Radiation biology and tissue interaction Flashcards
What are the effects of radiation?
DNA changes
Deterministic and stochastic (non-deterministic) effects
Tissue interactions
What are the direct effects of x-ray?
C-c bonds in the body
Ionisation event therefore able to disrupt the c-c bonds
What are the indirect effects of x-ray?
Human body comprises approx 60% water
Radiation interacting with water may produce free radicals
Free radicals are highly reactive and can damage DNA
What will the biological effect of radiation depend on?
Type of radiation
Tissue or cell irradiated
Amount of radiation (dose)
Time over which the dose is received (dose rate)
Determanistic effects?
High radiation doses received over a short time
Fairly severe reaction which occur above certain dose
May not develop immediately
Stochastic effects?
Non-determanistic
Low doses received over prolonged period
No threshold dose
Cannot predict occurrence or severity of effects
What are the effect of low dose of prolonged period?
Cancer
Leukemia
Genetic
What effects are dentist most concerned with?
Stochastic
What effect occursw wth scattering?
Compton effect
When an x-ray strikes matter, what are the 4 possible effects?
Absorption
Scattering
Transmission
Attenuation
WHAT IS ATTENUATION?
ABSORPTION AND SCATTERING
What effect does absorption have?
Photogenic effect - most likely to cause harm to tissue
What is the photoelectric effect?
Low energy photons
Incoming x-ray photon interacts with bound inner shell electron
What is the Compton effect?
High energy photons
Escape form the tissue
Absorption and redistribution of energy
Absorption in fat is predominantly due to Compton at 60kvp
Scattered radiation - known as Compton scatter
What is photoelectric effect?
Pure absorption
Predominates in tissue at <50kVp
Unlikely to occur n dentistry as we typically use 60-70kVp
