CHAPTER 34 - STOCHASTIC EFFECTS PF RADIATION

Deterministic Effect

___________ of radiation exposure are produced by high radiation doses.

Stochastic effects

___________ of radiation exposure are the result of low doses delivered over a long period

low dose and low linear energy transfer (LET)

Radiation exposures experienced by personnel in diagnostic imaging are ________ and __________

adiation-induced malignancy and genetic effects

The principal stochastic effects of low-dose radiation over long periods consist of ________ and ____________

chronic

The radiation exposures that we experience in diagnostic radiology are low and of low LET; they are ________ in nature because they are delivered intermittently over long periods

radiation-induced malignancy and genetic effects

The principal stochastic effects are _______ and __________.

No dose threshold

___________ has been established for a stochastic response

linear

The stochastic dose-response relationship is _______.

stochastic effects

Our radiation protection guides are based on the _________ of radiation and on linear, nonthreshold dose-response relationships.

epidemiologic studies

Studies of large numbers of people exposed to a toxic substance require considerable statistical analyses. Such studies, called _________, are required when the number of persons affected is small

severe nonmalignant changes.

In addition to the deterministic effects of erythema and desquamation and late-developing carcinoma, chronic irradiation of the skin can result in __________

radiodermatitis.

This stochastic effect was observed many years ago in radiologists and is called ____________

stochastic response

Irradiation of blood-forming organs can produce hematologic depression as a deterministic response or leukemia as a ___________

a deterministic and a stochastic response

Chromosome damage in the circulating lymphocytes can be produced as both ___________ and ___________.

cyclotron

In 1932 Ernest O. Lawrence of the University of California developed the first ________, a 12-cm-diameter device capable of accelerating charged particles to very high energies.

charged particles

These __________ are used as “bullets” that are shot at the nuclei of target atoms in the study of nuclear structure.

Argonne National Laboratory in the United States and at CERN in Switzerland.

The largest particle accelerators in the world are located at ____________________________.

nonlinear, threshold.

The dose-response relationship for radiation induced cataracts is ___________.

age dependent

The radiosensitivity of the lens of the eye is ___________.

increases

As the age of the individual__________, the radiation effect becomes greater and the latent period becomes shorter.

15 years

Latent periods ranging from 5 to 30 years have been observed in humans, and the average latent period is approximately _________.

posterior pole

Radiation-induced cataracts occur on the ___________ of the lens.

linear, nonthreshold

shows that the relationship between life span shortening and dose is apparently ______________.

10 days for every 10 mGyt

At worst, humans can expect a reduced life span of approximately _________.

male

As one can see, the most grievous risk is being ________ rather than female

12 days

Whereas the average life shortening caused by occupational accidents amounts to 74 days, for radiation workers, life is shortened by only ________.

occupation

Radiologic technology is a safe __________.

Radiation-induced life span shortening

_______________ is nonspecific, that is, no characteristic diseases are associated with it, and it does not include late malignant effects.

Radiation-induced life span shortening

It occurs simply as accelerated premature aging and death.

observe and measure

The deterministic effects of high-dose radiation exposure are usually easy to _______ and ______.

• relative,

• excess

• absolute risk

There are three types of risk estimates— ______, _________, and _______; all of these represent different statements of risk and have different dimensions.

relative risk

The ____________ is computed by comparing the number of persons in the exposed population showing a given stochastic effect with the number in an unexposed population who show the same stochastic effect.

1.0

A relative risk of _______ indicates no risk at all.

1.5

A relative risk of _______ indicates that the frequency of a late response is 50% higher in the irradiated population than in the nonirradiated population.

less than 1

Occasionally, an investigation results in the identification of a relative risk of __________

radiation hormesis

This indicates that the radiation exposed population receives some protective benefit, which is consistent with the theory of _________.

radiation hormesis

The theory of ___________ suggests that very low radiation doses are beneficial.

100 mGyt (10 rad)

Radiation hormesis suggests that low levels of radiation—less than approximately _________—are good for you

nonirradiated populations

Leukemia, for instance, is known to occur spontaneously in ____________.

Excess risk

___________ = Observed cases - Expected cases

absolute risk factor.

If at least two different dose levels are known, then it may be possible to determine an____________.

5 × 10−2 Sv−1 (5 × 10−4 rem−1 )

The absolute risk of a fatal radiation-induced malignant disease is _____________.

5 × 10^-2 Sv^-1 (5 × 10^-4 rem^-1 ).

This is the risk coefficient used by radiation scientists to predict stochastic radiation response in exposed populations

linear and nonthreshold.

The form of the dose-response relationship in Leukemia is ___________

linear, nonthreshold dose-response relationship.

Radiation-induced leukemia follows a ________________

4 to 7 years

Radiation-induced leukemia is considered to have a latent period of _________ and an at-risk period of approximately 20 years.

