Name: _________________________
Introductory Radiation Biology
Exam I, 2012
WHEREVER POSSIBLE, SHOW ALL WORK!!! AND UNITS!!!
(NO WORK, NO CREDIT!!!)
1.
The half-value layer (HVL) of a parallel beam of 120 keV gamma rays in soft tissue is 5
cm. How many cm of soft tissue are required to reduce the intensity (I) of this beam to
approximately 1% of its original intensity (I0)?
2.
The LET of a 1 MeV proton (i.e., 11H+) in water is 43 keV/μm. Estimate the LET of a:
3.
a.
1 MeV deuteron (i.e., 21H+)
b.
1 MeV alpha particle
The wavelength of a UV-B photon is 300 nm.
a.
Calculate the energy (in eV) of this photon.
b.
Exposure to UV-B can cause skin cancer, because it is ionizing radiation.
Circle the correct answer:
T
1
F
4.
5.
131
53I
(T1/2 = 8 days) decays by beta minus emission to 131Xe. In 82% of decay events, a
364 keV photon is emitted, while in 18% of events no photon is emitted.
a.
Sketch a decay scheme that is consistent with this information.
b.
The atomic number (Z) of 131Xe is
i.
51
ii.
52
iii.
53
iv.
54
v.
55
c.
At the MU Veterinary Medical Teaching Hospital, Dr. Jeff Bryan is going to treat
a dog with thyroid cancer using 50 mCi of 131I. He orders 131I from
DRAXIMAGE in Canada. The dose is calibrated to contain 220 mCi on
September 12. Because of an air traffic security problem, the border with Canada
is closed temporarily. Dr. Bryan does not receive the shipment until September
28. How much 131I arrives, and does Dr. Bryan have enough to treat his patient?
TRUE/FALSE
_____ a.
In soft tissue, the range of a 1 MeV electron is greater than that of a 1
MeV alpha particle.
2
6.
_____ b.
131
_____ c.
Bremsstrahlung radiation is emitted over a wide spectrum of energies,
while characteristic x-rays have relatively discrete energies.
_____ d.
Wilhelm Conrad Röntgen won the first Nobel Prize awarded, the 1901
Physics Prize, for the discovery of “a new kind of penetrating ray,” which
he called “x-rays.”
_____ e.
In radiation biology, the most important process by which photons interact
with soft tissue is the photoelectric effect.
_____ f.
The mean free path of 62 keV x-rays in water is greater than the mean free
path of 140 keV gamma rays in water.
_____ g.
When a 5 MeV alpha particle undergoes a single collision with a
molecule, an average of 60 eV of energy is transferred. That is enough
energy to ionize the molecule.
_____ h.
As the energy of a given type of charged particle increases, its range in
soft tissue decreases.
_____ i.
Because they are components of antimatter, positrons have the same
charge as electrons, but different mass.
Rank the following forms of ionizing radiation in order of increasing LET in soft tissue.
(Fill in the blanks: rank the lowest LET radiation number 1 and the highest number 6.)
a.
b.
c.
d.
e.
f.
7.
I is produced by spontaneous fission of 235U, following neutron
irradiation in a nuclear reactor. Therefore, it is totally useless for radiation
therapy.
500 keV positron
500 keV proton
15 MeV electron
500 keV alpha particle
140 keV gamma ray
5 MeV alpha particle
_____
_____
_____
_____
_____
_____
The difference between a 100 keV x-ray and a 100 keV gamma ray is:
a.
b.
c.
d.
e.
the x-ray has a lower velocity than the gamma ray.
unless one knows the origin, there is no detectable difference.
the x-ray originates from an orbital electron transition, while the gamma ray
originates from the excited nucleus of an atom during radioactive decay.
all of the above.
both (b) and (c) above.
3
8. You may have heard about the “radioactive Boy Scout,” who got busted by the police
while trying to build a breeder reactor in his garage, extracting large quantities of thorium
from Coleman lantern mantles and americium from smoke detectors.
(This is a true story!)
Suppose he succeeded in building his reactor and it underwent a critical “meltdown,”
causing him to absorb a lethal dose of radiation. In all likelihood,
a.
b.
c.
d.
9.
Which of the following is considered a low LET radiation?
a.
b.
c.
d.
e.
