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Introductory Radiation Biology
Exam I
2008
WHEREVER POSSIBLE, SHOW ALL WORK!!! AND UNITS!!!
NO WORK, NO CREDIT!!!
1.
The mean free path of the 662 keV gamma ray from a 137Cs source is 8 cm in water.
a.
What is the linear absorption coefficient (μ) of this photon in water?
b.
What is the half-value layer of this photon in water?
c.
How many cm of water are required to reduce the initial intensity (I0) of a narrow
beam of these gamma rays by 95% (i.e., It = 5% of I0)?
d. Approximately how many half-value layers (HVLs) is this?
2.
KBXR broadcasts at a frequency of 102.3 MHz (i.e., 1.023  108 s-1) on your radio dial.
Assuming this photon travels at the speed of light, what is the wavelength of the station’s
signal?
3.
Dr. Michael J. Welch, the most famous living radiopharmaceutical chemist in the world,
thinks it is very weird that 94m43Tc (T1/2 = 52 min) does not decay by isomeric transition
to 94g43Tc. It decays by two other modes: in 72% of all events, it decays to 9442Mo
(stable) with emission of a charged particle (Emax = 2.47 MeV), while in 28% of all
events, it decays to 9442Mo (stable), with no particle emission, but emission of a gamma
ray of 871 keV.
a.
Sketch a decay scheme that is consistent with the two decay modes of 94m43Tc to
94
42Mo. For each decay and/or de-excitation mode, identify the one major photon
or charged particle emitted.
b.
In addition to the gamma ray, ______________________ radiation is emitted
after one decay mode of 94m43Tc.
c.
Dr. Heather Hennkens, one of Dr. Welch’s graduate students and now a
postdoctoral fellow in Dr. Lewis’s research group, used a radiopharmaceutical
called 94mTc-sestamibi for PET imaging of MDR1, a protein that causes multidrug
resistance to chemotherapy in cancer patients. After production of 94mTc from
99
Mo on a cyclotron, Dr. Hennkens purifies the 94mTc in 21 min, synthesizes
94m
Tc-sestamibi in 1 min, and images a cancer subject 30 min after injection of 25
mCi of the radiopharmaceutical. How much 94mTc did Dr. Hennkens originally
need for this procedure, from the time after cyclotron production until imaging of
the subject?
d.
4.
5.
T or F (circle one) 94mTc is not a metastable radionuclide because it does not
undergo isomeric transition.
The range of a 1 MeV proton is 23 μm in soft tissue.
a.
What is the LET of this proton in soft tissue?
b.
Estimate the average LET of a 1 MeV alpha particle (i.e., 42He+2).
TRUE/FALSE
94m
_____ a.
The 871 keV gamma photon of
soft tissue as an 871 keV x-ray.
Tc will have equal ability to penetrate
_____ b.
Radionuclides produced by cyclotrons typically decay by β+ emission
and/or electron capture.
_____ c.
99m
43Tc
decays predominantly by isomeric transition to 99g43Tc. Because
no gamma ray is emitted, it cannot be used for nuclear medicine.
6.
_____ d.
Henri Becquerel won the 1903 Nobel Prize in Physics for the discovery of
naturally occurring penetrating radiation and the other winners of this
prize, Pierre and Marie Curie, called this phenomenon “radioactivity.”
_____ e.
As the LET of a charged particle decreases, its range in matter also
decreases.
_____ f.
Many people think that cellular phones cause brain tumors. They may be
right, because the electromagnetic radiation emitted from these devices
has a photon energy of about 10-6 eV. This energy is sufficient to ionize
molecules and produce latent cancer.
_____ g.
Alpha particles are emitted over a range of energies, while beta particles
are always emitted in a monoenergetic manner.
_____ h.
Without knowing the source, one can easily distinguish a 10 MeV βparticle from a 10 MeV LINAC electron, using conventional radiation
detection equipment.
Rank the following forms of ionizing radiation in order of increasing LET. (Fill in the
blanks: rank the lowest LET radiation number 1 and the highest LET radiation number
6.)
a.
b.
c.
d.
e.
f.
7.
