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FRCR Part 1 Physics > Radiation Safety and Dosimetry > Flashcards

Radiation Safety and Dosimetry Flashcards

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1
Q

Typical doses from medical exposures:
Extremity XR

A

<0.01 mSv

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2
Q

Typical doses from medical exposures:
CXR

A

0.02 mSV

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3
Q

Typical doses from medical exposures:
Lumbar spine

A

1.3 mSv

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4
Q

Typical doses from medical exposures:
Barium enema

A

7 mSV

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5
Q

Typical doses from medical exposures: CT head

A

2mSV

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6
Q

Typical doses from medical exposures: CT chest

A

8mSV

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7
Q

Typical doses from medical exposures: CTAP

A

10 mSv

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8
Q

Typical doses from medical exposures: Lung perfusion scan NM

A

1mSv

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9
Q

Typical doses from medical exposures: Bone scan NM

A

4 mSV

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10
Q

Typical doses from medical exposures: FDG PET scan

A

8 mSV

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11
Q

What foetal radiation dose will double the natural risk of paediatric cancer?

A

25mSV

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12
Q

What is the excess childhood cancer risk? (compared to adults) per msv

A

1 in 13,000 per mSv

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13
Q

Cancer risk is 1 in _____ for 1mSv exposure (adults)

A

Cancer risk is 1 in 20,000 for 1mSv exposure (population risk)

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14
Q

Units of absorbed dose?

A

mGy
mGy = 1miliJoule /kg

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15
Q

Units of equivalent dose?

A

mSv

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16
Q

Units of effective dose?

A

mSv

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17
Q

How is equivalent dose calculated?

A

Absorbed dose x radiation weighting factor (H=D*WR)

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18
Q

Radiation Weighting factor of XR/ gamma ray

A

1

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19
Q

Radiation Weighting factor of electrons/positrons

A

1

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20
Q

Radiation Weighting factor of Protons

A

5

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21
Q

What are the 2 ways DNA can be damaged?

A
  1. Indirect - damage caused by free radicals from radiolysis of water molecules (most common)
  2. Direct - radiation ionises molecules within the DNA molecule
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22
Q

How is absorbed dose calculated

A

radiation energy deposited in a medium/ the mass of the medium (D = E/m)

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23
Q

Tissue weighting factor:
bone marrow, breast, colon stomach

A

0.12

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24
Q

Tissue weighting factor:
Gonads

A

0.08

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25
Q

Tissue weighting factor:
Bladder, liver, oesophagus, thyroid

A

0.04

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26
Q

Tissue weighting factor:
Brain, bone, skin, salivary glands

A

0.01

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27
Q

Tissue weighting factor:
‘remainder’ organs

A

0.12

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28
Q

Effective dose can be directly measured (T/F)

A

False - it can only be calculated

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29
Q

What does effective dose tell you?

A

Estimates the overall radiation detriment (risk) from a medical procedure

30
Q

What does DNA damage result in? (3)

A
  1. No biological effect
  2. Cell death
  3. Cell mutation
31
Q

Deterministic effects are due to cell mutation (T/F)

A

False - they are due to cell death

32
Q

Deterministic effects occur quite soon after exposure (T/F)

A

True

33
Q

Deterministic effects only appear above a threshold dose (T/F)

A

True

34
Q

Examples of deterministic effects (5)

A
  1. cataract formation
  2. skin erythema/ulceration/necrosis
  3. Bone marrow suppression
  4. Sterility
  5. Death
35
Q

Deterministic effects thresholds: Bone marrow- depression of cell production

A

0.5 Gy

36
Q

Deterministic effects thresholds: skin erythema

A

2 Gy

37
Q

Deterministic effects thresholds: skin necrosis

A

10Gy

38
Q

Deterministic effects thresholds: cataract formation

A

0.5 Gy

39
Q

Deterministic effects thresholds: testes temporary sterility

A

0.15 Gy

40
Q

Deterministic effects thresholds: Ovaries

A

2.5

41
Q

Stochastic effects severity is dose dependent (T/F)

