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Chapter 4: Radiation Biology

Terms in this set (96)

The study of the effects of ionizing radiation on living tissue, to understand the harmful effects of x-radiation
radiation biology
Two specific mechanisms of radiation injury are possible, these are
ionization and free radical formation
___________ is produced through the photoelectric effect or Compton scatter and results in the formation of a positive atom and a dislodged negative electron. The ejected high-speed electron is set into motion and interacts with other atoms within the absorbing tissues
ionization
X-radiation causes cell damage primarily through the formation of
free radicals
______ ________ formation occurs when an x-ray photon ionizes water. This results in the production of hydrogen and hydroxyl free radicals
free radical
A free radical is an _________ atom or molecule that exists within a single, unpaired electron in its __________ shell. It is highly reactive and unstable; the lifetime of a free radical is approximately 10^-10 seconds
uncharged; outermost
To achieve stability, free radicals may
1) recombine without causing changes in the molecule
2) combine with other free radicals and cause changes
3) combine with ordinary molecules to form a toxin capable of producing widespread changes
Two theories are used to describe how radiation damages biologic tissues, these are
direct and indirect theory
The _______ theory of radiation injury suggests that cell damage results when ionizing radiation directly hits critical areas, or targets, within the cell
direct
The ________ theory of radiation injury suggests that x-ray photons are absorbed within the cell and cause formation of toxins, which in turn damage the cell
indirect
_________ injuries from exposure occur more frequently because of the high water content of cells.
indirect
True or False

All ionizing radiations are harmful. All ionizing radiations produce biological changes in tissues. There is no such thing as "safe" x-rays.
true
A ________________ can be used to correlate the "response" or damage, of tissues with the "dose" or amount of radiation received.
dose-response curve
When dose and damage are plotted on a graph, a _______, __________ relationship is seen
linear, nonthreshold (which suggests that no matter how small the amount of radiation received, some biologic damage does occur)
The deleterious effects of ionizing radiation can be divided unto two types
stochastic and nonstochastic
________ effects occur as a direct function of dose. The probability of occurrence increases with increasing absorbed dose; however the severity of effects does not depend on the magnitude of the absorbed dose. Occur due to the effect of ionizing radiation on chromosomes that result in genetic mutations.
stochastic
__________ effects have a threshold and increase in severity with increased absorbed dose. Only occur after a threshold of exposure has been exceeded. Because of an identifiable threshold level, appropriate radiation protection mechanisms and occupational exposure dose limits can be put into place to reduce the likelihood of these effects occurring. Caused by significant cell damage
nonstochastic
__________ effects require larger radiation doses than their counterpart to cause serious impariment of health
nonstochastic
True or False

Chemical reactions that follow the absorption of radiation occur rapidly at the molecular level. However, varying amounts of time are required for these changes to alter cells and cellular functions
true
A _______ period can be defined as the time that elapses between exposure to ionizing radiation and the appearance of observable clinical signs
latent
After the latent period, a period of _______ occurs.
injury
(a variety of cellular injuries may result, including cell death, changes in cellular function, breaking or clumping of chromosomes, formation of giant cells, cessation of mitotic activity, and abnormal mitotic activity)
The last event in the sequence of radiation injury is the ________ period.
recovery
True or False

The effects of radiation exposure are not additive, and effects of damage do not accumulate
false
________ ______ is the quantity of radiation received, or the total amount of radiation energy absorbed. More tissue damage occurs when tissues absorb large quantities of radiation
total dose
_______ ______ is the rate at which exposure to radiation occurs and absorption takes place. More radiation damage takes place with high dose rates because a rapid delivery of radiation does not allow time for the cellular damage to be repaired.
dose rate
More damage occurs in cells that are most _______ to radiation, such as rapidly dividing cells and young cells
sensitive
Who is more susceptible to radiation damage, children or adults?
children
Following the latent period, effects that are seen within minutes, days, or weeks are termed ______ term effects.
short
Short term effects are associated with _______ amounts of radiation in a _______ amount of time
large, short
_______ ______ syndrome is a short-term effect and includes nausea, vomiting, diarrhea, hair loss, and hemorrhage
acute radiation
Effects that appear after years, decades, or generations are termed ______ term effects
long
Long-term effects are associated with _____ amounts of radiation absorbed repeatedly over a long period
small
All cells in the body can be classified as either _______ or ______ cells
somatic or genetic
_________ cells are the cells in the body except the reproductive cells
somatic
The reproductive cells are termed ________ cells
genetic
_________ effects are seen in a person who has been irradiated.
somatic
______ effects are not seen in the irradiated person but are passed on to future generations. they affect the health of the offspring. These cannot be repaired
genetic
True or False

