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Radiation Protection > Week 9 - Stochastic Effects & Late Tissue Reactions > Flashcards

Week 9 - Stochastic Effects & Late Tissue Reactions Flashcards

1
Q

What are late effects?

A

Consequences of radiation exposure that appear months or years after the exposure.

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2
Q

What are the two types of late tissue effects?

A

Stochastic or Tissue reactions

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3
Q

What are Stochastic effects also known as?

A

Probabilistic effects

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4
Q

What are stochastic effects?

A

Mutational or randomly occurring biologic changes that occur months or years after high level and possibly low level of radiation exposure

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5
Q

What are examples of Stochastic effects?

A

Cancer and genetic effects

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6
Q

What is the relationship between stochastic effects and disease incidence?

A

Directly proportional - disease incidence increases proportionally with dose

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7
Q

What is relationship between severity of disease and dose?

A

They’re independent of each other - severity is not dose dependent

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8
Q

What is the threshold of Effects?

A

No threshold

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9
Q

What are examples of late biologic damage?

A
  • Cataracts (late tissue reaction)
  • Leukemia (stochastic)
  • Genetic mutations (stochastic)
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10
Q

What is epidemiology?

A

A science that deals with the incidence, distribution and control of disease in a population

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11
Q

What do epidemiological studies consist of?

A

Observations and statistical analysis of data, such as the incidence of disease within groups of people

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12
Q

What studies are included in epidemiologic studies?

A

The risk of radiation- induced cancer

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13
Q

What are the incident rates at which irradiation related malignancies occur determined by?

A

Comparing the natural incidence of cancer occurring in a human population with the incidence of cancer occurring in an irradiated population

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14
Q

What are determined from the epidemiologic studies?

A

Risk factors for the general human population

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15
Q

What is the significance of epidemiologic studies to radiobiologists?

A

They use the information from the studies to formulate dose-response estimates to predict the risk of cancer in human populations

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16
Q

What is another term for Carcinogenesis?

A

Tumorigenesis

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17
Q

What is carcinogenesis?

A

The formation of cancer

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18
Q

What is the most significant late stochastic effect?

A

Cancer

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19
Q

What is the occurrence of cancer and the threshold?

A

Random occurrence that does not have a threshold

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20
Q

Is the severity of cancer dose related?

A

No

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21
Q

How is a radiation dose-response relationship demonstrated?

A

Graphically through a curve

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22
Q

What does a radiation dose-response graph map?

A

The observed effects of radiation exposure in relation to the dose of radiation received

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23
Q

What is represented on the horizontal axis of the graph?

A

Dose received

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24
Q

What is represented by the vertical axis of the graph?

A

Biological effects observed

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25
Q

What is a general rule of the DR relationship?

A

As radiation dose escalated so do most effects

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26
Q

What are the DR relationship graphs used for?

A

To predict the risk of occurrence of malignancies in human populations that have been exposed to low levels of ionizing radiation

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27
Q

How are the observed effects of radiation demonstrated?

A

By the incidence of a disease or the severity of an effect

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28
Q

What are the two types of DR curves?

A

Linear and non-linear

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29
Q

What are the two types of threshold records in a DR curve?

A

Threshold or non-threshold

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30
Q

What is a Sigmoid DR curve?

A

An S shaped curve (non-linear)

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31
Q

What are Sigmoid curves generally used for?

A

In radiation therapy to demonstrate high-dose cellular response

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32
Q

What is a threshold?

A

A point at which a response or reaction to an increasing stimulation first occurs

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33
Q

How does threshold apply to radiation?

A

It means that below a certain radiation level or dose, no biological effects are observed

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34
Q

When would biological effects begin with a threshold relationship?

A

Only when the threshold or dose level is reached

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35
Q

What is non-threshold as it pertains to radiation?

A

Indicates that the radiation absorbed dose of any magnitude has the capability of producing biological effects

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36
Q

For the linear non-threshold curve, what is the relationship between dose and biological effects?

A

Directly proportional, the severity of biological effects increase directly with the magnitude of absorbed dose

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37
Q

What is a general rule of nonthreshold doses?

A

That no radiation dose can be considered absolutely safe

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38
Q

What is BEIR?

A

Committee on the Biological Effects of Ionizing Radiation

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39
Q

What did the BEIR committee concluded in 1980?

A

That most stochastic and hereditary effects at low dose levels from low-LET radiation, follow a linear-quadratic non-threshold dose response curve

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40
Q

What did BEIR do in 1990?

A

Revised risk estimates to conclude that the risk of radiation exposure was about 3-4 times greater than previously projected

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41
Q

What type of DR curve does the BEIR committee recommend for most types of cancer?

A

Linear non-threshold curve

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42
Q

What does the LNT curve imply?

A

That the biological response to ionizing radiation is directly proportional to the dose received

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43
Q

What must radiographers never fail to employ with diagnostic imaging?

A

Aggressive radiation safety measures since it follows an LNT curve and all radiation exposure levels possess the potential to cause biological damage

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44
Q

What does the BEIR committee believe the LQNT model is more accurate to reflect?

