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FRCR Part 1 Physics > Radiation Safety and Dosimetry > Flashcards

Radiation Safety and Dosimetry Flashcards

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
Tissue weighting factor: Bladder, liver, oesophagus, thyroid
0.04
26
Tissue weighting factor: Brain, bone, skin, salivary glands
0.01
27
Tissue weighting factor: 'remainder' organs
0.12
28
Effective dose can be directly measured (T/F)
False - it can only be calculated
29
What does effective dose tell you?
Estimates the overall radiation detriment (risk) from a medical procedure
30
What does DNA damage result in? (3)
1. No biological effect 2. Cell death 3. Cell mutation
31
Deterministic effects are due to cell mutation (T/F)
False - they are due to cell death
32
Deterministic effects occur quite soon after exposure (T/F)
True
33
Deterministic effects only appear above a threshold dose (T/F)
True
34
Examples of deterministic effects (5)
1. cataract formation 2. skin erythema/ulceration/necrosis 3. Bone marrow suppression 4. Sterility 5. Death
35
Deterministic effects thresholds: Bone marrow- depression of cell production
0.5 Gy
36
Deterministic effects thresholds: skin erythema
2 Gy
37
Deterministic effects thresholds: skin necrosis
10Gy
38
Deterministic effects thresholds: cataract formation
0.5 Gy
39
Deterministic effects thresholds: testes temporary sterility
0.15 Gy
40
Deterministic effects thresholds: Ovaries
2.5
41
Stochastic effects severity is dose dependent (T/F)
False - they are not dose dependent, probability of effect increases with dose
42
Cancer induction is the main concern for stochastic effects (T/F)
True
43
Unborn child radiation risks (4)
1. Death 2. Organ malformation 3. Mental retardation 4. Increased risk of childhood cancer
44
External radiation protection - Distance. Define inverse square law
Doubling your distance from an XR source decreases you dose by a factor of 4
45
External radiation protection - Shielding What percentage of the scattered beam do aprons absorb?
90% (note they absorbed scattered beam, not the primary beam)
46
Shielding materials for XR and gamma rays are made from low Z materials (T/F)
False - they are made from high Z materials eg lead and tungsten
47
A 0.25mm lead apron transmits around ???% of the photons
5%
48
Average background radiation is around ???mSv per year per person
2.2mSv
49
A trans-Atlantic flight confers around ???? of effective dose
0.08mSv
50
Radon gas decays by...?
alpha particle emission
51
Thickness of Lead aprons, to % of transmitted photons: 0.25mm = ??? 0.35mm = ??? 0.5mm = ???
0.25mm = 5% 0.35mm = 3% 0.5mm = 1.5%
52
IRR 17 states an employee must be classified if they…? (3)
1. Whole body dose > 6mSv 2. >3/10s of dose limit to extremities (150mSv) 3. >15mSv to the eyes is likely
53
Average annual dose to public from medical procedures is…?
400uGy
54
Controlled area dose rate limit per hour per day?
>7.5 uSv per hour per day
55
Which 4 organs have the same TWF?
Bladder, Liver, Thyroid and Oesophagus
56
Supervised area is where the dose to a person may exceed what dose per year…?
1mSv per year
57
Radiation Weighting factor of alpha particles
20
58
Effective dose equation
equivalent dose x tissue weighting factor
59
IRCP adopt the ... model for stochastic radiation risk assessment
Linear no threshold model
60
Regarding irradiation during pregnancy: At 0-3 weeks what is the mSv threshold risk of death
Death at 0-3 weeks 100mSV threshold
61
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
Organ malformation - Risk Weeks 3-12 - Does not occur at <200mSv
62
Regarding irradiation during pregnancy: When is the most sensitive period for risk of mental retardation
Mental or physical retardation - 8-25 weeks
63
What is the natural risk of paediatric cancer?
1 in 500
64
Low Z materials such as Al and Cu are used as(...) to preferentially (...)
Beam filters Remove low energy x-rays from spectrum.
65
Low Z materials must be used to shield X or Y emitters...(what is x and y)
B- beta decay positron emitters e.g. plastic or glass.
66
x-y mm of plastic will typically absorb all z radiation
x = 10 y = 15 z = beta
67
Radiation dosimeters can absorb doses as low as...?
0.02mSv
68
Radiation dosimeters are made of crystals of...?
Lithium fluoride
69
100g of Brazil nuts confers an effective dose of around…?
0.01mSv
70
Regarding irradiation during pregnancy: At >3 weeks what is the Sv threshold for foetal death
>3 weeks 1-2 Sv threshold (note SV not mSv)
71
Leakage radiation from xray tubes must not exceed what rate at 1 meter?
1mgy/hour
72
Radon gives an average dose per year of how many msV?
1.3mSv

FRCR Part 1 Physics (20 decks)

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