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BDS3 Radiology > Biological effects of Ionising Radiation and Radiation Risk Assessment > Flashcards

Biological effects of Ionising Radiation and Radiation Risk Assessment Flashcards

1
Q

what are the two main types of radiation that ionising radiation can be divided into

A

by-products of radioactive decay
artificially produced electromagnetic radiation

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2
Q

what categories can you divide by-products of radioactive decay into

A

alpha particles
beta particles
gamma rays

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3
Q

what is ionising radiation

A

ionising radiation has enough energy to turn atoms into ions by knocking away electrons

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4
Q

what is an ion pair

A

free electron and positively ionised atom

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5
Q

what is the most significant effect of ionising radiation

A

DNA damage

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6
Q

what can DNA damage be seen in

A

faulty repair of chromosome breaks, development of abnormal cell populations and development of cancer

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7
Q

what types of DNA damage is there

A

direct or indirect

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8
Q

what is direct DNA damage

A

radiation interacts with the atoms of a DNA molecule or another important part of the cell

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9
Q

what is indirect DNA damage

A

radiation interacts with water in the cell - when water molecule becomes ionised a highly reactive free radical ion is formed, two of these can combine to form a hydroxyl radical which can diffuse short distances and cause DNA damage

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10
Q

what is one advantage of DNA being a double helix

A

if one strand breaks it can still be held together by the strand that hasnt broken

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11
Q

why do double strand DNA breaks usually occur

A

alpha radiation

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12
Q

what does the biological effect of DNA damage depend on

A

type of radiation
amount of radiation
time over which the dose is received
the tissue or cell type irradiated

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13
Q

at what rate of delivering radiation is damage less likely to occur

A

low doses

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14
Q

what two factors is the radiosensitivity of tissue divide on

A

the function of the cells that make up the tissues
if the cells are actively dividing

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15
Q

what is an example of cells that divide frequently and are very radiosensitive

A

stem cells

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16
Q

what cells are less sensitive to radiation damage

A

differentiated cells

17
Q

what are examples of highly radiosensitive tissues

A

bone marrow
lymphoid
GI
gonads
embryonic

18
Q

what tissues are moderately radiosensitive

A

skin
vascular endothelium
lung
lens of the eye

19
Q

what tissues are least radiosensitive

A

central nervous system ‘bone and cartilage
connective tissue

20
Q

what are the two outcomes of radiation hitting nucleus

A

no change or DNA mutation

21
Q

what can happen if the cell is mutated

A

can repair
cell death
cell survives but mutated

22
Q

what is the absorbed dose

A

a quantity that can be measured - measures the energy deposited by radiation

23
Q

what is equivalent dose

A

a derived quantity - absorbed dose multiplied by a radiation weighting factor depending on type of radiation

24
Q

what is an effective dose

A

derived quantity - equivalent dose to each organ multiplied by the tissue weighting factor and summed (probability of cancer)

25
Q

what is the linear no threshold (LNT) model

A

estimates the long term biological damage from radiation - several small exposures can have same effect of one large exposure

26
Q

what are the two types of radiation effects

A

deterministic effects
stochastic effects

27
Q

what is a deterministic effect

A

tissue reactions
only occur above a certain threshold dose
the severity of the effect is related to the dose received

28
Q

what is stochastic effects

A

the probability of occurrence is related to the dose received

29
Q

what are two categories stochastic effects can be divided into

A

somatic - disease or disorder
genetics - abnormalities in descendants of those exposed

30
Q

what are some sources of background radiation

A

cosmic rays
internal radionuclides

31
Q

what is the effective dose value for an intra oral x-ray

A

0.005 mSv - negligible risk of cancer

32
Q

what is the controlled area

A

should extend at least 1.5m from the x-ray tube and patient

33
Q

what is justification of the x-ray

A

sufficient benefit to the individual to offset the detriment

34
Q

what is the optimisation of the optimisation

A

individual doses and number of people exposed should be kept as low as reasonably practicable

35
Q

how can you reduce damage to CR plates

A

insert plates between two plastic sheets
damaged detectors should be cleaned or replaced

BDS3 Radiology (9 decks)

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