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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
what does low doses result in?
cell damage
25
what is a controlled area?
restricting radiation exposures
26
what does dose monitoring help with?
- estimate radiation doses - determine if certain employees should be classified persons - wether or not individual should have personal monitoring
27
what is the 10/28 day rule?
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
room adaptations
- thick, specialised concrete walls - no windows - linac in bunker - maze layout
29
what are the local rules?
- relevant radiation personel, hazard and protective measures - prevent accidental irradiation - outline work systems
30
what are the general rules?
- warnings needed - dosimeters - machine must be supervised when on - operator can't be distracted
31
what is IRR17?
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
What is IR(ME)R designed for?
protect the patient undergoing treatment, doses need to be justified to reduce stochastic effects
33
what are employer procedures?
- 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
who are duty holders?
referrers, practitioners and operators
35
what is the role of a referrer?
must be regulated entitled with the accordance with employer procedures to refer individuals for exposure to a practitioner
36
what is a practioner?
must be entitled responsible for the patients exposure
37
what is an operator?
doesn't need to be registered, but CANT BE A STUDENT radiotherapists and assistant practitioners
38
what is the role in justification
each exposure must be justified, with doses kept low. Benefits must outweigh risks with clinical criteria being met
39
what is the role in optimisation?
ALARP treatment planning volume can be limited by using multiple beams
40
what is the role in limitation
shielding as well as radiation protection
41
what is the 3 things needed in identification
full name, address, DOB
42
What is the employers responsibility
that all operators and practitioners are trained properly
43
what are the three categories within radiation protection
distance, time, shielding
44
what is the factor of time?
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
what is the factor of distance?
ISL larger rooms have greater distance, less intense beams, wider primary beam due to divergence
46
what is the role of shielding?
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
what does the beam thickness depend on?
the beam energy
48
when is a maze layout used?
when rooms are using high MV or photons which will attenuate radiation via scatter processes. low kv may use a shielded door
49
when are dosimeters used?
for individuals who could receive more than 10% of the annual dose limit, allows us to monitor the shielding and local rules
50
what is the radiation protection for X-ray tube applicators
only 5% beam transmission Pb cut outs must have a varnish internal eye shields as the lens is radiosensitive
51
what are the energy and Pb thickness
240 kVp = 3.5 200 kVp = 2mm 90 kVp = 1mm
52
what is the acceptable primary beam transmission?
5%
53
why is lead used?
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
room adaptation?
- 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
what is the primary barrier?
it is the barrier at which the primary beam can be aimed at
56
what is the secondary barrier?
it is the barrier for any scattered radiation
57
what is the HVL
thickness of material, which reduces the intensity of the beam by 50%, which describes the penetrating ability of the beam.
58
what is the HVL equation
HVL = 0.693/ U 1/2^n = transmission %
59
what are MLC's
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
what are HVL?
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
what is 1TVL
10 HVL
62
what are LMPA blocks?
- 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
what is the proportion for high quality and low quality beams?
high = large amount of hard photons, small amount of soft photons low = small amount of hard photons, high amount of soft photons
64
what happens at each HVL
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
what is the limit of HVL/TVL within a room
2TVL = 20 HVL
66
what are the HVL materials?
aluminium, copper and tin

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