Chapter 9 Flashcards
Radiation-induced damage at the cellular level may lead to what type of damage
Somatic and genetic (late effects)
Examples of measurable late biologic damage
Cataracts
Leukemia
Genetic mutations
A science that deals with incidence, distriubution, and control of a disease in a population
Epidemiology
How are incident rates of irradiation-related malignancies determined
Comparing the natural incidence of cancer occuring in a human population with the incidence of cancer occuring in an irradiated population
Epidemiologic studies are of significant value to scientists to use the information from these studies to formulate:
Dose-response estimates
What are dose-response estimates used for
To predict the risk of cancer in human populations exposed to low doses of ionizing radiation
How are radiation dose-response relationships demonstrated on a graph
Observed effects of radiation exposure in relation to the dose of radiation received
What is the x-axis and y-axis of the radiation dose-response relationship curve
X-axis: Radiation dose
Y-axis: Biologic effects observed
How is the curve displayed for the radiation dose-response relationship
Linear or nonlinear
Threshold or nonthreshold
A point at which a response or reaction to an increasing stimulation first occurs
Threshold
What does threshold mean when it comes to ionizing radiation
Below a certain level, no biologic effects are observed
Any radiation dose has the capability of producing a biologic effect
Nonthreshold
Most stochastic effects and genetic effects at low dose levels from low-LET radiation, appear to follow what type of curve
Linear quadratic nonthreshold
BEIR committee recommends the use of what type of curve for most types of cancers
Linear nonthreshold
What does the LNT curve imply
The biologic response to ionizing radiation is direclty proportional to the dose received
BEIR committee believes the ___________ curve is a more accurate reflection of stochastic somatic and genetic effects
Linear-quadratic nonthreshold
Leukemia, breast cancer, and heritable damage are presumed to follow what curve
LQNT
Deterministic effects (skin erythema and hematologic depression) may be demonstrated graphically through what type of curve
Linear threshold
What type of curve depicts those cases for which a biologic response does not occur below a specific radiation dose
Linear threshold
What type of curve is used in radiation therapy to demonstrate high-dose cellular response
Sigmoid (nonlinear) threshold
When living organisms that have been exposed to radiation sustain biologic damage, the effects of this exposure are classified as:
Somatic effects
2 types of somatic effects
Stochastic
Deterministic
The probability that the effect happens depends upon the received dose, but the severity of the effect does not
Stochastic effects
Both the probability and the severity of the effect depend on the dose
Deterministic effects
Types of late deterministic effects
Cataract formations
Fibrosis
Organ atrophy
Loss of parenchymal cells
Reduced fertility
Sterility
Types of late stochastic effects
Cancer
Genetic effects
What effects show up months or years after radiation exposure
Late somatic effects
No conclusive proof exists that low-level ionizing radiation exposure below _____ causes a significant increase in the risk of malignancy
.1 Sv
What are the three categories of adverse health consequences that require study at low-levels of exposure
Cancer induction
Damage to the unborn
Genetic effects
Is carcinogenesis a stochastic or deterministic event
Stochastic
Is cataractogenesis a stochastic or deterministic event
Deterministic
Is embyologic a stochastic or deterministic event
Stochastic
Why is low dose risk not directly measurable in population studies
Risk is overshadowed by other causes
Risk is zero
This type of model predicts that a specific number of excess cancers will occur as a result of exposure
Absolute Risk Model
This type of model predicts that the number of excess cancers will increase as the natural incidence of cancer increases with advancing age in a population
Relative Risk Model
1989 BEIR V report supported the _______ model for leukemia only
Linear quadratic model
Most important late stochastic effect caused by exposure to ionizing radiation
Cancer
How many years does it take for cancer to develop in humans due to radiation
5+ years
Incidence of Leukemia has slowly declined; but other malignances have continuted to escalate. This includes a variety of tumors such as:
Thyroid
Breast
Lung
Bone
In general, Japanese women have a ________ incidence of breast cancer
Lower
Numerous studies of female survivors indicate a relative risk for breast cancer ranging from:
4:1 to 10:1
According to studies from Hiroshima and Nagasaki, for every 300 atomic bomb survivors, 1 died of a malignancy attributed to an average whole-body dose of appox:
0.14 Sv
Radiation-induced leukemia is assumed to follow a _________ dose-response curve
LNT
What was originally credited with the radiation dose and damage in Hiroshima
Neutrons
What was the bomb filled with that dropped on Hiroshima
Uranium fuel
What type of radiation inflicted the population of Hiroshima
50% gamma, 50% neutron
What type of radiation inflicted the population of Nagasaki
10% neutrons, 90% gamma
What was in the bomb released over Nagasaki
Plutonium
What was given to children after the Chernobyl disaster to prevent thyroid cancer
Potassium iodide
High probability that a single dose of ___ Gy will induce the formation of cataracts
2
Responsible for genetic mutations
Mutagens
Causes of genetic mutations
Radiation-induced damange to DNA
Natural spontaneous mutations
Resultant genetic disorders or diseases
Major types of late effects
Carcinogenesis
Cataractogenesis
Emryologic
What was the most pronounced health effect observed 10 years following the Chernobyl nuclear accident
Increase in thyroid cancer in children