8 MeV proton
500 keV alpha particle
8 MeV electron
1.33 MeV gamma ray
500 keV positron
8 MeV alpha particle
_____
_____
_____
_____
_____
_____
The dominant mechanism by which a 5 MeV photon interacts with soft tissue is:
a.
pair production.
b.
the photoelectric effect.
c.
d.
e.
Compton scattering.
transfer of an average of 60 eV per collision with an atom.
none of the above.
8.
A 70-kg student, at home studying late for this exam, drinks one sip of really hot coffee.
Because of this action, he will:
a.
b.
c.
d.
9.
The difference between a 250 keV x-ray and a 250 keV alpha particle is:
a.
b.
c.
d.
e.
10.
The alpha particle has greater penetrating ability in water or soft tissue.
The ionization density of the alpha particle is much higher than that of the x-ray.
of no consequence as far as the potential for biological damage is concerned.
all of the above.
none of the above.
Electron capture decay is:
a.
b.
c.
d.
e.
11.
severely scald his tongue and probably die of starvation before it heals.
win a major lawsuit against the manufacturers of the coffee and the coffee
machine, enabling him to retire a millionaire.
be so stimulated by the caffeine that his test score will improve by 10 points.
absorb the same amount of energy as a lethal dose of ionizing radiation.
always accompanied by emission of x-rays.
usually accompanied by emission of gamma rays.
an alternative to positron decay for proton-rich radionuclides.
all of the above.
none of the above.
Briefly define, identify, or describe:
a.
Ionizing radiation
b.
Radioactive decay
c.
LET
d.
Wilhelm Conrad Röntgen
e.
Half Value Layer
f.
Compton scattering
g.
Compare and contrast the ionization densities of a 5 MeV alpha particle versus a
5 MeV electron
(Consider the “tracks” of high LET radiation and low LET radiation across cells, shown on the
slide in class. What appearance or feature of these “tracks” provided evidence of the difference
in ionization density? A simple sketch and a couple of adjectives describing these “tracks”
would be helpful to supplement your
INTRODUCTORY RADIATION BIOLOGY
EXAM II, 2008
1.
2.
The report from health physics for a nuclear worker showed that he had received a whole
body dose of 1000 mrem from fast neutrons and 300 mrem from gamma rays (Total =
1300 mrem dose).
a.
Convert the total mrem dose to units of mSv.
b.
Assuming a QF of 10 for fast neutrons, calculate the dose this worker received
from fast neutrons in mrad units.
c.
What is the dose in mrad units, this worker received for his X-ray exposure?
Cell survival curves (A and B) for human lung cells irradiated with either 250 kVp Xrays or 2 MeV fast neutrons at high dose rates in the presence of 150 mm Hg of oxygen
are provided in the attached semi-log graph. Use the curves to answer the following
questions.
a.
Curve A is the one you would expect to result from the exposure of the cells to
the X-rays [i.e., NOT the fast neutrons] (True or False)
b.
The D37 for Curve A is ___________ rads
c.
D0 for Curve A is __________ rads.
d.
Assuming the slope of the straight line portion of Curve B is exactly parallel to
the slope of the Curve A line, the D0 for Curve B is ___________ rads.
e.
D20 for Curve B is approximately ___________ rads.
3.
Neutrons have a zero charge. Thus, fast neutrons are able to penetrate further into human
tissue than high energy protons with similar energies. Briefly explain why fast neutrons
are classified as a type of "high LET" radiation.
4.
When exiting MURR to leave the building, briefly explain the procedure used to make
sure you are not contaminated with radioactivity.
5.
Briefly describe (diagrams will help) the mechanisms by which irreparable damage to
DNA occurs via a:
a.
One-hit process
b.
Two-hit process
6.
Briefly describe how the oxygen effect plays an important role in reducing the ability of a
radiation oncologist to treat tumors with the high energy electron beams from
accelerators in Radiation Oncology facilities.
7.
Outline the steps in Nucleotide Excision Repair process (previously named "Cut and
Patch") that occurs on the DNA after exposure of cells to UV light. Identify enzymes (or
the functions they perform) at the corresponding steps.
8.
