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Radiographic Physics > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

What % change in mAs makes a visible difference in density?

A

30%

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2
Q

If 5% if an incident beam is transmitted through a body part then 95% of the beam was?

A

Absorbed, scattered and also attenuated

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3
Q

Principle function of grid

A

To increase radiographic contrast (because it is reducing scatter

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4
Q

When scatter radiation is removed image ____ improves.

A

contrast

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5
Q

The ____ protects the emulsion from scratches, pressure and contamination for relatively rough manipulation of x-ray film exposure.

A

Overcoat

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6
Q

Film that has emulsion coated on both sides is called?

A

Double Emulsion

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7
Q

Reduction of radiation intensity due to scattering and absorption is called…

A

Attenuation

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8
Q

Maintaining density when changing from screen to a grid technique

A

Multiply mAs by the Grid Factor

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9
Q

Patient does is ____ with added filtration?

A

Reduced

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10
Q

What is a compensating filter?

A

Shaped aluminum slide into collimator

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11
Q

The ____ is the foundation of radiographic film whose primary purpose is to provide a rigid structure on to which the emulsion can be coated.

A

Base

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12
Q

When kVp and/or filtration increases, beam quality _____.

A

increases (filtration lowers PT dose)

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13
Q

What kind of PT requires less radiographic technique and thin but appears to look/be healthy

A

Hyposthenic

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14
Q

Photon interaction free ____ from the silver & bromide atoms in the silver halide ____..

A

Electrons Crystal

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15
Q

With exposure to both x-ray and light ____ interactions occur in the emulsion.

A

photon

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16
Q

A low-contrast emulsion contains ____ silver halide grains that have a wider range of sizes.

A

Larger

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17
Q

What is AEC?

A

Automatic Exposure Control Proper density meets multiplier and it terminates

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18
Q

Reduction of radiation intensity due to scattering and absorption is called ____.

A

Attenuation

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19
Q

What focal spot provides for a shorter exposure time minimizing motion blur?

A

Large

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20
Q

Base & Emulsion Diagram

A
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21
Q

Original Base

A

1869 - Glass Not practical: too heavy, Breakability, Awkwardness in handling

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22
Q

Quantum Mottle refers to? and is a principal contributor to what?

A

-principal contributor to radiographie noise -random nature by which x-rays interact w/image receptor

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23
Q

The ____ of an x-ray beam is called x-ray quality.

A

penetrability

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24
Q

If the Grid Ratio increases then OD?

A

Decreases

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25
Q

What is the relationship in the characteristic curve?

A

Relationship between OD & Radiation Exposure

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26
Q

Short scale contrast means

A

Few shades of gray, Low kVp (i.e..extremity x-ray)

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27
Q

Latitude refers to…

A

The range of exposures over which the IR responds with OD’s in the diagnostically useful range.

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28
Q

Grid Ratio and PT Doe

A

Higher grid ratio, higher lead content Higher the lead content, higher the exposure factors needed Higher the exposure factors, higher the patient dose

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29
Q

What part of the image formation occurs during exposure?

A

Latent Image Formation

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30
Q

Grids are constructed with radiopaque ____ and radiolucent ____ materials.

A

Strips Interspace

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31
Q

The higher the grid ratio the better the ____ which increases ____.

A

“clean up” which increases radiographic contrast

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32
Q

Tight collimation, low kVp and PT compression increase ____.

A

contrast

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33
Q

Thicker body parts result in greater ____.

A

Attenuation

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34
Q

Too long of a scale of contrast what would you do?

A

Increase kVp by 15% and divide the mAs by half.

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35
Q

If the speed of the IR is doubled; what will you do maintain the density?

A

The mAs must be halved and no change is required in kVp

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36
Q

Base & Emulsion are two basic components of ____ ____.

A

Radiographic Film

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37
Q

What type of PT is big & overweight in frame?

A

Hypersthenic

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38
Q

The ____ has high subject contrast; the ____ has low subject contrast.

