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x-ray physics > Test 2 > Flashcards

Test 2 Flashcards

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1
Q

SID (Source Image Distance) aka

A

FFD (focal spot film distance)

TFD (target focal distance)

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2
Q

inverse square law

A

a change in beam intensity varies inversely with the square of the SID

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3
Q

exposure 3 ft from a source is 40 mR/hour; what is exposure rate at 6 ft?

A

(6^2/ 3^2) * (40/x) or 40*.25 because doubled

= 10 mR/hour

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4
Q

if SID is double, intensity is

A

1/4 original

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5
Q

if SID is halved, intensity is

A

4x original

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6
Q

if SID increases, # of x-rays reaching film

A

decreases

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7
Q

direct square law

A

old mAs/X = (old SID^2/new SID^2)

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8
Q

if SID doubled, mAs =

A

4x original

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9
Q

if SID halved, mAs=

A

1/4 original

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10
Q

classical unit of x-rays in air

A

Roentgen (R) or mR

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11
Q

classical unit of radiation absorbed dose (patient exposed)

A

RAD

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12
Q

SI unit for radiation absorbed dose (patient exposed)

A

Gray (Gy)

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13
Q

___ rad = 1 Gray

A

100 RAD = 1 Gy

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14
Q

classical unit for radiation equivalent man (occupational exposure)

A

REM

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15
Q

SI unit for radiation equivalent man (occupational exposure)

A

Sievert

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16
Q

equation for REM

A

rad * QF = REM

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17
Q

____ REM = 1 Sievert

A

100 rem = 1 Sievert

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18
Q

QF for x-ray

A

1

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19
Q

QF for alpha particles

A

20

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20
Q

QF for neutrons

A

5-20 dependent on energy

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21
Q

in x-ray, 1 R = __ RAD = ___ REM

A

1=1=1

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22
Q

classical unit for quantity of radioactive material

A

curie

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23
Q

SI unit for quantity of radioactive material

A

becquerel

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24
Q

important x-ray interactions important for diagnostic level radiography

A

photoelectric absorption
compton scatter
coherent (not as important)

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25
Q

The unit a physicist will use to name the ionization in air in classical nomenclature:

A

R

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26
Q

What is the Systems International Unit for REM?

A

Sievert

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27
Q

Unit used to describe energy absorption into matter

A

RAD

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28
Q

Milirad converted to RAD

A

1/1000 of a RAD

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29
Q

What is in the Systems International Unit for R?

A

Coulombs/kg

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30
Q

Unit of occupational exposure

A

REM

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31
Q

x-ray interaction that occurs with high atomic #

A

photoelectric effect (absorption)

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32
Q

x-ray interaction that is related to energy of x-ray photon

A

all of them (coherent, photoelectric, and compton scatter)

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33
Q

Which x-ray interaction is the most likely to occur at energies below 10 keV?

A

Coherent Scatter

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34
Q

Which x-ray interaction with matter is most likely to occur at energies between 10-60 keV?

A

Photoelectric absorption

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35
Q

Which x-ray interaction with matter is most likely to occur at energies greater than 60 keV?

A

Compton scatter

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36
Q

Which shell level is ionized in the photoelectric absorption interaction?

A

K

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37
Q

What happens to the original x-ray following the photoelectric interaction?

A

no longer exists

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38
Q

Which shell level is ionized in the Compton scatter interaction with matter?

A

outer

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39
Q

What happens to the original x-ray following the Compton scatter interaction?

A

scatters, then continues to ionize until it loses all it’s energy

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40
Q

What happens to the original x-ray following the Coherent scatter interaction?

A

scatters and changes direction, does not lose energy

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41
Q

State three other names for the Coherent scatter interaction:

A

Raleigh
Thompson
Classical

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42
Q

State at least 2 advantages of tissue compression

A

Decrease patient thickness
Decrease compton scatter
Hold patient to bucky

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43
Q

State at least 2 advantages of performing PA lumbar spine examinations instead of AP.

A

P-A uses compression and so it decreases mass: less mass less interactions
P-A retains shape so less shape distortion.

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44
Q

How does collimation to the film size or smaller effect the production of scatter radiation?

A

As collimated field decreases, compton scatter decreases

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45
Q

How does collimation to the smallest field size possible effect radiographic contrast?

A

Compton scatter decreases contrast, and collimation decreases Compton scatter, so collimation increases contrast
- Decreases density so you increase mAs by 50%

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46
Q

When collimating down “significantly”, what must be done to maintain radiographic density?

A
  • increase mAs by 50% to compensate for decrease in density
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47
Q

How does kVp effect the production of scatter radiation?