Define or describe what "Elkind Repair" is and how Elkind demonstrated that repair of
radiation damage occurs in mammalian cells using cell survival curves.
9.
A cell survival curve was generated by irradiation of human lung cancer cells with 4
MeV alpha particles at a high dose rate. You would expect that if these same cancer cells
were irradiated with these alpha particles at a very low dose rate, the slope of the straight
line portion of the resulting survival curve (in comparison to the one generated at high
dose rate) will be:
i.
ii.
iii.
10.
significantly steeper (i.e., a higher k)
about the same
about 1/3 as steep (i.e., a lower k)
Briefly define or describe:
a.
Direct effect
b.
Free radical
c.
Superoxide anion
d.
rad
e.
At least two differences between UV light and gamma-rays
f.
Sub-lethal damage
g.
RBE
h.
Mean Lethal Dose
11.
True-False
___
a.
Molecular oxygen (i.e., O2) is considered to be a free radical.
___
b.
DNA can be irreparably damaged by either a "one-hit" process or a "two-hit"
process.
___
c.
The D0 for human kidney cells irradiated at high dose rate, under 150 mm Hg 02,
with 100 keV X-rays is 150 rads. You would expect that the D0 for these cells
irradiated under the same conditions (i.e., 100 keV X-rays and 150 mm Hg 02) but
at LOW DOSE RATE will exhibit a lower D0 (e.g., 50 rads).
___
d.
The OER for human lung cells irradiated with 4 MeV protons will likely be
between 2.5 to 3.0.
___
e.
If one of the DNA bases (i.e., A, T, C or G) is directly damaged by ionizing
radiation or UV light, you would not expect breakage of the single strand of DNA
to which the base is attached, to occur during either the base excision or
nucleotide excision repair processes.
___
f.
You would expect that an organism which only has single stranded DNA or RNA
as its genetic component will be able to repair damage from X-ray exposure better
than cells that have double stranded DNA in the nucleus (e.g., human cells).
___
g.
You would expect the rate of generation of irreparable DNA damage by "one-hit"
processes to be more affected by varying the dose rate compared to irreparable
damage produced by "two-hit" processes.
Examination 3 - Introduction to Radiation Biology
November 13, 2008
Dr. Lattimer
Multiple choice examination. For each of the following please choose the one best answer.
Please record your answer on both the question pages and the answer sheet provided. 5 points
each. Score will be normalized to 100 points.
1.
DNA is the primary cellular target for injury by ionizing radiation, partly due to its very
large size. Which of the following represents the approximate number of nucleic acid base pairs
found in the typical mammalian genome?
a.
b.
c.
d.
e.
1 x 108
2 x 109
1 x 1010
2 x 1010
2 x 1011
2.
Susceptibility of the DNA to injury by ionizing radiation varies with the stage of the cell
cycle which the cell is in at the time of the irradiation. Partly this is due to the density of the
molecule at the time of irradiation. Which of the following phases of the cell is the one in which
the DNA is most condensed?
a.
b.
c.
d.
e.
G0
G1
G2
S
M
3.
Indirect radiation injury of the DNA occurs when free radical formed by the interaction
of the radiation with water molecules surrounding the DNA. Approximately what percentage of
the damage to the DNA by photon ionizing radiation occurs through this mechanism?
a.
b.
c.
d.
e.
25%
40%
50%
75%
90%
4.
There are several types of injury of the DNA which can occur. Some are more serious
than others. Which of the following types of injury is most difficult for the cellular repair
mechanisms to repair?
a.
Double Strand Break
b.
c.
d.
e.
Single Strand Break
Multiple Single Strand Breaks
Base Deletion
Sulfhydryl Cross Linkage formation
5.
Cells exhibit different sensitivity to radiation injury in different portions of the cell cycle.
The different portions of the cell cycle have different lengths. Which phase of the cell cycle is
the shortest?
a.
b.
c.
d.
e.
G0
G1
G2
S
M
6.
Repair of DNA injuries from radiation occurs through a number of pathways and
mechanisms. Which of the following is the repair mechanism which is least likely to preserve
the functional integrity of the DNA?
a.
b.
c.
d.
e.