10.
he would have glowed in the dark until he succumbed to radiation toxicity.
the radiation would have immediately induced spontaneous human combustion.
he would have preferred to absorb the same amount of energy by drinking one sip
of hot coffee.
he would have been posthumously awarded the radiation biology merit badge.
a 15 MeV LINAC electron
a 62 keV tungsten characteristic x-ray
a 140 keV gamma ray
a 573 keV beta minus particle
all of the above
Which of the following is true of annihilation reactions?
a.
b.
c.
d.
e.
It occurs when positrons combine with electrons in matter at the end of their path.
Each event produces two 511 keV (0.511 MeV) photons.
Annihilation photons are emitted in opposite directions (~180°).
All of the above.
None of the above.
4
11.
When a radionuclide undergoes positron decay, which of the following must occur?
a.
b.
c.
d.
e.
12.
emission of x-rays
creation of a neutrino
emission of Auger electrons
internal conversion
emission of an alpha particle
Briefly define, identify, or describe.
a.
Marie Curie
b.
Ionizing radiation
c.
The atomic mode of energy loss that competes with x-ray emission
d.
LET
e.
Radioactive decay, or radioactivity
f.
Half-value layer
5
Radiation Biology Exam 2 2012
Name:___________________________
SHOW ALL WORK ON THE EXAM TO RECEIVE FULL CREDIT
1.
In examining the survival curves as a result of irradiating three different kinds of human
cell lines with ionizing radiation, you would conclude that the following statements are
TRUE or FALSE.
___a. Curve A was likely to be produced by irradiating the cells under oxygen with 6 MeV
gamma rays at a low dose rate.
___b. The D0 for Curve A and B are approximately the same.
___c. Curve C represents cells that are less sensitive to ionizing radiation compared to cells
represented by Curve B, assuming both cells in B and C were irradiated under identical
conditions with the same type of radiation.
___d. The extrapolation number (n) for Curve B is higher than the extrapolation number for
either Curves A or C.
___e. Curve A is representative of killing cells by only a one-hit process.
6
2.
Outline the steps involved in the Nucleotide Excision Repair process and at appropriate
steps, identify the enzyme steps involved.
3.
Briefly define and/or explain
a. Sub-lethal radiation damage
b. The free radical most responsible for DNA damage with low LET radiation
4. Which of the following outlines the steps of dipyrimidine dimer formation by UV light?
a. UV light interacts with the sugar backbone of DNA causing an ionization that
results in binding of one thymidine to a thymidine on the opposite DNA strand
b. UV light interacts with a base on a strand of DNA, exciting the molecule and
causing covalent bonding between two adjacent thymidine bases.
c. UV light ionizes a thymidine base, making it reactive, and it forms a covalent
bond with an adjacent thymidine base
d. UV light causes disruption of the nucleotide excision repair (NER) mechanism,
resulting in many T-T dimers that lead to skin cancers.
7
5.
Using the curve above showing the oxygen enhancement ratio of radiation sensitivity of
cells in a culture sytem by oxygen tension, identify the following things:
a. The oxygen tension at which the OER is 2.0.
b. The OER for cells at normal blood oxygen tension.
c. Is this curve drawn for cells exposed to high LET radiation or low LET radiation?
6.
If a dose of 8 Gy of 250 keV x-rays is necessary to reduce the surviving fraction of cells
in a culture plate to 10% (0.1 of original cells), and the RBE of neutrons under these
conditions is 1.5, what is the dose of neutrons necessary to have the same effect?
8
7. True-False
___
a. Fast neutrons lose less energy, on the average, in a collision with a H-atom nucleus
(i.e., proton) compared to when they collide with the nucleus of a carbon atom (i.e., 12, 6
C).
___
b. Chinese hamster cells irradiated under oxygen at a high dose rate with a beam of 1
MeV alpha particles will be significantly more sensitive than if they are irradiated under
the same conditions at a low dose rate.
___
c. Humans with Ataxia Telangiectasia cannot readily repair damage to their DNA
produced by X-rays but can readily repair damage to their DNA caused by UV radiation.
___
d. Compounds containing sulfhydryl (-SH) groups are considered radioprotectors when
cells are irradiated under oxygen at a high dose rate with 4 MeV alpha particles.
___
e. High LET radiation causes DNA damage predominantly by direct DNA ionization,
while low LET radiation causes most of its damage by indirectly producing free radicals.
___
f. As LET of a radiation increases, cell radiation sensitivity increases.
8.
