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Image Prod & Eval > Image Eval Quiz 4 > Flashcards

Image Eval Quiz 4 Flashcards

1
Q

What makes it easier to identify objects in images?

A

A greater difference between the shade of the object and the background

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2
Q

What are intensity differences called?

A

Contrast

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3
Q

What does a greater difference in intensity produce?

A

Higher contrast

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4
Q

What is image noise?

A

Unwanted often grainy appearances in radiographs

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5
Q

What is one form of noise?

A

Scattered radiation

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6
Q

What are 2 other forms of noise in images?

A

Electronic and statistical

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7
Q

What is Electronic noise?

A

Mechanical noise from a machine (monitor)

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8
Q

What is Statistical noise?

A

Noise from an algorithm used to construct an image

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9
Q

What is quantum mottle?

A

Image noise that occurs from a lack of penetration due to low kVp or mAs

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10
Q

What is the predominant type of noise in digital images?

A

Quantum mottle

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11
Q

What does noise do to images?

A

Degrades the image and reduces contrast

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12
Q

When is scatter radiation generated?

A

When x-rays strike atoms in a patient, table or other objects

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13
Q

What direction does scatter travel?

A

In random directions

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14
Q

What contrast level is the goal of technologists?

A

Optimum contrast

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15
Q

How does noise affect contrast?

A

Noise reduces subject contrast

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16
Q

Can noise be entirely eliminated?

A

No

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17
Q

What are the three factors that make up the visibility of an image?

A
  • Intensity
  • Contrast
  • Noise
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18
Q

How should intensity and contrast be kept in an image?

A

At an optimal level

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19
Q

How should noise be kept?

A

At a minimum

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20
Q

What is gray scale?

A

The range of different brightness’s in an image

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21
Q

What is a long gray scale?

A

An image with many different grays with small differences between them

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22
Q

What is the contrast of long gray scale?

A

Low contrast

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23
Q

What is short gray scale?

A

An image with less gray and more differences between them

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24
Q

What is the contrast of short gray scale?

A

High contrast

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25
Q

How can digital images that appear on monitors have their contrast adjusted?

A

Through windowing

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26
Q

How does windowing work?

A

When the brightness levels are adjusted and the gray scale is changed from long to short and vise versa

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27
Q

How should images be presented on a screen?

A

Not entirely white or black, should be in an intermediate level of gray scales

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28
Q

What happens if an image is too long in contrast?

A

One gray may not be able to be distinguished from each other

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29
Q

What does an image that is overly dark indicate?

A

That the part/object was over penetrated

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30
Q

What does over penetration of an object mean in terms of attenuation?

A

Little attenuation

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31
Q

How can optical density be measure in film radiographs?

A

Using a densitometer

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32
Q

How is digital brightness indicated?

A

Numerically, usually known as level (c)

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33
Q

How are most images viewed?

A

As Negatives

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34
Q

What are the qualities of image negatives?

A

The tissues that attenuate the beam more are white and tissues that attenuate the beam less are black

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35
Q

What process is used to change a negative image to a positive image?

A

Subtraction

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36
Q

What are qualities of image positives?

A

The tissues that attenuate the beam more are black and the tissues that attenuate the beam less are white

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37
Q

What is radiographic contrast?

A

The proportional difference between the brightness of two adjacent details

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38
Q

What is image contrast independent of?

A

Brightness

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39
Q

How is contrast measured?

A

As a ratio between the darker detail and lighter detail

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40
Q

How can an image be darkened while retaining its contrast?

A

If the ratio between bright and dark shades stays the same

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41
Q

What kV produces a longer wavelength photon?

A

Low kV

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42
Q

What is the penetration of a longer wavelength photon?

A

Low penetration

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43
Q

What type of gray scale does a longer wavelength photon (low kV) create?

A

Short scale

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44
Q

How can the brightness of digital images be manipulated on a computer?

A

By leveling

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45
Q

What is signal?

A

All the desirable information for an object based on its contrast

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46
Q

How is signal calculated?

A

The total exposure minus the scatter

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47
Q

What is the Signal to Noise Ratio (SNR) compare?

A

The relationship between information and noise in an image

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48
Q

How can an image be made better regarding noise and signal?

A

By reducing noise or increasing signal

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49
Q

How does an increased signal usually appear on an image?

A

As a brighter overall image

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50
Q

What are artifacts?