Base excision repair
Nucleotide excision repair
Base sequence replication repair
Nonhomologous end-joining repair
Homologous recombination repair
7.
DNA repair begins quickly after the radiation injury occurs but takes some time to be
completed. Which of the following is the generally accept time which it will take for DNA
repair to be completed in most cells following a radiation exposure?
a.
b.
c.
d.
e.
1 minute
1 hour
6 hours
12 hours
1 day
8.
There are multiple different levels of severity of damage to the DNA and damage to the
DNA by ionizing radiation may be modified by environmental factors. Which of the following
classifications of damage to the DNA of G1 cells is most likely to be modified by environmental
factors affecting the cell?
a.
b.
c.
d.
e.
Non Lethal Damage
Sub Lethal Damage
Potentially Lethal Damage
Lethal Damage
Supra Lethal Damage
9.
Radiation exposure is more lethal to cells in some portions of the cell cycle. Following
the death of these cells, the cells in those phases of the cell cycle must be replaced by cell from
other phases of the cell cycle. What is the term that is used for this process?
a.
b.
c.
d.
e.
Recruitment
Reassortment
Repopulation
Reoxygenation
Repair
10.
There are many factors which influence the survival of a cycling cell population when it
is exposed to a dose of ionizing radiation. Which of the following has the greatest potential to
positively influence survival of a cycling clonogenic cell population receiving a given dose of
radiation?
a.
b.
c.
d.
e.
Very low oxygen levels in the population’s environment
Very low LET radiation
Very low growth factor
Very low dose rate
Very low temperature
11.
High LET radiation is generally considered to have a higher level of lethality to cells
which it impacts on. Which of the following is generally considered to be the reason for this?
a.
b.
c.
d.
e.
Increased number of Single Strand Breaks
Increased number of Double Strand Breaks
Increased number of Base Pair Deletions
Increased number of multiple Single Strand Breaks
Increased number of total injuries to the DNA
12.
In class we repeated emphasized that so-called stem or blast cells populations are at risk
for severe injury by ionizing radiation. Which of the following represents such a cell.
a.
b.
c.
d.
e.
Lymphocytes
Crypt cells of the intestinal mucosa
Glial cells of the white matter of the brain
Hepatocytes
Spermatigonia cells in the testes
13.
Cells in various types of tissue exhibit different "sensitivity" to radiation injury at the
tissue level. These cells have been classified by this apparent sensitivity to radiation. Which of
the following cell types is generally considered to be the most sensitive to radiation?
a.
b.
c.
Neurons
Endothelial cells
Basal cells of the skin
d.
e.
Muscle cells
Plasma cells
14.
When the majority of mammalian cells are place in cell culture and forced to divide the
differences in the sensitivity of the cells to radiation injury largely disappear. Most of the cells
exhibit D0 values within a relatively narrow range. Which of the following is that range?
a.
b.
c.
d.
e.
0.5-1.0 gray
1.0-1.5 gray
1.5-2.0 gray
2.0-2.5 gray
2.5-3.0 gray
15.
According to the classification of cell kinetics advanced by Michaelowski some cell
populations are comprised of cells which when they divide give rise to identical cells with the
same functional characteristics as the parent cells. Cells of this type are referred to as F-type
cells. Which of the following represents such a cell type?
a.
b.
c.
d.
c.
Bone marrow cells
Intestinal Crypt cells
Endothelial cells
Spermatigonia
Basal cells of the skin
16.
Certain cell lines in tissues are vital to the survival of the tissue and if they are killed by
irradiation then the tissue will die irregardless of the ability of the other cells in the tissue's
ability to survive that dose of radiation. The most sensitive of these cells in a tissue is referred to
as?
a.
b.
c.
d.
e.
The basal cell line
The parent cell line
The functional cell line
The cycling cell line
The critical cell line
17.
Evaluation of treatment effects for radiation treatments and for many other types of drug
and device treatment modalities usually begins with some form of laboratory assay. Which of
the following assays must essentially be performed in situ?
a.
b.
c.
d.
e.
Clonogenic assay
Transplantation assay
Functional assay
Lethality assay
in vitro assay
18.
