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Terri > Spatial Resolution > Flashcards

Spatial Resolution Flashcards

1
Q

F/S recorded detail definition

A

The sharpness of the structural LINES as recorded in the radiographic image.

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2
Q

Digital radiography spatial resolution definition ASRT

A

The sharpness of the structural EDGES recorded in the image.

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3
Q

What effect will the following change
Have on recorded detail:
From 100 mA to 200 mA

A

Impacts visibility of detail only

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4
Q

What effect will the following change
Have on recorded detail:
Change from 0.01 sec to 0.005 sec

A

Impacts visibility of detail;

And increases sharpness if motion is an issue.

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5
Q

What effect will the following change
Have on recorded detail:
60 kVp to 50 kVp

A

No change to sharpness of detail (SR)

Only impacts visibility of detail

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6
Q

What effect will the following change
Have on recorded detail:
8:1 grid to no grid

A

No change to sharpness of detail.

Impacts visibility of detail

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7
Q

What effect will the following change
Have on recorded detail:
2” OID to 6” OID

A

⬇️ spatial resolution

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8
Q

What effect will the following change
Have on recorded detail:
Large focal spot to small focal spot

A

⬆️ spatial resolution

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9
Q

What effect will the following change
Have on recorded detail:
Patient is moving

A

⬇️ spatial resolution

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10
Q

What effect will the following change
Have on recorded detail:
1mAs to 2mAs without changing time

A

Impacts visibility of detail only

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11
Q

What effect will the following change
Have on recorded detail:
40” SID to 72” SID

A

Increases spatial resolution/sharpness of detail

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12
Q

Define Focal Spot

A

The area of the target from which X-rays are emitted.

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13
Q

The size of large focal spots

A

Range from 1.2 to 2.0 mm

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14
Q

Size of small focal spots

A

0.1mm to 1.0mm

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15
Q

Large focal spots are generally used for mA over

A

200-300

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16
Q

Define ACTUAL FOCAL SPOT

A

The area of bombardment on the target where X-rays are produced.

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17
Q

Define EFFECTIVE FOCAL SPOT

A

The area projected onto the patient and the IR. The size of the focal spot is identified here.

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18
Q

Define LINE FOCUS PRINCIPLE

A

A design feature whereby the anode is angled, so that the effective focal spot is smaller that the actual focal spot.

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19
Q

What is the function of the line focus principle

A

Improve detail

Improve heat capacity

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20
Q

Diagnostic X-ray tubes have anode angles ranging from

A

5-17 degrees

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21
Q

What is the one disadvantage of the line focus principle?

A

The Heel Effect/Anode Heel Effect

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22
Q

Describe the Heel Effect

A

Because of the divergent beam, a portion of the useful beam, emitted towards the anode side of the tube is absorbed by the heel of the anode.
Thus there is reduced X-ray intensity on the anode side of the tube.
This difference can vary as much as 45%.
This can be useful when imaging body parts with uneven thickness. Positioning the cathode over the thicker part of the anatomy provides more uniform density.

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23
Q

Extra focal radiation results when

A

Electrons bounce off the focal spot and land on other areas of the target generating X-rays outside of the focal spot

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24
Q

Focal Spot Blooming is not constant. It broadens or blooms with: (3)

A
  1. Age and use
  2. Large mAs
  3. Decreasing kVp
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25
Q

How does large mAs influence fs blooming

A

Increase current to the cathode filament causes increased heat.
The hotter the filament, the larger the space charge, so the effective focal spot broadens. (Try to use lowest mA possible).

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26
Q

How does decreasing kVp influence f/s blooming

A

At lower kVps, the electrons flowing from the cathode to the anode tend to stray since the potential difference is not as great.
They hit a wider area of the anode and enlarge the effective focal spot.

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27
Q

Name Focal Spot QC tests

A
  1. Pinhole camera
  2. Resolution Test patterns: - star pattern resolution test
    - line pattern test
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28
Q

The line-focus principle allows

A

High anode heating with small effective focal spots.

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29
Q

As the target angle decreases, what happens to the effective focal spot

A

Decreases

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30
Q

How can we purposely distort anatomy

A

Angle tube

Oblique pt

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31
Q

To minimize distortion we can

A

Put part parallel to IR

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32
Q

What feature of X-ray equipment helps us minimize distortion

A

Detent

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33
Q

Two types of distortion we use in X-ray

A

Elongation

Foreshortening

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34
Q

What does “distortion of position” mean

A

Where you place part under CR and angled.