The report from health physics for a nuclear worker showed that he had received a whole
body dose of 1500 mrem from fast neutrons and 500 mrem from gamma rays (Total =
2000 mrem dose).
a.
Convert the total mrem dose to units of mSv.
b.
Assuming a QF (RBE) of 10 for fast neutrons, calculate the dose this worker
received from fast neutrons in Rad units.
c.
What is the dose in Rad units, this worker received for his gamma ray exposure?
9
9.
Briefly describe (diagrams will help) the mechanisms by which irreparable damage to
DNA occurs via a:
a.
One-hit process
b.
Two-hit process
10
10. For the above survival curve, estimate:
a. D37
b. D0
c. The extrapolation number (n)
11
Exam 3- Introduction to Radiation Biology (NSEI 7328)
November 8, 2012
Dr. Lattimer
Please select the one best answer for each question. Some answers may be partly
true. Variable credit. Negative credit is possible.
Place answers on answer sheet provided and test, Turn in both!
1.
Ionizing radiation affects tissues in a number of locations both within and without the cell.
Which of the following is considered to be the location at which the damage is least likely to
result in permanent or lethal injury to the cell?
A.
B.
C.
D.
E.
2.
Cellular DNA injury by ionizing radiation is may occur when a cell is exposed to ionizing
radiation. Which of the following types of injury is the most easily repaired by cellular
repair mechanisms?
A.
B.
C.
D.
E.
3.
Single Strand Break
Complementary base pair deletions
Single nitrogenous base deletion
Double Strand break
Sufhydrl exon crosslink deletion
Which of the following chromosomal aberrations can result from injury by ionizing
radiation.
A.
B.
C.
D.
E.
4.
The nuclear DNA
The nuclear RNA
The mitochondrial DNA
The cytoplasmic messenger DNA
The Cell Wall Membrane
Dicentric Chromosome
Acentric fragments
Ring recombination
Sister reunion with acentric fragment
All of the above.
Most of the injury to the cell is the result of indirect action by the ionizing radiation on the
target. By indirect I mean that the ionizing radiation results in a primary event which then
results in a secondary reaction which damages the target. Which of the following is
generally accepted as the most important primary event caused by ionizing radiation?
A.
B.
C.
D.
E.
Ionization of the disulfide crosslink bonds
Ionization of carbon hydrogen bonds
Ionization of water
Ionization of carbon phosphorous bonds
Ionization of peroxide molecules
12
5.
Susceptibility of the DNA to radiation injury changes as the cell passes through its various
phases of the cell cycle. During which of the following phases of the cell cycle is the DNA
most susceptible to radiation injury?
A.
B.
C.
D.
E.
6.
Radiation injury is manifest and results in cell death at division for which of the following
reasons?
A.
B.
C.
D.
E.
7.
E.
During G1 Phase
At the G1-S interface
During S Phase
During the G2 phase
At the M-G1 interface
The term apoptosis is a term that is used to refer to a specific type of cell death which is
characterized by which of the following.
A.
B.
C.
D.
E.
9.
The radiation injury prevents chromosomal replication
The radiation injury prevents the cell from being able to begin replication
The radiation injury results in loss of large pieces of chromosomes from the cell.
The radiation injury results in loss of large pieces of chromosomes from the nucleus.
The radiation injury results in inappropriate recombination of the chromosomes
during replication.
Relatively low doses of radiation to a cycling cell population may result in a phenomenon
known as mitotic delay. During this time there is presumably some repair of radiation
injury that is taking place. At what point in the cell cycle does the radiation injury occur
which causes this delay or arrest in progression through the cell cycle occur?
A.
B.
C.
D.
8.
G1
G0
S
G2
M
S-phase and M-phase
G2-phase an M-phase
G1 phase and M-phase
G1-S interface and M-G1 interface
S-G2 interface and G1-S interface
When mammalian cells are irradiated in cell culture they all have about the same level of
susceptibility to ionizing radiation. The cell death vrs. Radiation dose on a logarithmic linear plot is curved as described in class. What does this curved plot indicate?
A.
B.
C.
D.
E.
That the cells accrue injury at a faster rate as the dose goes up.
That there are two mechanisms of killing taking place.
That there are multiple targets being affected with more affected at higher doses.
That the cells have some ability to repair injury. Especially at low doses
That there are multiple killing mechanisms present and that some damage is
repaired.
13
10.
The apparent response of cells to irradiation within the body is frequently different than
that which they appear to manifest in cell culture. What is the major reason for this?