A

False - they are not dose dependent, probability of effect increases with dose

42
Q

Cancer induction is the main concern for stochastic effects (T/F)

A

True

43
Q

Unborn child radiation risks (4)

A
  1. Death
  2. Organ malformation
  3. Mental retardation
  4. Increased risk of childhood cancer
44
Q

External radiation protection - Distance.
Define inverse square law

A

Doubling your distance from an XR source decreases you dose by a factor of 4

45
Q

External radiation protection - Shielding
What percentage of the scattered beam do aprons absorb?

A

90% (note they absorbed scattered beam, not the primary beam)

46
Q

Shielding materials for XR and gamma rays are made from low Z materials (T/F)

A

False - they are made from high Z materials eg lead and tungsten

47
Q

A 0.25mm lead apron transmits around ???% of the photons

A

5%

48
Q

Average background radiation is around ???mSv per year per person

A

2.2mSv

49
Q

A trans-Atlantic flight confers around ???? of effective dose

A

0.08mSv

50
Q

Radon gas decays by…?

A

alpha particle emission

51
Q

Thickness of Lead aprons, to % of transmitted photons:
0.25mm = ???
0.35mm = ???
0.5mm = ???

A

0.25mm = 5%
0.35mm = 3%
0.5mm = 1.5%

52
Q

IRR 17 states an employee must be classified if they…? (3)

A
  1. Whole body dose > 6mSv
  2. > 3/10s of dose limit to extremities (150mSv)
  3. > 15mSv to the eyes is likely
53
Q

Average annual dose to public from medical procedures is…?

A

400uGy

54
Q

Controlled area dose rate limit per hour per day?

A

> 7.5 uSv per hour per day

55
Q

Which 4 organs have the same TWF?

A

Bladder, Liver, Thyroid and Oesophagus

56
Q

Supervised area is where the dose to a person may exceed what dose per year…?

A

1mSv per year

57
Q

Radiation Weighting factor of alpha particles

A

20

58
Q

Effective dose equation

A

equivalent dose x tissue weighting factor

59
Q

IRCP adopt the … model for stochastic radiation risk assessment

A

Linear no threshold model

60
Q

Regarding irradiation during pregnancy:
At 0-3 weeks what is the mSv threshold risk of death

A

Death at 0-3 weeks
100mSV threshold

61
Q

Regarding irradiation during pregnancy: during which weeks is there a risk of foetal organ malformation.

And

At what doses (mSv) do they NOT occur at

A

Organ malformation
- Risk Weeks 3-12
- Does not occur at <200mSv

62
Q

Regarding irradiation during pregnancy: When is the most sensitive period for risk of mental retardation

A

Mental or physical retardation
- 8-25 weeks

63
Q

What is the natural risk of paediatric cancer?

A

1 in 500

64
Q

Low Z materials such as Al and Cu are used as(…) to preferentially (…)

A

Beam filters
Remove low energy x-rays from spectrum.

65
Q

Low Z materials must be used to shield X or Y emitters…(what is x and y)

A

B- beta decay
positron emitters

e.g. plastic or glass.

66
Q

x-y mm of plastic will typically absorb all z radiation

A

x = 10
y = 15
z = beta

67
Q

Radiation dosimeters can absorb doses as low as…?

A

0.02mSv

68
Q

Radiation dosimeters are made of crystals of…?

A

Lithium fluoride

69
Q

100g of Brazil nuts confers an effective dose of around…?

A

0.01mSv

70
Q

Regarding irradiation during pregnancy:
At >3 weeks what is the Sv threshold for foetal death

A

> 3 weeks
1-2 Sv threshold
(note SV not mSv)

71
Q

Leakage radiation from xray tubes must not exceed what rate at 1 meter?

A

1mgy/hour

72
Q

Radon gives an average dose per year of how many msV?

A

1.3mSv

FRCR Part 1 Physics (20 decks)

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