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Radiology > Radiation Biology and Safety > Flashcards

Radiation Biology and Safety Flashcards

1
Q

Radiosensitivity is?

A

Relative susceptibility of cells and tissues to harmful effects of ionizing radiation

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2
Q

High sensitivity is?

A

Undifferentiated, well-nourished, high metabolism, quickly replicating.

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3
Q

Examples of high sensitive tissues

A

Lymphoid organs, bone marrow, testes, intestines and mucous membrane

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4
Q

Low sensitivity is?

A

Differentiated, limited nutrients, low metabolism, slow division.

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5
Q

Examples of low sensitive tissues

A

Neurons and muscles

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6
Q

Effective dose (E) is?

A

Measure of equivalent radiation exposure by accounting for radiosensitivities

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7
Q

Formula for effective dose? E = ?

A

E = sum of (Wt) * Ht (sum of tissue weight* radiation emitted from X-ray machine

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8
Q

Tissue weighting factor for bone marrow?

A

0.12

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9
Q

Tissue weighting factor for skin?

A

0.01

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10
Q

What is Ht?

A

Radiation emitted from X-ray machine that is irradiating all the tissue in the area (measured from machine) (eV)

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11
Q

Effective dose is measured in?

A

Sieverts (Sv)

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12
Q

What is the radiation limit for total effective dose?

A

<50mSv per year

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13
Q

What is the occupational dose radiation limit?

A

< 20 mSv per year, averaged over 5 years

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14
Q

What is the public dose (medical) radiation limit?

A

< 1 mSv per year

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15
Q

How much radiation do dentists receive per year?

A

0.2 mSv per year

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16
Q

How much background radiation is there?

A

3.1 mSv per year

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17
Q

Background Equivalent Radiation Time (BERT) is?

A

Number of days of background radiation that would equate to the amount of radiation experience in a procedure.

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18
Q

9 micro Sv ED =?

A

1 day BERT

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19
Q

What are direct effects of radiation?

A

Radiation forms unstable free radicals which cause direct molecular changes in cells.

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20
Q

Free radicals primarily form from?

A

Water

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21
Q

Direct effects of radiation causes _____ of biological effects from x-ray exposure.

A

1/3

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22
Q

Radiation of water causes?

A

Formation of hydroxyl (OH) radical.

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23
Q

Hydroxyl radical interacts with organic molecules to form?

A

Organic free radicals

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24
Q

Damage from indirect effects of radiation may take ______ to be evident.

A

hours to decades

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25
Q

Indirect radiation causes ____ of biological effects from x-ray exposure.

A

2/3

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26
Q

Deterministic effects are?

A

Lethal DNA damage (i.e. cell death) and resulting effects due to decreased tissue amount and function.

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27
Q

Cellular effects as deterministic effects?

A

Chromosome aberrations, DNA damage, apoptosis

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28
Q

In whole-body irradiation effects, in acute radiation syndrome, 1-2 Sv causes?

A

Blood changes and vomiting, recovering in 2 weeks.

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29
Q

In acute radiation syndrome, 2-6 Sv causes?

A

Hair loss, severe blood changes, recovery in 1 year

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30
Q

In acute radiation syndrome, 6-10 Sv causes?

A

Death in two weeks

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31
Q

Embryo and fetus (measured in Gy) would have whole-body irradiation effects that include:

A
  • Fail to implant
  • Reduced growth
  • Microcephaly
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32
Q

What are stochastic effects?

A

Non-lethal DNA damage (i.e. gene mutations) and resulting effects due to replication of mutated cells.

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33
Q

List possible stochastic effects

A
  • Carcinogenic and heritable effects
  • Cancer is a stochastic effects.
  • Occurs in random bias, independent of dose
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34
Q

Deterministic effects severity is?

A

Proportionate to dose. Higher dose kills more cells and has larger effect.

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35
Q

Stochastic effects severity is?

A

Independent of dose. Individual either has effect or not (all-or-none)

36
Q

Deterministic effects is caused by?

A

Too many cells being killed

37
Q

Stochastic effects is caused by?

A

Non-lethal DNA damage (mutations)

38
Q

Threshold for deterministic effects?

A

Yes. Cells exposed to radiation above threshold will be killed.

39
Q

Threshold for stochastic effects?

A

No. The amount of radiation to alter DNA varies

40
Q

Probability of effects and dose of deterministic effects?

A

Probability is independent of dose. Everyone above the threshold will have cells killed.

41
Q

Probability of effects and dose of stochastic effects?

A

Probability of effect is proportionate of dose. Higher dose, more chance that a mutation causes effect.

42
Q

Optimization as radiation protection follows?

A

ALARA principles (as low as reasonably achievable)

43
Q

Dose limitation for radiation protection is?

A

Stay under provided dose limits for occupational and public exposure.