A

The stochastic and genetic effects at low-dose levels from low-LET radiation

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45
Q

What effects are presumed to follow the LQNT curve?

A

Leukemia, breast cancer and heritable damage

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46
Q

What acute reactions to radiation exposure are demonstrated through a linear threshold dose-response curve?

A

Skin erythema and hematological depressions

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47
Q

Why are Sigmoid curves best used for radiation therapy?

A

They demonstrate high-dose cellular responses to radiation absorbed within specific locations, such as skin, lens of the eye and blood cells

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48
Q

What does the curve indicate for different effects?

A

Different effects require different minimal doses

49
Q

What happens at the tail of the sigmoid curve?

A

Indicates that limited recovery occurs at lower doses

50
Q

For the highest radiation doses what happens to the curve?

A

The curve gradually levels off and then veers downward because the specimen or tissue dies before observable effects appear

51
Q

What does continued use of the linear dose-response model have the potential to do?

A

Exaggerate the seriousness of radiation effects at lower dose levels from low-LET radiation

52
Q

What id the linear dose response model accurate in representing?

A

The effects of high-LET radiation at higher doses

53
Q

What approach have regulatory agencies adopted when assessing risk?

A

Use a conservative approach that may overestimate risk but will not underestimate it

54
Q

What are somatic effects?

A

When living organisms that have been exposed to radiation sustain biological damage

55
Q

What are the two classifications of somatic effects?

A

Stochastic and tissue reactions

56
Q

What are is a general rule of stochastic effects?

A

The probability that the effect happens depends on the dose received, but the severity of the effect is not based on dose

57
Q

What is an example of stochastic effect?

A

Occurrence of cancer

58
Q

What is a general rule for tissue reactions?

A

Both the probability and the severity of the effect depend upon dose

59
Q

What is an example of tissue reactions?

A

Cataracts

60
Q

What are the full list of Late Tissue reactions?

A
  • Cataract formation
  • Fibrosis
  • Organ atrophy
  • Loss of parenchyma cells
  • Reduced fertility
  • Sterility
61
Q

What are Teratogenic effects?

A

Effects of radiation on the embryo-fetus in utero that depend on the fetal stage of development and radiation dose received

62
Q

What are types of Teratogenic effects?

A
  • Embryonic, fetal or neonatal death
  • Congenital malformations
  • Decreased Birth weight
  • Disturbances in growth/development
  • Increased stillbirths
  • Infant mortality
  • Childhood malignancy
  • Childhood mortality
63
Q

What are the two types of stochastic effects?

A

Cancer and Genetic effects

64
Q

What are late somatic effects?

A

Consequences of radiation exposure that appear months or years after exposure

65
Q

What do late somatic effects result from?

A
  • previous whole or partial body acute exposure
  • previous high radiation doses
  • long term low level doses sustained over several years
66
Q

Why are risk estimates for humans contracting cancer from low level radiation controversial?

A

There is no conclusive proof that low level IR exposure below 0.1 Gy cause any significant increase in risk of cancer

67
Q

What are the 3 categories of adverse health consequences that the medical community believes require studies on at low-level?

A
  • cancer induction
  • damage to the unborn from irradiation in utero
  • genetic effects
68
Q

What does cells that survive initial irradiation possess?

A

They retain a “memory” of the event which are responsible for producing late effects

69
Q

In theory, what cells or organs could produce stochastic effects?

A

Damage to one or a few cells can produce stochastic effects

70
Q

What is the relationship between tissues reactions and late onset?

A

Typically tissue reactions do not usually demonstrate a late onset

71
Q

What are the 3 major types of late effects?

A
  • carcinogenesis
  • cataractogenesis
  • embryologist effects
72
Q

Which type of radiation dose can risk be measure for in human populations?

A

High doses of

73
Q

Why are low dose risk non directly measurable?

A

The risk is overshadowed by other causes of cancers in humans or the risk could be 0

74
Q

How are risk estimates for cancer determined for low-doses?

A

High dose data is extrapolated, where risk has been directly observed, and just applied to low-doses

75
Q

What are terms are risk models usually given in?

A

Absolute risk or Relative risk

76
Q

What do both risk models predict?

A

The number of excess cancers, or cancers that would not have occurred in the population in question without the exposure to ionizing radiation

77
Q

What does the absolute risk model forecast?

A

Forecasts that a specific number of malignancies will occur as a result of exposure

78
Q

What does the relative risk model forecast?

A

That the number of excess cancers will increase as the natural incidence of cancer increases with the advancing age of the population

79
Q

What have epidemiological studies for determining risk of cancer for diagnostic radiology?

A

That the benefit to that patient of the information gained from imaging greatly exceeds the minimal theoretical risk

80
Q

What type of effect does 1989 BEIR V report the LQNT model be used for?

A

Leukemia

81
Q

What model does BEIR Committee recommend Linear model be used for?

A

All other cancers

82
Q

How does the linear model apply to the occurrence of cancer from high and low doses?

