Radiation Safety Flashcards
what is the absorbed dose?
amount of ENERGY DEPOSITED in a medium per unit MASS of the medium
what is the absorbed dose measured in?
JOULES/Kg
what is the unit used for absorbed dose?
Grays (Gy)
The equivalent dose is…
a measure allowing different radio-biological effectiveness of different types of radiation into account.
the equivalent dose = (formula)
the absorbed dose x radiation weighting factor
what is the radiation weighting factor for X-rays, gamma rays and beta particles?
Wr = 1
what is the Wr for alpha particles?
20
Give an example of how the equivalent dose works?
- different types of radiation will penetrate tissues in very different ways…
- e.g, alpha particle will be totally absorbed but X-rays will have further penetration (the will both also have different absorbed doses)
the unit for equivalent dose is..
sievert (Sv)
if the radiation weighting factor is 1 then the absorbed dose is equal to the…
equivalent dose
The effective dose…
allows doses from different investigations of different parts of the body to be compared
the effective dose converts dose to an…
equivalent whole body dose
The tissue weighting factor is…
an indication of how sensitive an area is to radiation
name the 5 most sensitive areas
- thyroid
- gonads
- skin
- breasts
- red bone marrow
The effective dose = (equation)
equivalent dose x tissue weighting factor
the effective dose is measured in…
Sv (sieverts)
name 4 types of background radiation
- radon gas
- gamma rays
- cosmic rays
- food and drink
what is the average exposure to background radiation per year in the UK?
2.5mSv (m= x10-3)
Where does radon gas come from and how is it harmful?
- a breakdown product of uranium in the ground (natural) and is harmful if inhaled (can cause lung cancer)
the range of yearly exposure to radiation from radon gas is..
300-100,000 micro Sv
levels of radon gas are highest indoors or outdoor?
indoors as levels allowed to build up
gamma rays come from?
radioactivity in the earth and building materials (natural)
- the dose depends upon the material
levels of gamma rays are highest indoor or outdoors?
the same in both
the average yearly range of background radiation from gamma rays is..
100-1000 micro Sv
cosmic rays come from…
an increase in altitude and latitude
cosmic rays will readily penetrate…
aircraft and fabric of buildings
the average yearly range of cosmic rays is…
200-300 micro Sv
name 3 foods that are more radioactive than others?
- brazil nuts
- bananas
- shell fish
what percentage of radioactive exposure is medical?
14%
having a periapical or a bitewing is the equivalent of …hr long flight
2
what is the effective dose of a DPT?
20 milli Sv
20 milli Sv is the equivalent of a .. (2 things)
- chest x-ray
2. 3 days of background radiation
how many X-rays are taken a year for medical purposes?
40, 000, 000
how many of these are IO?
10, 000, 000
how many of these are DPT?
3, 000, 000
what % of dental radiographs are taken each year in the uk?
10 mil + 3 mil = 13 mil / 40 mil = 32.5%
give the 2 groups of biological effects of X-rays?
- somatic
2. genetic
what is the somatic effect?
one that affects the individual getting exposed
what is the genetic effect?
one that affects the offspring of those irradiated
which of the two biological effects has deterministic effects?
somatic
what can non-determinstic effects also be called?
stochastic
what are the somatic deterministic effects that will NOT happen in dentistry as the threshold isn’t high enough?
- hair loss
- erythema of skin
what are the somatic deterministic effects that should not but could occur in dentistry?
- eye cataract (due to scatter)
- GI upset
- suppression of erythropoiesis
what affects may occur to an unborn child? when are they most at risk?
- reduced growth/malformations
- death
most at risk between 2-9 weeks when organ formation occurring
