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Westmead Physics > Dosimetry/ Radiobiology > Flashcards

Dosimetry/ Radiobiology Flashcards

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1
Q

What is ‘exposure’ in radiation dosimetry?

A

the ionization created in air

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2
Q

unit for ‘exposure’ in radiation dosimetry

A

coulomb/ kg

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3
Q

What does KERMA stand for

A

Kinetic Energy Released per unit MAss

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4
Q

Unit for KERMAs

A

Gray

Joules/ kg

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5
Q

Does KERMA represent the quantity of radiation absorbed by patients?

A

No

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6
Q

Symbol for radiation exposure?

A

X

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7
Q

Symbol for Air Kerma?

A

K

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8
Q

Symbol for Absorbed Dose of radiation?

A

D

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9
Q

Unit for Absorbed Dose of radiation?

A

Gray

(Joules/ kg)

Old unit: Rad

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10
Q

Difference between ‘absorbed dose’ of radiation in comparison to air kerma?

A

radiation deposited rather than energy released

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11
Q

How is the Absorbed Dose of radiation often quoted?

A

Entrance Skin Dose

OR

Organ dose

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12
Q

Symbol for Equivalent Dose of radiation?

A

H

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13
Q

What is the relationship between absorbed dose and equivalent dose

A

Equivalent dose = Absorbed dose x Radiation Weighting

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14
Q

What is Linear Energy Transfer in Radiation?

A

How much radiation deposited per unit of distance

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15
Q

Unit for Linear Energy Transfer in radiation

A

keV/ micron

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16
Q

What is the radiation weighting factor for:

  1. x-ray/ gamma rays
  2. beta particles
  3. Alpha particles
  4. neutrons
A
  1. 1
  2. 1
  3. 20
  4. Variable
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17
Q

Unit or Equivalent dose of radiation (H)

A

Sievert

18
Q

Symbol for Effective Dose of Radiation?

A

E

19
Q

Term to describe different organs having different sensitivity to radiation?

A

radiosensitivity

20
Q

The calculation for Effective dose of radiation?

A

Effective dose =

```
SUM of
organ dose x Radiation Weighting x Tissue Weighting
~~~

21
Q

What is Collective Equivalent Dose of radiation?

A

total impact on all people exposed to that radiation

22
Q

Unit for Collective Equivalent Dose of radiation?

A

man-Sieverts

23
Q

How much background radiation are humans exposed to naturally?

A

2-3mSv/ year

24
Q

What are the main sources of background radiation for humans?

A 
Radionucleides in air (1.2mSV)
Internal Radionucleides (0.2mSv)
External Gamma (0.3mSv)
Cosmic Rays (0.3mSv)
25
Q

What is the predominant source of radiation from radionuclides in the air?

A

Radon

26
Q

What two pathways does cellular damage from radiation occur

A 
Direct pathway
Indirect pathway (reacts with water causing free radicals)
27
Q

Is single or double-strand DNA Break Worse?

A

Double strand is much worse and is difficult to repair

28
Q

What do deterministic vs stochastic radiation effects mean?

A

deterministic: minimum threshold beyond which guaranteed to occur, severity worsens with dose

Stochastic: probability increases with dose

29
Q

Examples of deterministic radiation adverse effects?

A 
Erythema
Hair loss (epilation)
Cataracts (may actually be stochastic)
Radiation poisoning
Depression of bone cell formation
30
Q

How are deterministic radiation effects caused?

A

apoptosis

31
Q

Lag time for stochastic radiation effects

A

leukaemia:
- start after 2 year
- peaks about 5-10 years

Other cancers:

  • at least 10-year lag
  • slowly increases to peak like 40 years later
32
Q

Are sperm of ova more sensitive to radiation?

A

sperm as they are in process of maturing still in adults

33
Q

Where does most information about risks of radiation exposure come from?

A

Life Span Study (following A-bomb in japan)

Radiation workers

34
Q

What are the proposed models of radiation risk at low doses?

A

Linear No Threshold
Linear Quadratic
Homesis

35
Q

What is the Linear No Threshold model of radiation risk?

A

Risk directly proportional to radiation exposure,

no safe dose

36
Q

What is the Linear Quadratic model of radiation risk?

A

Lower risk at a low dose then increases at an increasing rate

37
Q

What is the Homesis model of radiation risk?

A

Small doses of radiation may be protective, and then risk increases from there

38
Q

Which is the accepted model of radiation exposure risk?

A

The Linear Threshold is at present (as it’s the most conservative)

39
Q

What is the Doubling Dose of radiation?

A

Radiation dose required to double the number of spontaneous mutations in a given population

40
Q

What is the radiation risk factor/ mSV in the general population?

A

About 1 in 20,000 per mSv

41
Q

What is the relative radiation risk for children vs adults?

A

about 2-3 times as likely in children

42
Q

What are some deterministic complications of radiation in pregnancy?

A

failure to implant
organ malformation
foetal death
mental retardation

Westmead Physics (17 decks)

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