Chapter 9 Flashcards by Melissa Unknown

Means random in nature, probability of occurrence of events

Stochastic

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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

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stochastic effects

– radiation induced cancer, radiation induced genetic effects

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Factors that affect radiation

dose and rate
oxygen
-age
-chromosomal effects

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

threshold

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

nonthreshold

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

linear

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

nonlinear

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Factors that affect dose mode

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

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True or false:
all early effects that result from high radiation doses are deterministic

true

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what is also known as nonstochastic

deterministic

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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

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examples of deterministic

-cataracts
-erythema
-fibrosis
-hemopoietic damage

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What are some examples of measurable late biological damage?

-cataracts
-leukemia
-genetic mutations

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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

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

Epidemiology

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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

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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

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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

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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

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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

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

threshold

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

threshold

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Biologic effects begin to occur only when the threshold level or dose is reached

threshold

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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

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