A

Any objects that are not a part of the image

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51
Q

What are some types of artifacts?

A
  • Snaps on a hospital gown
  • Leads to EKGs
  • Zippers, Jewelry
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52
Q

How does a densitometer work?

A

Measures the darkness of a plastic film

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53
Q

What are not examples of Artifacts?

A

Bullets or objects swallowed

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54
Q

What is brightness?

A

The opposite of density and the degree of whiteness of an image

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55
Q

What is brightness caused by?

A

A lack of radiation exposure

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56
Q

What is density?

A

The opposite of brightness, and the degree of darkness in an image

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57
Q

What is density caused by?

A

The presence of radiation exposure

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58
Q

Diagnostic information can be lost if an image has these qualities?

A
  • Excessive contrast
  • Excessive grey scale
  • Excessive blur
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59
Q

How does focal spot relate to sharpness of detail?

A

The smaller the focal spot, the better the sharpness

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60
Q

What are the 3 formulas tied to geometrical qualities of the image?

A
  • Unsharpness Penumbra formula
  • Radiographic Sharpness formula
  • Magnification formula
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61
Q

What is geometrical integrity made up of?

A
  • Sharpness
  • Magnification
  • Shape Distortion
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62
Q

What is another name for geometric integrity?

A

Recognizability

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63
Q

Where is sharpness on a radiograph viewed from?

A

The edges of the object

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64
Q

What does sharpness measure?

A

The extent of blur at the edges of the object

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65
Q

What is the technical term for sharpness?

A

Spatial resolution

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66
Q

What is resolution?

A

The total amount of useful information in an image

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67
Q

What is spatial resolution?

A

The ability to distinguish two objects that are close in proximity to each other

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68
Q

What are two ways in which image resolution can be lost?

A

By blur or loss of contrast

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69
Q

What does a loss in image resolution result in?

A

Difficulty distinguishing details

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70
Q

What is blur?

A

The Unsharpness of an image

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71
Q

What is another name for blur?

A

Penumbra

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72
Q

What are the inner areas of an image without shadows called?

A

Umbra

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73
Q

What would a pure umbra image produce?

A

An image with perfectly sharp edges

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74
Q

Where is penumbra produced on an image?

A

At the edges of the object

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75
Q

What is magnification?

A

The difference between the size of the real object and the size of the projected image

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76
Q

What is magnification a type of?

A

Distortion that changes the size of the object

77
Q

At what level should magnification be kept in an image?

A

At a minimum

78
Q

Why is important to keep magnification to a minimum?

A

To make sure the physician sees the object as close to its true size

79
Q

What is shape distortion?

A

The difference between the shape of the real object and shape of the projected image

80
Q

What are the two forms of shape distortion?

A

Foreshortening and Elongation

81
Q

What is Foreshortening?

A

When the object gets compressed in the image

82
Q

How does Foreshortening occur?

A

When the object is not parallel to the IR or the IR is tilted

83
Q

What is Elongation?

A

When one portion of the object gets stretched out in the image

84
Q

What causes elongation?

A

The angle of the tube

85
Q

Which of the two shape distortions can be fixed?

A

Elongation

86
Q

How is shape distortion expressed in terms of length/width?

A

When the length or the width is changed by elongation/foreshortening, not both changed

87
Q

If all parts of an image is changed uniformly, what type of distortion does that represent?

A

Magnification

88
Q

What are the 3 things Unsharpness is controlled by?

A

SOD, OID and size of the focal spot in the tube

89
Q

What is the Unsharpness Penumbra formula?

A

Unsharpness = Penumbra = FS x OID/SOD

90
Q

What does the Unsharpness Penumbra formula measure?

A

The amount of unsharpness/penumbra that will be spread across a certain area

91
Q

What is the Radiographic Sharpness Formula?

A

Exposure B (SOD/OID) / Exposure A (SOD/OID)

92
Q

What does a higher radiographic number represent?

A

Higher relative sharpness

93
Q

What does the Radiographic Sharpness Formula measure?

A

The quantity of how much sharper one exposure is when compared to another

94
Q

What is a device used to measure sharpness?

A

A line pair tool

95
Q

What 5 factors affect the sharpness of a radiograph?

A

Motion
Geometry
Focal Spot size
Size of detector elements
Size of monitor picture elements (pixels)

96
Q

If motion could be controlled what would it lead to?