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35
Q

How does a ⬇️ in OID effect MF

A

Decrease

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36
Q

How does ⬆️SID effect MF

A

Decrease

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37
Q

Spatial resolution means

A

Visibility and Sharpness

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38
Q

Factors that influence visibility

A 
Are not IR specific
Contrast 
Grid
Scatter
kVp
mAs
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39
Q

Factors that influence Sharpness

A

IR
Physical factors
Geometric factors
Motion

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40
Q

How can we control the physical factors influencing sharpness

A

We need to control motion:

  1. Give good pt instruction
  2. Immobilization
  3. Short exposure time
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41
Q

Visibility means the image is in

A

Diagnostically useful range; density and contrast

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42
Q

Visibility factors for film screen IR

A
  1. Intensifying screen type and speed
  2. Film type and speed
  3. Processing time and temperature
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43
Q

Digital IR visibility factors

A

Indirect IR
Direct IR
Processing

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44
Q

Film screen IR sharpness factors

A

Intensifying screen type and speed
Film type and speed
F/s contact

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45
Q

Digital IR sharpness factors

A

Indirect DR
Direct DR
Matrix size
Pixel size

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46
Q

If the matrix size increases, the pixel size

A

Decreases

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47
Q

⬆️matrix size gives

A

⬆️ resolution (sharpness only)

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48
Q

The type and speed of CR

Influence

A

Visibility and Sharpness

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49
Q

How does the CR reader influence sharpness

A

The smaller the pinpoint of the laser, the better the sharpness

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50
Q

Why does direct DR influence visibility

A

Because there are no phosphors, so no spreading of light.

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51
Q

3 geometric factors influencing sharpness

A

OID
SID
Focal spot size

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52
Q

⬆️ OID with ? Sharpness

A

⬇️ sharpness

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53
Q

⬇️ SID will ? Sharpness

A

⬆️ sharpness

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54
Q

⬆️ Focal spot size ? Sharpness

A

⬇️ sharpness

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55
Q

As focal spot decreases, what happens to geometric blur and to sharpness

A

Geometric blur decreases

Sharpness increases

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56
Q

Which side of the image has more blur

A

The cathode side bc of the focal spot angle

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57
Q

If there is inherent OID due to anatomy, we repair it by

A

Increasing SID

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58
Q

Distortion

A

Misrepresentation of the size and shape of an object

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59
Q

Magnification is desirable, when?

A

When we are looking for borders of tiny areas

Like in mammo for smooth or rough borders

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60
Q

With size distortion, we increase OID, which will –resolution

A

Decrease

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61
Q

Shape distortion is good when?

A

ImAging a 3-D object because the image is 2-D
We angle the tube
Or
Oblique part

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62
Q

Can distortion be totally avoided?

A

No bc anatomy is 3-D and image is 2-D

63
Q

The further away the OID, how does it change the image size

A

Larger is the image size

64
Q

Magnification Factor

A

How much bigger the image is, compared to the object.

65
Q

3 qualities of an X-ray beam

A
  1. Heterogenous divergent beam- spreads out through distance.
  2. Heterogenous- made up of a variety of different energies
  3. Randomly distributed- the X-ray photons come down in a random pattern.
66
Q

Similar triangles mean

A

The 2 angles are the same size.

67
Q

If you want to magnify an object 2 times,

A

put it 1/2 way in the SID

68
Q

The decrease magnification:

A

Decrease OID

Increase SID

69
Q

Radiographic image quality

A

The accuracy that the anatomy being examined, is shown on the radiograph.

70
Q

High quality radiograph

A

Precisely reproduces structure and tissues.

71
Q

Spatial resolution

A

The ability to image small objects that have high subject contrast.
Such as bone-soft tissue interface
A breast micro calcification
Calcified lung nodule

72
Q

Screen-film radiography has—spatial resolution.

A

Excellent

73
Q

Spatial resolution — as blur decreases

A

Improves

74
Q

Spatial resolution aka

A

Detail

Recorded detail

75
Q

Visibility of detail refers to

A

The ability to visualize recorded detail when image contrast and optical density (OD) are optimized.