44
Q

Total effective dose:

A

<50 mSv per year

45
Q

Occupational dose limitation

A

<20 mSv per year, averaged over 5 years

46
Q

Public (medical) dose limitation

A

<1 mSv per year

47
Q

Justification for taking radiographs are?

A

If you have a normal patient (no 8’s) with no history of caries and you want to take a base-line assessing radiograph, take a pre-molar bitewing. If issues are detected with pre-molar bitewing, you can take more.

If diagnostic benefit from exposure exceeds the risk of harm.

48
Q

Rectangular collimator limits exposure by?

A

Reduces beam’s diameter which exposes 60% less tissue compared to round collimators (most effective way to reduce radiation)

49
Q

Distance for limiting exposure

A

Increase distance between you and radiation source (inverse square rule of distance with respect to radiation intensity).

Increasing distance by 2, decreases radiation dose by 4. Increasing distance by 3, decreases radiation dose by 9.

50
Q

Shielding for limiting exposure

A

Use lead shields when possible

51
Q

Positioning for limiting exposure

A

If shields are unavailable, standing at 90 degrees to 135 degrees from beam axis has the least back scatter radiation “safe zone”. Stand in the “safe zone” at a distance of 6 ft is sufficient to reduce radiation.

52
Q

Object localization techniques?

A

Methods used to determine relative position of two objects in the oral cavity, usually along the x-ray beam (i.e. don’t know if object is buccal or lingual to teeth)

53
Q

List 4 methods of object localization techniques

A
  • 90 degree method
  • Tube shift (SLOB rule)
  • Known object rule
  • Computed tomography (CT or cone beam CT)
54
Q

Indications for object localization

A
  • Impacted teeth
  • Foreign bodies
  • Residual root fragments
  • Periapical lesions
  • Correction of film fault
  • Endodontic treatment - identify canals/roots
55
Q

What’s 90 degree method

A

Take two radiographs at 90 degrees from each other: periapical or bitewing image and occlusal image

56
Q

Explain SLOB rule (same lingual; opposite buccal)

A

If the object shifts towards the same direction of the tube shift, the object is lingual with respect to the known fixed object.

57
Q

Define tube shift

A

Direction of tube head moves horizontally, do not consider the horizontal angulation

58
Q

Rule of thumb of tube shift

A

More opaque cusp is the lingual cusp (closer to film). Lingual cusp will move in the same direction as the tube shift.

59
Q

If lingual cusp (more radiopaque) moves mesially), the tube shift is?

60
Q

If radiopacity of lingual cusp moves distally, so must the?

A

buccal mass

61
Q

If tube shifts mesially (no change in angulation) and root moves mesially, which root is this?

A

Lingual root

62
Q

If tube head shifts upwards leading to radiopacity shifting upwards, then it must be ?

A

Palatal mass

63
Q

A structure that is closer to the film will appear more?

A

Radiopaque. e.g. the palatal cusps of the pre-molar appear more radiopaque than the buccal cusps.

64
Q

Palatal cusps (more radiopaque) appear too ____ with respect to buccal cusps.

65
Q

Code 0 (ICDAS classification)

A

Sound tooth surface

66
Q

Code 1 ICDAS

A

Enamel to outer 1/2

67
Q

Code 2 ICDAS

A

Enamel to inner 1/2

68
Q

Code 3 ICDAS

A

Dentine (just detectable)

69
Q

Code 4 ICDAS

A

Dentine (outer 1/3)

70
Q

Code 5 ICDAS

A

Dentine (inner 2/3)

71
Q

Cervical burnout vs root caries:

A

Confirm cervical burnout if radiolucency is confined to only between CEJ and alveolar crest.

Root caries -> radiolucency extends past CEJ or alveolar crest.

72
Q

Healthy alveolar crest is very?

A

Very radiopaque and is <2mm from CEJ

73
Q

Horizontal bone loss is?

A

Reduction in overall height of alveolar crest

74
Q

Vertical bone defects is?

A

Destruction of bone in a direction parallel to root axis

75
Q

Furcation involvement?

A

Loss of alveolar bone which exposes root furcation

76
Q

Mild horizontal bone loss and vertical bone defects

A

Coronal 1/3

77
Q

Moderate horizontal bone loss and vertical bone defect

A

Middle 1/3

78
Q

Severe horizontal bone loss and vertical bone defects

A

Apical 1/3

79
Q

Vertical bone defects refer only to?

A

Refers to “walls” remaining around defect.

80
Q

three-walled is?

A

Least severe, only 1 tooth surface affected; still interproximal bone

81
Q

Two walled is?

A

Two tooth surface affected; no interproximal bone

82
Q

One-walled is?

A

Most severe. Two tooth surfaces and alveolar bone border affected.

83
Q

Bite wings and paralleling PA is for?

84
Q

OPGs are for?

A

Generalized conditions (poor for premolar region)

85
Q

Cone Beam CT are used for?

A

High complexity conditions (e.g. determining walls of vertical bone defect)

Radiology (7 decks)

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