R: Radiation Biology and safety Flashcards
What is the difference between non ionising and ionising radiation? Which one are our cells more sensitive to?
cells, tissues, organs or organisms have can be sensitive to the
harmful effect of ionising radiation.
Which cells are more at risk with radiation?
Actively dividing cells or those not fully mature are most at risk from radiation. The most radio-sensitive cells are those which:
have a high division rate
have a high metabolic rate
are of a non-specialized type
are well nourished
Are all cells equally sensitive to radiation?
No. Not all living cells are equally sensitive to radiation. Cells that are actively reproducing/dividing (involves reproduction of DNA) are
more sensitive than those which are not. A direct interaction of radiation with an active cell could
result in the death or mutation of the cell, whereas a direct interaction with the DNA of a dormant cell (cell that divides much more slowly)
would have less of an effect.
What is the difference between cells that have: High sensitivity + Low sensitivity to radiation? Give examples.
Living cells can be classified according to their rate of reproduction, which also indicates
their relative sensitivity to radiation. This means that different cell systems have different sensitivities.
Lymphocytes (white blood cells) and cells which produce blood are constantly regenerating, and are,
therefore, the most sensitive. Reproductive and gastrointestinal cells are not regenerating as quickly and
are less sensitive. The nerve and muscle cells are the slowest to regenerate and are the least sensitive
cells.
Define ‘Effective Dose’
The Effective Dose (E) is used to estimate Radiation risk
* Measures the equivalent whole-body dose
* ‘E’ is measured in Sieverts (Sv)
How is Effective Dose determined?
It is the SUM radiosensitivities of different tissue types (each tissue will have a Tissue Weighting factor) MULTIPLIED by the amount of radiation is exposed.
E = ∑ WT x HT
Calculate the effective dose for:
a) 1 Gy of gamma rays on the skin (H = 1, Wt = 0.01)
b)1 Gy of x-rays on the ovaries (H = 1, Wt = 0.20)
a) 0.01 Sv of Effective dose
1Sv of radiation x 0.01 (the tissue weighting factor of skin) = 0.01 Sv
b) 0.2 Sv of effective dose, 20 times more risky than gamma on the skin (the previous case).
What is the prescribed dose limits in Australia?
Where it is expected that a worker will be exposed to radiation because of their employment, the worker must not exceed the prescribed dose limits.
The current limit of radiation exposure is 20 millisieverts (mSv) per year averaged over 5 years, and not more than 50 mSv received in any one year for effective (whole body) dose.
What is the allowable radiation exposure amt in Australia vs actual average amt that dental practitioners recieve?
Dental practitioners receive less significantly less radiation than the prescribed dose limits.
What is background radiation?
Background radiation= ionizing radiation present in the environment at a particular location which is not due to deliberate introduction of radiation sources.
Background radiation originates from a variety of sources, both natural and artificial. These include both cosmic radiation and environmental radioactivity from naturally occurring radioactive materials (such as radon (gas) and radium), as well as man-made medical X-rays, fallout from nuclear weapons testing and nuclear accidents.
How can we use the BERT (Background Equivalent Radiation Time) concept to educate/explain to patients who may worry about radiation from x-rays?
The BERT table converts the radiation dose to an equivalent period of natural background radiation. It is understandable, it does not mention risk, and it educates the patient that human-made radiation is the same as the background radiation which gives them most of their annual dose.
e.g. we receive more radiation going on an aero plane than taking a panoramic x-ray. (see table on lecture slides)
What is the difference between deterministic vs stochastic effects?
What is the difference between indirect and direct mechanism of radiation?
Give an example of a deterministic vs stochastic effect. Explain the nature of each effect in terms of (cause, threshold dose, severity of clinical effects and dose, and probability of having effect and dose)
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What are deterministic short vs long term effects? Discuss symptoms that may arise with Acute Radiation Syndrome based on exposure amount:
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3 principles of radiation protection?