76
Q

How does the speed of the image receptor influence spatial resolution

A

As IR speed increases:
Spatial resolution decreases
(High noise)

77
Q

⬇️ IR speed will – spatial resolution

A

⬆️ spatial resolution

78
Q

What are FILM FACTORS that affect f/s radiographic quality

A

Characteristic curve:

  1. Density
  2. Contrast
  3. Speed
  4. Latitude

Processing:

  1. Time
  2. Temperature
79
Q

What are GEOMETRIC FACTORS that affect f/s radiographic quality

A
  1. Distortion
  2. Magnification
  3. Blur
80
Q

What are SUBJECT FACTORS that affect f/s radiographic quality

A

Contrast:

  1. Thickness
  2. Density
  3. Atomic number

Motion

81
Q

As f/s development time ⬆️

A

Fog ⬆️
IR speed ⬆️
Spatial resolution ⬇️
Visibility ⬇️

82
Q

As f/s development temperature ⬆️

A

Fog⬆️
IR speed ⬆️
Visibility and spatial resolution ⬇️

83
Q

As OID ⬇️

A

Sharpness ⬆️

SR

84
Q

As SID ⬆️

A

Sharpness (SR) ⬆️

85
Q

3 geometric factors that affect radiographic quality

A

Magnification
Distortion
Focal-spot blur

86
Q

All images are larger than the object. This is a condition called

A

Magnification

87
Q

Quantitatively, magnification is expressed by the

A

Magnification factor

88
Q

Magnification Factor =

A 
ImAge Size/ Object Size
Or
SID / SOD
OR
IMAGE SIZE/OBJECT SIZE=SID/SOD
89
Q

2 factors that affect image magnification

A

SID

OID

90
Q

To minimize magnification

A

Large SID

small OID

91
Q

Shape distortion define

A

Unequal magnification of different portions of the same object

92
Q

3 conditions contribute to image distortion

A

Object: thickness
Position
Shape

93
Q

How does object thickness affect distortion

A

With a thick object, OID⬆️
So
Thick objects are more distorted.

94
Q

The image is not distorted if the object plane and the image plane are

A

Parallel

95
Q

The image is not distorted if the object plane and the image plane are

A

Parallel

96
Q

How do you increase the amount of foreshortening; extent of reduction in image size

A

Increase the inclination of angle will increase foreshortening

97
Q

What is the most important factor for determining spatial resolution

A

Focal-spot blur

98
Q

Focal spot blur is small when

A

The OID is small

99
Q

The focal-spot blur is small on the —side and large on the —side of the image.

A

Anode

Cathode

100
Q

How do you increase the amount of foreshortening; extent of reduction in image size

A

Increase the inclination of angle will increase foreshortening

101
Q

What is the most important factor for determining spatial resolution

A

Focal-spot blur

102
Q

Focal spot blur is small when

A

The OID is small

103
Q

The focal-spot blur is small on the —side and large on the —side of the image.

A

Anode

Cathode

104
Q

Reduce motion blur by

A

Restrict pt motion
Use shortest exposure
Time possible

105
Q

Small focal spots are used when?

A
  1. For fine detail
  2. For magnification studies
  3. For extremities
106
Q

Detail describes

A

The sharpness of appearance of small structures on the radiograph.

107
Q

Sharpness of image detail refers to

A

The structural lines or borders of tissues in the image and the amount of blur of the image.

108
Q

Factors that generally control the sharpness of image detail:3

A

Focal spot size
SID
OID

109
Q

Sharpness of image detail is influenced by

A

Type of intensifying screen
Presence
Of motion

110
Q

Key factors that provide the best visibility of image detail

A

Collimation
Grids
Other methods that prevent scatter

111
Q

Distortion can be minimized by 3

A

Proper tube alignment
Proper part alignment
Proper IR alignment

112
Q

What effect will the following change
Have on recorded detail:
2” OID to 6” OID

A

⬇️ spatial resolution

113
Q

Resolution

A

Measure of the ability of a system to image 2 separate objects and visually distinguish one from another

114
Q

In electronic imaging as digital image matrix size increases

A

Pixel size decreases

115
Q

Pixel depth is directly related to shades of gray, called?

