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Radiology Biology & Protection > Chapter 9: Stochastic Effects and Late Tissue Reactions of Radiation in Organ Systems > Flashcards

Chapter 9: Stochastic Effects and Late Tissue Reactions of Radiation in Organ Systems Flashcards

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1
Q

Radiation-induced damage at the cellular level may lead to measurable somatic and hereditary damage in the living organism as a whole later in life

A

Late effects

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2
Q

examples of measurable delayed biologic damage are:

A
  • Cataracts
  • Leukemia
  • Genetic mutations
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3
Q

are the long-term results of radiation exposure
- months and years later

A

late effects

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4
Q

Cataracts are considered to be a

A

late tissue reaction that is nonrandom

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5
Q

whereas leukemia and genetic mutations are viewed as

A

delayed stochastic or random consequences that, if these reactions do appear, they do not do so for extended periods.

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6
Q

occurs months or years after radiation exposure

A

late tissue reactions

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7
Q

is a “science that deals with the incidence, distribution, and control of disease in a population.” (Travis, 1989)

A

Epidemiology

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8
Q

studies consist of observations and statistical analysis of data, such as the incidence of disease within groups of people.

A

Epidemiology

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9
Q

The incident rates at which these irradiation-related malignancies occur are determined by comparing the natural incidence of cancer occurring in a human population with the prevalence of cancer occurring in an irradiated population.

A

Epidemiology

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10
Q

The later studies include the risk of radiation-induced cancer.

A

Epidemiology

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11
Q

Risk factors are then identified for the general human population

A

Epidemiology

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12
Q

studies are of significant value to radiobiologists who use the information from these studies to formulate dose–response estimates for predicting the risk of cancer in human populations exposed to low doses of ionizing radiation.

A

Epidemiologic

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13
Q

also called tumorigenesis, is the formation of a cancer

A

Carcinogenesis

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14
Q

Carcinogenesis, also called

A

tumorigenesis

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15
Q

is the most significant late stochastic effect caused by exposure to ionizing radiation

A

Cancer

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16
Q

Cancer is the name used for a substantial group of diseases in which healthy cells have been transformed into nonstandard cells that divide uncontrollably. The process leads to an expansive growth of abnormal structures within various locations in the body and the destruction of surrounding body tissues such as bone marrow. The altered or cancer cells readily demonstrate the potential to invade or spread to other parts of the body.

A

Carcinogenesis

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17
Q

is demonstrated graphically through a curve (the dose–response [DR] curve) that maps the observed effects of radiation exposure in relation to the dose of radiation received.

A

radiation dose–response relationship

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18
Q

Information obtained can be used to attempt to predict the risk of occurrence of malignancies in human populations that have been exposed to low levels of ionizing radiation

A

radiation dose–response relationship

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19
Q

The “effect” in question may be the incidence of a disease (e.g., cases of cancer per million in a population or fatalities due to cancer per million in a population), or the effect may be its degree of acuteness, such as the severity of cataracts as dose increases.
- The observed effects of radiation exposure may be the incidence of a disease, or it may be the severity of an effect

A

radiation dose–response relationship

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20
Q

The DR curve is either linear (straight line) or nonlinear (curved to some degree), and it depicts either a threshold dose or a nonthreshold dose

A

radiation dose–response relationship

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21
Q

straight line

A

linear

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22
Q

curved to some degree

A

nonlinear

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23
Q

medical term for eyes

A

cataracts

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24
Q

blood

A

leukemia

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25
Q

offspring

A

genetic mutations

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25
Q

cancer is

A

random

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25
Q

long term effects use what kind of dose

A

low doses of radiation

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26
Q

short term effects use

A

high doses of radiation

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26
Q

increase radiation

A

increase biological damage

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27
Q

anything below .1 sievert

A

cannot be measured

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28
Q

anything above .1 sievert

A

can be measured

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29
Q

is defined as a point or level at which a response or reaction to an increasing stimulation first occurs