A

Accurately assesses the risk for high dose information but exaggerates risk for low doses

83
Q

How does the linear quadratic model apply to the occurrence of cancer from high and low doses?

A

The model satisfactorily assesses risk from high doses but underestimates the risk for low doses

84
Q

What has been used to prove ionizing radiation induces cancer?

A

Lab experiments with animals and statistical studies of human populations

85
Q

How long can it take for cancer to appear in humans?

A

May take 5 or more years

86
Q

How does the physical appearance of cancer from ionizing radiation compare to cancer from different agents?

A

They don’t appear different at all

87
Q

What human evidence exists for radiation carcinogenesis?

A
  1. Radium watch dial painters from the 1920s
  2. Uranium miners from 1950s
  3. Early medical radiation workers
  4. Atomic bomb survivors
  5. Patients with benign postpartum mastitis who were given radiation therapy
  6. Evacuees from Chernobyl
88
Q

How has the incidence of leukemia changed over the years?

A

It has slowly declined since the late 1940s

89
Q

How has the incidence of other radiation-induced malignancies changed over the years? The

A

They have continued to escalate since the 1950s

90
Q

What types of cancers has there been an increase in since the 50s?

A

Solid tumors such as thyroid, breast and bone cancer

91
Q

In general what is the rate of natural incidence of breast cancer in Japanese women?

A

Much lower than incidence in women from the US or Canada

92
Q

What have studies of Japanese atomic bomb survivors proven in regards to breast cancer?

A

That ionizing radiation can induce breast cancer and incidence of breast cancer in these women has risen with radiation dose

93
Q

What is the relative risk for breast cancer for female atomic bomb survivors?

A

Ranges form 4:1 up to 10:1

94
Q

What have studies from Japan identified regarding ionizing radiation as a cancer causing agent?

A

That high doses of IR cause cancer, but radiation isn’t a highly effective cancer causing agent

95
Q

What was revealed in follow-up studies of bomb survivors from 1950-1987?

A

An excess of only 250 cancer deaths were attributed to radiation exposure, meaning that of 300 survivors only 1 died due to malignancies attribute to radiation exposure

96
Q

What have more recent studies of the atomic bomb attacks revealed?

A

That more gamma radiation exposure and less neutron exposure caused radiation damage

97
Q

What is the percent breakdown of neutron vs gamma radiation from the atomic bomb?

A

10% neutron and 90% gamma radiation

98
Q

What radioactive material was spread as a result of the Chernobyl disaster?

A

Iodine-131 was spread and concentrates in the thyroid of those exposed

99
Q

What is the most pronounced health effect of Chernoybl?

A

Thyroid cancer

100
Q

What was administered to children in Poland and other countries to prevent thyroid cancer?

A

Potassium iodide

101
Q

What is nonspecific lifespan shortening?

A

The reduction of lifespans as the result of ionizing radiation exposure

102
Q

What effect does a single dose of 2 Gyt have on the eyes?

A

Induces the formation to cataracts

103
Q

What is the result of cataractogenesis?

A
  • partial or complete loss of vision
104
Q

What type of radiation is effective in producing cataracts?

A

Highly ionizing neutron radiation

105
Q

What type of DR curve do radiation induced cataracts follow?

A

Threshold non-linear dose response relationship

106
Q

What are the 3 stages of gestation?

A
  • Pre-implantation (0-9 days after conception)
  • Organogenesis (10 days post conception - 12 weeks)
  • Fetal stage (12 weeks to term)
107
Q

What does the period of gestation dictate when it pertains to exposure?

A

It dictates the effects of ionizing radiation

108
Q

What trimester is the most radiocensitive?

A

1st trimester because its when the embryo begins to divide

109
Q

At which stage of gestation is the embryo most susceptible to congenital abnormalities?

A

The organogenesis stage

110
Q

What happens to a embryo in the first two weeks of fertilization?

A

If the embryo is irradiated its certain death

111
Q

What happens to embryo sensitivity as the pregnancy progresses?

A

It decreases as gestation progress

112
Q

What were the embryonic effects from Chernobyl?

A

No apparent abnormalities were seen in babies born immediately after the explosion, but in the 5 years after higher effects were reported

113
Q

What are genetic effects?

A

Biological effects of ionizing radiation on future generations

114
Q

What are types of irradiation mutation?

A
  • radiation-induced damage to the DNA molecule in the sperm or ova of an adult
  • may manifest as various diseases or malformations
  • may be transmitted to successive generations
115
Q

What are spontaneous mutations?

A

Modifications of genetic material that occur naturally and without cause

116
Q

What are examples of spontaneous mutations?

A

Hemophilia, Huntington’s disease, sickle cell anemia, cystic fibrosis and hydrocephalus

117
Q

What are mutant genes incapable of?

A

Governing cells chemical reactions or controlling amino acid sequence

118
Q

What is doubling dose?

A

The radiation dose that causes the # of mutations occurring in a given generation to increase to 2X their original occurance

Radiation Protection (15 decks)

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