6.1 Biologic Effects of Radiation Flashcards
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
The dose necessary to produce stochastic effect is very ____. No
such effects occur in the current practice of radiology
high
Irradiation of blood-forming organs can produce ____ as a deterministic response or _____ as a stochastic response
hematologic depression (d), leukemia (s)
_____ damage in
the circulating lymphocytes can be produced as both a
deterministic and a stochastic response
Chromosome
even a ___
dose of radiation can produce chromosome aberrations
that may not be apparent until many years after radiation exposure
low
This stochastic effect in chromosomes presumably occurs because of
radiation damage to the _____
lymphocytic stem cells
In 1932 _____ of the University of California developed the first cyclotron
Ernest O. Lawrence
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
By ___, every university
physics department of any worth had built its own cyclotron and was engaged in what has become high-energy physics
1940
is used principally to produce
radionuclides for use in nuclear medicine, especially
fluorine-18 for positron emission tomography
modern cyclotron
was the first physician to apply radionuclides (from his brother’s cyclotron) on humans
John Lawrence
received the 1939 Nobel Prize in Physics
Ernest O. Lawrence
is considered the Father of Nuclear Medicine
John Lawrence
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
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
In ____ the first paper reporting cataracts in cyclotron physicists appeared
1949
By ____, several hundred such
cases of radiation-induced cataracts had been reported. This was particularly tragic because there were few
high-energy physicist
1960
Radiation-induced cataracts occur on the
_____ pole of the lens
posterior
The radiosensitivity of the
lens of the eye is ___ dependent
age
As the age of the individual increases, the radiation effect becomes _____ and the latent period becomes _____
greater,
shorter
(Cataract) Latent periods ranging from _____ have been observed in humans, and the average latent period is approximately ____
5 to 30 years,
15 years
High-LET radiation, such as neutron and proton radiation, has a ____ for the production of cataracts
high relative biologic
effectiveness (RBE)
The dose-response relationship for radiation-induced cataracts is ______
nonlinear, threshold
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)
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
20
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
74
Expected Days
of Life Lost
-Speed limit increase from 55 to 65 mph
40
Expected Days
of Life Lost
-Radiation worker
12
Expected Days
of Life Lost
-Airplane crashes
1
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
20
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
