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Transition Block 2 > Radiation > Flashcards

Radiation Flashcards

1
Q

What flight is a CXR radiation roughly half the radiation of?

A

flight to new york (0.04 vs 0.02)

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2
Q

What are the two categories of radiation effects on humans?

A

deterministic effects and stochastic effects

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3
Q

When do deterministic efffectors occur?

A

when the cumulative effects on cells in the body are sufficient to produce a measurable clinical response

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4
Q

Which cells of the skin are the most radiosensitive?

A

basal stratum of the epidermis

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5
Q

What body area is most at risk from interventional radiation?

A

skin- erythema and hair loss

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6
Q

What is a stochastic effect?

A

frequency of the effect increases with radiation dose but the severity does not change

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7
Q

Why does the probability of cancer on a stochastic curve decrease at the highest doses of radiation?

A

cells which may have shown effect are killed

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8
Q

Give an example of a stochastic effect?

A

leukaemia

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9
Q

Give an example of la deterministic effect?

A

loss of fertility

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10
Q

What are the main non-cancer long-term stochastic effects?

A

CVS and cerebrovascular

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11
Q

What is the risk of hereditary effects of radiation?

A

no statistically significant increase in offspring of Japanese survivors

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12
Q

At what age does the lifetime excess risk of developing cancer plateau?

A

around 30 years

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13
Q

When is somoeone most likely to develop a solid tumour after receiving a large radiation dose?

A

when individiaul is between 60 and 90 years– highest natural incidence

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14
Q

What is the purpose of effective dose?

A

to provide a dose quantity related to risk

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15
Q

Which tissues have teh highest associated cancer rates linked with radiation exposure ?

A

bone marrow, lung, colon, stomach and brest

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16
Q

How is effective dose calculated?

A

sum of doses to individual organs weighted according to their radiosensitivities to create a number equivalent to a uniform whole body dose in terms of health risks

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17
Q

What term should be used for <0.1mSv?

A

negligible

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18
Q

What term should be used for 0.1-1mSv?

A

minimal

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19
Q

What term should be used for 1-10mSv?

A

very low

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20
Q

What term should be used for 101-100 mSv

A

low

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21
Q

How is Japanese data about cancer extrapolated?

A

based on absolute risk and partly on relative risk model based on background rates of cancer incidence in the population

22
Q

When does ovulation take place?

A

around the midpoint of hte menstrual cycle- 2 weeks, but rarely less than 10 days

23
Q

When does fertilisation of the ovum take place?

A

witihin 12 to 24 hours

24
Q

When does implantation of the embryo begin?

A

6-8 days after conception

25
Q

When is implantation of hte embyro complete?

A

2 weeks after conception

26
Q

When is the period of organogenesis?

A

from the 2nd to 8th weeks post conception

27
Q

When is the period of greatest sensitivity during organogenesis from radiation? What is being formed?

A

5th week post conception- during the formation of the early body axis and neural tube

28
Q

What is the effect of radiation until around the 2nd week post conception?

A

resorption

29
Q

What is the effect of radiation during organogenesis?

A

tissue malformation

30
Q

When does radiation cause mental retardation in a fetus?

A

from the end of organogenesis

31
Q

What is the likelihood that a potential radiation effect seen in a fetus is caused by radiation vs natural causes?

A

much more likely to have reulsted from natural causes

32
Q

When is the period of greatest sensitivty to damage by radiation to brain devleopment?

A

8th-15th weeks (significanat reduction in IQ to exposure to high exposure- Japanese hildren between weeks 8 and 25)

33
Q

What happens during the 8th-15th weeks in fetal brain development?

A

rapid increase in the number of neurons which migrate to their functional site in the cerebral cortex

34
Q

At what threshold dose does mental retardation in fetuses occur above?

A

200mGy- 10 times higher than the highest dose expected from a diagnostic medical exposure

35
Q

What is estimated to be the chance of induction of severe mental retardation following a dose of 1 Gy during the period 8-15 weeks post conception ?

A

40%

36
Q

What is the most significant effect of foetal exposure at low doses?

A

increased risk of cancer, especially leukaemia

37
Q

If the doses for all diganostic radiology procedures are well below thresholds for deterministic radiation effects why worry?

A

risk of stochastic effects

38
Q

What are the main risks to a foetus from diagnostic radiopharmaceuticals?

A

uptake of radionuclides in or neat he feotus- possible higher incidence of cancer, esp. during childhood and damage to teh thyroid from iodine administrations

39
Q

Why should particular care be given to radio-iodine?

A

iodine is taken up avidly during development of hte foetal thyroid

40
Q

Wehn does uptake in the foetal devleoping thyroid become significant?

A

from about the 10th week post conception

41
Q

What is the risk of radio-iodine administration during hte middle or later stage of pregnancy?

A

increased risk of hypothyroidism with potential for mental deficiency. But, no inc. risk of spontaneous abortion of foetal abnormalities

42
Q

How long are female patietns advised to avoid conception for post administration of radio-iodinine

A

4 months

43
Q

When is the risk of exposure from breast-feeding after radionuclides?

A

largest transfer early in lactation

44
Q

What is the threshold for mental retardation in a fetus?

A

200mGy (max for procedure- 20-30 mGy)

45
Q

Is there a significant risk of any radiation effect to a foetus conceived following exposure during the first 10 days of the menstrual cycle?

A

no

46
Q

Can embyro cells survive very early exposure?

A

can continue to reproduce and only effect would be delay in development

47
Q

Can a woman continue to breastfeed after administration of radio-iodine?

A

no, she should stop altogether

48
Q

What are the tenets for radiation protection?

A

should be justified and optimised

49
Q

What is ALARA

A

as low as reasonably achievable (process of optimisation for radiation protection)

50
Q

What is the result of increasing kVp when imaging using automatic exposure control?

A

reduced patient dose and also reduced contrast (image quality)

51
Q

How does distance protect from radiation?

A

the dose/ dose rate reduces as the square of the distance

52
Q

What is practical protection of individuals from external radiation based upon?

A

distnace, shielding and time

Transition Block 2 (2 decks)

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