A

threshold

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29
Q

means up to a certain point there’s no biological response. after it passes point there is

A

threshold

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30
Q

this means that below a certain absorbed radiation dose, no biologic effects are observed

A

threshold

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31
Q

The biologic effects begin to occur only when what kind of dose is reached

A

threshold

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32
Q

no dose is a safe dose

A

non threshold

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33
Q

indicates that a radiation absorbed dose of any magnitude has the capability of producing a biologic effect

A

non threshold

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34
Q

No radiation dose can be considered absolutely safe with the severity of the biologic effects increasing directly with the magnitude of the absoradiation not a direct effect

A

nonthreshold

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35
Q

how does linear effect radiation

A

direct effect to radiaton

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36
Q

how does non linear effect radiation

A

not a direct effect

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37
Q

biologic effect responses will be caused by ionizing radiation in living organisms in a directly proportional manner at any dose above zero

A

linear nonthreshold

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38
Q

biologic effect responses will be caused by ionizing radiation in living organisms in a directly proportional manner all the way down to dose levels approaching zero

A

linear nonthreshold

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39
Q

proclaims that no radiation dose can be considered absolutely “safe,” with the incidence of the biologic effects increasing directly with the magnitude of the absorbed dose.

A

a linear nonthreshold (LNT) relationship.

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40
Q

what is the radiation doubling equivalent dose for humans?

A

1.56 Sv

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41
Q

is the radiation dose that causes the number of spontaneous mutations occurring in a given generation to increase to two times their original number

A

doubling dose

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42
Q

what is the most important late effect

A

cancer

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43
Q

below how many sieverts cannot be measured

A

0.1

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44
Q

is long term low or high doses

A

low doses

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45
Q

is short term high or low doses

A

higher doses

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46
Q

implies that the equation that best fits the data has components that depend on dose to the first power (linear or straight-line behavior) and also on dose squared (quadratic or curved behavior).

A

linear-quadratic

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47
Q

recommends the use of the linear nonthreshold curve of radiation dose–response (LNT DR) for most types

A

of cancers

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48
Q

if the absorbed dose is doubled, the biologic response probability, and therefore its actual occurrence in a large population sample, is also doubled

A

linear nonthreshold curve (LNT DR)

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48
Q

quadratic means

A

unknown is over estimated

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49
Q

what graph does diagnostic radiology follow

A

linear-quadratic nonthreshold

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50
Q

This curve displays a more conservative dose–response outcome for low-level radiation

A

linear-quadratic nonthreshold dose ( LQNT DR)

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51
Q

relationship to be an improved reflection of stochastic and genetic effects at low-dose levels from low-LET radiation

A

linear-quadratic nonthreshold dose ( LQNT DR)

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52
Q

implies that the biologic response to ionizing radiation is directly proportional to the dose received

A

Linear nonthreshold (LNT)

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53
Q

what does a tail in a graph mean

A

recovery or death

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54
Q

what means random or unknown

A

stochastic

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55
Q

what does radation protection fall under in regards to radiation dose- response

A

linear non threshold

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56
Q

The curve estimates the risk associated with low-dose levels from low LET radiation

A

Linear quadratic nonthreshold

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57
Q

what committee believes that the linear-quadratic nonthreshold curve (LQNT) is a more accurate reflection of stochastic somatic and genetic effects at low-dose levels from low-LET radiation.

