Radiobiology

Question 1

How does ionisation affect the cells?

Answer 1

Directly and indirectly

Question 2

What are free radicals?

Answer 2

Atom with an unpaired electron in outer electron shell. Have no charge, are electrically neutral
Radicals want another electron to complete the shell
So will steal an electron from another atom causing damage to that atom
They do this by breaking chemical bonds or oxidation (Addition of oxygen atoms)
Major effect: DNA breaks

Question 3

What is DNA?

Answer 3

Deoxyribose Nucleic Acid: genetic material in cells

Question 4

What is a single strand break?

Answer 4

Base sequence on the other strand remains and serves as a template for repair

Question 5

What is a double strand break?

Answer 5

Genetic code is completely lost. DNA may attempt to repair incorrectly which can result in mutations, deletions or cell death.

Question 6

What are early and late affects in the human body?

Answer 6

Early: sufficient number of cells are killed, occurs within hours-weeks. eg. skin erythema
Late: cell survives but is damaged, takes many years, eg. cancer

Question 7

What is the Law of Bergonie and Tribondeau?

Answer 7

Radiation sensitivity of a tissue is proportional to the rate of proliferation of its cells and inversely proportional to the degree of cell differentiation

Question 8

Highly sensitive cells

Answer 8

Cells that have high division: in the young
Cells that have a high metabolic rate: greater oxygen concentration
Cells that are of a non-specialized: stem cells
Cells that are well nourished: higher mitotic rate

Question 9

What are deterministic effects vs. stochastic effects?

Answer 9

Deterministic:
Occur as a result of damage to a population of cells. Are predictable
Known threshold where damage will not occur
Severity of effect increases with dose
Recovery is possible
All early and most late effects are determinsitic

Stochastic effects:
Non-predictable/ random events
No threshold for effect
Probability of seeing effect increase with dose