A

Chest Abdomen

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39
Q

If the thickness of the part increases then OD?

A

Decreases

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40
Q

If you increase kVp then OD?

A

Increases

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41
Q

Factors affecting film speed.

A

-Concentration of silver halide crystals -Thickness of emulsion -Shape -Tabular grains: flat providing, more surface area to volume ratio

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42
Q

x-rays transmitted w/out interaction and scattered (or compton interaction) radiation are called ____ ____ ____.

A

image forming x-rays

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43
Q

How does speed affect detail?

A

Faster speed results in less detail. Slower speed results in more detail.

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44
Q

Thicker body parts result in greater ____.

A

Attenuation

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45
Q

What would display the most radiographic density?

A

Air

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46
Q

Low Noise Accompanies….

A

Slow image receptors high spatial resolution high contrast resolution

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47
Q

Size of phosphor crystals thickness of phosphor layer and its composition determine screen ____.

A

characteristics

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48
Q

A x-ray beam that could pass through ____ tissue would have high penetrability & quality.

A

dense

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49
Q

Latitude and Contrast are ____ ____ and wide latitude means the mAs can what?

A

Inversely Proportional and mAs can vary more and still produce a diagnostic image.

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50
Q

True or False: The use of radiographic intensifying screens with film allows reduced technique and therefore reduced PT dose. However, the image is more blurred than it would be after exposure without screen.

A

True

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51
Q

Variable collimators are the most commonly used ____ ____ ____.

A

beam restricting device

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52
Q

____ focal spot size is reserved for fine-detail radiography, in which the quantity of x-rays is relatively low.

A

Small

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53
Q

If the IR speed increases then OD?

A

Increases

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54
Q

How does Quantum Mottle appear on the image?

A

Quantum Mottle has a grainy appearance associated with using a low # of x-rays to produce

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55
Q

Main disadvantage of crossed grid

A

grid cut-off (orthopedic work)

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56
Q

Why is it important to keep exposure time as sure as possible?

A

To minimize motion blur

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57
Q

Why does an x-ray tube have 2 focal spot sizes?

A

Small Focal Spot - improves spatial resolution of high-contrast anatomy Large Focal Spot - useful when a high-intensity x-ray beam is required for thick anatomy.

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58
Q

To produce a long scale of contrast, a technologist would set a technique as follows

A

High kVp & High mAs

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59
Q

A ____ material emits light for a period of time after stimulation.

A

Phosphorescent

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60
Q

Tight collimation lowering kVp & PT compression increase ____.

A

contrast

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61
Q

What is the key when using a machine with AEC?

A

Positioning

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62
Q

What is inherent filtration?

A

-glass or metal envelope of x-ray tube -variable-aperture light-localizing collimator

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63
Q

Linear or Parallel Grid cleans scatter ….

A

in one direction - only transverse - across long axis of grid

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64
Q

High quality radiograph

A

faithfully reproduces structure and tissue

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65
Q

What is large focal-spot?

A

-generally used -assures sufficient mAs can be used thick dense part -shorter exposure: minimizes motion blur

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66
Q

Primary control for contrast is ____.

A

kVp (as kVp increases both quantity and quality of x-radiation increases so a higher portion of the primary beam reaches the image receptor)

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67
Q

Primary Control of contrast is ____.

A

kVp

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68
Q

Crossed Grid

A

Cleans up both directions of grid

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69
Q

What is contrast resolution?

A

The ability to distinguish anatomic structures of similar subject contrast.

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70
Q

What influences image receptor (film) contrast?

A

-contrast medium -thickness -atomic #

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71
Q

Gelatin makes up the ____ of protective covering on radiographic film.

A

overcoat

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72
Q

Grid Ratio

A

Height of grid strip divided by thickness of interspace material. H/D

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73
Q

General size & shape of a PT is referred to as?