A

BEIR committee

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58
Q

to be an improved reflection of stochastic and genetic effects at low-dose levels from low-LET radiation

A

Linear quadratic nonthreshold ( LQNT)

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59
Q

What curve does leukemia , breast cancer, and heritable damage follow

A

Linear quadratic nonthreshold ( LQNT)

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59
Q

what does leukemia follow

A

LQNT

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60
Q

what does breast cancer follow

A

LQNT

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61
Q

what does heritable damage follow

A

LQNT

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61
Q

long term effect follow what kind of radiation

A

low let radiation

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62
Q

short term effects follow what kind of radiation

A

high LET radiation

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63
Q

This depicts those cases for which a biologic response does not occur below a specific radiation dose

A

linear threshold

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64
Q

what curve represents skin erythema and hematologic depression

A

linear threshold

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65
Q

what curve does skin erythema follow

A

linear threshold

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66
Q

what curve does hematologic depression follow

A

linear threshold

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67
Q

Laboratory experiments on animals and data from human populations observed after high doses of radiation provided the foundation for this curve

A

linear threshold dose–response curve (LT DR)

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68
Q

is generally employed in radiation therapy to demonstrate the high-dose cellular response to the radiation absorbed doses within specific tissues, such as skin, the lens of the eye, and various types of blood cells.

A

sigmoid, or S-shaped (nonlinear), threshold curve

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68
Q

Sigmoid or S shaped

A

nonlinear

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68
Q

indicates that limited recovery occurs at lower radiation doses

A

tail of the curve

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69
Q

the curve gradually levels off and then veers downward because the affected living specimen or tissue dies before the observable effect appears

A

at the highest radiation doses
(tail)

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70
Q

what curve does radiation therapy use

A

nonlinear threshold

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70
Q

The continued use of the linear dose–response model for radiation protection standards has the potential to exaggerate the seriousness of radiation effects at lower dose levels from low-LET radiation. Regulatory agencies such as the Nuclear Regulatory Commission continue to review scientific literature to determine if the evidence supports changes in the use of this model for setting radiation protection standards. In establishing such standards, the regulatory agencies have chosen to be conservative—that is, to use a model that may overestimate risk at low doses but is not expected to underestimate risk.

A

The rationale for risk model selection

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71
Q

When living organisms that have been exposed to radiation sustain biologic damage, the effects of this exposure are classified as

A

Somatic effects

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72
Q

somatic effects, from the Greek sōmatikos, meaning

A

“of the body.”

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73
Q

The classification of somatic effects may be subdivided into:

A
  • stochastic effects
  • tissue reactions
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74
Q

the probability that the effect occurs depends upon the received dose, but the severity of the effect does not

A

stochastic effects

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75
Q

random / unknown
- is it going to happen or not
example: occurrence of cancer

A

stochastic effects

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76
Q

both the probability and the severity of the effect depend upon the dose.

A

tissue reactions (deterministic)

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77
Q

is going to happen
- increase dose increase severity
example: a cataract

A

tissue reactions

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78
Q

is an effect in the offspring of the individual who was irradiated.

A

A non-somatic effect

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78
Q

An example of a non-somatic effect is

A

the irradiation of an individual’s genetic material (sperm or eggs) leading to a genetic malformation in offspring

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79
Q

are consequences of radiation exposure that appear months or years afterwards

A

Late somatic effects

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79
Q

Late effects may be either

A

stochastic or tissue reactions

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80
Q

such as the incidence of cancers in a population, typically are not noticeable for many years in the exposed population.

A

Stochastic effects

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81
Q

such as skin effects, may be perceptible sooner in individuals, although months or years may pass before their full expression.

A

Tissue reactions

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82
Q

are the result of slowly developing changes to body tissues that may be modified by other factors, such as medical intervention, after the exposure.

A

Tissue reactions

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83
Q

such as the occurrence of cancer, are generally determined at the time of irradiation.

