Biological effects of radiation

What are the two mechanisms of radiation damage?

Direct damage

Indirect damage

What is direct damage?

Radiation directly damage DNA and double strand breaks

What are the impacts of direct damage on the cell?

Repaired and work normally

Repaired abnormally

Cell apotheosis

No damage

What is indirect damage?

Radiation interacts with non-critical targets in the cell, which produces highly reactive free radicals that attack the cells

What is linear energy transfer?

Average radiation energy deposited per length along the track of the ionising particle

What are the features of high LET?

Protons

Large mass and charge

Deposit lots of energy in a small distance

Causes lots of damage in a small area

What are the features of low LET?

External radiation

High penetrative power

Energy deposits are spread out so less damaging

What are the three types of dose quantities?

Absorbed dose

Equivalent dose

Effective dose

What is the absorbed dose?

How much energy is deposited per kilogram

What is equivalent dose

Absorbed dose multiplied by harm factor of different radiations

What is effective dose?

Equivalent dose multiplied by harm susceptibility of different tissues

What is relative biological effectiveness?

Ratio of doses required by two types of radiation to cause the same effect

What are tissue tolerances?

The threshold to which each type of tissue can recover from biological damage caused by radiation

What are the two types of physical effects?

Deterministic

Stochastic

What are the features of deterministic effects?

Occurs once a threshold of exposure is exceeded

Severity of effects increases as absorbed dose increases

Doses are substantial and delivered over a short period

What are the features of stochastic effects?

No threshold, occurs at any dose

Only likelihood increases not severity of damage

Difficult to detect on wide scale due to low exposure