A

Body Habitus

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74
Q

____ filters are shapes of Al mounted onto a transparent panel that slides in the grooves beneath the collimator?

A

compensating filter

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75
Q

The formation of the latent image is sometimes called the ____ effect.

A

Photographic

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76
Q

Name 3 common factors that determine amount of scatter absorbed with a grid.

A

-Angle of scattered photons -Height of grid strips & width H/D -Interspace Material

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77
Q

Attenuation

A

Reduction in x-ray intensity that results from absorption & scattering

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78
Q

Types of secondary radiation (2)

A

Scatter Radiation Leakage Radiation

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79
Q

The least dense body tissue is…

A

Fat

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80
Q

What is differential absorption?

A

Different degrees of absorption in different tissues that result in image contrast and formation of the x-ray image.

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81
Q

What subject factors attenuate the x-ray?

A

Chunky Parts & Parts with High Atomic Number (chunky + high atomic # = no remnant x-rays on the IR)

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82
Q

Film Contrast

A

characteristic inherent in film itself to emphasize high for low contrast imaging

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83
Q

When radiograph is over penetrated what happens?

A

Trabecular “burned out”

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84
Q

True our False kVp is the most important influence of film contrast.

A

True

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85
Q

Fast Image Receptors have…

A

High Noise Low Spatial Resolution Low Contrast Resolution

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86
Q

A radiographic can be adequately penetrated yet….

A

still be under or overexposed

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87
Q

How many components does radiographic noise have and what are their names?

A

4 components: film graininess structure mottle quantum mottle scatter radiation

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88
Q

Speed, contrast and sensitivity of screen film is determined by what 3 factors?

A

size, shape and distribution of silver halide crystals

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89
Q

If you increase SID then OD?

A

Decreases

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90
Q

Air gap technique

A

for trauma scatter goes in opposite direction

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91
Q

Grid surface x-ray absorption formula

A

% x-ray absorption width of grid strip / width of grid strip + width of grid interspace x 100

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92
Q

Properly exposed radiographs take place where? (Amounts?)

A

Straight Line Portion *Intermediate Levels 0.25 to 2.5 (a bit higher for mammo.)

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93
Q

Image Quality

A

The fidelity with which the anatomical structure that is being examined is rendered on the radiograph.

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94
Q

Density can be measured using a ____.

A

Densitometer

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95
Q

SHALL

A

Short Scale High contrast (low kVp B&W) Long scale Low contrast (high kVp Gray)

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96
Q

When mAs increases ____ increases

A

density

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97
Q

Cellulose Triacetate

A

-Same characteristics, not as flammable -Did not store well for long periods -Fire resistant, when burned releases nitrogen dioxide, a poisonous gas

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98
Q

Safelight

A

Red can be used for green or blue sensitive film.

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99
Q

The most dense body tissue is…

A

Bone

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100
Q

Short scale of contrast means you would?

A

decrease kVp 15% & double the mAs

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101
Q

The ____ layer adds to the light efficiency of intensifying screens.

A

Reflective

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102
Q

____ makes anatomy more visible.

A

Contrast

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103
Q

Cellulose Nitrate

A

-1st lightweight base -Developed WWI -Extremely flammable -Hospital fire’s -1930 cleveland hospital (150 ppl killed started in storage area

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104
Q

If the developing time increases then OD?

A

Increases

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105
Q

What is the velocity of all electromagnetic radiation?

A

3 x 10-8 m/s

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106
Q

____ ____ holds the silver halide crystals.

A

Gelatin Emulsion

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107
Q

2 terms that can be used for spatial resolution

A

Detail & Recorded Detail

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108
Q

Grid Frequency

A

of grid strips or lines per inch

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109
Q

When kVp increases ____ increases

A

density

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110
Q

What is attenuation?

A

Reduction in energy of beam.

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111
Q

Advantages of moving grids

A

blurs out grid lines; moves fast enough to clean page w/out lines on image

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112
Q

A high-contrast emulsion contains ____ silver halide grains with a relatively uniform grain size.