A

Stochastic effects

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84
Q

examples of late tissue reactions

A
  • Cataract formation
  • Fibrosis
  • Organ atrophy
  • Loss of parenchymal cells
  • Reduced fertility
  • Sterility
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85
Q

examples of Teratogenic effects

A

(i.e., effects of radiation on the embryo-fetus in utero that depend on the fetal stage of development and the radiation dose received)
- Embryonic, fetal, or neonatal death
- Congenital malformations
- Decreased birth weight
- Disturbances in growth and/or development
- Increased stillbirths
- Infant mortality
- Childhood malignancy
- Childhood mortality

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86
Q

examples of stochastic effects

A

Cancer
Genetic (hereditary) effects

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87
Q

late somatic effects may result from

A

Previous whole- or partial-body acute exposure
Previous high radiation doses
Long-term low-level doses sustained over several years

88
Q

Absolutely going to happen

A

Absolute risk

89
Q

looking at the probability

A

relative risk

90
Q

effects happening to fetus

A

teratogenic effects

91
Q

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

A

teratogenic effects

91
Q

examples of Teratogenic Effects

A

-embryonic, fetal, neonatal death
-congenital malformations
-decreased birth weight
-disturbance in growth and or development
-increased stillbirths
-infant mortality
-childhood malignancy
-childhood mortality

92
Q

Using all data available on high radiation exposure, members of the scientific and medical communities determined that three categories of adverse health consequences require study at low-levels of exposur

A

Cancer induction
Damage to the unborn from irradiation in utero
Genetic (hereditary) effect

93
Q

Low-level doses are a consideration for patients and personnel exposed to ionizing radiation as a result of diagnostic imaging procedures.
The risk estimate for humans contracting cancer from low-level radiation exposure is still controversial.
No conclusive proof exists that low-level ionizing radiation exposure below 0.1 Gy causes a significant increase in the risk of malignancy.
Risk may be negligible or even nonexistent

A

Risk Estimate for Contracting Cancer fromLow-Level Radiation Exposure

94
Q

Sources of such low-level radiation include the following:

A
  • X-rays and radioactive materials used for diagnostic purposes
  • Employment-related exposures in medicine and industry
  • Natural background exposure
95
Q

Cells that survive the initial irradiation may have incurred some form of damage.
Theoretically, radiation damage to just one or a few cells of an individual could actually produce a stochastic effect such as a malignancy or a hereditary disorder many years after radiation exposure.
Tissue reactions such as skin reactions do not usually demonstrate a late onset.
Extreme reactions associated with high skin doses may persist for some time, but will usually occur in weeks or months after the exposure

A

late effects
( Low-level effects)

96
Q

Tissue reactions such as skin reactions do not usually demonstrate a late onset you only see it when

A

when you can only see it in the beginning

97
Q

cells can either

A
  • survive
  • be damage
  • have cell death
98
Q

the three major types of late effects are:

A
  • Carcinogenesis
  • Cataractogenesis
  • Embryologic effects (birth defects)
99
Q

Carcinogenesis is considered a

A

stochastic event random which is your cancer

100
Q

Cataractogenesis is considered a

A

late tissue reactions is known you are going to get it

101
Q

Embryologic effects (birth defects) is considered a

A

stochastic events random not known if it will happen or not

102
Q

Exposure to ionizing radiation may cause cancer as a

A

stochastic effect

103
Q

At low equivalent doses, below 0.1 Sv, which includes groups such as occupationally exposed individuals and virtually all patients in diagnostic radiology, this risk is not directly measurable in population studies.
Reasons::

A

*The risk is overshadowed by other causes of cancer in humans.
*The risk is zero

104
Q

at high doses how is the risk measurable

A

At high doses, the risk is measurable in exposed human populations

105
Q

:Utilizes the linear nonthreshold dose–response relationship and assumes that risk still exists
May be determined by extrapolating from high-dose data, in which the risk has been directly observed, down to the low doses, in which it has not been observed (a controversial concept)

A

Current radiation protection philosophy

106
Q

-May be given in terms of absolute risk or relative risk caused by a specific exposure to ionizing radiation (over and above background exposure)
-Both models predict the number of excess cancers, or cancers that would not have occurred in the population in question without the exposure to ionizing radiation