A.
B.
C.
D.
E.
11.
Cell survival curves explain the situation in tissue culture but the conditions in the living
organism are far different than in cell culture. In living organisms many cell lines exhibit
substantial resistance to radiation injury. Which of the following cell types would generally
be expected to demonstrated the greatest resistance to radiation injury in a living animal?
A.
B.
C.
D.
E.
12.
Hepatocytes
Small circulating lymphocytes
Intestinal smooth muscle cells
Endothelial cells
Erythrocytes
Rubin and Casarett’s classification of cell populations on the basis of differences in cellular
reproductive kinetics is useful in explaining some of the tissue effects of irradiation. Which
of the following cell types is more likely to be associated with tissues exhibiting a late
response to irradiation?.
A.
B.
C.
D.
E.
13.
There is substantial protection of the cells from radiation injury within the body.
The lack of the influence of other cell lines makes the cells more resistant when in
cell culture.
The cell cycle times in living tissues are often radically different than those of the
same cells in cell culture.
Cells in cell culture are protected because they are less well oxygenated
It is more difficult to evaluate the response in tissue because cells that are killed
are replaced by adjacent uninjured cell divisions.
Vegetative Intermitotic Cells
Differentiating Intermitotic Cells
Multipotential Connective Tissue Cells
Reverting Postmitotic Cells
Fixed Postmitotic Cells
Some cells present in tissue require very large doses of radiation before they are killed
directly by irradiation but often die due to killing of cells which support them are often
examples of which of the following types of cells from the classification by Rubin and
Casserette.
A.
B.
C.
D.
Vegetative intermitotic cells
Differentiating intermitotic cells
Multipotential connective tissue cells
Reverting postmitotic cells
E.
Fixed Postmitotic cells
14
14.
Another classification system has be described by Michalowski which groups cells more
according to the type of reproductive pattern which is used to replace lost cells. This
system also is based principally on reproductive kinetics of the cell population of interest.
Which of the following cell types would represent a classic example of a F-type (flexible) cell
population?
A.
B
C.
D.
E.
Bone marrow stem cells
Intestinal Crypt cells
Hepatocytes
Spermatagonia
Neurons
15.
Which of the following represents the most extreme example of an H-type cell according to
the classification by Michalowsky?
A.
B.
C.
D.
16.
E.
The critical cell line
The determinate cell line
The dominate cell line
The early responding cell line
The late responding cell line.
The objective work describing the relationship of radiation dose to lethality has been done
in animals and cell culture using assays which related radiation dose to cell and organism
killing. A clonogenic assay is a measurement of which of the following.
A.
B.
C.
D.
E.
18.
Intestinal crypt stem cell.
Although classification systems are useful, tissues themselves are usually comprised of
multiple cell populations and the effects must be assessed for each cell type and the overall
effect on the tissue will probably be associated with the most “sensitive” cell in the tissue
required for that tissue to survive. This cell line is known as which of the following?
A.
B.
C.
D.
E.
17.
Fetal stem cell
Bone marrow stem cell
Neuron
Hepatocyte (liver cell)
The ability of cells in a given cell line to survive radiation injury.
The ability of cells in a given cell line to reproduce after radiation injury.
The ability of a tissue to survive a radiation dose to a given cell line.
The ability of cells in a given cell line to repair radiation injury.
The ability of cells in a given cell line to function after radiation injury.
Which of the following types of assay measures the survival of cells retaining clonogenic
capabilities within the normal living conditions for that cell type.
A.
B.
C.
D.
E.
In vivo transplantation assay
In vitro transplantation assay
In vivo In situ assay
In vitro In situ assay
In vivo implantation assay
15
19.
A lethality assay performed in normal animals at the organ level without regard to time
after irradiation indicates that there is a relatively narrow range of dose over which an
animal will go from virtually 100% survival to almost no survival. How much dose is
required to reach this sudden decline in survival is and indication of which of the following?
A.
B.
C.
D.
E.
20.
Late responding tissues have essential cell populations characterized by which of the
following?
A.
B.
C.
D.
E.
21.
A large complement of cells in the G0 phase of the cell cycle
A large cell loss population
A short cell cycle time
A long cell cycle time
Lack of apoptosis
Cells are the basic building blocks of most living things on earth. The intrinsic sensitivity of
cells to irradiation is different for differ Phyla of organisms. Based on the complexity of its
DNA, which of the following has the greatest resistance to injury by ionizing radiation?