A

Smaller

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113
Q

Factors that affect film contrast

A

-silver halide crystals size shape and distribution -High Contrast Emulsion: Small crystals, uniform size -Low Contrast Emulsion: Large crystals, wider range of sizes (shades of gray)

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114
Q

Beam quality is measured by ____ ____ ____.

A

Half Value Layer/Filtration

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115
Q

Size of phosphor crystals, thickness of phosphor layer & its composition determine screen ____.

A

characteristics

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116
Q

Radiographic Contrast is a product of what 2 factors.

A

Image Receptor Contrast Subject Contrast

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117
Q

Name the factors that control/affect detail?

A

Film Speed Focal Spot Size SID OID Motion Distortion

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118
Q

Grid use increases ____ and decreases.

A

unwanted, non-diagnostic density contrast

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119
Q

Variable collimators are the most commonly used?

A

Beam Restricting Device

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120
Q

Do filters have an affect on density?

A

Yes, it filters out the low energy photon therefore density is increased.

121
Q

Focusing distance is associated with which of the following?

A

Grids (Focusing distance or Focal Range is used to specify optimal OD)

122
Q

Formula for maintaining density from one grid to another

A

old mAs/new mAs = oldGF/newGF

123
Q

Film Resolution

A

-ability to image an object faithfully -measured in line pairs per mm

124
Q

____ contrast film contains smaller crystals of uniform size.

A

High

125
Q

Positive Beam Limiting

A

Feature of radiographic collimators that automatically adjusts the radiation field to the size of the image receptor.

126
Q

Unexposed x-ray film that has been processed appears _____ and easily transmits _____ but not _____.

A

Lucent Light Not Images

127
Q

Speed

A

Ability of an image receptor to respond to low x-ray exposure.

128
Q

High kVp/mAs produces

A

low contrast long scale, many shades gray wide latitude

129
Q

A parallel grid’s main disadvantage is ____.

A

Grid cut-off

130
Q

The thicker the PT the more x-radiation is required to penetrate the PT exposure and for this reason the Rad Tech. must use ____ to measure the thickness.

A

Calipers

131
Q

An ____ ____ is an example of both luminescence & fluorescence.

A

Intensifying screen

132
Q

Sensitometry

A

Study of the relationship between the: -intensity of exposure of the film and the -blackness after processing

133
Q

Image with high number of x-rays will have ____ quantum mottle.

A

Lower

134
Q

How does beam limitation affect density?

A

It reduces the density and the amount of scatter.

135
Q

Use of collimation ____ contrast and ____ PT dose.

A

improves reduces

136
Q

The only x-rays transmitted through a grid are those ……

A

traveling in the direction of the interspace. X-rays scattered obliquely through the interspace are absorbed.

137
Q

What happens to PT dose when kVp is increased?

A

It is reduced

138
Q

Subject (PT) Factors

A

Selection of radiographic technique that properly compensates for PT’s size, shape and tissue composition.

139
Q

Speed, contrast and sensitivity of screen-film is determined by what 3 factors?

A

The size, shape and distribution of silver halide crystals.

140
Q

Aluminum or plastic make up the ____ in grids.

A

Interspace material

141
Q

What is added filtration?

A

Inserted into the collimator.

142
Q

When scatter radiation is removed image ____ improves.

A

contrast

143
Q

Lowering kVp ____ PT dose and image contrast.

A

will increase

144
Q

____ is the sensitivity of the screen-film combo to x-rays and light.

A

Speed

145
Q

What are the two main parts of sensitometry used to describe characteristic curve?

A

1.) Exposure to the film. 2.) % of light transmitted through the processed film

146
Q

The purpose of a filter is to ____ ____ ____.

A

Reduce PT Dose

147
Q

Focal-Spot sizes and values

A

Small 0.5mm, 0.6mm Large 1.0mm, 1.3mm

148
Q

Biggest enemy of radiographic contrast is?

