Ionising radiation

Question 1

Natural sources of radiation

Answer 1

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

Question 2

Artificial sources of radiation

Answer 2

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

Question 3

physical characteristics of ionising radiation

Answer 3

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

Question 4

half-value layer

Answer 4

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

Question 5

half-life

Answer 5

time taken for half the atoms to decay

Question 6

inverse square law

Answer 6

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

Question 7

3 factors of radiation safety

Answer 7

time, distance and shielding

Question 8

time

Answer 8

radiation dose can be reduced by limiting exposure time

Question 9

distance

Answer 9

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

Question 10

shielding

Answer 10

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

Question 11

lead equivalent

Answer 11

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

Question 12

radon gas

Answer 12

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

Question 13

banana dose equivalent

Answer 13

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

Question 14

alpha decay

Answer 14

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)

Question 15

beta decay

Answer 15

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

Question 16

gamma decay

Answer 16

unstable atomic nucleus loses energy by emitting radiation.

the spontaneous emission of a high energy photon from a nucleus

Question 17

alpha radiation

Answer 17

helium 4 nucleus, stopped easily by a sheet of paper

Question 18

beta radiation

Answer 18

high energy electrons or positrons, stopped by an aluminium plate

Question 19

gamma radiation

Answer 19

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

Question 20

two types of radiation induced tissue damage

Answer 20

direct and indirect

Question 21

direct action tissue damage

Answer 21

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

Question 22

indirect action tissue damage

Answer 22

free radicals produced by ionisation of water

Question 23

process of indirect action

Answer 23

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)

Question 24

direct tissue damage leads to

Answer 24

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

Question 25

direct action

Answer 25

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

Question 26

Compton scatter

Answer 26

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

Question 27

linear energy transfer

Answer 27

how much energy is transferred per unit length

Question 28

biological effects of ionising radiation

Answer 28

tissue reactions and stochastic effects

Question 29

deterministic effects

Answer 29

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

Question 30

stochastic effects

Answer 30

cancer and genetic effects that may result or develop

Question 31

high dose patients eg

Answer 31

survivors of hiroshimi and Nagasaki, patients receiving radiotherapy

Question 32

absorbed dose

Answer 32

the energy deposited per unit mass of a irradiated material

Question 33

“kerma” stand for

Answer 33

kinetic energy released to matter

Question 34

kerma

Answer 34

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

Question 35

dose area product

Answer 35

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

Question 36

equivalent dose

Answer 36

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

Question 37

equivalent dose =

Answer 37

absorbed dose x radiation weighting factor

Question 38

effective dose

Answer 38

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