A.
B.
C.
D.
E.
22.
The functional reserve of the organ.
The repair capacity of the cells in that organ.
The length of the cell cycle time of the cells in that organ.
The amount of hypoxic tissue in that organ.
The degree of tissue differentiation in that tissue.
Bacteria
Fungi
Oak trees
Insects
Mammals
There are many different tissues in the body and each of them exhibits its own intrinsic
apparent sensitivity to irradiation based on the cell populations present in that tissue.
However all tissues share at least one cell type which often is the default dose limiting cell
type. That cell type is which of the following?
A.
B.
C.
D.
E.
Fibroblasts
Red blood cells
White blood cells
Vascular endothelium
Neurons.
16
23.
Tissue response to irradiation may include regeneration of the normal cell population of
that tissue. Which of the following scenarios is least likely to result in complete
regeneration of the original cell population of a tissue?
A.
B.
C.
D.
E.
24.
What is seen grossly in the tissue may not be as impressive as the microscopic changes seen
in a tissue. Which of the follow would you expect to be the most easily identified clinically?
A.
B.
C.
D.
E.
25.
Hair loss
Changes in pigmentation
Thinning of the skin.
Erythema (reddening of the skin)
All of the above.
One of the body systems which displays prominent early reaction to irradiation is the
digestive tract. It is one of the dose limiting systems that determines whether or not a
patient survives a moderate radiation dose to the whole body. Which of the following
portions of the digestive system is displays the most severe early changes following
irradiation?
A.
B.
C.
D.
E.
27.
Ulcerations on the skin
Edema under the skin
Fibrosis of the skin
Atrophy of the subcutaneous fat
Thinning and reduction of the blood supply to the skin
Which of the following is an effect on the skin which is likely to be seen in the radiation field
follow therapeutic irradiation of a tumor below the skin.
A.
B.
C.
D.
E.
26.
Low dose irradiation of an acutely responding tissue
High dose irradiation of an acutely responding tissue.
Low dose irradiation of a late responding tissue
High dose irradiation of a late responding tissue
Chronic low dose irradiation of a late responding tissue
The esophagus
The stomach
The small intestine
The colon
The oral mucosa
The reproductive organs (ovaries and testes) are considered to be the major dose limiting
tissues for whole body radiation exposure for occupationally exposed workers. Which of
the following represents the reason for this?
A.
B.
C.
D.
E.
Irradiation of the reproductive organs can lead to mutations in offspring
Even very low dose irradiation of the reproductive organs results in sterility.
Low dose irradiation of the reproductive organs causes hormonal imbalances.
The ovaries and testes are extremely prone to carcinogenisis following irradiation
Low dose irradiation of the ovaries and testes increases early embryonic death
17
28.
Many patients are irradiated for lung cancer therapy every year. In general the lung is
considered to be relatively radiosensitive. How is it, then that radiation therapy of the lung
does not usually result in severe clinical pulmonary dysfunction?
A.
B.
C.
D.
E.
29.
Irradiation of growing bone and cartilage can lead to deformities of the skeleton later in life.
At which of the following ages is irradiation of part of the skeleton at levels above 2Gy most
likely to result in skeletal growth abnormalities later in life?
A.
B.
C.
D.
E.
30.
The vascular endothelium
The glial cells
The neurons
The ependymal cells
Small lymphocytes in the circulating blood.
Under most circumstances irradiation (especially with particle beams) of the eyes is
avoided if at all possible. Why?
A.
B.
C.
D.
E.
32.
1-5 years of age
5-10 years of age
10-15 years of age
15-20 years of age
20-25 years of age.
Which of the following cells in the central nervous system is considered to be the most
radioresistant?
A.
B.
C.
D.
E.
31.
The lung is able to regenerate it’s epithelium readily
The radiation dose to the lung is less than to the tumor due to the air in the lung.
The lung is a late responding tissue and is able to repair injury well.
The lung has a very large functional reserve.
I lied. The lung is very radioresistant
The retina is very sensitive to radiation injury.
The lens of the eye is very sensitive to radiation injury
The eyes are very close to the brain, which should be avoided.
The vascular supply to the cornea of the eye is very tenuous and easily depleted.
The supporting epithelium of the lens is very sensitive and does not regenerate.