A

Scatter or Fog

149
Q

Grid cleans up what?

A

scatter

150
Q

Grids are constricted with radiopaque ____ & radiolucent ___ materials.

A

Radiopaque Strips Radiolucent Interspace

151
Q

Gelatin makes up the ____ of protective covering on Radiograph film.

A

overcoat

152
Q

A radiograph that has small differences in OD are ____ ____ radiographs.

A

low contrast

153
Q

If you increase mAs then OD?

A

Increases

154
Q

Manifest Image

A

Processed image (aka latent image)

155
Q

Contrast Resolution

A

Ability to distinguish anatomical structures of similar subject contrast ie. Liver/Spleen or Gray Matter/White Matter

156
Q

Less Grid Frequency translate to

A

more distinct grid lines on film

157
Q

When OD is out side the diagnostic range what is lost? and why?

A

Contrast, because the image is in the “Toe” or “Shoulder” of the characteristic curve.

158
Q

A term borrowed from electrical engineering is called…

A

noise

159
Q

Resolution

A

The ability to image 2 separate objects and visually distinguish one from the other.

160
Q

If the Mass Density increases then the OD?

A

Decreases

161
Q

Radiographic Contrast = ____ x ____

A

Image Receptor Contrast x Subject Contrast

162
Q

Screens Spectral Matching

A

-Calcium Tungstate emits blue or blue violet -Exposed w/ silver halide film -Rare earth - green sensitive film (orthochromatic film) -Colors not matched: speed of system greatly reduced increased PT dose

163
Q

Phosphorescence

A

Phosphor continues to emit light after stimulation.

164
Q

Which of the following is most likely to result from the intro. of a grid to a particular exam?

A

Increased PT does and Increased Contrast

165
Q

Contrast is the degree of difference in ____ between areas of an image.

A

Optical Density

166
Q

What factors the visibility of detail?

A

Image contrast and Optical density

167
Q

Image with low number of x-rays will have ____ quantum mottle.

A

Higher

168
Q

An x-ray beam that could pass through ____ tissue would have high penetrability & quality.

A

dense

169
Q

Name 2 important characteristics of radiographic film base.

A

lucency dimensional stability

170
Q

High Spatial Resolution and High Contrast Resolution require?

A

Low Noise and Slow Image Receptors

171
Q

In the 1950’s a stronger and thinner film base was introduced. What material was this film base made of?

A

Polyester

172
Q

What improves as screen blur decreases, motion blur decreases and geometric blur decreases?

A

Spatial Resolution

173
Q

____ are designed to remove scattered x-rays before they reach the IR?

A

Grids

174
Q

Rule for Grid Use

A

Use for parts 8cm and up smaller? no grid larger? grid shoulder or knee optional

175
Q

4 Subject Factors for OD & Contrast

A

Thickness of the part Density of the part Atomic # of the part Motion

176
Q

What is between the emulsion and the base of radiographic film that holds it together during the process?

A

Adhesive Layer

177
Q

The body tissue with the highest absorption…

A

Bone

178
Q

An ____ ____ is an example of both luminescence and fluorescence,

A

Intensifying screen

179
Q

An increase of 15% in kVp is equivalent to increasing mAs by ____.

A

Double (100% increase)

180
Q

Focused grid is designed to

A

minimize grid cut-off

181
Q

Film base can maintain its size and shape during use and processing so that it doesn’t contribute to image distortion. This characteristic is best defined as ____ stability.

A

Dimensional

182
Q

A radiograph can be under or over penetrated yet still…

A

have adequate density

183
Q

Quantum mottle is similar to the ____.

A

sowing seeds of grass

184
Q

Latent Image

A

Unprocessed but exposed (photoelectric effect)

185
Q

Grid strips height divided by width (distance) of interspace determines ____ ____.

A

Grid Ratio

186
Q

What is small focal-spot size for?

