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000 Radiobiology > Ch 34 Stochastic Effects > Flashcards

Ch 34 Stochastic Effects Flashcards

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1
Q

What are Stochastic effects?

A

Late Effects

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2
Q

Stochastic effects follow a…

A

Linear, non-threshold dose response relationship

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3
Q

What are principle stochastic effects?

A
  • Radiation induced malignancy

- Genetic effects

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4
Q

What type of effects are the result of low doses of radiation over a long period of time

A

Stochastic Effects

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5
Q

What are Local tissue Stochastic effects?

A
  • Erythema (sunburning)
  • Desquamation
  • Late developing carcinoma
  • Radiodermatitis
    • Calluses
    • Discoloration
    • Tight, Brittle skin
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6
Q

What are local tissue effects of Chromosomes?

A
  • Leukemia
  • Chromosome damage to circulating lymphocytes
  • Chromosome aberration that may not be apparent for years
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7
Q

What are cataracts?

A

Caused by high radiation to the lens of the eye

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8
Q

Test

Where do radiation induced cataracts occur?

A

Posterior pole of the lens

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9
Q

Who were the first people to have their lens affected by radiation?

A

Cyclotron physicists (1949)

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10
Q

By 1960 hundreds of cases of radiation induced ______ were reported.

A

Cataracts

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11
Q

Radiosensitivity of the eye is _____ ______

A

Age dependent

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12
Q

Radiation effect increases as…

A

Age increases

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13
Q

What is the latent period for radiation causing cataracts?

A
  • 5-30 years

- Average is 15 years

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14
Q

Radiation induced cataracts follow a…

A

Non linear, threshold dose response relationship

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15
Q

During occupational exposure, are protective shields required for protection of the lens?

A

No, it is too low

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16
Q

What is the threshold dose before causing cataracts?

A

200 rad (2 Gy t)

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17
Q

At what dose do nearly 100% of irradiated subjects get cataracts?

A

Greater than 1,000 rad (Gy t)

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18
Q

At worst, humans can expect a reduced life span of ____ days for every rad (mGy t)

A

10

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19
Q

What causes radiation induced life span shortening?

A

Accelerated premature aging and death

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20
Q

What are some risky conditions that shorten life span?

A
  • Being male (2,800)
  • Heart disease (2,100)
  • Smoker (1,600)
  • Cancer (980)
  • MVA (200)
  • Occupational accidents (74)
  • Rad worker (12)
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21
Q

What are the (3) ways to calculate risk?

A
  1. Relative
  2. Excess
  3. Absolute
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22
Q

What is Relative Risk?

A

Estimation of late radiation effects in large populations without knowing radiation dose

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23
Q

What is Radiation Hormesis?

A

Low radiation doses can be beneficial (less than 10 rad)

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24
Q

Relative risk =

A

Observed Cases
______________
Expected Cases

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25
What is Excess Risk?
Difference between observed and expected number of cases
26
Excess risk =
Observed cases - Expected cases
27
What is Absolute Risk?
- At least two different dose levels are known - Other data, such as # of cases, dose etc are known - Predicts stochastic radiation response in exposed population
28
What is the ideal risk?
Absolute Risk
29
Radiation induced Leukemia follows a...
Linear, non threshold dose response relationship
30
What is the latent period of Radiation induced Leukemia?
4-7 years
31
After being exposed to radiation how long are you at risk for acquiring Leukemia?
20 years
32
Who provided the greatest amount of information about radiation induced leukemia in humans?
Atomic bomb survivors
33
Do radiologists have an elevated risk of Leukemia?
No
34
Patients started to develop Leukemia after being treated with radiation for what?
Ankylosing Spondylitis
35
Can radiation cause cancer?
Without question
36
What are types of cancer associated with radiation:
- Thyroid cancer - Bone cancer - Skin cancer - Breast cancer - Lung Cancer - Liver cancer
37
What is the risk of death from radiation induced malignancy
5/100 or 0.05%
38
What is the at risk period after exposure to radiation?
20-25 years
39
Overall absolute risk for induction of malignancy is approximately...
8 caser per 100 Sv
40
What are the concerns of radiation effects before pregnancy?
Interrupted Fertility
41
What are the concerns of radiation effects during pregnancy?
Congenital effects on newborns
42
What are the concerns of radiation effects after pregnancy?
Suspected genetic effects
43
During pregnancy, what is the most radiosensitive period?
1st trimester
44
Low dose chronic irradiation does not impair fertility? T/F
True
45
The effects of irradiation in utero are time and dose related? T/F
True
46
What are the possible effects of irradiation in utero?
- Prenatal death - Neonatal death - Congenital abnormalities - Malignancy induction - Growth impairment - Genetic effects - Mental retardation
47
Out of all the possible effects of irradiation in utero, which one stays constant?
Leukemia
48
Within (2) weeks of fertilization, what can high radiation doses cause?
Spontaneous abortion (miscarriage
49
What dose level can cause a 0.1% spontaneous abortion rate?
10 rad dose
50
What is the normal chance of spontaneous abortion without radiation?
25-50%
51
What period of time is of least concern because the response is all or none?
The first 2 weeks
52
What weeks of pregnancy is the period of major organogenesis?
Weeks 2-12
53
What two effects during pregnancy can occur as a result of radiation exposure?
1. Skeletal and organ abnormalities | 2. Congenital abnormalities of the CNS
54
An Oxford survey (1946) found that childhood malignancy is associated with...
Irradiation in utero
55
The relative risk of childhood leukemia after irradiation in utero is...
1.5, which is a 50% increase
56
What does radiation exposure in utero do?
Retards the growth and development of the newborn
57
How often does a 10 rad dose occur in radiology?
Very rarely
58
Radiation exposure in utero can result in what?
Microcephaly (small head) and mental retardation
59
What was Muller's study on genetic effects about?
Fruit flies were irradiated to determine if radiation altered mutations
60
What did Muller's study conclude?
That radiation does not alter the quality of the emulations, but did increase the frequency of the mutations
61
Muller's study concluded that...
Irradiation did not alter quantity, but frequency
62
What was Russell's study?
He irradiated a large mouse colony with different doses of radiation
63
What did Russell's study show?
- A dose rate effect does exist | - Confirmed the linear, non threshold dose response relationship
64
What is doubling dose?
The dose of radiation that produces twice the frequency of genetic mutations as would have been observed without the radiation
65
What is the doubling dose in humans?
50-250 rad (0.5-2.5 Gy t)
66
If 7% of the offspring in each generation are born with mutation, the doubling dose eventually increases the number of mutations to how many?
14%
67
Are radiation doses used occupationally or medically, responsible for any effects on fetal growth or development?
No
68
Congenital abnormalities mentioned in this chapter are based on...
Doses greater than 100 rad
69
What does a high dose of radiation over a short period of time result in?
Early effects
70
What are radiation protection guidelines based on?
Stochastic effects

000 Radiobiology (52 decks)

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