Data from clonogenic assays and lethality assays usually produce curves of very different
shapes when the survival vs. dose is plotted on a graph. Why is this the case?
a..
b.
c.
d.
capacity
e.
Cells in tissue exhibit a different sensitivity for reproductive and functional
capabilities
Damage to the function capacity of cells in a tissue is expressed all at once.
Cells in tissues often retain clonogenic ability after they lose their functional
capacity.
Cells in tissues often have much more functional capacity than clonogenic
Cells in tissues usually have markedly excessive numbers to perform the tissue's
function.
19.
Lethality assays and statistics are usually expressed in terms of % death in so many days
(LDx/y). Why is this so?
a.
b.
c.
d.
e.
The % lethality usually reaches it maximum by the time specified.
The % lethality usually peaks at this time post irradiation
Lethal effects of the irradiation are not manifest until this time post irradiation
There is usually a flattening of the lethality curve after this point.
Death by other mechanisms may occur later on after the specified time period.
20.
Following a clinically significant radiation exposure there may be a number of tissue
responses seen, particularly if the radiation field is more than 5 cm square. These responses are
typically broken down into acute and chronic changes. Which of the following is both?
a.
b.
c.
d.
e.
Erythema
Edema
Desquamation
Hemorrhage
Necrosis
21.
Some tissues respond to or exhibit reactions from irradiation much more noticeably than
other tissues. Why is this so?
a.
b.
c.
d.
e.
Tissues with a high percentage of rapidly cycling cells compress the total reaction
into a much shorter time than tissues with few rapidly cycling cells.
Tissues which have good blood supplies are less likely to have severe reactions
because they heal more quickly.
Tissues which exhibit more noticeable and severe reactions are those which have
more sensitive critical cell lines.
Tissues that are adjacent to bone in the body exhibit a more severe response
because the bone absorbs more radiation and deposits the energy around it.
Tissues which have slowly cycling cells are unable to repopulate the cells
lost to radiation damage and therefore exhibit more sever reactions.
22.
When all is said and done after irradiation there is one effect of radiation injury which
usually occurs when relatively high doses of radiation are received, provide of course the
individual survives. What is that effect or response?
a.
b.
c.
d.
e.
Atrophy
Necrosis
Fibrosis
Revascularization
Cancer induction
23.
The various stem cells in the bone marrow give rise to the various cells in the blood.
These blood cells have a different life span for each type. Which of the following would cell
types would be expected to drop off first based on its half life in blood?
a.
b.
c.
d.
e.
Platelets
Macrophages
Lymphocytes
Erythrocytes
Plasma cells
INTRODUCTORY RADIATION BIOLOGY
FINAL EXAM – 2008
1.
A population of 100,000 people received a whole body dose of 30 rem each of gammaray exposure. According to the risk factor (i.e., # cancer deaths/million persons per rem)
that is based on the BEIR Report, the total number of cancer deaths induced in this
population by the 30 rem can be estimated to be:
a.
b.
c.
d.
300
1,500
15,000
60,000
2.
It is currently estimated that the probability that a citizen in the U.S. will get cancer at
least once in their lifetime is approximately ____%
3.
A radiation worker receives a whole body dose of 500 mrads from gamma-ray and 25
rads from fast neutrons this past year. Assuming the QF for fast neutrons is 20;
a.
Calculate the total equivalent dose (in mrem units) this person received (Show
work).
b.
Convert this person's dose (mrem) to mSv units
4.
Human lung cells were irradiated with a beam of high energy electrons (e.g., 2 MeV
electrons) at a high dose rate in the presence of oxygen (i.e., 150 mm Hg = p02) to
produce a cell survival curve.
a.
You would expect that the extrapolation number (n) on the cell survival curve will
be:
i)
ii)
iii)
iv)
b.
The degree of "Elkind Repair" observed in the cells remaining alive after a dose
of 300 rads would be:
i)
ii)
iii)
5.
one
less than one
greater than one
higher than D0
Greater, if the cells received a 300 rad dose from a beam of 2MeV alpha
particles under the same conditions
About the same as, if the cells were irradiated with a dose of 300 rads
from a beam of 2 MeV alpha particles.
