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Terri > Contrast > Flashcards

Contrast Flashcards

1
Q

Arrt f/s

scale of contrast

A

Refers to the number of densities visible (or the number of shades of gray).

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2
Q

Arrt f/s

long scale

A

Term used when slight differences between densities are present (low contrast) but the total number of densities is increased.

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3
Q

Arrt Film screen

contrast

A

Radiographic contrast is defined as the visible differences between any two selected areas of density levels within the radiographic image.

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4
Q

Arrt f/s

short scale

A

Term used when considerable or major differences between densities are present (high contrast) but the total number of densities is reduced

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5
Q

Arrt f/s

film latitude

A

The inherent ability of film to record a long range of density levels on the radiograph.
Film latitude and film contrast depend upon the sensiometric properties of the film and processing conditions, and are determined directly from the H and D curve.

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6
Q

ARRT f/s

Film Contrast

A

The inherent ability of the film emulsion to react to radiation and record a range of densities.

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7
Q

Arrt f/s

exposure latitude

A

The range of exposure factors which will produce a diagnostic radiograph.

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8
Q

Arrt f/s

subject contrast

A

The difference in the quantity of radiation transmitted by a particular part as a result of the different absorption characteristics of the tissues and structures making up that part.

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9
Q

Arrt digital radiography

contrast

A

Image contrast of display contrast is determined primarily by the processing algorithm. The default algorithm determines the initial processing codes applied to the image data.

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10
Q

Arrt digital radiography

scale of contrast

A

Is synonymous to “gray scale” and is linked to the bit depth of the system.
Gray scale is used instead of scale of contrast when referring to digital images.

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11
Q

Algorithm

A

Mathematical codes used by the software to provide the desired image appearance.

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12
Q

Arrt digital radiography

dynamic range

A

The range of exposures that may be captured by a detector. The dynamic range for imaging is much larger than film.

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13
Q

Arrt digital radiography

receptor contrast

A

The fixed characteristics of the receptor. Most digital receptors have an essentially linear response to exposure. This is impacted by contrast resolution (the smallest exposure change or signal difference that can be detected.)
Ultimately, contrast resolution is limited by the dynamic range and the quantization (number of bits per pixel) of the detector.

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14
Q

Arrt digital radiography

exposure latitude

A

The range of exposures which produces quality images at appropriate patient dose.

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15
Q

Arrt digital radiography

subject contrast

A

The magnitude of the signal difference in the remnant beam.

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16
Q

Windows level

A

Identifies the brightness of the type of tissue imaged.

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17
Q

Window width

A

The gray scale representation of the tissue.

The wider the window width, the longer the gray scale.

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18
Q

What factor affect contrast

A 
kVp
Grids
Processing 
IR speed
Subject 
Beam restriction
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19
Q

Contrast resolution means

A

The smallest exposure changes and signal differences that can be detected

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20
Q

Quantization

A

Number of bits per pixel

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21
Q

Dynamic range

A

Range of values over which a system

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22
Q

Low contrast aka

A

Long scale
Reduced contrast
Diminished contrast

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23
Q

High kVp exposure gives — contrast

A

Low contrast

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24
Q

If there are lots of shades of gray, the image is —- contrast, and —- scale.

A

Low contrast

Long scale

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25
Q

If there are less density differences on an image, it is —- contrast

A

Low

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26
Q

Low kVp exposure produces —- contrast

A

High

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27
Q

High contrast aka

A

Short scale contrast

Increasing contrast

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28
Q

If there are fewer shades of gray between black and white the image is —– scale contrast

A

Short

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29
Q

If there are big density differences on the image, it is —contrast

A

High

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30
Q

What controls the penetrability of the beam

A

kVp

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31
Q

A thicker object density will produce

A

Less density on the image

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32
Q

Long scale contrast with have a —- straight line portion on an HD curve.

A

Flatter

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33
Q

A steeper straight line portion of the HD curve means

A

Short scale/ high contrast

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34
Q

A sensiometric strip is created with

A

Stepwedge

Penetrometer

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35
Q

The thinner end of the stepwedge will create more —- on the strip.

