Week 6: Biological effects of radiation (part 2) Flashcards
What is an acute dose?
When a dose is accrued in a short period of time.
What is a chronic dose?
When a dose is accrued over a long period of time.
What are the problems with receiving a large acute dose?
Observable health effects:
Early onset symptoms such as nausea and vomiting.
Hair loss, fatigue and medical complications.
Burns and wounds heal slowly.
Give two examples of acute doses.
Medical exposures
Accidental exposure to sealed sources
How does the body’s reaction to a chronic dose differ to that of an acute dose?
The body more easily repairs damage from chronic doses.
There is a lower likelihood of causing observable effects.
Give two examples of chronic doses.
Natural background radiation
Fallout from nuclear weapons testing
What is fractionation?
When a single lethal dose is split into smaller doses, with a time interval in-between such that biological damage to healthy cells is considerably reduced.
State the equation for the approximation of dose rate. State all the units and meanings of the symbols used.
(32)
What is an internal dose?
Where the radionuclides are taken into the body and the dose is received from inside.
Why can internal doses be very serious?
As they are bypassing the body’s defence mechanisms.
What is the committed dose?
This is the dose expected to occur over a given time period. This is usually 50 years for an adult.
What are the two kinds of radiation exposure consequence?
Harmful tissue reactions
Stochastic
What examples are there of harmful tissue reactions?
Radiation burns
Cataracts
Infertility
Acute radiation syndrome (ARS)
What syndromes are the symptoms of ARS divided into?
Haematopoietic
Gastro-intestinal
Neurovascular
What ARS symptoms are haematopoietic?
Decrease in the number of blood cells
Possibility of infection
Bleeding
Anaemia
What ARS symptoms are gastro-intestinal?
Nausea
Vomiting
Loss of appetite
Abdominal pain
What ARS symptoms are neurovascular?
Dizziness
Headache
Loss of consciousness
What does LD50/60 mean?
The dose that will kill 50% of the exposed population within 60 days.
How do stochastic effects of radiation exposure differ with dose size?
They increase in probability however the severity does not change.
Why is it difficult to produce good statistics on the relationship between low doses of radiation and cancer?
It is impossible to distinguish a radiation-induced cancer from one that occurs due to other causes.
What is assumed with the linear no-threshold model?
The risk of cancer increases linearly with dose and that there is no lower threshold below which the risk does not increase.
What other models have been proposed for cancer risks?
Linear with threshold:
No increase in risk below a certain
dose, and risk rises linearly above that
point.
Hormesis:
Low radiation exposures decrease the
risk of stochastic effects, while higher
exposures increase them.
Supra-linear:
Low doses are actually more
dangerous than high doses per unit
dose.
What does a dose of 1 Sv to members of the public represent?
A 5% increase in the risk of death.
A 5.5% increase in the risk of cancer.
A 0.2% increase in the risk of inheritable effects.
What are the fundamental principles of radiation protection?
Justification
Optimisation
Limitation
