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Radiation protection Flashcards

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1
Q

what are the three stochastic effects

A

genetic, somatic and in-utero

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2
Q

what is genetic effects?

A

mutation within the gametes, radiation increases the spontaneous mutation rate (DOESNT PRODUCE NEW MUTATIONS)

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3
Q

what are somatic effects?

A

stochastic and deterministic, suffered by the exposed individual, not inherited

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4
Q

what are in-utero effects?

A

found in developing embryos

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5
Q

what is the effective dose?

A

determines stochastic biological consequences of all radiation types

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6
Q

what does dose limit take into account

A

the effective dose and apply it to individuals for protection

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7
Q

what are biological effects of radiation

A

somatic and hereditary

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8
Q

what is absorbed dose?

A

Gray
amount of energy transferred from the radiation beam to the material

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9
Q

what is the SI unit for radiation dose

A

mSV
SV = effective dose
1 SV = 1Gy of gamma rays

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10
Q

what is the equation for dose equivalent

A

absorbed dose (Gy) x quality factor

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11
Q

what is absorbed dose dependent on

A

photon beam energy and absorbing energy. A higher beam = less absorbed dose, with more photons transmitted without absorption

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12
Q

what is effective dose?

A

it is dependent on the irradiated area, a tissue weighting factor is used for all different tissues

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13
Q

what is the equation for the effective dose?

A

dose equivalent x tissue weighting factor

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14
Q

what is a weighting factor?

A

it is when the equivalent dose is determined by the absorbed dose in a tissue, which is weighted to represent relative contribution to the tissue based on the radiation type absorbed.

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15
Q

what is a higher absorbed dose equal to

A

high effective proton number

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16
Q

what is a tissue weighting factor?

A

effective dose is weighted to represent tissue contribution to the total health detriment resulting from the uniform body irradiation. Which measures the risks of stochastic effects.

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17
Q

name a physical carcinogen

A

radiation

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18
Q

what does high doses increase risk of?

A

severity of deterministic effects as well as early/ late effects

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18
Q

what does high doses increase risk of?

A

severity of deterministic effects as well as early/ late effects

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19
Q

what is the aim of dose limits

A

to limit stochastic effects to a acceptable level and prevent deterministic effects

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20
Q

what are stochastic effects?

A

random in nature, which occur without a threshold level dose. These occur even with small doses, incidence rates increase with high dose rates
occurrence is proportional to dose
severity is independent on dose

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21
Q

what is an acute dose?

A

occurs over a short period of time

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22
Q

what is a chronic dose?

A

dose which continues over a period of time

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23
Q

what does high doses result in?

A

cell kill

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24
Q

what does low doses result in?

A

cell damage

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25
Q

what is a controlled area?

A

restricting radiation exposures

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26
Q

what does dose monitoring help with?

A
  • estimate radiation doses
  • determine if certain employees should be classified persons
  • wether or not individual should have personal monitoring
27
Q

what is the 10/28 day rule?

A

it is for pregnant women
10 days = only abdominal pelvic x-rays
28 days = all other examinations can be carried out
must be justified exposure
organogenesis occurs 3 weeks post contraception

28
Q

room adaptations

A
  • thick, specialised concrete walls
  • no windows
  • linac in bunker
  • maze layout
29
Q

what are the local rules?

A
  • relevant radiation personel, hazard and protective measures
  • prevent accidental irradiation
  • outline work systems
30
Q

what are the general rules?

A
  • warnings needed
  • dosimeters
  • machine must be supervised when on
  • operator can’t be distracted
31
Q

what is IRR17?

A

ALARP to protect workforce and public
Medical exposure to IR to a medical examination or treatment directed by a qualified individual
- risk assessment before equipment use
- estimate public dosage
- records kept for 30 years
- identifies dose limits

32
Q

What is IR(ME)R designed for?

A

protect the patient undergoing treatment, doses need to be justified to reduce stochastic effects

33
Q

what are employer procedures?

A
  • patient identification
  • identification of refers, practitioners and operators
  • pregnancy status
  • QA programme
  • assessment of patient doses
  • provision of patient info and written instructions
  • dose evaluation
  • reporting accidental exposure and reduction
34
Q

who are duty holders?

