contrast

A

radiographic contrast is the product of ______ and ______

100
Q

Reverse:

calculate the avg gradient

A

how do you calculate the slope of a characteristic curve

101
Q

Reverse:

sharpness, recorded detail, distortion

A

3 principal geometric factors that affect XR quality?

102
Q

Reverse:

size, shape, SID & OID

A

factors that affect magnification?

103
Q

Reverse:

increase SID, decrease OID

A

how can you minimize magnification?

104
Q

Reverse:

unequal magnification of different portions of the same object

A

what is shape distortion?

105
Q

Reverse:

object thickness, object position, object shape, SID/OID

A

what factors affect distortion?

106
Q

Reverse:

foreshortened

A

if img of an object is smaller than the object, the img is _________

107
Q

Reverse:

elongated

A

if img of object is longer than the object, it is said to be _________

108
Q

Reverse:

misrepresentation in the img of the actual spatial relationships among objects

A

what is spatial distortion?

109
Q

Reverse:

pt thickness, tissue mass density, effective atomic #, object shape, kVp, subject contrast

A

6 factors that affect subject contrast?

110
Q

Reverse:

kVp, field size, pt thickness

A

3 factors that control the amount of scatter produced?

111
Q

Reverse:

to prevent off-focus rad

A

f(x) of the 1st stage entrance shutter?

112
Q

Reverse:

to limit the field size to the IR size

A

f(x) of PBL?

113
Q

Reverse:

Grid and beam restrictors (*variable aperture collimator, cones, cylinders, aperture diaphragm)

A

what devices can be used to minimize the amount of rad reaching the IR?

114
Q

Reverse:

ratio of the height of pb strips to the D btw them

A

what is the grid ratio?

115
Q

Reverse:

the # of pb strips per unit length (in/cm)

A

what is grid frequency?

116
Q

Reverse:

less contrast, removes less scatter

A

main disadvantages of a parallel grid?

117
Q

Reverse:

less pos latitude, absorbs more primary beam (may need to increase mAs to replace beam, which is more pt dose)

A

main disadvantages of crossed grids?

118
Q

Reverse:

screen blur, geometric blur, and motion blur

A

factors that control/affect detail?

119
Q

Reverse:

25-45 lines/cm or 60-110 lines/in

A

what is the avg grid frequency used in rad depts?

120
Q

Reverse:

spatial res., contrast res., noise & artifacts

A

what are the most important characteristics of img qual? (4)

121
Q

Reverse:

kVp

A

primary control of rad contrast?

122
Q

Reverse:

mAs

A

primary control of OD?

123
Q

Reverse:

characteristic curve, OD, film processing

A

film factors? (3)

124
Q

Reverse:

magnification, distortion, focal spot blur, (heel effect)

A

Geometric factors? 3(4)

125
Q

Reverse:

focal spot size; SID/OID and motion

A

detail is controlled by what? influenced by?

126
Q

Reverse:

screen blur, geometric blur, & motion blur

A

factors that control/affect detail?

127
Q

Reverse:

reduce mAs by 1/2 new IR speed/old IR speed = old mAs/new mAs

A

if the speed of the IR is doubled, what will you do to maintain the density?

128
Q

Reverse:

img contrast approximately doubles

A

what happens to img contrast when grids are used?

129
Q

What is IR contrast?

A

inherent in screen-film and is somewhat influenced by film processing

130
Q

What is subject contrast?

A

determined by size, shape, and XR attenuating char.’s of anatomy and the energy (kVp) of XR

RTE 1418 (3 decks)

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