20 years

Radiation-induced leukemia is considered to have a latent period of 4 to 7 years and an at-risk period of approximately ________.

Acute leukemia and chronic myelocytic leukemia

__________ and _____________ were observed most often among atomic bomb survivors.

Chronic lymphocytic leukemia

___________ is rare and therefore is not considered to be a form of radiation-induced leukemia.

20%

Approximately ______ of all deaths are caused by cancer; therefore, any radiation-induced cancers are obscured.

Thyroid cancer

______________ has been shown to develop in three groups of patients whose thyroid glands were irradiated in childhood.

thymus

The ________ is a gland lying just below the thyroid gland that can enlarge shortly after birth in response to infection.

cancer

The implication of a linear, nonthreshold dose response relationship for ______ is clear

radium

When ingested, the ______ behaves metabolically similar to calcium and deposits in bone.

500 Gyt (50,000 rad).

Because of radium’s long half-life (1620 years) and alpha emission, these employees received radiation doses to bone of up to _________

radiodermatitis.

Skin cancer usually begins with the development of a _________.

orthovoltage (200 to 300 kVp) or superficial x-rays (50 to 150 kVp).

Significant data have been developed from several reports of skin cancer induced in radiation therapy recipients treated with ______________ and ______________.

threshold dose-response relationship

Radiation-induced skin cancer follows a ___________

isolation

Tuberculosis was for many years treated by ________ in a sanitarium.

linear, nonthreshold dose-response relationship

Radiation-induced breast cancer exhibits a ___________________

Uranium

_______, which is radioactive with a very long half-life of 109 years, decays through a series of radioactive nuclides by successive alpha and beta emissions, each accompanied by gamma radiation.

Radon

______ is an alpha-emitting radionuclide that adsorbs on dust particles, which lodge in the alveolar spaces of the lung

radon ( 222Rn)

One of the decay products of uranium is ___________.

radon ( 222Rn)

This radionuclide is a gas that emanates through the rock to produce a high concentration in air.

stable isotope of lead.

When breathed, radon can be deposited in the lung, where it undergoes an additional successive series of decay to a __________

Thorotrast

Thorium dioxide (ThO2) in a colloidal suspension known as _________ was widely used in diagnostic radiology between 1925 and 1945 as a contrast agent for angiography.

8 cases/100 Sv,

The overall absolute risk for induction of malignancy is approximately____________ with the at-risk period extending for 20 to 25 years after exposure.

offshore oilfield worker

Working as an _____________ is far more hazardous than a nuclear power plant worker

10 mGyt

The BEIR committee has further stated that because of the uncertainty in its analysis, less than _____ may not be harmful.

1 mGyt/yr

Finally, they considered excess radiation-induced cancer mortality after a continuous dose of __________

absolute or relative

The BEIR committee also has analyzed available human data with regard to age at exposure, a limited time of expression of effects, and whether the response was___________ or _________

interrupted fertility.

Before pregnancy, the concern is __________.

congenital effects

During pregnancy, concern is directed to possible___________ in newborns.

genetic effects

Post-pregnancy concerns are related to suspected __________

radiation dose related

The deterministic effect of high-level radiation on the interruption of fertility in both men and women. Ample evidence shows that such an effect does occur and is ___________.

fertility

Low-dose, chronic irradiation does not impair _________.

that of the radiation worker and that of the patient

Irradiation in utero concerns the following two types of radiation exposures: ________ and _____________.

age

After maturity has been reached, radiosensitivity increases with _________.

first trimester

All observations point to the __________during pregnancy as the most radiosensitive period.

time related and radiation dose related

The effects of radiation in utero are _________ and ___________.

prenatal death

Within 2 weeks of fertilization, the most pronounced effect of a high radiation dose is _________, which manifests as a spontaneous abortion.

Prenatal Death (first 2 weeks of pregnancy)

this response is of the all-or-none variety

all-or-nothing.

The first 2 weeks of pregnancy may be of least concern because the response is ___________.

major organogenesis

During the period of __________, from the 2nd through the 12th weeks, two effects may occur.

major organogenesis (2nd through the 12th weeks)

Early in this period, skeletal and organ abnormalities can be induced.

major organogenesis

As __________ continues, congenital abnormalities of the central nervous system may be observed if the pregnancy is carried to term

1.5

The relative risk of childhood leukemia after irradiation in utero is ______.

growth and development

Radiation exposure in utero does retard the _________ and __________ of the newborn

microcephaly (small head)

Irradiation in utero, principally during the period of major organogenesis, has been associated with ____________ and, as discussed, mental retardation.

Spontaneous abortion

___________ causes the least concern because it is an all-or-none effect.

radiation genetics.

Unfortunately, our weakest area of knowledge in radiation biology is the area of ________.