A

compton scatter increases as kVp increases

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48
Q

range of optimum kVp for radiographic examinations of the spine.

A

70-90

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49
Q

For every 4cm of tissue thickness increase mAs should be

A

doubled

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50
Q

Another name for radiographic grid

A

Bucky

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51
Q

Purpose of a radiographic grid

A

decrease compton scatter;

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52
Q

Causes severe underexposure on both lateral edges of the radiograph?

A

upside down grid

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53
Q

Grid, in which strips are angled toward the center so that the divergent x-ray beam coincides with the angled strips?

A

focused grid

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54
Q

Above this energy Compton scatter increases so much that it is necessary to use a radiographic grid?

A

> 60 kVp

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55
Q

The height of the lead strip in relation to the distance between them (the width of the interspace strip)?

A

grid ratio

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56
Q

Use of a 12:1 compared to an 8:1 grid causes this to occur?

A

Increase radiation exposure

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57
Q

Typical grid strip interspace material?

A

Aluminum, plastic, carbon fiber

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58
Q

The number of grid strips per centimeter or inch?

A

grid frequency

59
Q

Photographic factor that improves with the use of a radiographic grid?

A

contrast

60
Q

Direction that the x-ray tube can not be angled when using a radiographic grid?

A

laterally

61
Q

Must be precise when using a focused grid?

A

SID

62
Q

Direction that the x-ray beam may be angled when using a parallel or focused grid?

A

Direction of strips (Vertical not horizontal)

63
Q

Causes “fog” density?

A

compton scatter

64
Q

Causes the shadows of the grid strips blur out and become almost invisible?

A

Moving grid

65
Q

High frequency radiographic grid does this?

A

decrease visibility of grid lines

66
Q

Radiographic grid that is not useful in chiropractic because it will not allow an angled central ray (tube tilt)?

A

cross-hatched

67
Q

Ratio grid adequate for low amounts of scatter production such as that produced in 8X10” and 10x12” upper cervical techniques?

A

8:1 or 10:1

68
Q

This happens when the lead strips absorb the primary radiation on one or both lateral edges of the image?

A

grid cut off

69
Q

CM thickness of the patient’s anatomy in which it becomes necessary to use a radiographic grid?

A

= to or >10cm

70
Q

This will be indicated on a focused grid?

A

tube side

71
Q

3 types of grid movement

A

Single stroke/manual cocked
Reciprocating
Oscillating

72
Q

type of chiropractic practice would require a relatively low grid ratio

A

upper cervical

73
Q

type of chiropractic practice would require a relatively high grid ratio?

A

14X36 FILM, FULL SPINE, GONSTEAD

74
Q

Is a grid a radiation protection device - for the patient

A

no

75
Q

Which ratio grid would require the greatest increase in exposure?

A

Higher grid ratio = higher mAs

76
Q

There are 3 types of grids - name them

A

parallel
focused
cross-hatched

77
Q

Why would you not want to purchase a crosshatch grid?

A

Can’t angle beam in any direction

78
Q

define grid radius

A

focal range, proper focal range (proper SID)

79
Q

Describe a radiograph taken at the improper grid radius.

A

Lateral cut off on both edges

80
Q

Describe a radiograph that is taken with the central ray off center.

A

Primary x-rays collide with strips –> grid cut off on lateral edges

81
Q

Describe a radiograph that is taken with the beam angled to the left or the right.

A

Cut off on one lateral edge

82
Q

grid cut off

A

underexposed, due to scatter and diverging rays

83
Q

Why are intensifying screens used with x-ray film?

A

visible light from intensifying screens produce image by stimulating silver halide on film

84
Q

Film emulsion made of

A

silver hallide crystals suspended in gelatin

85
Q

Film base made of

A

plastic/ mylar

86
Q

Why does a double-coated film emulsion result in a decrease in sharpness?

A

The faster the film or screen, the thicker the emulsion, light diverges over emulsion producing pneumbra

87
Q

Image on the film that is not yet developed

A

latent image

88
Q

image actually screen on screen after processing

A

manifest image

89
Q

How is film manufactured to increase its’ speed?

A

Increased thickness= increased speed

90
Q

Which of these imaging systems would you choose if you were imaging extremities?

A

100 speed

91
Q

Which of these imaging systems would result in the most radiation exposure to the patient?

A

100 speed

92
Q

Which of these imaging systems would result in the least radiation exposure to the patient?

A

1200 speed

93
Q

Which of these imaging systems is the most consistent with the ALARA concept?

A

1200 speed

94
Q

What is the cause of quantum mottle? What does it look like?

A

caused by decreased x-rays used to produce the image

- looks grainy, like low megapixel image

95
Q

Which of these imaging systems would result in a radiograph with the most quantum mottle?

