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RT 204 > 2. Radiographic Contrast II > Flashcards

2. Radiographic Contrast II Flashcards

1
Q

It is the range of differences in the intensity of the x-ray beam after it has been attenuated by the subject

A

Subject Contrast

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2
Q

is the primary controller of subject contrast

A

Kilovoltage (kVp or kilovoltage peak)

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3
Q 
The \_\_\_\_\_ the range of 
photon energies, the 
\_\_\_\_\_ the ability of 
the photons to 
penetrate the body 
tissues
A

wider,

greater

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4
Q

SID

A

Source to Image Receptor Distance

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5
Q

As long as the kVp
is adequate to penetrate the part being examined,
___ kVp will produce ___ subject contrast

A

low,

high

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6
Q

It produces higher subject contrast because most of these low energy photons
are absorbed by thicker parts while more penetrate the thin
part.

A

Low kVP

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7
Q 
\_\_\_\_\_ causes 
density differences that 
were previously undetectable to become 
visible, resulting in an 
increase in the diagnostic 
information provided by 
the image
A

Increasing kVp

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8
Q 
In \_\_\_\_\_\_\_\_ –
low kVps are used to 
enhance the 
differences between 
the air-filled lungs 
and the overlying 
bony structures
A

rib radiography

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9
Q

In addition to kVp, _______ has a significant effect on

contrast

A

radiation fog

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10
Q

Radiation fog is a result of x-ray interactions with matter, primarily _____

A

Compton scatter

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11
Q 
These changes 
cause the lightest 
film densities to be 
“\_\_\_\_\_\_” so 
they can no longer 
be distinguished 
from one another
A

fogged over

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12
Q

Fog can be caused by factors other than scatter radiation and includes :

A

subjecting film to heat, low level ionizing radiation, or

chemical fumes

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13
Q

may also

cause objectionable fog levels.

A

Developer temperature, replenishment,

and developer contamination

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14
Q

depends on the
thickness of the body
part and the field size

A

Amount of Irradiated Material

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15
Q

Factors affecting scatter radiation

A

Field size

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16
Q

most important factor in the production of scatter radiation

A

Field size

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17
Q

a small x-ray field usually called ______ irradiate less tissue and generates fewer scattered photons

A

Narrow beam

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18
Q

As body part thickness decreases so does ______

A

absorption

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19
Q

When the difference between adjacent thicknesses of

various body parts is great, subject contrast is _______

A

increased

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20
Q

When little difference exists in the thickness of

adjacent body parts, subject contrast is ______

A

decreased

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21
Q

When the overall thickness of a body part increases when a
field size increases, the amount of scatter created will
______

A

increased

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22
Q

A decrease in overall body part thickness or field size results in ______ subject contrast

A

increased

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23
Q

Controlling factors:

A

kVp,
Amount of Irradiated Material,
Type of Irradiated Material

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24
Q

is influenced by the atomic number of the material and its tissue density

A

Type of Irradiated Material

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25
Q

Materials with a high atomic number absorb a ______ percentage of the x-ray beam
than low atomic number materials

A

greater

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26
Q

high atomic number example

A

Lead and iodine

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27
Q

low atomic number materials

A

hydrogen, carbon and

calcium

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28
Q

When the difference between the average atomic number

of adjacent tissues is great, subject contrast is ______

A

increased

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29
Q

When little difference exists between them, subject contrast

is _______

A

decreased

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30
Q

Contrast media ______ subject contrast by introducing
greater differences in atomic number variations than those
than exist naturally

A

increase

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31
Q

describes how tightly the atoms of a given

substance are packed together

A

Tissue density

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32
Q 
When the difference 
between the densities of 
adjacent tissues is great, 
subject contrast is 
\_\_\_\_\_\_
A

increased

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33
Q

When little difference exists between the densities of adjacent tissues, subject contrast _____

A

decreased

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34
Q

The major consideration in evaluating visible contrast is verification that a _____ range of densities is _____ throughout the anatomical area of interest on the image

A

proper,

visible

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35
Q

Unlike the evaluation of density, contrast assessment

requires ____ than just sufficient density within the visibility range

A

more

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36
Q

Because there is more information recorded on an image
than is seen, the diagnostic importance of contrast is a
matter of how many densities are included in the ______
contrast range

A

visible

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37
Q

is limited in its ability to discern light and dark
and this essentially establishes a value for the lightest and
darkest visible shades of gray

A

Human eye

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38
Q

A____ exposure difference has been used as the minimum
change to cause a visible differenced because this
magnitude is discernible by nearly everyone.