A

referrers, practitioners and operators

35
Q

what is the role of a referrer?

A

must be regulated
entitled with the accordance with employer procedures to refer individuals for exposure to a practitioner

36
Q

what is a practioner?

A

must be entitled
responsible for the patients exposure

37
Q

what is an operator?

A

doesn’t need to be registered, but CANT BE A STUDENT
radiotherapists and assistant practitioners

38
Q

what is the role in justification

A

each exposure must be justified, with doses kept low. Benefits must outweigh risks with clinical criteria being met

39
Q

what is the role in optimisation?

A

ALARP
treatment planning
volume can be limited by using multiple beams

40
Q

what is the role in limitation

A

shielding as well as radiation protection

41
Q

what is the 3 things needed in identification

A

full name, address, DOB

42
Q

What is the employers responsibility

A

that all operators and practitioners are trained properly

43
Q

what are the three categories within radiation protection

A

distance, time, shielding

44
Q

what is the factor of time?

A

it is dependent on the dose rate, only the patient should be in the room
IRR limits the amount of treatment however IR(ME)R breaks this rule

45
Q

what is the factor of distance?

A

ISL
larger rooms have greater distance, less intense beams, wider primary beam due to divergence

46
Q

what is the role of shielding?

A

to protect OAR, avoiding unnecessary irradiation
- there must be a protective barrier between the source and area you want to protect
- application of EM radiation
- material choice, thickness of barrier
- patient shielding
- staff protection
- public

47
Q

what does the beam thickness depend on?

A

the beam energy

48
Q

when is a maze layout used?

A

when rooms are using high MV or photons which will attenuate radiation via scatter processes. low kv may use a shielded door

49
Q

when are dosimeters used?

A

for individuals who could receive more than 10% of the annual dose limit, allows us to monitor the shielding and local rules

50
Q

what is the radiation protection for X-ray tube applicators

A

only 5% beam transmission
Pb cut outs must have a varnish
internal eye shields as the lens is radiosensitive

51
Q

what are the energy and Pb thickness

A

240 kVp = 3.5
200 kVp = 2mm
90 kVp = 1mm

52
Q

what is the acceptable primary beam transmission?

A

5%

53
Q

why is lead used?

A

it is a shielding material used for absorption with the sides being straight allowing high % of transmission penumbra. Must be covered to prevent absorption through the skin.

54
Q

room adaptation?

A
  • walls are made from a denser form of concrete with high Z materials added
  • Pb glass and an oil is used when there is windows
  • door is made from pressed wood/ alternate metals
  • monitors are placed around the whole machine sea outside the room
  • immobilisation to ensure TA is irradiated
55
Q

what is the primary barrier?

A

it is the barrier at which the primary beam can be aimed at

56
Q

what is the secondary barrier?

A

it is the barrier for any scattered radiation

57
Q

what is the HVL

A

thickness of material, which reduces the intensity of the beam by 50%, which describes the penetrating ability of the beam.

58
Q

what is the HVL equation

A

HVL = 0.693/ U
1/2^n = transmission %

59
Q

what are MLC’s

A

multi leaf collimators, which are found in the head of the machine, which are positioned 90 degrees to the patient which are made from tungsten.

60
Q

what are HVL?

A

they are dependent on the material type, which measures beam output and quality. It used bremsstrahlung - a continuous process (heterogeneous only). Each photon energy is dependent on the tube design.

61
Q

what is 1TVL

A

10 HVL

62
Q

what are LMPA blocks?

A
  • a manual block cutter, with a hot wire to cut from styrofoam
  • an electronic block, with a hot wire which is computer controlled so an image is digitalised
63
Q

what is the proportion for high quality and low quality beams?

A

high = large amount of hard photons, small amount of soft photons
low = small amount of hard photons, high amount of soft photons

64
Q

what happens at each HVL

A

the beam hardens, improving the quality of the beam however it becomes less intense. There is an increase in energy due to the removal of soft photons

65
Q

what is the limit of HVL/TVL within a room

A

2TVL = 20 HVL

66
Q

what are the HVL materials?

A

aluminium, copper and tin

Physics (25 decks)

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