Radiation

Question 1

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

Answer 1

flight to new york (0.04 vs 0.02)

Question 2

What are the two categories of radiation effects on humans?

Answer 2

deterministic effects and stochastic effects

Question 3

When do deterministic efffectors occur?

Answer 3

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

Question 4

Which cells of the skin are the most radiosensitive?

Answer 4

basal stratum of the epidermis

Question 5

What body area is most at risk from interventional radiation?

Answer 5

skin- erythema and hair loss

Question 6

What is a stochastic effect?

Answer 6

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

Question 7

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

Answer 7

cells which may have shown effect are killed

Question 8

Give an example of a stochastic effect?

Answer 8

leukaemia

Question 9

Give an example of la deterministic effect?

Answer 9

loss of fertility

Question 10

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

Answer 10

CVS and cerebrovascular

Question 11

What is the risk of hereditary effects of radiation?

Answer 11

no statistically significant increase in offspring of Japanese survivors

Question 12

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

Answer 12

around 30 years

Question 13

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

Answer 13

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

Question 14

What is the purpose of effective dose?

Answer 14

to provide a dose quantity related to risk

Question 15

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

Answer 15

bone marrow, lung, colon, stomach and brest

Question 16

How is effective dose calculated?

Answer 16

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

Question 17

What term should be used for <0.1mSv?

Answer 17

negligible

Question 18

What term should be used for 0.1-1mSv?

Answer 18

minimal

Question 19

What term should be used for 1-10mSv?

Answer 19

very low

Question 20

What term should be used for 101-100 mSv

Answer 20

low

Question 21

How is Japanese data about cancer extrapolated?

Answer 21

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

Question 22

When does ovulation take place?

Answer 22

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

Question 23

When does fertilisation of the ovum take place?

Answer 23

witihin 12 to 24 hours

Question 24

When does implantation of the embryo begin?

Answer 24

6-8 days after conception

Question 25

When is implantation of hte embyro complete?

Answer 25

2 weeks after conception

Question 26

When is the period of organogenesis?

Answer 26

from the 2nd to 8th weeks post conception

Question 27

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

Answer 27

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

Question 28

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

Answer 28

resorption

Question 29

What is the effect of radiation during organogenesis?

Answer 29

tissue malformation

Question 30

When does radiation cause mental retardation in a fetus?

Answer 30

from the end of organogenesis

Question 31

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

Answer 31

much more likely to have reulsted from natural causes

Question 32

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

Answer 32

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

Question 33

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

Answer 33

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

Question 34

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

Answer 34

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

Question 35

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 ?

Answer 35

40%

Question 36

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

Answer 36

increased risk of cancer, especially leukaemia

Question 37

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

Answer 37

risk of stochastic effects

Question 38

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

Answer 38

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

Question 39

Why should particular care be given to radio-iodine?

Answer 39

iodine is taken up avidly during development of hte foetal thyroid

Question 40

Wehn does uptake in the foetal devleoping thyroid become significant?

Answer 40

from about the 10th week post conception

Question 41

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

Answer 41

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

Question 42

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

Answer 42

4 months

Question 43

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

Answer 43

largest transfer early in lactation

Question 44

What is the threshold for mental retardation in a fetus?

Answer 44

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

Question 45

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

Answer 45

no

Question 46

Can embyro cells survive very early exposure?

Answer 46

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

Question 47

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

Answer 47

no, she should stop altogether

Question 48

What are the tenets for radiation protection?

Answer 48

should be justified and optimised

Question 49

What is ALARA

Answer 49

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

Question 50

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

Answer 50

reduced patient dose and also reduced contrast (image quality)

Question 51

How does distance protect from radiation?

Answer 51

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

Question 52

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

Answer 52

distnace, shielding and time