6.1 Biologic Effects of Radiation Flashcards by Dana Athena Augusto

Early radiologists who performed fluoroscopic
examinations without protective gloves developed a
very callused, discolored, and weathered appearance to the skin of their hands and forearms.
In addition, the
skin would be very tight and brittle and sometimes
would severely crack or flake.
This stochastic effect was observed many years ago
in radiologists and is called ______

radiodermatitis

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The dose necessary to produce stochastic effect is very ____. No
such effects occur in the current practice of radiology

high

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Irradiation of blood-forming organs can produce ____ as a deterministic response or _____ as a stochastic response

hematologic depression (d),
leukemia (s)

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_____ damage in
the circulating lymphocytes can be produced as both a
deterministic and a stochastic response

Chromosome

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even a ___
dose of radiation can produce chromosome aberrations
that may not be apparent until many years after radiation exposure

low

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This stochastic effect in chromosomes presumably occurs because of
radiation damage to the _____

lymphocytic stem cells

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In 1932 _____ of the University of California developed the first cyclotron

Ernest O. Lawrence

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a 12-cm-diameter
device capable of accelerating charged particles to very high energies. These charged particles are used as “bullets” that are shot at the nuclei of target atoms in the study of nuclear structure

cyclotron

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By ___, every university

physics department of any worth had built its own cyclotron and was engaged in what has become high-energy physics

1940

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is used principally to produce
radionuclides for use in nuclear medicine, especially
fluorine-18 for positron emission tomography

modern cyclotron

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was the first physician to apply radionuclides (from his brother’s cyclotron) on humans

John Lawrence

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received the 1939 Nobel Prize in Physics

Ernest O. Lawrence

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is considered the Father of Nuclear Medicine

John Lawrence

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The largest particle accelerators in the world are located at _____ in the United
States and at CERN in Switzerland. These accelerators
are used to discover the ultimate fine structure of matter
and to describe exactly what happened at the moment
of creation of the universe

Argonne National Laboratory

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Cyclotron physicists used a tool of the radiologic
technologist, the _____, to aid
them in locating the high-energy beam.
Unfortunately,
in so doing, these physicists received high radiation doses to the lens of the eye because they had to look
directly into the beam

radiographic intensifying screen

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In ____ the first paper reporting cataracts in cyclotron physicists appeared

1949

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By ____, several hundred such
cases of radiation-induced cataracts had been reported. This was particularly tragic because there were few
high-energy physicist

1960

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Radiation-induced cataracts occur on the

_____ pole of the lens

posterior

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The radiosensitivity of the

lens of the eye is ___ dependent

age

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As the age of the individual increases, the radiation effect becomes _____ and the latent period becomes _____

greater,

shorter

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(Cataract) Latent periods ranging from _____ have been observed in humans, and the average latent period is approximately ____

5 to 30 years,

15 years

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High-LET radiation, such as neutron and proton radiation, has a ____ for the production of cataracts

high relative biologic

effectiveness (RBE)

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The dose-response relationship for radiation-induced cataracts is ______

nonlinear, threshold

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If the lens dose is high enough, in excess of approximately _____, cataracts develop in nearly
100% of those who are irradiated

10 Gyt (1000 rad)

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The precise level of the threshold dose is difficult to assess. Most investigators would suggest that the threshold after an acute x-ray exposure is approximately _____

2 Gyt | 200 rad

The threshold after fractionated exposure, | such as that received in radiology, is probably in excess of _____

10 Gyt (1000 rad)

Occupational exposures to the lens of the eye are too ____ to require protective lens shields for radiologic technologists. It is nearly impossible for a medical radiation worker to reach the threshold dose

low

Cataracts were first manifested as an effect of radiation by

High-energy physicists after receiving high radiation doses to the lens of the eye

Radiation administered to patients who are undergoing head and neck examination by fluoroscopy or computed tomography can be significant. In computed tomography the lens dose can be ____

50 mGyt (5 rad)

In either case, protective lens shields are not normally required. However, in computed tomography, it is common to modify the examination to ____ the dose to the eyes