A

Risk Estimates To Predict Cancer Incidence

107
Q

This model forecasts that a specific number of malignancies will occur as a result of exposure. definitely going to happen

A

absolute risk

108
Q

model predicts that the number of excess cancers will increase as the natural incidence of cancer increases with advancing age in a population. in the sense that this model predicts a percentage increase in incidence rather than a specific number of cases.
- a probability type of a model
- increase radiation dose increase probability of biological damage

A

relative risk

109
Q

suggest that although the radiation doses received by patients in diagnostic radiology imaging could be considered in determining the risk of cancer, the benefit to the patient of the information gained from an imaging procedure greatly exceeds the minimal theoretical risk to the patient for developing cancer as a late stochastic response to diagnostic radiation exposure.

A

Epidemiologic Studies for Determining the Risk of Cancer

110
Q

Researchers commonly use two models for extrapolation of risk from high-dose to low-dose data,

A

Linear
Linear-quadratic

111
Q

-supported the linear-quadratic model for leukemia only
- For all other cancers recommended adoption of the linear model to fit the available data.

A

BEIR V Committee

112
Q

is the most important late stochastic effect caused by exposure to ionizing radiation

A

cancer

113
Q

This reaction is a random occurrence that does not seem to have a threshold and for which the severity of the disease is not dose-related

A

Carcinogenesis (Cancer)

114
Q

Laboratory experiments with animals and statistical studies of human populations exposed to ionizing radiation prove that radiation induces:

A

cancer

115
Q

a patient’s leukemia induced by a low-dose exposure is no different from a person’s leukemia that was caused by a high-dose exposure)

true or false

A

true

115
Q

cancer is

A

random and unknown

116
Q

may take 5 or more years to develop in humans

A

radiation induced cancer

117
Q

true or false:
Cancer caused by low-level radiation is difficult to identify

A

true

118
Q

true or false
The physical appearance of cancer induced by ionizing radiation does not appear different than a cancer caused by other agents.

A

true

119
Q

first radiation induce cancer happened when

A

1902

120
Q

Human evidence of radiation carcinogenesis comes from

A

epidemiologic studies conducted many years after subjects were exposed to high doses of ionizing radiation

121
Q

which cancer is more common

A

Cancer from natural causes family cancer

122
Q

Incidence of leukemia has slowly declined since the late 1940s and early 1950s.Occurrence rates of other radiation-induced malignancies have continued to escalate since the late 1950s and early 1960s.Includes a variety of solid tumors such as thyroid, breast, lung, and bone cancers

A

Incidence of Leukemia Rate of Other Radiation-Induced Malignancies

123
Q

leukemia will have its peak at

A

5 years and then slowly down to zero

124
Q

every other type of cancer will peak at

A

at 10 years and then down to 30 and 40

125
Q

Hence radiation-induced leukemia is assumed to follow

A

an linear nonthreshold

126
Q

The 1986 nuclear power station accident at Chernobyl requires long-term follow-up studies to assess the magnitude and severity of late effects on the exposed population. Detailed observations investigating potential increases in the

A

incidence of leukemia, thyroid problems, breast cancer, and other possible radiation-induced malignancies will continue.

127
Q

Radiation was then believed to have accelerated all causes of death. This reduction in the life cycle is known as

A

nonspecific life span shortening

128
Q

true or false
Incidence of leukemia has slowly declined since the late 1940s and early 1950s

A

true

129
Q

what type of cancer would develop after five years and then dwindle off

A

leukemia

130
Q

this type of cancer is the same low vs high dose

A

leukemia

130
Q

what cancer would you see after ten years and then it would peak down the road

A

any other cancer other than leukemia

130
Q

The probability that a single dose of ionizing radiation of approximately 2 Gyt will induce the formation of

A

cataracts (Cataractogenesis)