The cell cytoplasm is more sensitive to ionizing radiation than the nucleus
false (damage to the nucleus affects the chromosomes containing DNA and results in disruption of cell division which may lead to disruption of cell function or cell death)
A cell than is sensitive to radiation is termed _______; one that is resistant is termed _______
radiosensitive, radioresistant
What are some characteristics of cells that make them more sensitive to radiation?
-cells that divide frequently or undergo many divisions over time
-cells that are immature or are not highly specialized
-cells that have a higher metabolism
Cells that are radiosensitive include
blood cells, immature reproductive cells, young bone cells
What is the cell that is most sensitive to radiation?
the small lymphocyte
What are some radioresistant cells?
cells of bone, muscle, and nerve
What are the radiosensitive organs?
lymphoid tissues, bone marrow, testes, and intestines
What are the critical organs?
organs of the body that when they are exposed to radiation may become damaged and diminish the quality of life

includes the thyroid gland, bone marrow, skin, lens of the eye
What are the three units used to define the quantities of radiation?
exposure, dose, and dose equivalent
What are the traditional and SI units for exposure?
Roentgen (R) and C/kg
What are the traditional and SI units for absorbed dose?
rad (radiation absorbed dose), and gray (Gy)
What are the traditional and SI units for dose equivalent?
rem (roentgen equivalent in man) and Sievert (Sv)
The term ______ refers to the measurement of ionization in air produced by x-rays
exposure
One roentgen is equal to the amount of radiation that produces approximately
2 billion ion pairs in one cubic centimeter of air
Describe the limitations that the roentgen has as a unit of measurement
it measures the amount of energy that reaches the surface of an organism but doesn't describe the amount of radiation absorbed, therefore it is essentially limited to measurements in the air (only used for x-rays and gamma rays)
No SI unit for exposure is equivalent to the roentgen, so exposure is simply stated in _______ per ______
coulombs per kilogram
What is the conversion for roentgen and coulombs
1R = 2.58 x 10^-4 C/kg
_______ can be defined as the amount of energy absorbed by a tissue
dose
The _______ ______ _____ is the traditional unit of dose
radiation absorbed dose
True or False

The rad is not restricted to air and can be applied to all forms of radiation
true
Using SI units, 1 rad is equivalent to
0.01 joule per kilogram
The ______ ______ measurement is used to compare the biologic effects of different types of radiation, since different types of radiation have different effects on tissues
dose equivalent
The traditional unit of the dose equivalent is the
roentgen equivalent (in) man (rem)
To place the exposure effects of different types of radiation on a common scale, a _____ _______, or dimensionless multiplier, is used
quality factor
The SI unit equivalent of the rem is
sievert
In dental imaging the grey and ______ are equal. Additionally, roentgen, rad, and ____ are considered approximately equal
sievert, rem
_________ radiation is the greatest contributor to human-made radiation exposure
medical
On average, ________ exposure makes up about half the annual dose of ionizing radiation
background
The potential risk of dental imaging inducing fatal cancer in an individual has been estimated to be approximately ___ in ___
3 in 1 million
The latent period in radiation biology is the time between
exposure to x-radiation and clinical symptoms
A free radical

a. is an uncharged molecule
b. has an unpaired electron in the outer shell
c. is highly reactive and unstable
d. combines with molecules to form toxins
e. all of the above
e
Direct radiation injury occurs when

a. x-ray photons hit critical targets within a cell
b. x-ray photons pass through a cell
c. x-ray photons are absorbed and form toxins
d. free radicals combine to form toxins
e. none of the above
a
Indirect radiation injury occurs when

a. x-ray photons hit critical targets within a cell
b. x-ray photons pass through a cell
c. x-ray photons are absorbed and form toxins
d. x-ray photons hit the DNA in a cell
e. none of the above
c
Which relationship best describes the response of tissue to radiation?

a. linear
b. linear, threshold
c. linear, nonthreshold
d. nonlinear, nonthreshold
e. none of the above
c
Which factor(s) contribute to radiation injury?

a. total dose
b. dose rate
c. cell sensitivity
d. age
e. all of the above
e
Long-term effects are seen with ______ amounts of radiation absorbed in a _______ period
small, long
Radiation injuries that are not seen in the person irradiated but that occur in future generations are termed

a. somatic effects
b. genetic effects
c. cumulative effects
d. short-term effects
e. long-term effects
b
Which is most susceptible to ionizing radiation?