Less, if the cells received a 300 rad dose from the 2 MeV alpha particle
irradiation.
Naturally occurring background radiation (Excluding the radiation dose from radioactive
radon) to all humans (and animals) comes from which of the following sources.
a.
b.
c.
d.
radiation from radioisotopes always present in the blood and tissues in our bodies.
radiation from radioisotopes present in soil, rocks and various building materials
cosmic radiation
all of the above
6.
Briefly explain or outline (in 2 or 3 sentences) why epidemiology studies are able to
demonstrate statistically significant increased levels of radiation induced thyroid cancers
in lower dose ranges (i.e., 10-20 rad levels) from low LET radiation while a statistically
significant increase in lung cancer incidence can only be demonstrated at higher doses
(i.e., 30-200 rads).
7.
Briefly explain, in one or two sentences, why a statistically significant radiation-induced
increase of most cancers (e.g., skin cancer, liver cancer, etc.) cannot be demonstrated by a
whole body dose of 40-50 rads of X—rays or gamma rays.
8.
The Dose Rate Effectiveness Factor (DREF) used by the BEIR and UNSCEAR
committees to estimate the risks of cancer induction by whole body gamma-ray radiation
at low dose rates relative to the risks at high dose radiation is approximately.
a.
b.
c.
d.
1.0
2.0
3.5
5.0
9.
Identify three potential radiation induced effects that can result from in utero radiation of
an embryo or fetus with a dose of 100 rads within the first 10 weeks after conception.
10.
Briefly explain why 131I (as radioiodide) in "fallout" from a nuclear weapon has the
potential to increase the risk of inducing thyroid cancers in populations exposed to this
"fallout".
11.
The free radical considered to be most damaging to the DNA of cells irradiated with low
LET radiation is:
a.
b.
c.
d.
the H-atom
H2O2
OH radical
Hydrated electron
12.
Briefly outline a couple of the positions and/or themes discussed by Bruce Ames in the
paper "How the body defends itself from the risky business of living" that was provided
in the booklet of reading material for this class.
13.
Briefly define or explain
a.
The "Roentgen" Unit
b.
Excision repair (one or two sentences)
c.
Radiation Dose Rate
d.
14.
TRUE/FALSE
___
a.
It has been shown (statistically) that an in utero radiation dose of 4-5 rads from an
X-ray dose to the embryo or fetus in the first trimester increases the probability of
congenital malformations in human bibies
___
b.
Studies to assess the risk of radiation induced genetic effects from the A-bomb
survivor population have been performed over the past 50 years. Results from examining
the first generation off-spring of the A-bomb survivors were unable to demonstrate a
statistically significant increase in genetic effects produced by the A-bomb radiation
exposure.
___
c.
Neutrons have a zero charge. Thus, irradiation of tissues by fast neutrons is
considered to be delivery of a "Low LET" radiation dose.
___
d.
Radiation induced single strand breaks on DNA are to be considered more likely
to be repaired than are double strand breaks.
___
e.
Studies to assess populations living for generations in areas of the world where
they are exposed to high levels of "natural background" (not including radon) radiation
(e.g., 300-500 mrem/year) have been able to demonstrate a statistically significant
increase in the cancer incidence compared to similar populations living in "normal"
natural background environments (i.e., about 200 mrem/year).
___
f.
If a tissue in the body received a dose of 5 Gy, this dose "in rad units" would be
higher.
___
g.
The fetus is considered to be more sensitive to in utero radiation in the first
trimester compared to its sensitivity to in utero radiation during the third trimester.
Introductory Radiation Biology
Final 2008 – Dr. Lattimer
1.
Which of the following represents the primary mechanism by which radiation causes
injury to the nuclear DNA of the cell?
a.
b.
c.
d.
e.
2.
Which of the following is the type of damage is associated with DNA double strand
breaks?
a.
b.
c.
d.
e.
3.
Very low dose rate and low LET radiation and normal oxygen tension
High dose rate and low LET radiation and normal oxygen tension
Very low dose rate and high LET radiation and normal oxygen tension
High dose rate and low LET radiation and normal oxygen tension
High dose rate and high LET radiation and low oxygen tension.
