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Radiology > Radiation Protection > Flashcards

Radiation Protection Flashcards

1
Q

what is the absorbed dose?

A

amount of energy deposited in a medium per unit mass of material
SI unit - gray Gy
measured in joules/kg
subunit - miligray mGy x 10-3

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2
Q

Equivalent dose H?

A

Take into account the different radio biological effectiveness of different types of radiation

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3
Q

what does the equivalent dose equal to?

A

absorbed dose x radiation weighting factor

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4
Q

what is weighting factor?

A

Wr
xrays, gamma rays, b particles Wr=1
alpha particles = 20

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5
Q

units of equivalent dose?

A

SI unit = sievert
milisieverts mSv x 10-3
microsievert uSv x 10-6

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6
Q

equivalent dose equals what if xrays weighting factor is 1?

A

absorbed dose

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7
Q

what is the effective dose?

A

allows doses from different investigations of different parts of the body to be compared
converts dose to an equivalent whole body dose
some body parts more susceptible to radiation than others

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8
Q

what is Wt?

A

tissue weighting factor

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9
Q

Effective dose equals?

A

= equivalent dose x tissue weighting factor

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10
Q

units of effective dose?

A

SI unit = sievert

sub unit = mSV

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11
Q

the term dose is actually what?

A

effective dose

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12
Q

what is the average yearly uk background radiation?

A

2.5mSv/year

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13
Q

radiation from a periapical? dpt?

A

1-8.3mSv ~ 8-40 hours

4-30mSv

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14
Q

Somatic?

A

affecting those irradiated

deterministic or non deterministic - stochastic

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15
Q

genetic?

A

affects offsrping of those irradiated

non deterministic - stochastic

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16
Q

deterministic affects of radiation?

A

will occur
threhsold of which symptoms will occur
above threshold - severity increases with dose

17
Q

symptoms of deterministic radiation?

A 
skin erythema
hair loss
cataracts
GI upset
suppression of erythropoiesis
18
Q

does deterministic radiation occur in dentistry?

A

no

19
Q

effects on an unborn child?

A

related to dose = deterministic
susceptible when organs are developing - 2-9 weeks
can cause malformation (reduced growth) and death

20
Q

stochastic effects?

A

may occur/random development
no threshold at which events start to occur
any dose may cause stochastic effects
increased probability with increased dose
severity of effect not affected by dose
leukaemias/solid tumours

21
Q

do non deterministic effetcs occur in dentistry?

A

yes

22
Q

what cells are radiosensitive?

A

cells with high mitotic rate
cells undergoing many future mitoses
most primitive in differentiation
lymphocytes.oocytes are highly differentiated and non dividing

23
Q

direct effects of radiation?

A

interacts with biologic macromolecules causing ionisation/damage

24
Q

indirect effects of radiaiton?

A

water balance in body = most common damage
hydrogen/hydroxyl free radicals produced by action of radiation on water
free radicals = toxic substances e.g hydrogen peroxide

25
Q

changes in biologic molecules?

A

DNA - breaks strands, loss/change of base, disrupt bonds between strands = cell death, mutation, carcinogenesis

26
Q

what happens if both strands of DNA are broken?

A

misrepair

intact strand is usually the template

27
Q

genetic effects?

A

radiation to reproductive organs can damage DNA in sperm/egg
may cause congenital abnormalities in offspring of those irradiated
no threshold

28
Q

cancer risk from intra oral?

dpt?

A
  1. 06-0.7 in 1 000 000

0. 29-1.9 in 1 000 000

29
Q

young pt’s more at risk?

A

yes
more radiosensitive cells
longer lifespan to develop a cancer

30
Q

stages of radiation protection?

A

justfication
optimisation
dose limitation

31
Q

what is justification?

A

every radiograph must be justified

benefit of exam must outweigh detrimental effects

32
Q

what is optimisation?

A

doses kept as low as reasonably practicable and consistent with intended diagnostic purposes

33
Q

distance from x ray?

A

inverse square law

staff sufficient distance from pt and not in direction of primary beam

34
Q

what is the controlled area?

A

within 1.5m of tube and patient in any other direction
only pt in that area during exposure
size depends on kV of machine
1.5m

35
Q

warnings?

A

noise/light when xrays produced
operator prevents access to controlled areas
switches outwith controlled area

36
Q

monitoring of radiation to worker if?

A

> 1mSv / year
100 intra orals/week
50 dpt’s/week

37
Q

lead protection used?

A

thyroid collar if thyroid in primary beam

lead aprons dont protect from radiation scattered in body

38
Q

foetus most susceptible when?

A

2-9 weeks

Radiology (17 decks)

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