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Radibio > Stochastic Effects > Flashcards

Stochastic Effects Flashcards

1
Q

The principal stochastic effects of low-dose radiation over long periods consist of

A

Radiation induced malignancies and genetic effects

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2
Q

Radiation protection guides are based on

A

Suspected or observed stochastic effects of radiation

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3
Q

With increasing dose, stochastic effects of radiation exposure exhibit

A

And increasing incident response, not severity.

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4
Q

Stochastic effects of radiation follow what type of dose response relationship

A

Linear, non-threshold

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5
Q

Epidemiologic studies

A

Are required when the number of people affected is small

Studies of large numbers of people exposed to a toxic substance require considerable statistical analysis

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6
Q

What are two reasons that epidemiologic studies of people exposed to radiation are difficult

A

The dose usually is not known but is presumed to be low.

The frequency of response is very low.

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7
Q

Radiodermatitis

A

Stochastic effect of skin.

Dose to produce the effect is very high.

Early radiologist who performed fluoroscopy without protective gloves developed very calloused, discolored and weathered appearance to the skin of their hands and forearms. The skin would be very tight, brittle, severely cracked or flake.

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8
Q

Irradiation of blood forming organs can produce —- as a deterministic response or —– as a stochastic response.

A

Hematologic depression

Leukemia

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9
Q

Cyclotron

A

A 12 cm diameter device capable of accelerating charge particles to very high energy.

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10
Q

How did cyclotron physicist get cataracts

A

They received high radiation doses to the lens of the eye because they had to look directly into the beam

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11
Q

The radiosensitivity of the lens of the eye is — dependent

A

Age

As the age of the individual increases, the radiation effects become greater and the latent. Becomes shorter

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12
Q

Latent periods for radiation induced cataracts

A

5 to 30 years

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13
Q

High LET radiation, such as —-, has a high relative biological effectiveness RBE for the production of cataracts.

A

Neutron and proton radiation

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14
Q

If the lens does exceeds — Cataracs develop in 100% of those irradiated

A

10 Gy

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15
Q

For radiation workers life is shortened by

A

12 days

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16
Q

Since dose response relationship are not possible to formulate for late response effects of earlier radiation exposure we resort to

A

Risk estimates

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17
Q

Three types of risk estimates

A

Relative
Excess
Absolute

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18
Q

If one observes a large population for stochastic radiation effects without having any precise knowledge of the radiation dose to which they were exposed, then —- risk is used

A

Relative

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19
Q

The relative risk is computed by comparing the number of persons—

A

In the exposed population showing a given stochastic effect with the number in an unexposed population who show the same stochastic effect.

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20
Q

A relative risk of 1.0 indicates

A

No risk at all

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21
Q

A relative risk of 1.5 indicates that the frequency of a late response is

A

50% higher in the irradiated population then in the non-irradiated population

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22
Q

A relative risk of less than 1 indicates

A

That the radiation exposed population receives some protective benefit.

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23
Q

The theory of radiation hormesis suggests that radiation less than — is good for you because ?

A

100 mGY

Stimulates molecular repair and immunologic response mechanisms

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24
Q

When an investigation of human radiation response reveals the induction of some Stochastic effect, The magnitude of the effect is reflected by

A

The excess number of cases induced

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25
Q

Excess risk is calculated

A

Observed cases - expected cases

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26
Q

If at least two different dose levels are known, then it may be possible to determine —- risk factor

A

Absolute

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27
Q

The absolute risk of total radiation induced malignant disease has been determined by who

A

National Academy of Science (NAS) Committee on the Biologic Effects of Ionizing Radiation (BEIR)

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28
Q

The absolute risk of total radiation induced malignant disease, value is

A

8 x 10^-2 Sv^-1

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29
Q

The absolute risk of a fatal radiation induced malignant disease, value is ? What is this used to predict?

A

5 x 10^-2 Sv-1

This risk coefficient is used to predict stochastic radiation response in exposed populations

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30
Q

To determine the absolute radiation risk, one must assume a —- dose response relationship.

A

Linear

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31
Q

The value of the absolute radiation risk is equal to the

A

Slope of the linear, non-threshold dose response relationship.

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32
Q

Types of radiation induced malignancies include

A

Leukemia

Cancers : bone, lung, liver, breast

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33
Q

Relative risk =

A

Observed cases/expected cases

34
Q

Excess Risk =

A

Observed cases - Expected cases

35
Q

When an investigation of human radiation response reveals the induction of some stochastic effect, the magnitude of the effect is reflected by the ______ number of cases induced.

A

Excess

36
Q

NAS BEIR is

A

National Academy of Science Committee on the Biologic Effects of Ionizing Radiation

37
Q

Absolute risk =

A

(Risk factor) x (dose) x (# of population)

38
Q

Absolute risk value for non-fatal radiation-induced malignancy

A

8 x 10^-2 Sv^-1

39
Q

Effective dose units is

A

Sb

40
Q

Absolute risk value for fatal radiation-induced malignant disease

A

5 x 10^-2 Sv^-1

41
Q

1mSv= __ Sv

A

0.001

42
Q

0.5mSv= __Sv

A

0.0005 Sv

43
Q

Tuberculosis was treated with?

A

Non-image intensified fluoroscopy, up to several hundred tx.