In which of the following phases of the cell cycle are double strand breaks most likely to
be repaired?
a.
b.
c.
d.
a.
5.
Sublethal Damage
Potentially Lethal Damage
Lethal Damage
Potentially Sublethal Damage
Non-Repairable Sublethal Damage
DNA repair of radiation injury is dependent on many different factors. Which of the
following is the most favorable condition for DNA repair to occur?
a.
b.
c.
d.
e.
4.
Direct ionization of the DNA by the radiation.
Indirect ionization of the DNA by the radiation
Secondary DNA ionization through free radical formation from oxygen
Secondary DNA ionization through free radical formation from water
Secondary DNA ionization through free radical formation from the DNA
G0 phase
G1phase
S phase
G2 phase
Anaphase
Is one mechanism by which a tissue can recover from radiation injury. Which of the
following types of cells has the greatest ability of repopulate a tissue following radiation
injury to that tissue?
a.
b.
Vegetative Intermitotic cells
Differentiating Intermitotic cells
c.
d.
e.
6.
Which of the following types of assays of radiation injury would have the greatest
relevance to a situation in which all or most of a major organ would receive radiation
injury without substantial radiation exposure to the rest of the body such as would occur
in the case of a course of radiation therapy.
a.
b.
c.
d.
e.
7.
Multipotential Connective Tissue Cells
Reverting Post Mitotic Cells
Fixed Post Mitotic Cells
in vitro clonogenic assay
in vivo clonogenic assay
in vivo Transplantation assay
in vivo Functional assay
in vivo Lethality assay
Irradiation of a fetus even at quite low doses can result in death or serious birth defects.
At which of the following times post conception is a dose of 0.25 gray most likely to
result in fetal death?
a.
b.
c.
d.
e.
Week 2
Week 5
Week 12
Week 22
Week 31
8.
Whole body radiation injury in adults can have a marked effect on the immune system.
Which of the following would likely be the effect of a one gray whole body dose of
radiation on the immune response to an antigen to which the immune system was
exposed 4 days before the irradiation event?
a.
b.
c.
d.
e.
9.
The immune response would be completely blocked.
The immune response would be delayed but essentially complete
The immune response would occur at normal rate but be weakened
The immune response would be substantially heightened
The immune response would be relatively unaffected
The development of cancer in an individual, even that arising from radiation exposure is
controlled by numerous gene functions arising from the DNA. Which of the following
set of conditions would be most likely to promote the development of a cancerous cell
line?
a.
Down regulation of a proto-oncogene, up regulation of a DNA stability gene
and down regulation of the p53 gene.
b.
Up regulation of a proto-oncogene, down regulation of a DNA stability gene
and up regulation of the p53 gene
c.
Down regulation of a proto-oncogene, up regulation of a tumor suppressor
gene and up regulation of the p53 gene.
d.
Up regulation of a proto-oncogene, down regulation of a tumor suppressor
gene and down regulation of the p53 gene.
e.
Up regulation of a proto-oncogene, up regulation of a tumor suppressor gene
and up regulation of the p53 gene
10.
Which of the following represents a result of irradiation in cancerous tissues which is not
seen in normal tissues?
a.
b.
c.
d.
e.
11.
Repair
Reoxygenation
Repopulation
Recruitment
Reassortment
Tumors, even those of the same general type, often will respond to irradiation at
substantially different times after irradiation. Which of the following is the best reason
why this occurs?
a.
b.
c.
d.
e.
Differences in the cell loss fractions between the two tumors
Differences in the average cell cycle time between the two tumors
Differences in the level of hypoxia present between the two tumors
Differences in the number of clonogenic cells present in the two tumors
Differences in the cellular repair capacity present in the two tumors
12.
Modern radiation therapy schemes are designed to maximize injury to the tumor and
minimize the damage to normal tissues. One way in which this is done is through
fractionation. Which of the following is most responsible for the fractionation effect?
a.
b.
c.
d.
e.
13.
It has been shown that using a small number of relatively large radiation dose fractions
will lead to increased severity of late effects in many tissues. Which of the following
would be expected to demonstrate this effect the least?
f.
g.
h.
i.
j.
