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Diagnostic Imaging (1.3) > XRay Physics > Flashcards

XRay Physics Flashcards

1
Q

When fast moving electrons collide with matter in any form, what is produced?

A

X-Rays

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2
Q

In an x-ray tube, this is done by directing a stream of electrons at a high speed against a ….

A

metal target

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3
Q

As they interact with the atoms of the target, the electrons give up most of their energy in the form of…

A

Heat

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4
Q

However, about 1% of their energy is emitted as….

A

X-Radiation

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5
Q

The x-ray tube is inside a heavily lead-lined protective housing & is located…

A

Within a glass envelope (Pyrex) inside the tube housing

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6
Q

The tube consists of 2 electrode called the…

A

Cathode & Anode

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7
Q

Which electrode consists of a large filament, a small filament, and a focusing cup.

A

Cathode

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8
Q

The filaments serve as the source of _____ in the production of x-rays, and are made of _____.

A

Electrons

Tungsten

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9
Q

What occurs when a current is applied to the filament?

A

Thermionic Emission

The coil of the wire becomes very hot, boiling off electrons

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10
Q

What controls the quantity of electrons (mA) emitted from it?

A

Temperature of the filament

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11
Q

What determines the number of x-rays created?

A

Number of electrons

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12
Q

This is part of the cathode and encases the two filaments. Place where thermionic emission occurs.

A

Focusing Cup / Filament Cup

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13
Q

The Positive Electrode in the x-ray tube

A

Anode

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14
Q

Most x-ray tubes consist of a _____ anode.

A

Rotating

Rotating target receives electrons as they move from cathode to anode.

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15
Q

What is the reason for the rotating target?

A

Dissipate the heat generated

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16
Q

Rotating Anode exposes an area of the tungsten target of the anode, which is called the _____.

A

Focal Spot

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17
Q

The focal spot will be determined by the …

A

Size of Filament chosen

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18
Q

Smaller filament = ?

A

Better detail

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19
Q

The Line Focus Priniciple has the effect of making the actual focal spot size appear _____ when viewed from the position on the film.

A

Smaller

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20
Q

The smaller the target angle = ?

A

The smaller the effective spot

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21
Q

Stream of electrons narrows down to an….

A

effective beam

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22
Q

What heats the filament causing a boiling off of electrons?

A

Milliamperage (mA)

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23
Q

Milliamperage Per Second (mAs)

More Current = ?

A

More Current = More electrons produced = more x-rays produced = greater radiograph density (darker)

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24
Q

The overall blackening on a film?

A

Density

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25
Q

Density term used to describe structures that produce more blackening on the film

A

Radiolucent

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26
Q

Density term used to describe structures that produce less blackening on the film (whiter on x-ray)

A

Radio-opaque

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27
Q

T/F: The relationship between mAs and density are directly proportional

A

True

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28
Q

What is the primary method to control the blackening on the film?

A

Changing the mAs

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29
Q

mAs increases = ?

A

More film exposure

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30
Q

What is the minimum change of mAs that it takes to see a minimum change in density on the film?

A

30%

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31
Q

If the mAs is doubled, the density is ….

A

Doubled

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32
Q

If the mAs is halved, the density is…

A

Halved

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33
Q

The force applied to accelerate the electrons from the cathode to the anode at the time of exposure is…

A

Kilovoltage (kVp)

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34
Q

T/F: The greater the force of the kVp, the greater the numbers of high energy x-ray photons will be produced.

A

True

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35
Q

T/F: Wavelength and frequency are inversely related

A

True

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36
Q

T/F:
Low kVp = low energy = weak penetration
High kVp = high energy = strong penetration

A

True

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37
Q

Higher kVp produces (longer or shorter) wavelengths with a greater ability to penetrate the body tissue

A

Shorter

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38
Q

The difference in density between two structures.

A

Contrast

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39
Q

Contrast makes detail….

A

visible

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40
Q

T/F: kVp controls contrast but they are inversely related

A

True

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41
Q

Low kVp = ____ Contrast = Short Scale

A

High

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42
Q

Low kVp film will have _____ differences in dark and light areas. (ex: Black & White film; bone = Underexposed)

A

Sharp

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43
Q

Low kVp produces ____ scatter, however, the amount of radiation absorbed by the patient is ____

A

Less Scatter

Increased Radiation

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44
Q

High kVp = ____ Contrast = Long Scale

A

Low

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45
Q

T/F: High kVp film shows very little differences between densities. (ex: more shades of grey; soft tissue)

A

True

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46
Q

High kVp produces ____ scatter, however, the amount of radiation absorbed by the patient is ____

A

More Scatter

Less Radiation

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47
Q

To lower your contrast - longer scale of contrast - more shades of grey - you must:

A

Increase kVp by 15% & Decrease mAs by 50%

Double Density

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48
Q

To raise your contrast - shorter scale of contrast - fewer shades of grey - more black & white - you must:

A

Decrease kVp by 15% & Increase mAs by 100%

Half Density

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49
Q

What is the prime method to control density?

