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Finals > Radiology > Flashcards

Radiology Flashcards

1
Q

What does ionising radiation do?

A

Turns atoms into ions by knocking away electrons orbiting the nucleus

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2
Q

How much eV does each ionisation deposit?

A

35eV

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3
Q

What is are the direct effects of radiation on DNA?

A

Radiation interacts with the atoms of a DNA molecule or another important part of the cell

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4
Q

What are the indirect effects of radiation on DNA?

A

Radiation interacts with water in the cell producing free radicals which cause damage

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5
Q

What is the usual outcome for a single strand DNA damage?

A

Usually repaired

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6
Q

What is the usual outcome for double strand damage?

A

Sometimes repaired
May be faulty repair —> leads to mutations that affect cell function

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7
Q

What are the biological effects of radiation dependent on?

A

Type of radiation
Amount of radiation (dose)
Time over which the dose is recieved
Type of tissue/cell type irradiated

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8
Q

What is tissue radio sensitivity dependent on?

A

Function of the cells that make up tissues
If the cells are actively dividing (increased division = increased risk)

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9
Q

Which tissues are highly radiosensitive?

A

Bone marrow
Lymphoid tissue
Gastrointestinal glands
Gonads
Embryonic tissue

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10
Q

What tissues are moderately radiosensitive?

A

Skin
Vascular endothelium
Lungs
Lens of eye

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11
Q

What tissues are least radiosensitive?

A

Central nervous system
Bone and cartilage
Connective tissue

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12
Q

What are the three outcomes of DNA mutation?

A

Mutation repaired = viable cells
Cell death = unviable cells
Cell survives but is mutated = cancer

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13
Q

What is the absorbed dose?

A

Measurement of the energy deposited by radiation
Measures in Grays (Gy)

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14
Q

What is the equivalent dose?

A

Absorbed dose x weighting factor
Measured in Sieverts (Sv)

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15
Q

What is the equivalent dose of alpha?

A

20 Sv

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16
Q

What is the equivalent dose of beta, gamma and X-rays?

A

1 sV

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17
Q

What is the risk of cancer with a dose of 1mSv?

A

1 in 20,0000

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18
Q

What is the risk of cancer with an intra-oral x-ray?

A

1 in 10,000,000

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19
Q

What are the determinstic effects of radiation?

A

Tissue reactions (decreased bone marrow cells, cataract, sterility, hair loss)
Occur over certain (threshold) dose
Severity of effect related to dose

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20
Q

What are the stochastic effects of radiation?

A

The probability of occurence is related to dose received
Somatic: results in disease or disorder
Genetic: abnormalies in descendent

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21
Q

What are the effects of radiation during pregnancy?

A

Lethal potential with doses 100mGy before or immediately after after implantation of the embryo into uterine wall
During organogenesis >250mGy dose leads to growth retardation

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22
Q

What is the cancer risk in utero?

A

1 in 13,500 per 1mGy exposure

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23
Q

What is the effective dose of an intra-oral radiograph?

A

0.005mSv

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24
Q

What is the staff dose limit for body, skin and eyes?

A

Body: 20mSv
Skin/extremities: 500mSv
Eye: 20mSv

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25
Q

What is the minimum distance for staff from the X-ray machine?

A

1.5m

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26
Q

What percentage do circular collimators increase the dose by?

A

40%

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27
Q

What are the four factors of dose optimisation?

A

E speed or faster (film); fewer X-ray photons
KV range of 60-70kV
Fsd: >200mm
Rectangular collimation

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28
Q

What are the diagnostic reference levels in an adult for a digital sensor?

A

0.9mGy

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29
Q

What are the diagnostic reference levels in an adult for phosphor plates and film?

A

1.2mGy

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30
Q

What are the diagnostic reference levels in a child for a digital sensor?

A

0.6mGy

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31
Q

What are the diagnostic reference levels in a child with a phosphor plate and film?

A

0.7mGy

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32
Q

What are the two types of receptors?

A

Digital and Film

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33
Q

What are digital receptors made up of?

A

Phosphor plate
Solid state sensor

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34
Q

What are film receptors made of?

A

Direct action film
Indirect action film

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35
Q

How many shades of grey are in 8 bits?

A

256

36
Q

What does DICOM stand for?

A

Digital Imaging and Communications in Medicine

37
Q

What does PACs stand for?

A

Picture Archiving and Communication System

38
Q

What are the two needs for radiographic localisation?

A

To determine location of a structure in relation to other structures
Only if clinical examination is insufficient to provide an answer

39
Q

What are 5 clinical situations where radiographic localisation may be used?

A

Position of unerupted teeth
Location of roots/root canals
Relationship of pathological lesions
Trauma
Soft tissue swelling

40
Q

What is required for radiographic localisation?

