Chapter 9 Flashcards
Means random in nature, probability of occurrence of events
Stochastic
is stochastic threshold or non threshold
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 thresh
stochastic effects
– radiation induced cancer, radiation induced genetic effects
Factors that affect radiation
- dose and rate
- oxygen
-age
-chromosomal effects
point at which a response or reaction to an increasing stimulation first occurs
- below a certain radiation dose, no biological effects are observed.
threshold
any radiation dose has the capability of producing a biologic effect. No radiation dose is safe, exhibits some effect no matter how small
nonthreshold
biological response to radiation is directly proportional to dose received, straight line when graphed
linear
No fixed proportional response between dose and response, form a curved line when graphed
nonlinear
Factors that affect dose mode
– time period over which radiation is delivered, age, state of health, time between exposures
True or false:
all early effects that result from high radiation doses are deterministic
true
what is also known as nonstochastic
deterministic
is deterministic threshold or nonthreshold
threshold - there are always doses below which the effectis not observed (cataracts, erythema, fibrosis, hemopoetic damage) - relevant to serious radiation accidents – not likely during diagnostic or occupational exposur
examples of deterministic
-cataracts
-erythema
-fibrosis
-hemopoietic damage
What are some examples of measurable late biological damage?
-cataracts
-leukemia
-genetic mutations
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. long term results of radiation exposure.
Late effects
A “science that deals with the incidence, distribution, and control of disease in a population.”
Epidemiology
what are some studies of epidemiology ?
Studies consist of:
-observations and statistical analysis of data, such as the incidence of disease within groups of people
- Studies include the risk of radiation-induced cancer
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 incidence of cancer occurring in an irradiated population
is demonstrated graphically through a curve that maps the observed effects of radiation exposure in relation to the dose of radiation received
Radiation dose–response relationship
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
radiation dose - response relationship
The observed effects of radiation exposure may be the incidence of a disease, or it may be the severity of an effect.
The curve is either linear or nonlinear and depicts either a threshold dose or a nonthreshold dose
Radiation Dose- Response Relationship
a point at which a response or reaction to an increasing stimulation first occur
threshold
means that below a certain radiation level or dose, no biologic effects are observed
threshold
Biologic effects begin to occur only when the threshold level or dose is reached
threshold
indicates that a radiation absorbed dose of any magnitude has the capability of producing a biologic effect
nonthreshold
No radiation dose can be considered absolutely safe with the severity of the biologic effects increasing directly with the magnitude of the absorbed dose
nonthreshold
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
what curve does this represent:
linear nonthreshold
what is the radiation doubling equivalent dose for humans?
1.56 Sv
is the radiation dose that causes the number of spontaneous mutations occurring in a given generation to increase to two times their original number
doubling dose
what is the most important late effect
cancer
below how many sieverts cannot be measured
0.1
is long term low or high doses
low doses
is short term high or low doses
higher doses
what is xrays an example of regarding radiation dose- response
linear quadratic
what means no dose is a safe dose?
nonthreshold
direct effect to radiation
linear
The straight-line curve passing through the origin in this graph indicates both that the response to radiation (in terms of biologic effects) is directly proportional to the dose of radiation and that no known level of radiation dose exists below which the chance of sustaining biologic damage is zer
linear nonthreshold
what does a tail in a graph mean
recovery or death
what means random or unknown
stochastic
what does rad protection fall under in regards to radiation dose- response
linear non threshold
curve implies that the biologic response to ionizing radiation is directly proportional to the dose received.
LNT
The curve estimates the risk associated with low-dose levels from low LET radiation
Linear quadratic nonthreshold
what curve do most committees recommend for response for most types of cancer
Currently the committee recommends the use of the linear nonthreshold curve of radiation dose–response for most types of cancer.
what committee believes that the linearr-quadratic nonthreshold curve (LQNT) is a more accurate reflection of stochastic somatic and genetic effects at low-dose levels from low-LET radiation.
BEIR committee
What curve does leukemia , breast cancer, and heritable damage frollow
LQNT
is a more accurate reflection of stochastic somatic and genetic effects at low-dose levels from low-LET radiation
LQNT
This depicts those cases for which a biologic response does not occur below a specific radiation dose
linear threshold
what curve represents skin erythema and hematologic depression
linear threshold
has the potential to exaggerate the seriousness of radiation effects at lower dose levels from low-LET radiatio
Continued use of the linear dose–response model for radiation protection standards
Sigmoid or S shaped
nonlinear
is generally employed in radiation therapy to demonstrate high-dose cellular response to the radiation absorbed within specific locations, such as skin, lens of the eye, and various types of blood cells
Sigmoid or S-shaped (nonlinear) Threshold curve of radiation dose–response relationship
indicates that limited recovery occurs at lower radiation doses
tail of the curve
, the curve gradually levels off and then veers downward because the affected living specimen or tissue dies before the observable effect appears
at the highest radiation doses
Absolute risk
Absolutely going to happen
relative risk
looking at the probability
relationship generally employed in radiation therapy to demonstrate high-dose cellular response
Sigmoid (S-shaped, hence nonlinear) threshold curve of radiation dose–response
When living organisms that have been exposed to radiation sustain biologic damage, the effects of this exposure are classified as
somatic (i.e., body) effect
The probability that the effect happens depends upon the received dose, but the severity of the effect does not.
*Example: Occurrence of cancer
Stochastic Effects
Both the probability and the severity of the effect depend upon the dose.