A

Fine Detail (x-ray quantity low)

187
Q

mAs =

A

of photons

188
Q

____ ____ holds the silver halide crystals.

A

Gelatin Emulsion

189
Q

True or False

High contrast is also known as a short scale of contrast, which produces an image composed with more B&W’s and not as many shades of gray.

A

True

190
Q

What when raised increases the penetrating quality of the central ray?

A

Filtration and kVp (Both)

191
Q

Photons interactions free ____ from the silver and bromide atoms in the silver halide ____.

A

electrons crystal

192
Q

Exposed processed x-ray film can be ____.

A

Opaque

193
Q

What focal spot provides for a shorter exposure time minimizing motion blur?

A

Large

194
Q

x-rays transmitted without interaction & scatter (or compton interaction) radiation care called ____.

A

Image forming x-rays

195
Q

Film Contrast

A

Characteristic inherent in film itself to emphasize high or low contrast imaging.

196
Q

Disadvantages of moving grids

A

bulky, complicated subject to failure increases OFD poor design can cause motion longer minimum exposure time advantages outweigh disadvantages

197
Q

Most x-ray tubes are equipped with two?

A

focal spots sizes

198
Q

After photons interact releasing negatively charged e where do these e migrate to?

A

Sensitivity Center

199
Q

Contrast

A

Differences in Optical Density (degree of diff btw the light and dark areas of a radiograph)

200
Q

Name two important characteristics of radiographic film base.

A

lucency & dimensional stability

201
Q

When an image is under penetrated what happens?

A

Trabeculae “whited out”

202
Q

Because of the anode heel affect density is less @ which end of the x-ray beam?

A

Anode

203
Q

Radiographic Contrast is the product of ____ contrast & ____ contrast.

A

Image Receptor Subject

204
Q

2 basic parts of Radiographic Film

A

Base and Emulsion

205
Q

PT does is increased with a ____ in kVp.

A

Decrease

206
Q

The effects described as differential absorption are?

A

1) Responsible for radiographic contrast 2) Result of attenuating char. of tissue. 3) Minimized by using High kVp

207
Q

The ____ of an x-ray beam is called x-ray quality. (HVL decrease total # of x-rays)

A

penetrability

208
Q

Properly exposed film appears ____ and heavily exposed film appears ____.

A

with various shades of gray black

209
Q

A radiograph that has marked differences in OD is a ____ ____ radiograph.

A

high contrast

210
Q

To produce a long scale of contrast, a technologist would set a technique as follows:

A

High kVp and High mAs

211
Q

Speed of the image receptor is ____ but it very much influences ____.

A

Not apparent on the radiographic image Resolution and Noise

212
Q

Factors Affecting Film Speed

A

-Thickness of the emulsion -Concentration of Silver Halide Crystals -Shape–>used to be fate 3 dimensional then changed to–> -Tabular Grains -flat providing more surface area and volume ratio

213
Q

What controls PT radiation dose?

A

mA (or x-ray quantity)

214
Q

High spatial resolution and high contrast resolution require?

A

Low Noise & Slow Image Receptors

215
Q

Off-Level Grid

A

Grid not perp. to CR x-rays abnormally angulated grid cut-off across entire radiograph reduced density

216
Q

kVp is the primary control of ____ & ____

A

x-ray beam quality and beam penetrability

217
Q

A technologist is standing next to a portable examination of the abdomen at 50” and receives 3rem. The image is of poor quality and the technologist must return to repeat the exam. This time he stands at 70” what is the rem now?

A

I1/I2 = (D2/D1)2

3/x = (70/50)2

3/x = 4900/2500

4900x = 7500

x = 7500/4900

x = 1.53 rem

218
Q

The emulsion consists of a homogenous mixture of ____ & ____.`

A

Gelatin and Silver Halide Crystals

219
Q

One difference between large & small focal spots is the _____?

