Biological Effects of Ionising Radiation Flashcards
when ionisation occurs what is deposited locally
energy (35eV)
what happens when radiation passes through matter
it will ionise atoms along its path
where can evidence of DNA damage be seen
in the faulty repair of chromosome breaks
where is DNA damage seen
in individuals who are exposed to large doses
what is the direct effect of radiation damage on DNA
radiation interacts with the atoms of a DNA molecule or another important part of the cell
what is the indirect effect of radiation damage on DNA
radiation interacts with water in the cell, producing free radicals which can cause damage
why are double strands of DNA more difficult to repair
it usually occurs due to alpha radiation and if the repair is faulty it can lead to mutations which affects cell function
what does the biological effect of DNA damage depend on
type of radiation, amount of radiation, time over which the dose is received, the tissue or cell type irradiated
why is radiation delivered at a lower dose less damaging
cells can repair less serious DNA damage before further damage occurs
what organs are at risk from cancer following large radiation exposures
oesophagus, thyroid, lungs, skin, breast, stomach, liver, colon, gonads
what is the radiosensitivity of tissues dependent on
function of the cells that make up the tissues
if cells are actively dividing
what kind of cells are very radiosensitive
stem cells
why are stem cells radiosensitive
they divide very frequently
what cells are highly radiosensitive
bone marrow, lymphoid tissue, GI, gonads, embryonic tissues
what cells are moderately radiosensitive
skin, vascular endothelium, lungs, lens of eye
what are the least radiosensitive cells
CNS, bone and cartilage, connective tissue
what are the possible outcomes after radiation hits a cell nucleus
no change
mutation repaired
cell death
cell survives but is mutated - cancer?
what is absorbed dose
measures the energy deposited by radiation
in Grays
what is equivalent dose
absorbed dose multiplied by a weighting factor depending on the type of radiation
in Sieverts (Sv)
what does the linear no threshold model estimate
long term biological damage from radiation
what does the linear no threshold model assum
the damage is directly proportional to radiation dose and radiation is always harmful with no safety threshold
what is response linearity
several small exposures would have the same effect as one large exposure
what are the 2 types of radiation effects
deterministic and stochastic
what is the deterministic effects of radiation
tissue reactions
only occur above a certain dose
severity of effect is related to the dose received