And is measured in?

A

Dynamic range

Bits

116
Q

The greater the number of bits, the more?

A

Shades of gray

117
Q

Is pixel depth related to resolution

A

No

118
Q

A digital image is formed by a

A

Matrix of pixels in rows and columns

119
Q

Field of view

A

Used to describe how much of the patient is included in the matrix

120
Q

SID affects recorded detail in which way

A
  1. Directly related

2. As SID increase, recorded detail increases

121
Q

Why don’t we always use an large SID?

A

Because it would require a higher radiation dose to the patient.

122
Q

How does field size affect detail visibility

A

Because it decreases scatter radiation produced, it will result in improved detail visibility

123
Q

Which has better partial resolution, F/S or CR?

A

Film Screen has three times better spatial resolution than CR.

124
Q

4 acceptable ways to minimize motion unsharpness

A
  1. Use shortest possible exposure time
  2. Accurate patient instructions
  3. Suspended respiration
  4. Immobilization
125
Q

Subject / object unsharpness can result from ? Name 3

A
  1. Object shape does not coincide/conform with the shape of x-ray beam.
  2. Object plane is not parallel wth x-ray tube and / or IR
  3. Anatomic object is a distance from the IR
126
Q

As matrix size increase, spatial resolution

A

Improves / increases

127
Q

How does the size of the PSP affect spatial resolution?

A

Smaller phosphor size improves resolution, because there will be less spreading of light.

128
Q

How does the size of the scanner laser affect spatial resolution

A

The smaller the laser beam, the better the spatial resolution

129
Q

As FOV increases, how does it affect the pixels of a fixed matrix size? And affect the spatial resolution?

A

Size of each pixel increases.

The spatial resolution decreases.

130
Q

For the same FOV,spatial resolution will be improved using?

A

A larger matrix

131
Q

If matrix size increases, and fixed FOV, than pixel size will

A

Decrease, and better spatial resolution

132
Q 
All the following are related to recorded detail except:
mA
Focal spot size
SID
OID
A

mA

133
Q

Focal Spot blur is greatest towards the —- end of the beam?

A

Cathode end

134
Q

Focal spot blur / geometric blur is caused by

A

Photons emerging from a large focal spot.

135
Q

Factors that determine recorded detail in digital imaging include? 3.

A
  1. Motion
  2. Geometric Factors (OID, SID, and focal spot size)
  3. Spatial resolution
136
Q

In analog systems, spatial resolution is related to the?

A

Speed of the system/ intensifying screen speed

137
Q

The spatial resolution of direct digital system is?

A

Fixed
Related to the detector element (DEL) size of the thin film transistor (TFT).
Smaller DEL SIZE, better resolution

138
Q

DEL size of 200 in general radiography provides a spatial resolution of

A

2.5 lp/mm

139
Q

A 100 speed intensifying screen system offers a spatial resolution of

A

10 lp/mm

140
Q

How is OID related to recorded detail?

A

Inversely

As OID increases the detail decreases; magnification increases

141
Q

In digital imaging as DEL sizes decreases, spatial resolution

A

Increases

142
Q

Recorded detail is inversely related to

  1. SID
  2. OID
  3. Part motion
A

OID

Part motion

143
Q

Does mAs affect recorded detail

A

No

144
Q

What are the geometric factors that influence recorded detail

A

Focal spot
OID
SID

145
Q

In film screen imaging spatial resolution is related to the

A

Speed of the imaging system / intensifying screen speed

146
Q

The spatial resolution of direct digital systems is related to

A

Detector element size of the thin film transistor

147
Q

When involuntary motion must be considered, the exposure time may be cut in half if the kilovoltage is?

A

Increased by 15%

148
Q

The greatest enemy of resolution

A

Motion

149
Q

Focal spot blur is related to

A

Focal spot size

150
Q

Which focal spot size produce less Blur and better resolution

A

Smaller focal spots

151
Q

What term is used to describe unsharp edges of tiny radiographic details

A

Geometric Blur

152
Q

Recorded detail can be improved by decreasing which:

  1. SID
  2. OID
  3. Part motion
A

OID

Part motion

153
Q

What units are used to express resolution

A

Line pairs per millimeter

Terri (8 decks)

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