A

capacity to produce x-rays

220
Q

Name 3 common factors that determine amount of scatter absorbed with a grid.

A

Angle of scattered photons. Height of grid strips. Width of interspace material.

221
Q

Almost 99% of latent image is created by ____ from the screens.

A

Light

222
Q

Velocity of Light is constant and symbolized?

A

3 x 10-8 m/s

223
Q

When raised ____ & ____ increases the penetrating quality of the central ray.

A

Filtration & kVp

224
Q

What part of the image formation occurs during exposure?

A

Latent Image Formation

225
Q

Grid Material

A

Lead

226
Q

Developing stage

A

stage of processing during which the latent image is converted to a manifest or visible image

227
Q

What is the primary controlling factor for contrast?

A

kVp

228
Q

mAs controls

A

Optical Density

229
Q

Polyester

A

-Introduced in 1950 -Thinner, stronger, more fire resistant, less toxic -Stronger than cellulose triacetate -Stands up to processing, handling, and storage better

230
Q

Silver bromide and silver iodide make up the ____ in film emulsion.

A

Crystals Bromide 98% Iodide 2%

231
Q

Grid Purpose

A

-designed to transmit x-rays whose direction if on line from source (primary) -x-rays at an angle (scattered) are absorbed by grid materials -decreases scatter to the film -principle function to increase radiographic contrast

232
Q

Radiographic noise is …

A

the random fluctuation in the OD of the image

233
Q

What effect does doubling the SID have on density?

A

Density will be reduced by 1/4

234
Q

Subject Contrast

A

Determined by the size, shape and x-ray attenuating characteristics of the anatomy being examined & energy (kVp)

235
Q

On a focused grid grid strips are placed

A

at angle = primary beam

236
Q

____ contrast film contains smaller crystals of uniform size.

A

High

237
Q

If the collimation increases then OD?

A

Decreases

238
Q

Radiographic Film contains OD’s that range from ____ to ____.

A

0 Clear/Lucent (unexposed/ processed film transmits light not images) 4 Black/Opaque (processed exposed)

239
Q

kVp & mAs directly affect

A

density

240
Q

What is the most common error when grid cut off appears across the image?

A

grid is off-level

241
Q

Together the filtering effect of the x-ray tube’s glass envelope and its oil coolant are referred to as? (3 forms)

A

Inherent Filtration (.5 mm Al) Added Filtration (1 mm Al) Compensating Filtration (1 mm Al) (2.5 mm Al)

242
Q

How does kVp relate to differential absorption?

A

Higher kVp will allow more photons to transfer through.

243
Q

What has the greatest effect on contrast?

A

kVp

244
Q

Grid Covering

A

thin aluminum casing

245
Q

Primary control of OD is ____.

A

mAs (as mAs increases radiation quantity increases therefore the # of x-rays @ the image receptor increases for higher OD)

246
Q

Main disadvantage of parallel grid

A

grid cut-off (have to use correct SID)

247
Q

4 Film Factors

A

-Density or OD -Contrast (depends on kVp) -Speed (film screen mostly) -Latitude

248
Q

How does filtration affect the primary beam?

A

It increases the average energy of the primary beam.

249
Q

Silver Bromide & Silver Iodide make up the ____ in film emulsion.

A

Silver Halide Crystals

250
Q

Types of moving grid mechanisms include (2)

A

Reciprocating and Oscillating

251
Q

____ are designed to remove scattered x-rays B4 they reach the IR.

A

Grids

252
Q

The ____ beam refers to the x-rays that remain as the useful beam exits the PT. It consists of x-rays scattered away from the IR and image forming IR.

A

Exit

253
Q

Sthenic

A

Strong or Active

254
Q

With exposure to both x-ray & light ____ interaction occurs on the emulsion?

A

Photon

255
Q

Spatial Resolution

A

Ability to image small objects that have high subject contrast (bone-soft tissue interface)

256
Q

Examples of Low, Moderate and High Contrast

A

Low - Abdomen Moderate - Elbow (Fat Pads) High - Hand

257
Q

What recess motion blur?