A

mAs

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50
Q

T/F: The relationship between kVp and density is NOT proportional.

A

True

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51
Q

Explain the 15% rule?

A

An increase in kVp by 15% will double overall density of the film, whereas, a decrease by 15% will cut the density in half.

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52
Q

Denser tissue absorbs x-rays whereas less dense tissue transmits more x-rays. What are the radiographic densities as seen on an x-ray:

  • Gas
  • Fat
  • Muscle, Water, Soft Tissue
  • Bone, Metal
A

Gas - BLACK
Fat - BLACK
Muscle, Water, Soft Tissue - GRAY
Bone, Metal - WHITE

53
Q

T/F: The rotating target is angled thus producing a varied intensity

A

True

54
Q

The intensity of the x-ray is greater at the ____ side.

A

Cathode

55
Q

Since intensity and density decrease on the anode side of the film, place the thinner portion of what is being x-rayed towards the anode end.

A

Anode-Heel Effect

56
Q

Cathode or Anode?

  • Less X-Ray
  • Smaller effective focal spot
  • More detail
  • Thinner body part
A

Anode side

57
Q

Cathode or Anode?

  • More XRay
  • Larger effective focal spot
  • Less detail
  • Thicker body part
A

Cathode side

58
Q

This represents the length of space from the focal spot (or tube) to the recording medium (or film)

A

Focal Film Distance (FFD) / Source Image Distance (SID)

59
Q

What happens when you increase the FFD?

A

Image gets smaller & clearer, which decreases magnification and distortion.

60
Q

What happens when you decrease FFD?

A

Image gets bigger & blurrier

61
Q

Intensity of radiation varies inversely with the square of the distance from the source.

A

Inverse Square Law

62
Q

If a 40” FFD is doubled to an 80” FFD, the intensity of the radiation is ____, so the mAs must be increased _____ to maintain same amount of film blackening.

A

Intensity is 1/4

mAs must increase by 4x

63
Q

If an 80” FFD is halved to a 40” FFD, the intensity of the radiation is _____ the intensity from the 80” if no factors are changed.

A

4x

64
Q

Intensifying screens consist of _____ crystals.

A

Fluorescent

65
Q

Large crystals (more light) work quickly, but yield…

A

Less detail

66
Q

Faster screens = Higher Contrast = Short Scale = ?

A

Less pt exposure

67
Q

Small crystals (less light) work slowly, but offer….

A

More detail

68
Q

Slow screens = Lower Contrast = Long Scale = ?

A

More pt exposure

69
Q

Intensifying screens increase density on the film by…

A

Intensifying the action of the x-rays

70
Q

_____ is the picture made by the useful beam

A

Umbra

71
Q

_____ is the blurry halo parts of the image (unsharpness)

A

Penumbra

72
Q

What is caused by having the tube too close to the film (short FFD), having the pt too far from the film (long OFD), or having too big of a filament on the cathode making the focal spot too big.

A

Penumbra

73
Q

Distance between the patient and the film

A

Object Film Distance (OFD)

74
Q

As you increase the OFD, the image becomes….

A

bigger & blurrier (more penumbra)

75
Q

As you decrease the OFD, the image becomes…

A

smaller & more clear (more detail)

76
Q

T/F: Object should be as close to film as possible for better detail.

A

True

77
Q

The pressure exerted by the film holder as it encloses the x-ray film. Pressure should be evenly distributed across the surface of the film.

A

Screen-film contact

78
Q

What is the best test for screen film contact?

A

Wire-Mesh test

79
Q

T/F: Poor screen film contact reduces the image sharpness of the image.

A

True

80
Q

What are the two types of distortion?

A

Size & Magnification

81
Q

Distortion can be affected by…

A

OFD & FFD

82
Q

When x-rays strike an object one of three things can occur…

A

Scattered, Absorbed, or Penetrated

83
Q

How can you reduce scatter radiation?

A
  1. Grids
  2. Air Gap Technique
  3. Collimators
  4. Filters
84
Q

A device of alternating strips of lead and spacer material. This is placed between the patient and the film. The sole purpose is to improve quality of the radiograph by absorbing scatter radiation. The use of this will require an increase in exposure factors to maintain density. This increases patient dose of radiation.

A

Grids

85
Q

What is the Grid Ratio?

A

Height of the lead strips to the distance b/t the strips

86
Q

What is the Grid Ratio in a chiropractic office?

A

12:1

87
Q

What is the Air Gap Technique?