A

Density / blackness

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36
Q

The function of contrast

A

To make detail visible

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37
Q

Fog will — contrast

A

Decrease

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38
Q

Contrast aka

A

Density differences

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39
Q

Factors that do not influence contrast

A

mA
Time
SID

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40
Q

Factors that influence contrast in f/s and digital

A 
kVp
Subject 
IR
Collimating 
Beam restriction
Grid
Compression
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41
Q

Factors that influence contrast in f/s

A

Chemical processing
Intensifying screen
Film speed

42
Q

Factors that influence contrast in digital

A

IR
Digital processing
Bit depth

43
Q

Increasing kVp from 80 to 95 will effect contrast how?

A

More long scale

Low contrast

44
Q

Changing from no grid to 8:1 grid will effect contrast how?

A

More short scale

High contrast

45
Q

If chemistry was hot, adding chemical fog to film

A

More long scale

Low contrast

46
Q

Change from 200 speed screen to CBH and correct mAs will effect contrast how?

A

More long scale

Low contrast

47
Q

As screen speed increases then

A

Contrast increases
Higher contrast
Shorter scale

48
Q

As grid ratio increases then

A

Contrast increases
Shorter scale
Higher contrast

49
Q

As speed screen decreases

A

Contrast decreases

50
Q

Going from no cone to extended cone will effect contrast how?

A

Increase contrast

51
Q

Why does adding an extension cylinder increase contrast

A

Less scatter is produced

52
Q

Why does adding compression increase contrast/more short scale

A

Less matter less scatter

53
Q

A patient with osteoporosis will —contrast. Why?

A

Increase contrast/more short scale
Because the part is less dense; so image is more black and white
( this pathology needs less kVp)

54
Q

Do a patient with ascites

A

More long scale

Because more matter, more scatter; it needs more kVp

55
Q

The more you collimate

A

Less scatter
Less grey
Short scale contrast
Higher contrast

56
Q

Bit depth

A

How many bits you are stacking

Stacking of digital brightness

57
Q

Define aerial beam/remnant beam

A

The beam that emerges from the body.

58
Q

What is subject contrast and what does it contain

A

The contrast in the remnant beam.
Contains wanted information derived from the patient
And also unwanted information–scatter.

59
Q

4 factors that affect subject contrast

A

Radiation Quality
Radiographic Object
Scatter Radiation
Fog

60
Q

How does radiation quality affect subject contrast

A

⬆️ kVp = ⬆️ penetrating ability
Thereby producing a longer scale of contrast
⬇️ contrast

61
Q

Radiographic object means

A

Body part
Thickness
Nature of part: tissue density and pathology-additive and destructive

62
Q

Name 5 radiographic objects ranging from greatest to least radiopacity

A
  1. Tooth enamel
  2. Bone
  3. Tissues of H2O density such as muscle, glands, liver, spleen, pancreas, kidney
  4. Adipose tissue
  5. Gas/ air filled structures
63
Q

Scatter is

A

A noise factor obscuring information or detail

Impairs contrast by a fogging affect

64
Q

Scatter radiation can be controlled by

A

Beam restriction and grid

65
Q

Fogging

A

From any other source, contributes to noise.

Imparting an overall grey appearance to the image and reducing contrast

66
Q

—-interferes with our ability to see something

A

Scatter

67
Q

Is subject contrast is unaffected by

A

The type of image receptor used to create image

68
Q

Image receptor contrast includes 3 components

A

Film/Screen combinations

Development Process

Digital Systems

69
Q

Image receptor contrast
F/S combinations;
Film emulsions are designed by manufacturers to

A

Display different scales of contrast

Depends on facility’s body parts imaged

70
Q

Intensifying Screens convert what?

A

Over 98% of X-ray photons to light

71
Q

Why does the IS conversion process enhance contrast

A

Because S/F is designed to respond to the light emitted by the IS

72
Q

As film-screen system speed ⬆️ then contrast

A

As film-screen system speed ⬆️ then contrast ⬆️ (shorter scale), and latitude ⬇️ (less steps in the range).

