Biological Effects of Ionising Radiation & Radiation Risk Assessment Flashcards
1
Q
What are the interactions of radiation passing through matter?
A
- radiation ionises atoms along its path
- each ionisation process deposits around 35eV
- energy is greater than energy involved in atomic bonds (4eV)
2
Q
What is the most significant effect of ionising radiation?
A
- DNA damage
- majority if damage easily repaired
3
Q
What are the different ways that ionising radiation can cause damage to DNA?
A
- direct DNA damage
- radiation interacts with atoms of DMA molecule
- can be other important part of the cell
- indirect DNA effect
- radiation interacts with water in the cell
- produces free radicles which cause damage
4
Q
What are free radicals?
A
- unstable, highly reactive molecules
5
Q
What are the different types of DNA damage?
A
- single strand break
- can usually be repaired
- double strand breaks
- usually occurs as a result of alpha radiation
- if repair is faulty can lead to mutations
- can affect cell function
6
Q
What does the biological effect of DNA damage depend on?
A
- type of radiation
- amount of radiation
- time over which the dose is received
- tissue type or cell type irradiated
7
Q
What does the radiosensitivity of tissues depend on?
A
- the function of cells that make up the tissues
- if the cells are actively dividing
- stems cells are very radiosensitive
- differentiated cells are less radiosensitive
8
Q
What are the possible outcomes after radiation hits a cell nucleus?
A
- no change
- DNA mutation
- mutation repaired
- viable cell - cell death
- unviable cell - cell survives but is mutated
- cancer
- mutation repaired
9
Q
What is absorbed dose?
A
- energy deposited by radiation
- Grays (Gy)
10
Q
What is equivalent dose?
A
- absorbed dose multiplied by a weighting factor depending on the type of radiation
- x-ray assigned 1
- Sieverts (Sv)
11
Q
What are the two types of biological effects of radiation?
A
- deterministic
- tissue reactions
- only occur above a certain dose
- severity is related to dose received
- unusual to see in radiology
- effects after several days
- stochastic
- probability of occurrence related to dose received
- no dose beneath which effects will not occur
- cannot predict if events will occur and their severity
- effects after years
- somatic
- results in disease or disorder - genetics
- abnormalities in descendents
12
Q
What is the effect of radiation during pregnancy?
A
- damage to kill enough cells for embryo resorption
- 100mGy
- around implantation of embryo
- growth retardation
- during organogenesis
- 2-8 weeks
- > 250mGy
- dental radiographs much smaller doses
- pregnancy does not need to be taken into account
13
Q
What sources of natural background radiation exist?
A
- cosmic rays
- internal radionuclides from diet
- radionuclides in the air (radon)
- external gamma radiation (soil, rocks and building materials)
- air travel
- estimated annual dose is 2.2mSv
14
Q
What distance should the controlled area be from the X-ray tube and patient?
A
- 1.5m
- x-ray beam should always be directed away from staff members
15
Q
What is ALARP?
A
- As Low As Reasonably Practicable
- still maintain image quality
- use of rectangular collimators
