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Medical Physics: Radiation Safety > Biological Effects of Radiation > Flashcards

Flashcards in Biological Effects of Radiation Deck (8)
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1

What are the three electron interactions with matter?

Ionisation
Excitation
Heat Production

2

What is the energy loss of an electron for each ionisation caused?

34eV

3

State and explain the three light production methods on irradiation.

fluorescence: prompt light emission
phosphorescence: delayed light emission
thermoluminescence: light emission when heated

4

Explain how indirect damage can arise from radiation.

Action of radiation leads to excited macromolecules (RH -> RH*) and then to the production of free radicals R• and H •

5

Which is more likely at diagnostic levels: direct or indirect action?

Indirect

6

Define Linear Energy Transfer (LET)

LET is a measure of the rate at which energy is transferred to the medium (i.e. ionisation density along the track of the particle)
A more penetrating beam has a lower LET

7

Define Radiobiological Effectiveness (RBE)

RBE = dose of 200kVp x-rays/dose of other radiation to give same biological effect

8

What does RBE vary with?

- dose
- dose rate
- fractionation
- physiological conditions (e.g. oxygen concentration)
- biological species
- biological end point chosen for comparison
- time after irradiation when measurements made