*Example: A cataract
Tissue Reactions
-cataracts formation
-fibrosis
-organ atrophy
-loss of parenchymal cells
-reduced fertility
-sterility
late tissue reactions
-cancer
-genetic effects
stochastic effects
effects happening to fetus
teratogenic effects
effects of radiation on the embryo -fetus in utero that depend on the fetal stage of development and the radiation dose recieved
Teratogenic Effects
-embryonic, fetal, neonatal death
-congenital malformations
-decreased birth weight
-disturbance in growth and or development
-increased stillbirths
-infant mortality
-childhood malignancy
-childhood mortality
Teratogenic Effects
Are consequences of radiation exposure that appear months or years after such exposure
late somatic effects
some late somatic effects may result from
Previous whole- or partial-body acute exposure
Previous high radiation doses
Long-term low-level doses sustained over several years
Previous whole- or partial-body acute exposure
Previous high radiation doses
Long-term low-level doses sustained over several years
Late somatic effects
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 exposure
Cancer induction
Damage to the unborn from irradiation in utero
Genetic (hereditary) effect
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
late effects
Major Types of Late Effects
Carcinogenesis (stochastic event)
Cataractogenesis (late tissue reaction)
Embryologic effects (birth defects) (stochastic events)
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::
*The risk is overshadowed by other causes of cancer in humans.
*The risk is zero
at high doses how is the risk measurable
At high doses, the risk is measurable in exposed human populations
what type of effect may exposure to ionizing radiation may cause cancer
stochastic effect
: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)
Current radiation protection philosophy
-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
Risk Estimates To Predict Cancer Incidence
This model forecasts that a specific number of malignancies will occur as a result of exposure
Absolute risk
This 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
Models used by researchers for extrapolation of risk from high-dose to low-dose data
Linear
Linear-quadratic
-supported the linear-quadratic model for leukemia only
- For all other cancers recommended adoption of the linear model to fit the available data.
BEIR V Committee
is the most important late stochastic effect caused by exposure to ionizing radiation
cancer
This effect is a random occurrence that does not seem to have a threshold and for which the severity of the disease is not dose-related
Carcinogenesis
Laboratory experiments with animals and statistical studies of human populations exposed to ionizing radiation prove that radiation induces:
cancer
may take 5 or more years to develop in humans
radiation induced cancer
true or false:
Cancer caused by low-level radiation is difficult to identify
true
true or false
The physical appearance of cancer induced by ionizing radiation does not appear different than a cancer caused by other agents.
true
first radiation induce cancer happened when
1902
what event is carcinogenesis
stochastic
what reaction is cataractogenesis
late tissue reaction
what event is embryologic effects (birth defects)
stochastic
Occurrence rates of other radiation-induced malignancies have continued to escalate since the late 1950s and early 1960s
Includes:
Includes a variety of solid tumors such as thyroid, breast, lung, and bone cancers
true or false
Incidence of leukemia has slowly declined since the late 1940s and early 1950s
true
what type of cancer would develop after five years and then dwindle off
leukemia
this type of cancer is the same low vs high dose
leukemia
what cancer would you see after ten years and then it would peak down the road
any other cancer other than leukemia
what type of cancer was seen a lot in chernobyl
-a lot of thyroid cancer
-increased risk of breast cancer
at what dose will you get cataracts
2 Gy
what is the threshold for cataracts to form
0.5 gy
what curve is cataracts
non linear threshold
what is the most sensitive part of the eye
the lens
result of cataractogenesis
Partial or complete loss of vision
Results of laboratory experiments with mice
Radiation-induced cataracts in humans follow a threshold, nonlinear dose–response relationship
stages of gestation in humans
-preimplantation
-organogenesis
-fetal stage
0-9 days
-if you received 0.05-0.15 gy there will be death of the baby
preimplantation
what is the preimplantation stage
0-9 days
how much dose recieved will cause death of the baby in preimplantation
0.05-0 .15gy
what is the organogenesis stage
10 days to 12 weeks
which is the most susceptible stage of gestation
organogenesis
(because its the first trimester)
what is the fetal stage
12 weeks to full term
true or false
the further you are along in pregnancy, the more mature the baby is
true
what percentage of all births have some sort of hereditary disorder
10 percent
what level does genetic mutations happen
genetic mutations happen at the molecular level
radiation dose required to double the genetic diseases
doubling dose
what curve is cataracts
nonlinear threshold and nonstochastic
what curve is thyroid
Linear nonthreshold and stochastic
what curve is breast cancer
Linear non threshold and stochastic
what curve is bone marrow
- Linear threshold
what curve is skin
Non stochastic(deterministic) and threshold
in men, what dose causes permanent sterility
5-6 gy
what curve is stochastic
Follows nonthreshold
what curve is dterministic
- follow a threshold
-tissue reactions
who holds and who doesnt
- students dont hold
-occupational radiological workers don’t hold
-male before female in child bearing age
who should hold:
-65 yo radiologist
-40 yo male tech
-25 yo student tech
-21 female nurse
the 21 yo female nurse
who should hold
-60 yo male tech
-42 yo baby mama
-21 yo baby daddy
58 yo gma
-the 58 yo gma
Cause of genetic mutations
Radiation-induced damage to the DNA molecule in the sperm or ova of an adult
Natural spontaneous mutations
Resultant genetic disorders or diseases
what curve is skin erythema
Linear Threshold
what curve is hemotologic depression
linear threshold
what curve is cataractogenesis
linear threshold
what curve is radiation protection
linear non threshold
what curve is radiation therapy
nonlinear threshhold
what curve is teratogenic
nonlinear threshold
what curve is diagnostic xray
LQNT
what curve is leukemia
LQNT
what curve is breast cancer
LQNT
what curve is heretiable damge
LQNT
examples of linear threshold:
-skin erythema
-hematologic depression
-ctaractogenesis
examples of linear non threshold
-radiation protection
-stochastic
examples of nonlinear threshold
-radiation therapy
-teratogenic
example of linear quadratic
-diag. xray
-leukemia
-breast cancer
-heritable damage
-stochastic
