Radiobiology Flashcards
1
Q
Why is the probability of an x-ray photon interacting with an orbital electron very low?
A
Due to the relationship between the nucleus, circulating electrons and the atomic radius:
- Atoms consists of almost entirely free space
- Electrons are constantly moving
- Electrons are small
- X-rays have a very small radius
2
Q
Why are photon interactions relatively possible?
A
Despite random nature of interactions there will be a region of high interactions due to the number of photons involved.
3
Q
What are the two ways interactions damage human issue?
A
- Direct effects: when the photon interacts with a biological molecule
- Indirect effects: when the photon interacts with a water molecule
4
Q
What is the process following the direct/indirect effects of x-ray interactions?
A
- Ionisation causes dissociation of the molecule
- Forming free radicals
- Free radicals produce abnormal chemical reactions
5
Q
What are the effects of x-ray interactions on cells?
A
- Cell death (not at dental levels)
- Prevention/delay of cell division (not likely at dental dose levels)
- Mutation (will occur at dental dose levels)
6
Q
What will be affected by x-ray interactions at dental doses?
A
- DNA - complete repair, no repair or faulty repair (mutation)
- Cytoplasmic organelles
7
Q
What are the major effects of radiation exposure?
A
- Stochastic effects: effects that occur by chance without a threshold (probability is proportional to dose but severity if independent of dose)
- Deterministic effects: effects that have a threshold below which it will not occur (although threshold may be high for one person and lower for another)