131
Q

at what dose will you get cataracts

A

2 Gy

132
Q

what is the threshold for cataracts to form

A

0.5 gy

133
Q

what curve does cataracts follow

A

non linear threshold

134
Q

what is the most sensitive part of the eye when it comes to radiation

A

the lens

135
Q

The lens of the eye contains

A

transparent fibers that transmit light

136
Q

result of cataractogenesis

A

Partial or complete loss of vision
Results of laboratory experiments with mice
Radiation-induced cataracts in humans follow a threshold, nonlinear dose–response relationship

136
Q

Evidence of human radiation cataractogenesis originates from

A

the observation of small groups of people who accidentally received substantial doses to the eyes

137
Q

Gestation in humans is divided into three stages or periods:

A
  1. Preimplantation
  2. Organogenesis,
  3. The fetal stage
138
Q

0-9 days
-if you received 0.05-0.15 gy there will be death of the baby

A

preimplantation

139
Q

what is the preimplantation stage

A

which corresponds to 0 to 9 days after conception

140
Q

how much dose recieved will cause death of the baby in preimplantation

A

the range of 0.05 to 0.15 Gyt,

141
Q

what is the organogenesis stage

A

which lasts approximately from 10 days postconception to 12 weeks after conception

142
Q

which is the most susceptible stage of gestation
- most sensitive least resistant

A

organogenesis
(because its the first trimester)

142
Q

Abnormalities may include:
* skeletal damage
* Growth inhibition
* Intellectual disability
* Microcephaly
* Genital deformities
* Sensory organ damage

A

organogenesis

143
Q

what is the fetal stage

A

which extends from the 12th week to term

144
Q

true or false
the further you are along in pregnancy, the more mature the baby is

A

true

145
Q

Fetal radiosensitivity decreases

A

as gestation progresses

146
Q

during the second and third trimesters of pregnancy when lesser numbers of cells are differentiating, the developing fetus is

A

less susceptible to ionizing radiation exposure

147
Q

most sensitive part in trimester

A

first trimester

148
Q

stem cells are

A

immature and very sensitive

149
Q

first trimester most sensitive then

A

third trimester

150
Q

Biologic consequences of ionizing radiation on future generations are termed

A

genetic or hereditary effects

151
Q

They can occur as a result of radiation-induced damage to the DNA molecule in the sperm or ova of an adult, leading to germ cell alterations, which cause incorrect genetic information to be transmitted to the offspring.

A

irradiated mutations

152
Q

Cause of genetic mutations:

A

Radiation-induced damage to the DNA molecule in the sperm or ova of an adult
Natural spontaneous mutations
Resultant genetic disorders or diseases

153
Q

what percentage of all births have some sort of hereditary disorder

A

10%

153
Q

what level does genetic mutations happen

A

molecular level

153
Q

radiation dose required to double the genetic diseases

A

doubling dose

154
Q

what curve is cataracts

A

nonlinear threshold and nonstochastic

154
Q

what curve is thyroid

A

Linear nonthreshold and stochastic

154
Q

what curve is breast cancer

A

Linear non threshold and stochastic

155
Q

what curve is bone marrow

A

linear threshold

156
Q

what curve is skin

A

Non stochastic(deterministic) and threshold

157
Q

in men, what dose causes permanent sterility

A

5-6 gy

157
Q

what curve is stochastic

A

Follows nonthreshold

157
Q

what curve is deterministic

A

follow a threshold
-tissue reactions

158
Q

who holds and who doesnt

A

students dont hold
-occupational radiological workers don’t hold
-male before female in child bearing age

159
Q

who should hold:
-65 yo radiologist
-40 yo male tech
-25 yo student tech
-21 female nurse