14.
Bone marrow
Muscle
Tumor tissue
Spinal cord
Kidney
Despite the problems associated with using hyperthermia in conjunction with radiation in
the treatment of cancer there are many reasons why it would make a good combination
with radiation. Which of the following is not generally considered an effect of
hyperthermia?
k.
l.
m.
n.
o.
15.
Cellular reassortment in the tissue
Cellular repopulation of the tissue
Cellular repair processes
Cellular reoxygenation in the tumor
Cellular apoptosis promotion in normal tissues
Hyperthermia promotes killing of hypoxic cells
Hyperthermia inhibits intracellular repair
Hyperthermia promotes revascularization
Hyperthermia promotes killing of S-phase cells
Hyperthermia inhibits growth of cells at low pH.
Brachytherapy has many advantages and some disadvantages in the treatment of cancer.
Which of the following would be considered a disadvantage?
p.
q.
r.
s.
t.
Often requires only a single treatment.
The isotope used can be tailored to the situation and needs of the treatment
The total dose is delivered in a shorter time than with external beam.
Implants move with shrinkage or growth of the tumor
The total body dose to the patient is lower
INTRODUCTORY RADIATION BIOLOGY 4328/7328
FINAL EXAM 2008 -- DR. LEWIS
WHEREVER POSSIBLE, SHOW ALL WORK!!! NO WORK, NO CREDIT!!!
1.
Rank the following radioactive emissions in ability to penetrate matter (i.e., beginning
with the least penetrating radiation; e.g., A < B < C < D, but please note that this may or
may not be the correct answer!).
A.
B.
C.
D.
2.
6 MeV proton
140 keV gamma photon
12 MeV electron
5.98 MeV alpha particle
Fluorine 189F decays in 97% of all events to give oxygen 188O. Its half-life is 2 hours, and
it is widely used for PET.
a.
b.
c.
d.
e.
f.
Sketch a decay scheme for 189F.
True or False (circle one): 18F is useful for targeted radiotherapy.
In the other 3% of radioactive events, 18F decays by _______________________.
True or False (circle one): 18F is a proton-rich radionuclide.
PET is an abbreviation for ____________ ____________ __________________.
[18F]FDG is a radioactive analogue of which one of the following molecules?
(1)
glutamic acid
(2)
dextran
(3)
glucose
(4)
DNA
g.
18
F is most often used to synthesize FDG, which is FDA-approved for diagnosis,
staging, and restaging of many types of human cancer. Typically, an injected dose of
15 mCi is required for these purposes in PET evaluations of oncology patients. If the
last patient of the day undergoes an FDG procedure at 4 pm, and the FDG is prepared
at 8 am, how much FDG (in mCi) must be synthesized initially in order to image that
patient?
3.
Briefly define or describe (no more than 1-2 sentences):
a.
Beta minus particle (β-)
b.
LET
c.
Wilhelm Conrad Rőntgen
d.
Ionizing radiation
e.
Radioactivity
4.
MULTIPLE CHOICE
The predominant process by which photons with energies between 100 keV and 10 MeV
interact with soft tissue is:
a.
collisional loss of 22 to 60 keV per event.
b.
Compton scattering.
c.
the photoelectric effect.
d.
pair production.
e.
nuclear fission.
5.
Which radiopharmaceutical treats bone cancer?
a.
b.
c.
d.
6.
7.
[18F]fluorodeoxyglucose
[11C]raclopride
[153Sm]samarium-EDTMP
[131I]sodium iodide
131
I is a radioisotope used in nuclear medicine for treatment of thyroid cancer and
hyperthyroidism. Which one of the statements below is correct?
a.
131
I decays by spontaneous fission
b.
131
I emits both beta minus particles and gamma rays
c.
131
I emits positrons but no gamma rays
d.
131
I emits alpha particles and gamma rays
If [18F]FDG is administered to patients, it will concentrate in tissues with high rates of
glucose metabolism.
a.
Briefly explain (no more than 3 sentences) one reason why FDG concentrates in
these tissues.
b.
Name one tissue with high uptake of FDG.