A

Increased image resolution

97
Q

What does motion cause on an image?

A

Blurriness

98
Q

In a magnified image, how are length and width different from the original image?

A

They are both measured larger

99
Q

On radiographs of bones, why is there always some inherent magnification?

A

Because of the soft tissue

100
Q

What is the magnification formula?

A

Image Size/object size = SID/OID

101
Q

What does the magnification formula calculate?

A

The projected size of an image

102
Q

What does SOD equal?

A

SID-OID

103
Q

What are the two factors of resolution (image quality)?

A

Visibility
Recognizability

104
Q

What are 3 factors of Visibility?

A

Brightness
Contrast
Noise

105
Q

What are 3 factors of Recognizability?

A

Sharpness
Magnification
Shape Distortion

106
Q

What is magnification affected by?

A

SID, OID and to an extent SOD

107
Q

What happens to magnification when the SID is lower?

A

Magnification increases

108
Q

What happens to spatial resolution when magnification increases?

A

It becomes worse

109
Q

What positive role does magnification play in imaging?

A

It can help identify smaller details that otherwise wouldn’t be visible on an actual sized object

110
Q

Which type of x-ray produces the most Foreshortening?

A

Portable x-rays

111
Q

How can you counteract unwanted OID?

A

By increasing SID

112
Q

How does SID relate to magnification?

A

As SID is decreased, magnification increases

113
Q

How is magnification related to sharpness?

A

As magnification is decreased, sharpness increases

114
Q

How does SID relate to sharpness?

A

As SID is increased, sharpness increases

115
Q

Where is milliamperage adjusted?

A

By the technologist on the console

116
Q

What does milliamperage control?

A

Resistance in the wire leading to the filament

117
Q

What happens to electrons when mA is increased?

A

The flow of electrons are increased and the filament heats up which allows more electrons to be boiled off

118
Q

What impact does an increase in mA have on photon quantity?

A

Increases the quantity (intensity)

119
Q

What is the proportional relationship between mA and photons?

A

Directly proportional

120
Q

What controls the intensity of the x-ray beam?

A

The mA station on the console

121
Q

If mA is doubled how many x-rays will be produced?

A

X-rays will be doubled

122
Q

How is exposure time measured?

A

In seconds (usually milliseconds)

123
Q

What is exposure?

A

The amount of time the beam is activated

124
Q

What is the proportional relationship between exposure and intensity?

A

Directly proportional

125
Q

What is the proportional relationship between mA and time?

A

They are inversely proportional

126
Q

If you want to maintain an exposure, how would mA or time be adjusted?

A

Raise mA and lower time OR raise time and lower mA

127
Q

What is the formula for reciprocity law?

A

mAo x so = mAn x sn

128
Q

How does the reciprocity law work?

A

The product of mA and time must yield the same mAs to maintain a specific exposure

129
Q

How is mAs defined?

A

The product of milliamperage and seconds

130
Q

What is the primary factor of exposure?

A

mAs

131
Q

What does a primary factor mean?

A

Its the preferred way to adjust exposure

132
Q

What is the mAs formula?

A

mA x time = mAs

133
Q

What causes quantum mottle?

A

A lack of exposure

134
Q

What are examples of a lack of exposure?

A

Low mAs, less photon/quanta

135
Q

When does mottle show more?

A

When an image is magnified which is why its important to look at exposure indicator

136
Q

Which systems have noise levels exaggerated in images?

A

Digital systems

137
Q

How do digital systems create exaggerated levels of noise?

A

Amplify signals from pixels

138
Q

How should technologists ensure proper exposure to the IR?

A

Minimize mAs and enter enough kVp to penetrate the part

139
Q

How does mAs affect dose?

A

It directly affects dose

140
Q

How can mAs be realized in imaging?

A

By looking at exposure indicator numbers

141
Q

Is mAs a factor in determining contrast?

A

No because its an electrical factor which can’t be related to recognizability features

142
Q

What does mAs control in an image?

A

Intensity of an exposure, which bears upon brightness and quantum mottle

143
Q

How does motion show in a radiograph?

A

Shows like blur

144
Q

How can motion be reduced in an image?

A

By reducing exposure time

145
Q

What are different types of motion?

A

Movement of hands or peristaltic waves of the esophagus

146
Q

How can motion be reduced in a patient?