Total body radiation syndromes are the result of uniform irradiation of all of the major
organ systems of the body. This means that the radiation dose is sufficient in all of these
areas of the body for significant cell death to occur. It does not preclude the possibility that
some parts of the body may get lower or higher doses. At which of the following dose
ranges would you expect to begin to see clinical signs from a “total body” irradiation?
A.
B.
C,
1-2 Gy
3-5 Gy
6-8 Gy
18
D.
E.
33.
We all hope that we never see a whole body radiation syndrome as the result of an accident.
What is the most likely outcome of a whole body radiation dose of 1.5 Gray?
A.
B.
C.
D
E.
34.
Early embryonic death or no effect
Early embryonic death or severe birth defects.
Early embryonic death or mental retardation
Early embryonic death or severe permanent immunological deficiency
No effect on an embryo at this dose.
A 1.0 Gray pulse dose of x-ray irradiation to a fetus during the sixth month of gestation is
most likely to result in permanent reduced development of which of the following
organs/tissues?
A.
B.
C.
D.
E.
36.
Transient decreased ability to respond to disease challenge
Bone marrow syndrome
Sterility
GI syndrome
Central Nervous System syndrome
Radiation doses delivered to a fetus are always of concern. This true at even relatively low
doses of about 0.5 Grey. Which of the following is the most probable result of this dose to a
human embryo that is about 12 days old?
A.
B.
C.
D.
E.
35.
9-10 Gy
11-12 Gray
The central nervous system
The skeletal system
The heart
The reproductive tract
The intestinal tract
Low whole body radiation doses may not result in any manifest illness however damage to
the body may still be detectable by laboratory tests. Doses on the order of 1 Gy to the whole
body can significantly impact the function of the immune system. Which of the following
immune system functions is most likely to be affected by a radiation dose of this magnitude?
A.
B.
C.
D.
E.
Recognition of a foreign antigen presented to the body
Lymphocyte production by the bone marrow
Maturation of lymphocytes into plasma cells in the tissues
Antigen antibody complex phagacytosis my monocytes
Production of antibodies by the plasma cells.
19
37.
One of the greatest dangers from radioisotope is ingestion of the isotope from
contamination of foodstuffs or drinking water. One of the favorite targets of such ingested
radioisotopes is the bone marrow. Which of the following would be the most probable
effect of radioisotope ingestion resulting in a acute dose of 0.8 Gy over a 2 day period of
time to the entire bone marrow?
A.
B.
C.
D.
E.
38.
Tumor radiation biology is a specialized branch of radiation biology which deals with the
response of neoplastic diseases to ionizing radiation. Tumors have a different physiology
than that of normal tissues. Which of the following is a feature in which tumors resemble
some normal tissues?
A.
B.
C.
D.
E.
39
Tumors have no lymphatic drainage.
Tumors often have a phenotypically very heterogenous cell population
Tumors usually have about the same cell cycle time as the cells in the tissue of
origin.
Tumors have cells in their cycling cell population which undergo apoptosis.
Tumors tend to have sinusoidal blood supplies with sluggish blood flow.
In recent years many studies have made great strides in elucidating the mechanisms by
which cancers develop. Typically cancers develop due to changes in regulation of gene
expression in some cells. Which of the following would be a mechanism likely to lead to
formation of a cancerous cell?
A.
B.
C.
D.
E.
40.
Severe drop in white blood cell counts.
Severe drop in platelet counts.
Severe drop in red blood cell counts
Blunting of antibody response to a new pathogen at the time of the irradiation.
Severe suppression of the body’s cellular immunity system
A mutation which alters the shape of the functioning DNA
Up regulation of an oncogene and down regulation of tumor suppressor genes
Up regulation of a tumor suppressor gene and down regulation of a DNA stability
gene
Loss of DNA stability and repair promoter genes.
A mutation causing up regulation of a protooncogene and tumor suppressor genes
The occurrence of a mutated cell is only the first step in a series of events required for a
cancerous cell population to form. Which of the following represents the final step in the
development of a cancer cell population?
A.
B.
C.
D.
E.
Loss of phenotypic stability
Loss of response to contact cellular inhibitory signaling
Acquisition of an imortalized clonogenic reproductive capability
Acquisition of a blood supply
Ability of cells in the cancer cell population to escape apoptosis
20
41.
