Dosimetry Flashcards
What are the radiation core safety principles?
(3)
Justification
Optimisation
Limitation
How do we know that radiation is harmful?
Atomic bomb survivors
How do atomic bomb survivors tell us that radiation is harmful?
Survivors were tested for how close they were from the epicentre, which indicated the dose that they received. The further they were, the less dose they got. They compared the number of cancers these people got to a normal population.
The further the distances from the epicentre, the lower occurrence of cancer. This allowed the creation of the linear non-threshold model for stochastic effects
What does the linear non-threshold model for stochastic effects say?
The higher the dose of radiation someone receives, the higher their risk of cancer
Why may the linear non-threshold model for stochastic effects be inaccurate?
Because the information to create it was from atomic bomb survivors, yet all of them had high doses- just in different quantities
What are the 2 types of quantities of radiation?
Direct quantities (radiation that’s directly measured)
Derived quantities (radiation that’s not directly measured)
What are the direct quantities of radiation?
(3)
Exposure
KERMA
Absorbed dose
What are the derived quantities of radiation?
(5)
Equivalent dose
Effective dose
DAP
DLP
Personal dose equivalent
What is exposure?
The amount of ionisation caused by an x-ray or a gamma ray in air
What does the exposure measure?
The total charge produced in air by ionising radiation
What does the exposure not include?
The extra ionisation caused by the slowing of electrons (brehmstrahlung)
What is the unit of exposure?
Coulombs per kilogram (C/kg)
What direct quantity is usually used instead of exposure?
KERMA
What is KERMA?
A measure of kinetic energy released per unit mass. It includes the effects of brehmstrahlung
What is the unit for KERMA?
Gray (Gy)
What is the absorbed dose?
The amount of energy deposited in a material
What is the absorbed dose equal to?
KERMA in air
What is the unit for the absorbed dose?
Gray (Gy)
What is linear energy transfer (LET)?
It defines how damaging a radiation is based on charge, mass and energy
What does it mean if there’s a higher LET?
The DNA breaks are more irreparable
Do alpha particles have a high or low LET?
Why?
High LET
So that they can slow down quickly in tissue and cause more damage in the DNA