A

1200 speed

96
Q

What is the lowest film-screen system speed that you should consider using for routine spinal radiographs?

A

400 speed

97
Q

What does the term film latitude mean?

A

ability of film screen to allow for error (long latitude is more forgiving); wide range of useful densities

98
Q

How is film contrast related to film latitude?

A

as film latitude increases, film contrast decreases – INVERSELY related

99
Q

What color safelight is safe to use with both green and blue sensitive film?(“Universal”)

A

red, GBX safelight

100
Q

How far away from the work surface should a safelight be hung?

A

4 ft

101
Q

How do you know that the safelight filter is installed properly?

A

Writing is on the outside and read from L to R

102
Q

What is the maximum wattage of a light bulb for the safelight?

A

What the manufacturer says or less than 15 watts

103
Q

What color of light do rare earth screens emit? What type of film must be used with them?

A

green yellow, green sensitive film

104
Q

What color of light must the intensifying screen emit for orthochromatic film to respond?

A

green

105
Q

What color of light do calcium tungstate screens emit? What type film must be used with them?

A

blue violet, blue sensitive film

106
Q

If a technique is based on 200 speed imaging system and requires 30 mAs, 80 kVp, 40” SID, what must be done to compensate if a new 600-speed system is used?

A

USE 1/3 mAs=10 mAs

107
Q

When an artifact is demonstrated on a film as a result of something on the screen, what color will it appear? Will it be sharp or blurred? Why?

A

white, sharp, debris blocking light from intensifying screen

108
Q

What should be used to clean an intensifying screen?

A

screen cleaner and lint free gauze

109
Q

What temperature and humidity should film be stored at?

A

68 degrees and 40-60% humidity

110
Q

Where is the film’s expiration date located? What is the result of using film that is out of date?

A

On the box; increase fog, decrease contrast, breakdown silver halide crystals

111
Q

What may appear on the film if the humidity is too low?

A

Black artifacts from static

112
Q

Bending film produces

A

black crescent moon

113
Q

in x-ray tube, kVp:

A

accelerates electrons toward focal spot

114
Q

As kvP increases, x-ray energy

A

increases

115
Q

When kVp decreases by 15%, density ______

A

density decreases by 1/2

116
Q

when Kvp increases by 15%, density _____

A

density increases by 2x

117
Q

long scale = ___ contrast

A

low

118
Q

short scale = _____ contrast

A

high

119
Q

15% rule for kVp

A
  • if kVp increases by 15%, mAs decreases by 1/2
    if
  • if kVp decreases by 15%, mAs increases by 2x
    (Keeps density the same)
120
Q

long scale is used for

A

soft tissue

121
Q

at long SID, relative _____ x-rays produce image

A

perpendicular

122
Q

the use of 40”/72” SID will cause more heat in the tube

A

72”

123
Q

___ % change in mAs is required to notice a minimal change in radiographic density

A

30%

124
Q

5:1 grid ratio: non-grid mAs

A

x2

125
Q

6:1 grid ratio: non-grid mAs

A

x3

126
Q

8:1 grid ratio: non-grid mAs

A

x4

127
Q

10:1 grid ratio: non-grid mAs

A

x4

128
Q

12:1 grid ratio: non-grid mAs

A

x5

129
Q

16:1 grid ratio: non-grid mAs

A

x6

130
Q

radiographic density can be doubled by (2)

A

increasing kVp 15%

increasing mAs 50%

131
Q

if the scale of contrast is too long, it is a ____ scale and the change is ____ to kVp and ___ to mAs

A

low contrast scale
lower kVp 15%
increase mAs 2x

132
Q

if the scale of contrast is too high, it is a ____ and the change is ____ to kVp and ___ to mAs

A

short scale
increase kVp 15%
decrease mAs 1/2

133
Q

when SID increases, exposure to patient ____

A

decreases

134
Q

As SID increases, radiographic density ______

A

increases

135
Q

As SID increases, magnification and blur _____

A

decrease

136
Q

As OID increases, radiographic density ____

A

decreases

137
Q

As OID increases, magnification/blur ______

A

increase

138
Q

why does radiographic density change when OID is increased?

A

decrease in scatter decreases fog density

139
Q

chiropractic view that uses air gap technique?

A

lateral cervical

140
Q

why is air gap technique for lateral cervical better than bucky?

A

less exposure to patient

141
Q

if you increase kVp by 15%, and decrease mAs by 1/2, ____ scale of contrast is created

A

short

142
Q

low kVp and high mAs relationship results in a ____ scale of contrast

A

long

143
Q

short scale of contrast is aka

A

high contrast

x-ray physics (2 decks)

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