Ionising radiation Flashcards

1
Q

Natural sources of radiation

A

cosmic radiation, animals, rocks, buildings, soil, plants

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2
Q

Artificial sources of radiation

A

X-ray machines, nuclear power, nuclear missiles, nuclear weapons testing

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3
Q

physical characteristics of ionising radiation

A

penetrating, invisible to the eye, reduces in intensity, can cause biological effects

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4
Q

half-value layer

A

thickness of a substance which will transmit one 1/2 of the intensity of the radiation incident upon it

the thicker the material is, the less photons will be passed through

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5
Q

half-life

A

time taken for half the atoms to decay

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6
Q

inverse square law

A

total amount of radiation in the beam doesn’t change, but the concentration decreases with increasing distance from the source

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7
Q

3 factors of radiation safety

A

time, distance and shielding

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8
Q

time

A

radiation dose can be reduced by limiting exposure time

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9
Q

distance

A

amount of radiation exposure depends on the distance from the source of the radiation

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10
Q

shielding

A

shielding, such as lead aprons should be used if the radiation source is too intensive

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11
Q

lead equivalent

A

the thickness of lead would absorb the same amount of radiation as the given material

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12
Q

radon gas

A

radioactive, colourless, tasteless gas which is formed by small amounts of uranium

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13
Q

banana dose equivalent

A

informal way of comparing doses of ionising radiation to the dose received by eating a single banana of average size.

useful concept to help explain relative radiation risk to the public

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14
Q

alpha decay

A

process which an unstable atomic nucleus loses energy by emitting radiation.

consists of two protons and two neutrons tightly bound together (most ionising and destructive form of ionising radiation)

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15
Q

beta decay

A

unstable atomic nucleus loses energy by emitting radiation

spontaneous emission of a fast moving particle with the mass of an electron from a nucleus

negative and positive beta particles are produced by the decay

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16
Q

gamma decay

A

unstable atomic nucleus loses energy by emitting radiation.

the spontaneous emission of a high energy photon from a nucleus

17
Q

alpha radiation

A

helium 4 nucleus, stopped easily by a sheet of paper

18
Q

beta radiation

A

high energy electrons or positrons, stopped by an aluminium plate

19
Q

gamma radiation

A

high energy photon emitted by the nucleus, eventually absorbed as it penetrates a dense material such as lead

20
Q

two types of radiation induced tissue damage

A

direct and indirect

21
Q

direct action tissue damage

A

ionisation of macromolecules, such as DNA, RNA, proteins and enzymes

22
Q

indirect action tissue damage

A

free radicals produced by ionisation of water

23
Q

process of indirect action

A
  1. radiation - h2o loses an electron making it positive
  2. positive ion immediately breaks up
  3. electron attaches to Neuton water molecules
  4. resulting in negatively charge molecule dissociate
  5. H and OH are free radicals, which are unstable and can combine together or with oxygen to give H2O2 (hydrogen peroxide) or HO2 (hydroperoxyl radical)
24
Q

direct tissue damage leads to

A

inhibit tumor suppression genes, which then could further produce radiation-induced cancer

25
Q

direct action

A

breakage if chemical bonds leads to abnormal structure which then leads to inappropriate chemical reaction. This affects are abnormal replication and cell death.

26
Q

Compton scatter

A

ejected electron goes on to interact with other atoms via ionisation and excitation

27
Q

linear energy transfer

A

how much energy is transferred per unit length

28
Q

biological effects of ionising radiation

A

tissue reactions and stochastic effects

29
Q

deterministic effects

A

non-cancer damaging effects that will definitely result from high dose radiation

30
Q

stochastic effects

A

cancer and genetic effects that may result or develop

31
Q

high dose patients eg

A

survivors of hiroshimi and Nagasaki, patients receiving radiotherapy

32
Q

absorbed dose

A

the energy deposited per unit mass of a irradiated material

33
Q

“kerma” stand for

A

kinetic energy released to matter

34
Q

kerma

A

represents the energy transferred per unit mass of irradiated material from photons to electrons at specified position

35
Q

dose area product

A

used to estimate the total radiation energy delivered to a patient during a radiographic procedure

36
Q

equivalent dose

A

a measure of the radiation dose to tissue with the allowance for the different relative biological effects for different types of ionising radiation

37
Q

equivalent dose =

A

absorbed dose x radiation weighting factor

38
Q

effective dose

A

to compare the stochastic risk of non-uniform exposure to radiation