Patient Dose Flashcards
What are the 3 types of ‘dose’?
Absorbed, equivalent and effective
what is absorbed dose?
how much energy is deposited in a kg of a substance. energy/mass
what is equivalent dose?
tells us how dangerous the radiation is to an organ our tissue and depends on the type of radiation. you apply a weighting factor to account for the fact that different types of radiation will affect the tissue differently
why is alpha radiation more damaging?
it has a higher linear energy transfer alpha particles are big and heavy so only travel a short distance before interacting
what is linear energy transfer?
amount of energy an ionising particle transfers to the material per unit distance. if the radiation has high LET then more double strands will break. High LET radiation is attenuated more quickly so less shielding is required but is more damaging to the tissue.
what is effective dose?
it tells us the potential for future long term effects and depends on the sensitivity of the particular tissue that has been irradiated. Bone marrow, lungs and stomach are the most sensitive. = tissue weighting factor x equivalent dose.
how do we work out the absorbed dose?
energy/ mass
how do we work out equivalent dose?
absorbed dose x radiation weighting factor
how do we work out effective dose?
equivalent dose x tissue weighting factor.