a. bone tissue
b. small lymphocyte
c. muscle tissue
d. nerve tissue
e. epithelial tissue
b
The sensitivity of tissues to radiation is determined by

a. mitotic activity
b. cell differentiation
c. cell metabolism
d. all of the above
e. none of the above
d
Which is considered radioresistant?

a. immature reproductive cels
b. young bone cells
c. mature bone cells
d. epithelial cells
e. none of the above
c
An organ that, if damaged, diminishes the quality of an individuals life is termed

a. critical
b. somatic
c. cumulative
d. radioresistant
e. none of the above
a
The traditional unit for measuring x-ray exposure in air is termed

a. gray
b. coulombs per kilogram
c. rem
d. rad
e. roentgen
e
Which radiation unit is determined by the quality factor?

a. roentgen
b. rad
c. rem
d. gray
e. coulombs per kilogram
c
The term for measuring absorption of x-rays is termed

a. roentgen
b. rad
c. rem
d. quality factor
e. sievert
b
Which conversion is correct?

a. 1 R = 2.58x10^-4 C/kg
b. 1 rad = 0.1 Gy
c. 1 rem = 0.1 Sv
d. 1 Gy = 10 rad
e. 1 Sv = 10 rem
a
Which traditional unit does not have an SI equivalent?

a. roentgen
b. rad
c. rem
d. quality factor
e. none of the above
a
Which is used only for x-rays?

a. sievert
b. gray
c. rem
d. rad
e. roentgen
e
Which conversion is correct?

a. 1 R = 2.58 x 1-^-4 C/kg
b. 1 Gy = 100 rad
c. 1 Sv = 100 rem
d. 1 rem = rad x QF
e. all of the above
e
What is the approximate average dose of background radiation received by an individual in the United States?

a. 100mrem/0.01 mSv
b. 100 mrem/1.0 mSv
c. 300 mrem/3.0 mSv
d. 500 mrem/ 5.0 mSv
e. 1000 mrem/ 10.0 mSv
c
What is the greatest contributor to artificial radiation exposure?

a. radioactive materials
b. medical radiation
c. consumer products
d. weapons production
e. nuclear fuel cycle
b
The amount of radiation exposure an individual receives varies depending on

a. receptor type
b. collimation
c. technique
d. both a and b
e. all of the above
e
A single intraoral image using a digital sensor results in an effective exposure dose of

a. 0.002 mSv
b. 0.020 mSv
c. 0.200 mSv
d. 2.000 mSv
e. 20.00 mSv
a
What is the dose at which leukemia induction is most likely to occur?

a. 500 mrad
b. 1000 mrad
c. 2000 mrad
d. 5000 mrad
e. none of the above
d
Which statement is incorrect?

a. X-radiation is not harmful to living tissue
b. Dental images benefit the patient
c. In dental imaging, the benefit of disease detection outweighs the risk of damage from radiation
d. Dental images should be prescribed only when the benefit outweighs the risk
e. Biologic damage results from x-ray exposure
a
Which of the following is true of nonstochastic effects of radiation?

a. Effects occur as a direct function of the dose.
b. The severity of effects does not depend on the magnitude of the absorbed dose.
c. Effects have a threshold.
d. The probability of occurrence increases with increasing absorbed dose.
c

(nonstochastic effects are somatic effects that have a threshold and increase in severity with increasing absorbed dose. Compared with stochastic effects, nonstochastic effects require larger radiation doses to cause serious impairment of health. Stochastic effects occur as a direct function of dose. The severity of stochastic effects does not depend on the magnitude of the absorbed dose.The probability of occurrence increases with increasing absorbed dose for stochastic effects of radiation.)
Identify the reduction in absorbed dose when changing from D-speed film to F-speed film:
20%
40%
60%
80%
60%
Identify which of the following is true concerning radiation injury:

a. all radiation injuries are evident immediately
b. x-radiation only injures somatic cells
c. acute injury due to x-radiation exposure is common
d. cumulative effects of x-radiation exposure lead to health problems
d
Identify the most dangerous time for a fetus to be exposed to ionizing radiation:

first trimester
second trimester
third trimester
all of the above
first trimester
Identify the x-rays that are most likely absorbed by the skin, thus causing x-ray injury:

a. deep, penetrating x-rays
b. aluminum-filtered x-rays
c. long-wavelength x-rays
d. short-wavelength x-rays
c
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