A

30%

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39
Q

Some professionals may be able to discern as little contrast as a ____ difference which means they are capable of seeing
twice as many shades of gray as someone who can discern
only a 30% change

A

15%

40
Q

can be made only when sufficient density exists to permit the range of contrast to be seen

A

Contrast evaluation

41
Q

is a simple tool to help us focus on the

contrast in a selected area

A

contrast mask

42
Q

When contrast mask is used with an image, adjacent

information is ______

A

eliminated

43
Q

A visible change in contrast will not be perceived until kVp

is changed by _____ depending on the kVp range

A

4%-12%

44
Q

CHANGE NECESSARY TO PRODUCE VISIBLE CHANGE:

30-50 kVp

A

4-5 percent

45
Q

CHANGE EQUAL TO PERCENT CHANGE:

30-50 kVp

A

1-3 kVp

46
Q

CHANGE NECESSARY TO PRODUCE VISIBLE CHANGE:

50-90 kVp

A

8-9 percent

47
Q

CHANGE EQUAL TO PERCENT CHANGE:

50-90 kVp

A

4-8 kVp

48
Q

CHANGE NECESSARY TO PRODUCE VISIBLE CHANGE:

90-130 kVp

A

10-12 percent

49
Q

CHANGE EQUAL TO PERCENT CHANGE:

90-130 kVp

A

9-16 kVp

50
Q

The effects of mAs and the influencing factors on image contrast are _____ because of the wide variety of
variables that are part of the imaging system

A

not exact

51
Q

Both the quality and

the quantity of the x-ray beams will vary with changes in

A

kilovoltage

52
Q

When a radiograph is outside acceptable limits, it needs to be _____

A

repeated

53
Q

The rule for contrast changes is to make adjustments in increments of ______

A

15 or 8 percent

54
Q

Radiographic image contrast occurs due to the ________ total absorption of photons in the subject

A

photoelectric effect’s

55
Q

is directly related to the number of
photoelectric effect’s total absorption of photons in the
subject

A

High contrast

56
Q

Compton interactions produce ______,

A

scatter

57
Q

low contrast is

directly related to the amount of _____ that occurs in the subject

A

Compton scatter

58
Q

can be determined by matching the average

incident photon energy with the average inner-shell binding energy of the predominant subject material

A

Contrast

59
Q

FACTORS AFFECTING CONTRAST

A

controlling factor,

influencing factors

60
Q

that affects contrast has the most direct effect on the image

A

controlling factor

61
Q

have a less direct effect on the image or change other factors as well as
contrast

A

influencing factors

62
Q

is the controller of contrast

A

kVp

63
Q

Kvp increases = contrast ______and vice-versa

A

decreases

64
Q

controls the amount of scatter radiation produced

A

kVp

65
Q

changes the penetrability (quality) + quantity

A

kVp

66
Q

Increasing kVp will ______ the amount of radiation fog,

thereby ______ contrast

A

increase,

decreasing

67
Q

changes the amount of x-rays (quantity)

A

mAs

68
Q

alters image receptor
exposure and film density of the image and therefore affects
contrast

A

mAs

69
Q

10 INFLUENCING FACTORS OF CONTRAST

A 
mAs, 
Focal Spot Size,
Anode Heel Effect,
SID and OID,
Filtration,
Beam Restriction,
Anatomical part,
Grids,
Image Receptor,
Processing
70
Q

OID

A

Object-to-image receptor distance

71
Q

possibility of the focal spot size altering

contrast enough to be visible is extremely ______

A

unlikely

72
Q

alters the intensity of radiation and

therefore affects image receptor exposure and film density which can effect contrast

A

Anode Heel Effect

73
Q

alters the intensity of the beam reaching the image receptor

according to the inverse square law

A

Source-to-Image receptor distance (SID)

74
Q

has an effect

on image receptor exposure/film density and contrast

A

Object-to-image receptor distance (OID)

75
Q

As the x-ray beam diverges, the image produced on the film is always slightly _____ than the original image

A

larger

76
Q

As the x-ray beam diverges, the image produced on the film is always slightly larger than the original image, this effect is called _____

A

Magnification

77
Q

increases the effect of kVp by changing the

average photon energy of the beam

A

Filtration

78
Q

All types of filtration (_______) alter image

receptor exposure/film density and contrast

A

inherent, added, total

79
Q

The increase in the average photon energy causes _____ Compton scatter production and this ____ contrast

A

more,

decreases

80
Q

reduces the total

number of photons available

A

Restricting the beam, collimating, or

reducing the primary beam field size

81
Q

Restricting the beam, collimating, or

reducing the primary beam field size

A

Beam Restriction

82
Q

is the prime attenuator of the beam, both the amount and type of tissue being examined
greatly influence density and contrast

A

Patient

83
Q

As tissue density increases, the amount of scatter radiation ______, which also results in a _____ in contrast

A

increases,

decrease

84
Q

primary function is contrast improvement

A

Grids

85
Q

Improve contrast by ______ scatter before it reaches the image receptor

A

removing

86
Q

is the best measure of

how well a grid accomplishes this function

A

The contrast improvement factor (K)

87
Q

“Clean up” scatter radiation

A

Grids

88
Q

With ______
systems, the primary determinant of the shape of the D log E
curve is the physical composition of the film emulsion

A

Film/Screen image receptor

89
Q

With _______, sufficient differences in
exposure to the receptor are necessary for the individual
pixels to exhibit different exposure values

A

Digital Image Receptors

90
Q

Increasing film developer time, temperature, or replenishment rate from the optimal range
will increase the chemical fog on the film

A

Processing

91
Q

shadow, space between the focal spot

A

Penumbra

92
Q

common SID distance

A

40 inches

93
Q

view box

A

Negatoscope

94
Q

fastens the production of image

A

Intensifying screen

95
Q

kVp’s increment is by __, mAs is by __

A

1,

decimals

RT 204 (11 decks)

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