A

the 21 yo female nurse

160
Q

who should hold
-60 yo male tech
-42 yo baby mama
-21 yo baby daddy
58 yo gma

A

-the 58 yo gma

161
Q

what curve is skin erythema

A

Linear Threshold

162
Q

what curve is hemotologic depression

A

linear threshold

163
Q

what curve is cataractogenesis

A

linear threshold

164
Q

what curve is radiation protection

A

linear non threshold

165
Q

what curve is radiation therapy

A

nonlinear threshold

165
Q

what curve is teratogenic

A

nonlinear threshold

166
Q

what curve is diagnostic xray

A

LQNT

167
Q

what curve is leukemia

A

LQNT

168
Q

what curve is breast cancer

A

LQNT

168
Q

what curve is heretiable damge

A

LQNT

169
Q

Some modifications in genetic material occur naturally, without a known cause. They are referred to as
- These can be transmitted from one generation to the next and may cause a wide variety of disorders or diseases,

A

spontaneous mutations

169
Q

increase radiation dose increase biological damage

A

increase chance of mutations

170
Q

a dominant gene is

A

a gene pass to the offspring

171
Q

what is a recessive gene

A

a gene pass on to it future generations

171
Q

Point mutations (genetic mutations at the molecular level) may be either

A

dominant (probably expressed in the offspring) or recessive (perhaps not expressed for several generations).

172
Q

Radiation is thought to cause primarily

A

recessive mutations

172
Q

Radiation-induced hereditary effects in humans have not been demonstrated

A

persons employed in diagnostic imaging or in patients undergoing radiologic examinations

173
Q

is, by definition, the radiation dose that causes the number of spontaneous mutations occurring in a given generation to increase to two times their original occurrence

A

doubling dose

174
Q

the radiation doubling dose for humans, as determined from studies of the children of the atomic bomb survivors of Hiroshima and Nagasaki, is estimated to have a mean value of

A

1.56 Sv

175
Q

A linear nonthreshold (LNT) curve is currently used for most types of

A

cancers

175
Q

Risk of leukemia, breast cancer, and genetic effects associated with low-level radiation is typically estimated with the

A

linear-quadratic nonthreshold (LQNT) curve

175
Q

Late tissue reactions may be demonstrated graphically through the use of

A

a linear threshold (LT) curve of radiation dose–response.

176
Q

High-dose cellular response may be demonstrated through the use of a

A

(nonlinear) sigmoid threshold curve.

176
Q

Late effects include:

A
  • carcinogenesis,
  • cataractogenesis,
  • embryologic (birth) defects.
176
Q

Effects thaestimates that a specific number of malignancies will occur as a result of radiation exposure.t have no threshold, that occur arbitrarily, that have a severity that does not depend on dose, and that occur months or years after exposure are called

A

stochastic effects

177
Q

is the most significant stochastic somatic effect caused by exposure to ionizing radiation.

A

cancer

177
Q

estimates that a specific number of malignancies will occur as a result of radiation exposure

A

The absolute risk model

178
Q

predicts that the number of excess cancers rises as the natural incidence of cancer increases with advancing age in a population.

A

The relative risk model

179
Q

are used for extrapolation of risk from high-dose to low-dose data.

A

Linear and linear-quadratic models

180
Q

Radiation-induced congenital abnormalities can occur approximately

A

from 10 days to 12 weeks after conception

180
Q

is the most critical period for radiation exposure of the embryo-fetus.

A

The first trimester of pregnancy

181
Q

skeletal abnormalities most frequently occur from

A

weeks 3 to 20

181
Q

Radiation exposure even in the second and third trimesters can potentially cause:

A
  • congenital abnormalities,
  • functional disorders,
  • predisposition to the development of childhood cancer
181
Q

measures the effectiveness of ionizing radiation in causing mutations; it is the radiation dose that causes the number of spontaneous mutations in a given generation to increase to two times their original occurrence.

