Biological effects of radiation

Question 1

Give the units and definition of absorbed, equivalent and effective dose

Answer 1

Gray - average ABSORBED DOSE to organ/tissue (j/kg)

Sievert - EQUIVILENT DOSE is absorbed dose to organ/ tissue weighted for type of radiation

Sievert - EFFECTIVE DOSE is absorbed dose to organ or tissue weighted for type of radiation AND type of tissue

Question 2

What is the typical amount of energy released when one atom is ionised (in tissue)

Answer 2

35eV

Question 3

Why do ionisation evens comprise of small clusters of ion pairs?

Answer 3

secondary electrons that are liberate in initial ionisation process often have enough energy to ionise other atoms

Question 4

What are the 2 types of interactions that ionising radiation can damage biological molecules

Answer 4

direct and indirect

Question 5

what is direct interaction of ionising radiation can damage biological molecules

Answer 5

release of energy from an ionisation event (35eV) is sufficient to break molecular bonds

Question 6

what is indirect interaction of ionising radiation can damage biological molecules

Answer 6

damage may be induced by interaction of free radicals made by ionisation.

80% tissue is made of water, when water molecules ionise H+ ions and OH. free radicals are formed

Question 7

OH. radical is thought to be responsible for ?/3 of all damage made by exposure of body to all x-rays

Answer 7

2/3

Question 8

Give 3 things that free radical reactions can cause damage to

Answer 8

proteins
enzymes
DNA

Question 9

What 3 things can happen to damaged cells/DNA?

Answer 9

1. repaired perfectly
2. mutation
3. die (deterministic effect)

Question 10

What type of effect is mutated cell becoming cancerous classified as?

Answer 10

stochastic

Question 11

Give a few examples of deterministic effects of radiation exposure

Answer 11

• erythema
• nausea
• depilation (hair removal)
• cataracts

Question 12

What is erythema

Answer 12

reddening of skin due to blood vessel dilation (greater than 2Gy)

burns and ulceration (greater than 10-20Gy)

Question 13

What 3 things causes stochastic effects in terms of biological damage?

Answer 13

1. prevention or delay of cell division
2. modification of normal cell - neoplastic (abnormal growth of cells/tumour) transformation
3. modifications to germinal cells of reproductive tissues which are passed onto daughter cells

Question 14

What are the risks included within stochastic effects?

Answer 14

DNA disruptions resulting in cancer or hereditary disorders

Question 15

What is a somatic cell

Answer 15

cell of organism other than reproductive cells (body cell but not reproductive cells)

Question 16

Probability of cancer induction is proportional to dose but severity is unrelated to dose

Question 17

a modified gamete cell may lead to effects being expressed in children of exposed person. (but no proper evidence supporting this)

Question 18

What is epidemiology?

Answer 18

study of health effects associated with exposure to ionising exposure

Question 19

What are the 6 forms of background radiation?

Answer 19

• radon
• terrestrial
• nuclear and weapons
• medical exposure
• cosmic
• intake of radionuclide

Question 20

What is radon gas/ where from

Answer 20

• seeps from ground into gaps in buildings
• radioactive decay of uranium in soil and rocks

Question 21

What type of radionuclide do we intake from plants?

Answer 21

14C - plants
87 Rb - plants and animals

Question 22

where does cosmic radiation come form

Answer 22

high energy particles from sun and outside of solar system

Question 23

give the percentages of how much each of the 6 different forms account for background radiation

Answer 23

48% radon
16% medical exposure
13% terrestrial gamma radiation
12% cosmic
11% intake radionuclides