Neoplasms usually have relatively large populations of clonogenic cells as well as large
populations of cells which may not retain clonogenic capability. Clonogenic cells are
responsible for the regrowth of a tumor follow irradiation. How many viably clonogenic
tumor cells must remain in a tumor following radiation therapy or any other cancer
treatment for the tumor to regrow?
A.
B.
C.
D.
E.
42.
One of the major challenges in the treatment of neoplasias with radiation is to deal with the
fact that many tumors contain many hypoxic cells. Why does this make the treatment of
tumors with radiation less effective?
A.
B.
C.
D.
E.
43.
Hypoxic cells cannot be killed with radiation.
The hypoxia prevents the cellular repair mechanisms from repairing injury.
Hypoxia inhibits “fixation” of DNA injuries.
Hypoxic cells can reproduce better than normal cells
Hypoxic cells are not part of the cycling tumor cell population.
Neoplasms grow within normal tissues and generally arise from a single cell. It therefore
requires many cell division cycles to occur before a tumor reaches clinically detectable size.
Which of the following would you expect to appreciably decrease the time that it would take
a tumor to reach clinically detectable size?
A.
B.
C.
D.
E.
44.
10,000
1000
100
10
1
Increase in the cell cycle time
Increased numbers of hypoxic cells in the neoplasm
Increase in the cell loss fraction
Increase in the cell growth fraction
Increased heterogeneity of the neoplastic phenotype
The cellular kinetics within a tumor are very important to the planning of radiation therapy
for a given tumor. Most tumors fall into one category but there are a few that must be
evaluated and treated in a different manner. Which of the following cellular kinetics factors
is most influential in determining what the clinically evident response of the tumor is.
A.
B.
C.
D.
E.
The cell growth fraction.
The cell death fraction
The hypoxic cell fraction
The cell cycle time
The cell loss fraction.
21
45.
The Four (or five) R’s of radiation biology can be used to explain many of the clinically
observed effects of radiation on tumors and normal tissues. Which of the following is an
effect which is of very little or no importance in normal tissues?
A.
B.
C.
D.
E.
46.
Following irradiation of a neoplasm or normal tissues there may be regrowth of the tumor
cell or normal cell populations from the surviving cells. This is known as which of the
following?
A.
B.
C.
D.
E.
47.
Redistribution
Reoxygenation
Repopulation
Recruitment
Repair
Reoxygenation of hypoxic cells is important in the successful treatment of tumors with
radiation. This is especially true as the size of the tumor to be treated increases. Which of
the following is not method by which the number hypoxic tumor cells is reduced?
A.
B.
C.
D.
E.
48.
Redistribution (reassortment)
Regeneration (Repopulation)
Repair
Reoxygenation
Recruitment
Oxic tumor cells killed by radiation are replaced by hypoxic cells
The tumor vasculature releases a spasm and more blood flows into a hypoxic area.
Surgical removal of the bulk of the tumor mass..
Giving the patient pure oxygen to breath for a few minutes before the treatment.
Shedding of oxic cells into the blood stream
One of the major effects of fractionated radiation therapy on tumor cell populations is the
movement of cells from the non-cycling G0 pool into the cycling cell population. This is
referred to as which of the following?
A.
B.
C.
D.
E.
Redistribution (Reassortment)
Regeneration (Repopulation)
Repair
Reoxygenation
Recruitment
22
49.
The linear quadratic equation is a mathematical model which provides a relatively good fit
for the shape of radiation survival curves, at least in the upper 5-6 logs of the curve. The
equation is based on what is called the alpha/beta dose (ratio). At what point on the cell
survival curve is the alpha/beta dose determined.
A.
B.
C.
D.
E.
50.
A single dose of radiation to a tumor site has insufficiently different effect on tumor cells
from that seen in normal cells to result in significantly more damage to the tumor than the
normal tissues so single dose irradiation of a tumor is only applicable if only the tumor and
no normal tissue can be irradiated. Otherwise fractionation is employed. Fractionation has
the greatest benefit for which of the following:?
A.
B.
C.
D.
E.
51.
Acute effects in early responding tissues
Late effects in early responding tissues
Late effects in late responding tissues
Acute effects in late responding tissues
There are no differences for any of the above
With regards to tumor cells, which of the following is true of the application of radiation
therapy in a fractionated dosing regime using x-rays?
A.
B.
C.
D.
E.
52.
The point at which the repair shoulder straightens out.
The point at which the repair shoulder begins
The point at which the slope of the curve is half way between the slope at the
beginning and the straight portion of the curve.