A

Doubling dose

182
Q

For humans, the doubling dose is estimated to have a mean value of

A

1.56 Sv.

182
Q

lens of the eye in sievert

A

150 sv

183
Q

all other organs in sievert

A

500 sv

184
Q
  • killing the cells with high doses of radiation
  • threshold
  • appears above a given threshold
A

deterministic

185
Q
  • severity does not depend on dose
  • nonthreshold
  • random in nature
  • found in low dose radiation
  • cancer, genetic effects
A

stochastic effects

186
Q
  • random, unpredictable, probablistic
  • probability of an effect occuring increases with exposure
  • severity of an effect is not affected by the dose
  • no relationship between dose and severity
  • nonthreshold
  • cancer, genetic effects
  • linear nonthreshold model
A

stochastic

187
Q
  • predictable
  • effects occur at specific dose thresholds
  • examples; cataracts, epilation, skin erythema, decreased sperm counts
  • threshold model
A

deterministic

188
Q

states that NO level of radiation can be considered completely safe and the degree of response is directly proportional to the amount of radiation received

A

Linear-non threshold relationship

189
Q

States that a dose of radiation exists below which a response does not occur; when that threshold is crossed, the response is directly proportional to the dose received(i.e. cataractogenesis does not occur at low levels of radiation exposure; therefore there is a threshold, or a safe dose.

A

Linear-threshold relationship

190
Q

states that a safe (threshold) dose of radiation exists, when exceeded, results in responses that are not directly proportional to the dose received.

A

Nonlinear-threshold relationship

191
Q

States that no level of radiation can be considered safe and the degree of the response is not directly proportional to the dose received.

A

Nonlinear-non threshold relationship

191
Q

Randomly occurring effects of radiation; the probability of such effects is proportional to the dose ( increased dose equals increased probability, not severity, of effects.)

A

Stochastic effects

191
Q

Effects that become more severe at high levels of radiation exposure and do not occur below a certain threshold dose.

A

deterministic (non stochastic)

192
Q

means random in nature – probability of occurrence of effects, rather than severity, increase with dose (leukemia at 1 Gy is same at 1 cG

A

stochastic

193
Q

thought to be nonthreshold – damage to multiple or single cell can cause risk (linear and linear quadratic) – even small exposures can carry risk – risk proportional to dose with no threshold

A

stochastic

194
Q

– radiation induced cancer, radiation induced genetic effects

A

Stochastic effect

195
Q

are main health risk from low dose radiation in diagnostic

A

stochastic effects

195
Q

– thought to be threshold
– there are always doses below which the effect is not observed (cataracts, erythema, fibrosis, hemopoetic damage)
- relevant to serious radiation accidents
– not likely during diagnostic or occupational exposure
-Increase in severity with dose

A

Nonstochastic (deterministic)

196
Q

point at which a response or reaction to an increasing stimulation first occurs
-Below a certain radiation dose, no biological effects are observed

A

threshold

197
Q

any radiation dose has the capability of producing a biologic effect. No radiation dose is safe, exhibits some effect no matter how small

A

nonthreshold

198
Q

biological response to radiation is directly proportional to dose received, straight line when graphed

A

linear

198
Q

No fixed proportional response between dose and response, form a curved line when graphed

A

nonlinear

199
Q

Factors that affect dose mode

A

– time period over which radiation is delivered, age, state of health, time between exposures

200
Q

Early effects result from high radiation doses – they are all
– most frequent is skin injury higher the dose, faster the onset of symptoms

A

deterministic

201
Q

What examples fall under Linear Nonthreshold (LNT) curve?

A
  • stochastic
  • cancer
  • radiation protection
  • thyroid
  • breast tissue
202
Q

What examples fall under Linear Threshold (LT) curve?

A
  • skin erythemaa
  • hematologic depression
  • bone marrow
203
Q

What examples fall under Nonlinear Threshold (NLT) curve?

A
  • caractogenesis
  • radiation therapy
  • teratogenic effects
204
Q

What examples fall under Linear Quadratic Nonthreshold (LQNT) curve?

A
  • diagnostic x-ray
  • leukemia
  • breast cancer
  • heritable damage

Radiology Biology & Protection (9 decks)

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