A

6-10” between the patient and the film
This distance b/t the body part and the film causes scatter radiation to diverge away from the film, which reduces pt dose but can distort or magnify the image.

88
Q

Limits the size of the beam to the size of the body part you need to capture on film.

A

Collimation

89
Q

What is the best way to reduce scatter radiation to the patient as well as to the film?

A

Collimation

90
Q

Preferential removal of low energy photons (those not capable to get all the way to the screen). This stops the weak photons from entering the patient’s body thus protecting them from scatter radiation.

A

Filtration

91
Q

What are filtrations usually made from?

A

Aluminum

92
Q

Used to identify irradiation of patients; measures the radiation energy absorbed.

A

Radiation Absorbed Dose (RAD)

93
Q

1 RAD = ___ REM

A

1

94
Q

This unit is typically applied to occupationally exposed persons. It identifies the biological effectiveness of the radiation absorbed. It’s measured on radiation workers by a photosensitive badge worn on the collar.

A

Radiation Equivalent Man (REM)

95
Q

What is the safe limit of REM per year?

A

5 REMs (or RADs) per year

96
Q

The number of REMs a person can get in a lifetime without getting radiation poisoning.

A

Maximum Permissible Dose (MPD)

97
Q

What is the MPD in a lifetime?

A

MPD = 5 (age 18)

98
Q

Type of radiation: majority of useful beam; interacts with the target nucleus; a high intensity electron hits an inner shell electron, which is knocked out of its position in orbit, and an outer shell electron then fills its spot.

A

Bremsstrahlung aka Braking Radiation

99
Q

Primary form of scatter

A moderate energy x-ray knocks out an outer-shell electron, which causes a loss of energy.

A

Compton scatter

100
Q

A low energy x-ray that changes direction with no energy loss. Contributes to film fog.

A

Classical Scatter aka Thompson Scatter aka Coherent Scatter

101
Q

A low energy photon is absorbed by the subject creating a latent image on the film.

A

Photoelectric Effect

102
Q

This is caused by the fluctuation of the number of photons absorbed by the intensifying screens to form the image on the film. Faster screens produce more of this. The use of high mAs, low kVp will decrease this.

A

Quantum Mottle aka Radiographic Noise

103
Q

Solution temperatures that are too hot will _____ density.

A

Increase

104
Q

Solution temperatures that are too low will produce radiographs with _____ density

A

Insufficient

105
Q

Processing factor that brings out the latent image by developing the exposed silver halide crystals.

A

Developer

106
Q

The component of the Developer that produces shades of gray and black & uses Phenidone/Hydroquinone.

A

Reducer/Developer

107
Q

The component of the Developer that produces swelling of emulsion using Na+ Carbonate.

A

Accelerator/Activator

108
Q

The component of the Developer that controls oxidation using Na+ Sulfite or K Sulfite

A

Preservative

109
Q

The component of the Developer that protects unexposed crystals & uses Potassium Bromide/Iodine

A

Restrainer

110
Q

The component of the Developer that controls swelling of emulsion & uses Glutaraldehyde.

A

Hardener.

111
Q

Processing factor that removes the exposed silver halide crystals

A

Rinse

112
Q

Processing factor that hardens the image, making it permanent on the film

A

Fixer

113
Q

The component of the Fixer that neutralizes the developer aka “Stop Bath” & uses Acetic Acid.

A

Acidifier/Activator

114
Q

The component of the Fixer that removes undeveloped Ag Halide aka “Hypo Solution” & uses Ammonium/Na+ Thiosulfate

A

Clearing Agent

115
Q

The component of the Fixer that stiffens/shrinks the emulsion & uses Potassium Aluminum

A

Hardener

116
Q

The component of the Fixer that maintains the pH of the fixer & uses Sodium Sulfite

A

Preservative

117
Q

Processing factor that removes the developer & the fixer

A

Washing

118
Q

If light leak, developer temperature too hot, overexposure

A

Dark Films

119
Q

If developer temperature too low, chemicals need replacing

A

Light films

120
Q

Inadequate developer

A

Brown films

121
Q

Inadequate fixer

A

Milky films

122
Q

Insufficient washing

A

Greasy films

123
Q

Old film, hot developer, contaminated chemicals

A

Increased fog

124
Q

Insufficient fixing

A

Soft Emulsion

125
Q

How should you store the film to avoid pressure damage

A

Vertically

126
Q

Steps up or steps down the power

A

Transformer

127
Q

One form of energy to another

A

Transducer

128
Q

Beam of radiation loses energy as it passes thru matter

A

Attenuation

129
Q

What is added to the base of xray rilm to reduce glare

A

Green or blue tint

Diagnostic Imaging (1.3) (14 decks)

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