Safe use of IR and doses Flashcards
Describe the stochastic biological effects of ionising radiation according to LNT model?
However small the radiation dose
No safe dose
Effect is directly proportional to dose at all dose levels
Definition of absorbed dose? (D)
A measure of the amount of energy absorbed form the radiation beam per unit mass of tissue and can be measured using a dosimeter (J/kg), Gray (Gy)
It does not reflect biological damage
Equivalent dose definition?
This measures the effects of different types of radiation on tissues e.g. alpha particles are completely absorbed, x-rays are only partially absorbed
Effective dose definition?
Takes account of the fact that different tissues show different sensitivities to radiation, and allows comparison of risk of different types of radiation exposure
What stops alpha radiation?
Paper
What stops beta radiation?
Skin
What stops medical x-ray?
Cement
What stops gamma and neutron radiation?
Nothing
What does effective dose tell you?
The doses to a number of different organs are used in the calculation of effective dose
Effective dose allows comparison between whole body irradiation and a radiation dose which is not uniformly distributed
WHAT IS EFFECTIVE DOSE MEASURE IN?
Sieverts (Sv)
Tissues most affected by radiation?
Breast
Stomach
Lungs
Colon
Red bone marrow
Daily background dose?
7.5uSv/day
Major source of radiation?
Radon
Dose limits for unclassified workers vs others?
Workers: 6mSv pa
Others: 1mSv pa
This is effective dose
Dose for an intraoral radiograph?
0.3-21.6uSv