The point on the curve where the number of cells killed per Gray is proportional to
the radiation dose is equal to the number of cells killed per Gray is proportional to
the square of the dose.
The point on the curve which indicates that equal numbers of cells are being killed
by single hit killing and by multihit killing.
Fractionation has no effect on the total dose of radiation required to kill the tumor
Fractionation decreases the total dose of radiation required to kill the tumor
Fractionation increases the total dose of radiation required to kill the tumor
Fractionation accelerates the killing of the tumor.
Fractionation increases the number of tumor cells killed per Gray of radiation
The effect of fractionation for increasing the effect of radiation on tumors versus normal
tissues is different at different doses per fraction and different dose rates. Therefore
fraction size is usually chosen at a point on the survival curve which will maximize the
effect. Which of the following represents the point on the dose curve which is usually
chosen as the approximate fraction size?
A.
B.
C.
D.
E.
Dq
D0
10% survival
80% survival
The end of the linear part of the curve
23
53.
When considering the timing of radiation fraction delivered in multifractionate dose
regimes it is important the take into account the effect of repair on the tissue’s response to
irradiation. Which of the following is generally considered to be the minimum time one
should wait between delivering radiation fractions so that intracellular repair can be
complete?
A.
B.
C.
D.
E.
54.
The size of radiation fraction delivered to the tumor is very important but it is even more
important for normal tissues in the radiation field. Increasing the radiation fraction size has
which of the following effects.
A.
B.
C.
D.
E.
55.
Spinal cord
Bone marrow
Intestinal epithelium
Skin
Kidney
Radiation therapy using protons is of great interest for which of the following reasons?
A.
B.
C.
D.
E.
57.
Increased tumor cell kill and reduced normal tissue late effects
Increased tumor cell kill and increased normal tissue late effects.
Decreased tumor cell kill and increased normal tissue early effects
Decreased tumor cell kill and decreased normal tissue effects
Increased tumor cell kill and increased normal tissue late and early effects.
Which of the following tissue types would benefit most by changing the fraction size in a
radiation therapy regime from 4 Gray to 2 Gray?
A.
B.
C.
D.
E.
56.
1 hour
6 hours
12 hours
18 hours
24 hours
Cells irradiated with proton irradiation exhibit no repair shoulder
Because of the increased RBE with protons less radiation dose is required.
Irradiation with protons requires less sophisticated planning than with x-rays
The dose deposition profile can result in increased tumor dose and decreased
normal tissue dose.
Proton irradiation results in fewer severe side effects than x-ray therapy
Many man-years of effort and tens of millions of dollars have been spent in trying to find
ways to chemically modify the response of normal tissues and tumors to irradiation with
ionizing radiation. Which of the following is the most potent (powerful) chemical modifier
of cellular radiation injury?
A.
B.
C.
D.
Misonidazole
WR-2721 (Amophostine)
Halogenated pyrimadines
Chemotherapy drugs
24
E.
58.
Hyperthermia is of great interest for use in conjunction with radiation therapy because of
its synergistic cell killing effects when combined with radiation. Which of the follow
attributes of hyperthermic therapy is not a synergistic effect with that of irradiation?
A.
B.
C.
D.
E.
59.
Hyperthermia kills S-phase cells preferentially
Hyperthermia is not oxygen dependent.
Hyperthermia tends to destroy tumor vasculature
Hyperthermia tends to kill cells in low pH environments.
Hyperthermia inhibits intracellular repair of SLD and PLD
Electrons have a significant advantage in the treatment of superficial diseases. Which of the
following is probably the most significant advantage of electron beam treatments.
A.
B.
C.
D.
E.
60.
Oxygen
The electrons are high LET at the end of the tract and deliver increased dose there
The electrons are absorbed over a narrow range and there is little dose beyond the
tumor.
The electrons deposit the dose only in the tumor
Electrons are high LET particles and therefore do not require fractionation so the
number of treatments is reduced.
Because they are charged particles there is less surface dose that with high energy
photons.
Radiation biology as we have discussed in class has many facets. Which of the following is a
recurring factor which impacts the effect of radiation on living organisms in all of the
situations we have discussed.
A.
B.
C.
D.
E.
The cell growth fraction.
The cell death fraction
The length of the cell cycle of the irradiated cells.
The level of cellular oxygenation.
The extent of damage to the DNA.
25