Biological Effects of Radiology

Question 1

direct effect on DNA

Answer 1

radiation interacts with atoms of DNA molecule

Question 2

indirect effect on DNA

Answer 2

radiation interacts with water in cell producing free radials which can cause damage
free radicals are unstable highly reactive molecules

Question 3

biological effect depends on what factors (4)

Answer 3

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

Question 4

radiosensitivity of tissues depends on

Answer 4

1. function of cells that make up tissue
2. if cells actively dividing

Question 5

the more rapidly a cell is dividing

Answer 5

the greater the sensitivity to radiation

Question 6

2 types of radiation effects

Answer 6

1. deterministic
2. stochastic

Question 7

deterministic effects

Answer 7

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

Question 8

stochastic effects

Answer 8

probability of occurrence is related to dose received

Question 9

dose optimisation in ptx

Answer 9

1. use E speed film or faster (fewer x ray photons required)
2. use kV range of 60-70kV
3. FSD should be >200mm
4. rectangular collimation