A

2 views required
Views should be at right angles in their projection geometry
Aid of opaque objects

41
Q

What is the rule for parallax?

A

Same
Lingual
Opposite
Buccal

42
Q

What is the definition of parallax?

A

An apparent change in the position of an object caused by a real change in the position of the observer

43
Q

What are the uses of radiographs?

A

Diagnosis
Treatment planning
Monitoring

44
Q

What is the difference between radiology and radiography?

A

Radiology is a specialty of medicine
Radiography is an imaging technique

45
Q

What does ALARA stand for?

A

As Low As Reasonably Practitionable

46
Q

What is the main risk of dental radiology?

A

Carcinogenesis

47
Q

What does IRR 2017 stand for?

A

Ionising Radiation Regulations 2017

48
Q

What does IR(ME)R stand for?

A

Ionising Radiation (Medical Exposure) Regulation

49
Q

What are some examples of justifications for radiographs?

A

Caries detection
Investigating infection
Orthodontic planning

50
Q

What are the principles for radiographic protection?

A

Justification
Optimisation
Dose Limitation

51
Q

What is processing in radiology?

A

Conversion of a latent image to a permanent visible image
Either digitally or chemically

52
Q

What is the kV of a dental machine?

A

60-70kV

53
Q

What are the three interactions with matter?

A

No effect
Complete absorption
Absorption and scatter

54
Q

What is the receptor size for an anterior periapical?

A

0

55
Q

What is the receptor size for a posterior periapical?

A

2

56
Q

What is the receptor size for a bitewing?

A

2

57
Q

What is the receptor size for an occlusal?

A

4

58
Q

What side of the receptor should face the X-ray beam?

A

Blank side

59
Q

What can be used to orientate a bitewing?

A

Curve of Spee

60
Q
A
61
Q

What are the specific attenuation interactions?

A

Photoelectric effect: complete absorption
Compton effect: partial absorption and scattering

62
Q

When does the photoelectric effect take place?

A

Occurs when the energy of the incoming photon is equal to or just greater than the binding energy of an inner shell electron

63
Q

What does the photoelectric effect result in?

A

Prevents X-ray photons from reaching the receptor- leads to lighter area on radiograph

64
Q

What is the formula for the probability of the photoelectric effect?

A

Pe= p x Z3 / E3
P= proportion to physical density
Z3= cubed atomic number
E3= photon energy cubed

65
Q

What is E3 affected by?

A

KV

66
Q

What is the Z3 of lead?

A

551,368

67
Q

What is the dose of a Periapical or Bitewing?

A

5uSV

68
Q

What is the dose of a maxillary occlusal radiograph?

A

8

69
Q

What is the dose of a lat cephalogram?

A

3

70
Q

When does the Compton effect occur?

A

Energy of proton is much greater than binding energy of the electron

71
Q

What do recoil electrons do?

A

Ionise and cause potential damage to adjacent tissues

72
Q

Which photons cause forward scatter?

A

Higher energy

73
Q

Which photons cause back scatter?

A

Lower energy

74
Q

What does forward scatter present as

A

Darkening or fogging

75
Q

What factors are associated with the probability of the Compton effect?

A

Independent of Z
Weakly proportionate to photon energy
Proportionate to density of material

76
Q

What is the effect of collimation?

A

Decreased irradiated surface area
Decreased volume of irradiated tissue
Decreased number of scattered photons in tissue
Decreased scattered photons interacting with receptor
Decreased loss of contrast on image

77
Q

What is the effect of lowering the kV?

A

Lower x-ray tube potential difference (kV)
Overall lower photon energy produced
Increased photoelectric interaction
Increased contrast between tissues with different Z (good)
Increased absorbed dose (bad)

78
Q

What is electomagnetic radiation?

A

Flow of energy created by simultaneously varying electrical and magnetic fields

79
Q

What are the features of electromagnetic radiation?

A

No mass
No charge
Travels at speed of light
Can travel in a vacuum

80
Q

What is frequency in regard to EM waves?

A

How many waves per unit time
Measured in Hertz

81
Q

What is speed in regard to EM waves?

A

Speed= frequency x wavelength

82
Q

What is eV?

A

Energy gained by one electron moving across a potential difference of one volt

83
Q

What are x ray photon energies?

A

124eV-124keV

84
Q

What is amps?

A

How much charge flows past a point per second

85
Q

What is current?

A

Flow of electrical charge

86
Q

What is voltage?

A

Difference in electrical potential between two points in an electrical field
Synonymous with potential difference

87
Q

What is the annual background radiation dose?

A

2.2mSv

Finals (20 decks)

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