A

Communicate with a patient, lower time and increase mA

147
Q

What is milliamperage a unit for measuring?

A

Rate of electrical current flowing during an exposure

148
Q

How does angling the x-ray beam distort the image?

A

Causes elongation

149
Q

What is another way shape distortion can be achieved on an image?

A

By off-centering the beam

150
Q

How does angling the part distort the image?

A

Causes foreshortening

151
Q

What is kilovoltage?

A

The electrical force that pushes electrons across the tube

152
Q

What are the abbreviations for kilovoltage?

A

KV or keV

153
Q

What is placed upon a tube to get the electrons to move from the negative cathode to positive anode?

A

Potential Difference

154
Q

How is potential difference adjusted?

A

By the technologist by their kVp selection

155
Q

What does a greater potential difference bring about?

A

The greater the KV and measure of electrical quality and intensity

156
Q

How is kVp based on alternating current AC measured?

A

By looking at the peak or average values as a sine wave function

157
Q

What is tissue penetration a direct function of?

A

The average energy of the x-rays

158
Q

What are the two ways kV must be measured?

A

Average kV or peak kV (kVp)

159
Q

Why does Kv need to be measured as an average or peak?

A

Because the kilovoltage is constantly changing and the peak or average are the only ways to capture the measurement with movement taken into account

160
Q

What is the function of kVp?

A

To penetrate the part and to achieve the best subject contrast in an image

161
Q

What level should kVp be set to meet its function?

A

Optimal level (not too high or low)

162
Q

What does an optimal level of kVp ensure for tissues?

A

That all tissues are represented at some degree

163
Q

What is a rule of thumb for kVp?

A

To set it high enough to penetrate the part

164
Q

What is a general rule for the relationship between kVp and mAs?

A

No amount of mAs (radiation) can compensate for insufficient kVp (penetration)

165
Q

If kVp is low but mAs is high, what effect does it have on an image?

A

The part will not be properly penetrated and anatomical details will be missing in the image

166
Q

What does a higher kVp provide an image with?

A

More gray levels

167
Q

What do more gray levels (long contrast) demonstrate?

A

Demonstrates more anatomy as more tissues are able to be captured at varying degrees

168
Q

What type of contrast is produced with higher kVp?

A

Low contrast

169
Q

What is a minimum kVp?

A

The lowest kVp that still provides some degree of penetration through all tissues of interest

170
Q

How does higher KV affect dose?

A

Higher KV reduces dose

171
Q

What type of relationship exists between kVp and exposure?

A

An exponential relationship

172
Q

What is the 15% rule as it pertains to kVp and exposure?

A

An increase in 15% of kVp changes the exposure of the IR by a factor of 2

173
Q

What percent of increase does a factor 2 change create?

A

100%

174
Q

An increase in which technical factor is worse for patient exposure?

A

MAs

175
Q

How much does a 15% increase in kVp raise dose?

A

24-40%

176
Q

How would dose be affected by a 2X increase in mAs?

A

Exposure will be doubled as well which produces more exposure to the patient

177
Q

What effect does an increase in kVp have on contrast?

A

Lowers contrast

178
Q

Why has the definition of optimal kVp changed over time?

A

Because of the move from film processing to digital reconstructed images

179
Q

If there is enough kVp to penetrate the part, what will the computer do?

A

Still resolve a good image by using the algorithm

180
Q

How is optimal kVp defined now?

A

The amount that is well above the minimum required

181
Q

What happens if kVp is increased but mAs is not compensated?

A

The image will be overexposed and will be too dark

182
Q

How is an increase in kVp related to scatter?

A

As kVp increase more scatter will appear

183
Q

How would scatter impact an image?

A

Produce fog on an image which changes contrast

184
Q

Where does scatter radiation originate from within the body?

A

Primarily from large body parts where a large focal spot is used

185
Q

What is the significance of the origin of scatter as it pertains to kVp?

A

Since its produced from large body part and focal size, it means that kVp is not responsible directly for scatter

186
Q

If higher kVp is used on a smaller body part using a smaller focal spot how will scatter be affected?

A

The scatter will increase but not substantially enough to affect the overall image

187
Q

How do changes in kVp affect spatial resolution?

A

They do not affect it

188
Q

How much change in KV will produce a significant increase in exposure intensity?

A

4 KV change

Image Prod & Eval (10 decks)

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