biological effects of ionising radiation

Question 1

what are the 2 forms of ionising radiation

Answer 1

by products of radioactive decay e.g gamma rays
artificially produced electromagnetic radiation e.g x rays

Question 2

what is the difference between an atom and an ion

Answer 2

atom has equal numbers of protons and electrons
ion has an unequal number of protons and electrons giving it a positive or negative charge

Question 3

what is an ion pair

Answer 3

newly formed ion and its displaced electron

Question 4

what effect does ionising radiation have on atoms

Answer 4

turns atoms into ions by displacing electrons

Question 5

what is the most significant effect in humans of ionising radiation and how does this cause an issue

Answer 5

DNA damage
Faulty repair of the damage leads to abnormal cell population development and possible cancer development
single strand break is an easy repair but double strand break repair is difficult and may lead to mutations

Question 6

in what two ways can DNA be damaged due to ionising radiation

Answer 6

Direct - radiation interacts with atoms of a DNA molecule
Indirect - radiation interacts with water in a cell producing a free radical which can diffuse short distances and cause DNA damage

Question 7

what 2 things is tissue radiosensitivity dependent on

Answer 7

function of cells that make up tissue
are the cells actively dividing
more dividing = more radiosensitive e.g stem cells are very radiosensitive

Question 8

absorbed dose (Gy)

Answer 8

measures energy deposited by radiation

Question 9

Equivalent dose (Sv)

Answer 9

absorbed dose multiplied by radiation weighting factor
Weighting factor dependent on type of radiation - x ray WF = 1, gamma ray WF = 20

Question 10

Effective dose (Sv)

Answer 10

equivalent dose multiplied by tissue weighting factor

Question 11

linear no threshold model

Answer 11

estimates the long term biological effects of radiation
assumes radiation is always harmful with no safety threshold, several small doses is equal to one large dose

Question 12

deterministic effects of radiation

Answer 12

concerns tissue reactions that only occur above a certain threshold therefore effects are dependent on dose recieved
rare in radiology , effects take several days to appear
perhaps radiotherapy and hairloss

Question 13

stochastic effects of radiation

Answer 13

uses LNT model
no known threshold i.e no dose below which no effects will occur
risks are always present no matter how low the dose
effects can develop years after exposure and there are 2 types
somatic - disease/disorder e.g cancer
genetic - abnormalities in descendants

Question 14

Does pregnancy need to be taken into account when taking dental x rays

Answer 14

no as dose to foetus is so low - usually less than daily background radiation it would receive
beam is pointed no where near the abdomen

Question 15

name 3 sources of background radiation

Answer 15

cosmic rays
radionucleotides from diet and air
gamma radiation from soil/rocks etc

Question 16

what does IRMER17 concern

Answer 16

patients

Question 17

what does IRR17 concern

Answer 17

staff and public

Question 18

what should the focus to skin distance be for dental x rays

Answer 18

more than 200mm

Question 19

what size should the controlled area be for dental x rays

Answer 19

1.5m from x ray tube and patient

Question 20

what is the effective dose for intra oral x rays

Answer 20

0.005msv