A

short exposure time

258
Q

____ is the most critical consideration when using a crossed grid.

A

alignment

259
Q

If the x-ray is totally absorbed its interaction is ____.

A

Photoelectric

260
Q

Because of WWI something needed to change in the acquisition of images in diagnostic imaging ____.

A

Radiographic Film was developed

261
Q

Most important characteristics of radiographic image quality are?

A

Spatial Resolution Contrast Resolution Noise Artifacts

262
Q

Contrast is the degree of difference in ____ ____ between areas of an image.

A

Optical Density

263
Q

A group of atomic silver is called a?

A

Latent Image Center

264
Q

3 types of x-ray filtration are?

A

Inherent Added Compensating 2.5mm Al

265
Q

OD has a ____ ____ ____ that can be calculated if?

A

Precise Numeric Value If the level of light incident on a processed ilm and the level of light transmitted through that film are measured

266
Q

Beam quality is affected by____.

A

kvP and Filtration

267
Q

The degree of blackening of the x-ray image is ____.

A

Density

268
Q

Base & emulsion are 2 basic components of ____.

A

Radiographic Film

269
Q

Latitude can be thought of as…

A

the margin of error for technical factors

270
Q

A ____ material emits light for a period of time after stimulation.

A

phosphorescent

271
Q

In the toe and shoulder of characteristic curve large variations in ____ result in a small change to ____.

A

exposure OD

272
Q

Aluminum or plastic make-up the ____ in grids.

A

Interspace Material

273
Q

Fluorescence

A

Visible Light is only emitted while the phosphor is stimulated.

274
Q

kVp in relation to density is not…

A

linear

275
Q

Grid strips height divided by width (distance) of interspace material determines ____.

A

Grid Ratio

276
Q

How does kVp control OD?

A

Helps determine the # of x-rays (in the image forming beam) hence the average OD

277
Q

____ is the material with which x-rays or light photons from intensifying screens interact and transfer information.

A

Emulsion

278
Q

The image forming x-rays include those which have been…

A

remnant and scatter

279
Q

What happens to PT does when kVp is increased?

A

Reduced

280
Q

Spatial Resolution improves as….does what?

A

Motion, Screen, Geometric blur DECREASE

281
Q

On a focused grid grid strips are placed

A

at angle = primary beam

282
Q

Thermionic Emission at the filament creates a?

A

space charge

283
Q

Almost 99% of latent image is created by ____ from the screen.

A

Light

284
Q

Emulsion is enclosed by a protective covering of gelatin called ____.

A

Overcoat

285
Q

PT dose is ____ w/ added filtration

A

Reduced

286
Q

Biggest enemy of Radiographic Contrast?

A

Scatter or Fog

287
Q

When kVp and/or filtration increases beam quality ____.

A

increases

288
Q

The ____ layer adds to the light emitting efficiency of intensifying screens.

A

Reflective

289
Q

What is the controlling factor of density?

A

mAs

290
Q

Image Receptor Contrast

A

Inherent in the screen-film combo. and is influenced somewhat by processing of the film.

291
Q

When the grid frequency is higher it….

A

allows more to be captured

292
Q

High kVp results in reduced ____ ____

A

image contrast

293
Q

Grid interspace material can be made of ____ or ____.

A

Plastic (most often) Aluminum

294
Q

____ ensures the x-ray beam is collimated to the IR size.

A

Positive beam limiting device

295
Q

True or False The size and concentration of silver halide crystals primarily affect film speed.

A

True

296
Q

____ makes up the base of radiographic film.

A

polyester

297
Q

The ____ principle function is to provide mechanical support for silver halide crystals by holding them uniformly dispersed in place.

A

Gelatin’s

298
Q

Which grid ratio is generally for portable is

A

6:1

Radiographic Physics (1 decks)

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