Radiobiology 4 Flashcards
1
Q
What does a Cell Survival Curve show?
A
- A plot of the number of cells surviving a given radiation dose (single exposure)
2
Q
Where did the cell survival curve come from?
A
- Cells from stock culture, put into suspension in petri-dishes and counted
- After irradiation, cells are incubated and viable cells will form colonies. Evidence of survival.
3
Q
How do Indirect effects relate to the cell survival curve?
A
- A hypoxic environment will make a difference as less oxygen means that indirect action (free radicals) are less likely to happen
- More oxygen = more chemical agents to do the damage, and by fixing the damage
4
Q
How much damage is caused by indirect effects?
A
-2/3rds
5
Q
How can free radical formation be affected?
A
- Chemical sensitizers - will promote free radicals
- Chemical protectors - will remove free radicals
6
Q
What is the OER?
A
- The oxygen enhancement ration
- The difference in radiation needed to achieve self kill between oxic vs hypoxic environments
7
Q
RBE means…
A
- Relative biological effectiveness.
- defined relative to a standard type of radiation
- RBE= dose of standard radiation to produce given effect/ dose of test radiation to produce same effect
8
Q
What factors cause RBE radiation?
A
- the given biological effect
- type of cell or tissue
- LET of radiation
- oxygen conc.
- presence of sensitizers or protectors
9
Q
What level LET do photons and electrons have?
A
- Low LET radiations, with RBE figures of about 1.0.
10
Q
What level LET do heavier ions/neutrons/alpha particles have?
A
- High LET radiations
- they have high RBE figures
11
Q
What are possible effects of radiation on cells?
A
- none
- delay in division
- cell death
- reproductive failure
- genomic instability
- mutation
- transformation
- adaptive response
- bystander effect (induce damage in neighbours)
- Abscopal effect (damage induced elsewhere in the body, i.e. at a distance)