reduce

the relationship between | life span shortening and dose is apparently ______

linear, non-threshold

At worst, humans can expect a reduced life span | of approximately ___ days for every ____

``` 10, 10 mGyt (0.01 Gyt) ```

Expected Days of Life Lost -Being male rather than female

2800

Expected Days of Life Lost -Heart disease

2100

Expected Days of Life Lost -Being unmarried

2000

Expected Days of Life Lost -One pack of cigarettes a day

1600

Expected Days of Life Lost -Working as a coal miner

1100

Expected Days of Life Lost -Cancer

980

Expected Days of Life Lost -30 pounds overweight

900

Expected Days of Life Lost -Stroke

Expected Days of Life Lost -All accidents

435

Expected Days of Life Lost -Service in Vietnam

400

Expected Days of Life Lost -Motor vehicle accidents

200

Expected Days of Life Lost -Average occupational accidents

Expected Days of Life Lost -Speed limit increase from 55 to 65 mph

Expected Days of Life Lost -Radiation worker

Expected Days of Life Lost -Airplane crashes

Radiation-induced life span shortening is ______, that is, no characteristic diseases are associated with it, and it does not include late malignant effects. It occurs simply as accelerated premature aging and death

nonspecific

RSNA

Radiological Society of North America

ACP

American College of Physicians

AAOO

American Academy of Ophthalmology and Otolaryngology

The _____ effects of high-dose radiation exposure are usually easy to observe and measure

deterministic

_____ are also easy to observe, but it is nearly impossible to associate a particular late response with a previous radiation exposure

stochastic effects

Consequently, precise dose-response relationships | are often not possible to formulate, and we therefore resort to ____

risk estimates

There are three types of risk estimates

relative risk, excess risk, and absolute risk

If one observes a large population for stochastic radiation effects without having any precise knowledge of the radiation dose to which they were exposed

Relative risk

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

Relative risk

Relative risk =

Observed cases/Expected cases

A relative risk of ___ indicates no risk at all

1.0

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

1.5

The relative risk for | radiation-induced stochastic effects of particular importance observed in human populations is in the range of _____

1 to 2

Occasionally, an investigation results in the identification of a relative risk of less than 1. This indicates that the radiation exposed population receives some protective benefit, which is consistent with the theory of radiation _____

hormesis

The theory of radiation _______ suggests that | very low radiation doses are beneficial

hormesis

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

100 mGyt (10 rad)

when an investigation of human radiation response reveals the induction of some stochastic effect, the magnitude of the effect is reflected by the excess number of cases induced

Excess Risk

the difference between the observed number of cases and the expected number

Excess Risk

Excess risk =

Excess risk = Observed cases - Expected cases

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

Absolute Risk

In contrast to the relative risk, which is a dimensionless ratio, the ______ consists of units of cases/ population/dose

absolute risk

is a considerable simplification of the | results of many studies

8×10^−2 Sv^−1 / (8×10^−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

5×10^−2 Sv^−1 / (5×10^−4 rem^−1)

To determine the absolute radiation risk, one must | assume a _____ dose-response relationship

linear

If the dose-response relationship is assumed to be ______, | then only one dose level is required

nonthreshold

The value of the | absolute radiation risk is equal to the ____ of the dose-response relationship

slope

The absolute risk of total radiation-induced malignant disease as determined by the National Academy of Science Committee on the Biologic Effects on Ionizing Radiation (BEIR)

8×10^−2 Sv^−1 (8/10,000/10 mSv)

The absolute risk of fatal radiation-induced malignant disease as determined by the National Academy of Science Committee on the Biologic Effects on Ionizing Radiation (BEIR)

5×10^−2 Sv^−1 (5/10,000/10 mSv)

Leukemia dose-response relationship is _____

linear and nonthreshold

A number of human population groups have exhibited an elevated incidence of leukemia after radiation exposure:

- atomic bomb survivors (Hiroshima and Nagasaki), - (American) radiologists, - radiotherapy patients, - children irradiated in utero

Probably the greatest wealth of information that we have accumulated regarding radiation-induced leukemia in humans has been drawn from observations of survivors of the atomic bombings of _____

Hiroshima and Nagasaki

At the time of the bombings, approximately _____ people lived in those two cities. Nearly _____ were killed from the blast and from deterministic effects of radiation. Another _____ people received significant doses of radiation and survived

300,000, 100,000, 100,000

The remainder were unaffected of the bombing because their | radiation dose was less than _____

100 mGyt (10 rad)

After World War II, scientists of the ______, attempted to determine the radiation dose received by each of the atomic bomb survivors in both cities

Atomic Bomb Casualty Commission (ABCC), now known as the Radiation Effects Research Foundation (RERF)

They estimated the dose to each survivor by considering not only distance from the explosion but also terrain, type of bomb, type of building construction if the survivor was inside, and other factors that might influence radiation dose

Atomic Bomb Casualty Commission (ABCC), now known as the Radiation Effects Research Foundation (RERF)

ABCC

Atomic Bomb Casualty Commission

RERF

Radiation Effects Research Foundation (RERF)

A rather rapid rise in leukemia incidence reached a | plateau after approximately _____

5 years

The incidence declined slowly for approximately ____ years, when it reached the natural level experienced by the nonexposed

Radiation-induced leukemia is considered to have a latent period of ____ years and an at-risk period of approximately ___ years

4 to 7, | 20

is that time after irradiation during | which one might expect the radiation effect to occur

at-risk period

The at-risk period for radiation-induced cancer is

lifetime

Of the 300,000 total residents, ___ persons are estimated to have survived doses in excess of ____

``` 335, 6 Gy (600 rad) ```

were observed most often | among atomic bomb survivors

Acute leukemia, | chronic myelocytic leukemia

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

Chronic lymphocytic leukemia

By the second decade of radiology, reports of pernicious anemia and leukemia in _____ began to appear

radiologists

It has been estimated that some of these early radiologists received doses exceeding ______

1 Gyt/yr (100 rad/yr)

is an arthritis-like condition of the vertebral column

Ankylosing spondylitis

Other population groups that have provided evidence, both positive and negative, regarding the leukemia-inducing action of radiation include

-radium watch-dial painters, -children receiving superficial x-ray treatment, -some additional adult radiation therapy groups

6.1 Biologic Effects of Radiation Flashcards

(98 cards)