73
Q

Image Receptor Contrast
Development Process
What affects contrast

A

Different chemicals/ingredients within the developer; excess chemical ⬆️ fog and ⬇️ contrast.

Excessive temperature or other processor problems; ⬆️ temperature ⬆️ fog ⬇️ contrast

74
Q

Image Receptor Contrast
Development Process
How do you ensure optimum quality

A

Daily sensitometry

Strict adherence to QC

75
Q

Bushong defines Contrast Resolution as

A

The ability to distinguish anatomical structures of similar subject contrast

76
Q

All digital systems have better ——- than F/S systems.

A

Contrast resolution

77
Q

Windowing

A

Changing the image brightness and/or contrast scale

78
Q

Why doesn’t doubling mAs change gray scale?

A

Because every step gets twice as dark, but the density differences between the steps has not changed.

79
Q

When is contrast ideal?

A

When you see what you need to see

80
Q

When would you want long scale contrast

A

To see detail; and subtle changes in density

81
Q

Histograms and LUTS in digital systems

A

Is the recipe card; processing algorithms

82
Q

Differential absorption

A

Different degrees of X-ray absorption based on the body tissue and densities and thickness

it determines subject contrast

83
Q

If you need to produce the same OD at a slightly reduce contrast scale

A

5% rule

84
Q

5% rule

A

⬆️kVp 15% and ⬇️ mAs 30%

85
Q

If image has too many gray/ long scale, or too black and white

A

Apply 15% change while either 1/2 or double mAs

86
Q

4 factors that RT must judge

A

Anatomical part
Body habitus
Suspected pathology
X-ray IR characteristics

87
Q

Pixel represent a

A

BIT

88
Q

4 factors that RT must judge

A

Anatomical part
Body habitus
Suspected pathology
X-ray IR characteristics

89
Q

Pixel represent a

A

BIT

90
Q

Image contrast is a result of which

  1. Differential tissue absorption
  2. Atomic number of tissue being traversed
  3. Proper regulation of mAs
A
  1. Differential tissue absorption

2. Atomic number of tissue being traversed

91
Q

In comparison with 60kV, 80 kV will?

  1. Permit greater exposure latitude
  2. Produce more scatter radiation
  3. Produce shorter scale contrast
A
  1. Permit greater exposure latitude

2. Produce more scattered radiation

92
Q

Which of the following technical changes would best serve to remedy the effect of very different tissue densities?

  1. Use of a small focal spot
  2. Use of a high ratio grid
  3. High kilovoltage exposure factors
  4. High MAS
A
  1. High kVp
93
Q

A 15% decrease in kilovolt age accompanied by a 50% increase in MAS will result in?

  1. Shorter scale of contrast
  2. Increase in exposure latitude
  3. Increase in radiographic density
  4. Decrease in recorded detail
A

Shorter scale of contrast

94
Q

Under exposure of a radiograph can be caused by all of the following except insufficient

  1. mA
  2. Exposure time
  3. KVp
  4. SID
A

SID

Insufficient SID will result in increased exposure rate and radiographic overexposure.

95
Q

All The following have an impact on contrast except?

  1. Photon energy
  2. Grid ratio
  3. OID
  4. Focal spot siz
A

Focal spot size

96
Q

An increase in kilovoltage will serve to produce — scale contrast

A

Long

97
Q

Brightness and contrast resolution in digital imaging can be influenced by

  1. Window level
  2. Window width
  3. Look up table
A

All of them

98
Q

Which of the following are associated with subject contrast?
1 patient thickness
2. Tissue density
3. Kilovoltage

A

All of them

99
Q

As kilovoltage increases, beam attenuation is decreased and subject contrast

A

Decreases

100
Q

As grid ratio is decreased the scale of contrast becomes

A

Longer

101
Q

As window level increases

A

Brightness increases

Terri (8 decks)

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