44
Q

The relative risk for the tuberculosis pts, for developing breast cancer was as high as

A

10:1

45
Q

Patients treated for postpartum mastitis with doses 0.75 to 10 Gy, the relative risk for breast cancer

A

3:1

46
Q

A-bomb survivors relative risk for breast cancer

A

4:1

47
Q

Absolute Risk for radiation-induced breast cancer

A

6 x 10^-2 Sv-1

48
Q

Uranium miners in the 50s and 60s had and in lung cancer because

A

Uranium decays to Radon
Decays to lead
Alpha particles are high LET radiation and high RBE

49
Q

Over 4,000 uranium miners receives doses to lung, up to 30 Gy. Relative Risk for lung cancer?
If they were smokers?

A

8: 1
20: 1 (8 times higher)

50
Q

______ was contrast agent used in angiography, which caused Liver Cancer.

A

Thoratrast

51
Q

Radioactive isotopes of thorium

A

Thorium dioxide

52
Q

Latent period for liver cancer caused by thorotrast.

A

15 to 20 years

53
Q

Thorium dioxide particles are deposited

A

In phagocytic cells of the reticuloendothelial system and are concentrated in the liver and spleen

54
Q

The alpha rays from he radioactive isotopes of thorium, have ____ LET

A

High

55
Q

Physical aspect/ absorbed dose

A

Gray

56
Q

Biological aspect/effective dose

A

Sv

57
Q

Risk of death from rad-induced malignant disease

A

5 cases/100Sv

58
Q

At risk period for risk of death from rad-induced malignant disease

A

20 to 25 years

59
Q

Effective dose of 10 mSv has a risk of ___ for malignant disease induction, half will die

A

10 mSv

60
Q

3 mile island

A 
1979
2 million population
Natural incidences of cancer  is 300,000
15uGy
Dose estimates expect additions cases 1.5 additional cases
61
Q

BEIR Committee

A

Biologic Effects of Ionizing Radiation

Reviewed the data on stochastic effects of low-dose, low LET radiation.

62
Q

One of the situations BEIR examined

A

They estimated the excess deaths from malignant disease after a 1 time accidental exposure to 10 mGy.
800 cases
100,000 population
Absolute Dose 8 x 10 ^-2 Sv^-1

63
Q

BEIR considered the response to a dose of 10 mGy/year for life; what population?

A

A very busy IR Rad guy

64
Q

BEIR considered excess rad.-induced cancer death after a continuous dose of 1 mGy/year for life.
For who?

A

Us and general public
Excessive risk= 550 deaths/100,000 people
This is in addition to the normal incidence f cancer deaths of 20,000 per 100,000 people

65
Q

BEIR analyzed human data with regard to

A
  1. Age at exposure
  2. A limited time of expression of effects
  3. Whether the response was absolute or relative
66
Q

If one is irradiated at an early age, and the response time is limited, rad-induced excess mal disease appears as a ?

A

Bulge on the age response relationship

67
Q

Absolute age-response relationship

A

Predicts that the excess rad-induced cancer risk is constant for life.

68
Q

Relative Risk

A

Predicts that the excess rad induced cancer risk is proportions to the natural incidence.
Increase is likely as age increases.

69
Q

Does low dose impair fertility

A

No

70
Q

Higher doses of radiation 100mGy during 1st 2 weeks of pregnancy

A

.1% rate of loss of preg

71
Q

Natural loss of pregnancy

A

20 to 50% in 1st 2 weeks

72
Q

After 2nd week to 12th week of pregnancy, with high rad dose

A

Major organogenesis, radiosensitive.
Can get congenital defects with high dose.
Skeletal or organ abnormalities

73
Q

In mice during the early pregnancy:
Dose of 2 Gy, nearly 100% of fetuses……
And 80%….
Dose under 100mGy….

A
  1. Significant abnormalities
  2. Died
  3. No observable effects
74
Q

What did the Oxford Survey findings indicate for rad-induced leukemia

A

A relative risk of 1.5 for the development of childhood leukemia after irradiation in utero is significant.
This indicates an increase of 50% over the nonirradiated rate.

75
Q

A finding in offspring of A-Bomb survivors

A

Mental retardation

A 100mGy dose in utero s expected to increase the incidence to an additional 0.5%

76
Q

Relative risk of childhood leukemia after irradiation in utero by trimester

  1. First trimester
  2. Second trimester
  3. Third trimester
A
  1. 8.3
  2. 1.5
  3. 1.4
77
Q

Effects after 100 mGy in utero

  1. 0-2 weeks
  2. 2-10 weeks
  3. 2-15 weeks
  4. 0-9 months
A 
Increase of response to radiation:
1. 0.1% spontaneous abortion
2.  1% congenital abnormalities
3.  0.5% Mental retardation
4. Malignant disease 12/10,000
 Impaired growth and development nil
Genetic mutation nil
78
Q

We do not have any data that suggest that radiation -induced genetic effects occurs in humans, so most of the data is from?

A

Large scale experiments with flies and mice

79
Q

Geneticist, H.J. Muller reported the results of his irradiation of Drosophilia, the fruit flies and genetic effects to be

A

Linear, nonthreshold.
Radiation does not alter the quality of mutations but increases the frequency of those mutations
That such mutations were single-hit phenomena

80
Q

On the basis of Muller’s work, the NCRP in 1932 lowered?

A

The recommended dose limit and acknowledged officially the existence of nonthreshold radiation effects.
Since then, all rad protection guides have assumed a linear, nonthreshold DRR

81
Q

The only other significant genetic experiment was ?

A

Russell’s experiment on mice

Radibio (4 decks)

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