Introductory Radiation Biology 2002
Exam I
WHEREVER POSSIBLE, SHOW ALL WORK!!!

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. , I_t = 5% of I₀)?
   d. Approximately how many half-value layers (HVLs) is this?
   
   
2. An FM radio station broadcasts at a frequency of 102.3 MHz (i.e., 1.023 ´ 10 8 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. ²¹³₈₃Bi (T_1/2 = 46 min) is a radionuclide used to treat leukemia when attached to tumor-targeting monoclonal antibodies. It decays by two different modes: in 97.8% of all events, it decays to an excited state that lies 440 keV above the ground state of ²¹³₈₄Po (T_1/2= 4 µs), while in 2.2% of all events, it decays to the ground state of ²⁰⁹₈₁Tl (T_1/2= 2.2 min). Note that these two modes account for 100% of the decay of ²¹³₈₃Bi. Both daughter radionuclides, ²¹³₈₄Po and ²⁰⁹₈₁Tl, decay exclusively to the ground state of ²⁰⁹₈₂Pb(T_1/2 = 3.25 h), which finally decays to the ground state of ²⁰⁹₈₃Bi, which is stable.
   a. Sketch a decay scheme that is consistent with the decay of ²¹³₈₃Bi to ²⁰⁹₈₃Bi. For each decay and/or de-excitation mode, identify the one major photon or charged particle emitted.
   b. Circle the correct answer: the total yield of high LET radiation from the decay of ²¹³₈₃Bi is: (HINT: Think in terms of all the heavy charged particles emitted.)
   2%, 97.8%, 100%
   c. You are a radiochemist who is labeling a monoclonal antibody with ²¹³Bi in order to treat a leukemia patient at Memorial Sloan-Kettering Cancer Center in New York. After you elute 44 mCi of pure ²¹³Bi from an 225 Ac generator, it takes 9 min to label the antibody, with 100% incorporation of ²¹³Bi, 9 min to purify the labeled antibody, 5 min to perform quality control analysis to make sure the dose is radiochemically pure, 5 min to dilute the dose for injection, and 18 min to deliver the dose and inject it into the patient. What dose (in mCi) of ²¹³Bi-labeled antibody did the patient receive?
   d. List all the types of emissions ( i.e. , photons and particles) that will occur during the decay of ²¹³Bi.
   
   
4. The average LET of a 200 keV electron is 3 keV/µm in soft tissue.
   a. What is the range of this electron in soft tissue?
   b. Estimate the average LET of a 200 keV deuteron ( i.e. , 2 1 H + ).
   
   
5. TRUE/FALSE
   _____ a. A 100 keV gamma photon will have a greater ability to penetrate soft tissue than a 100 keV x-ray.
   _____ b. Radionuclides produced by spontaneous fission or thermal neutron capture reactions typically decay by ß - emission.
   _____ c. The gamma-emitter 99m 43 Tc decays predominantly by isomeric transition to 99g ⁴³Tc. However, the radioisotope 94m ⁴³Tc decays only to ⁹⁴₄₂Mo, which is highly unusual for a metastable isomer. The charged particle emitted during the decay of 94m Tc makes it potentially useful for positron emission tomography imaging.
   _____ d. Wilhelm Conrad Röntgen won the 1901 Nobel Prize in Physics for the discovery of naturally occurring penetrating radiation, which Pierre and Marie Curie called "radioactivity."
   _____ e. As the LET of a charged particle increases, its range in matter 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, which can ionize molecules and produce latent cancer.
   _____ g. Alpha particles are always monoenergetic, while beta particles are emitted over a wide spectrum of energies.
   _____ h. Without knowing the source, one can easily distinguish a 10 MeV ß^- particle from a 10 MeV LINAC electron, using conventional radiation detection equipment.
   
   
6. 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. 8 MeV proton _____
   b. 62 keV x-ray _____
   c. 8 MeV electron _____
   d. 1.33 MeV gamma ray _____
   e. 500 keV electron _____
   f. 8 MeV alpha particle _____
   
   
7. The dominant mechanism by which a 5 MeV photon interacts with soft tissue is:
   a. pair production.
   b. the photoelectric effect.
   c. Compton scattering.
   d. transfer of an average of 60 eV per collision with an atom.
   e. 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. severely scald his tongue and probably die of starvation before it heals.
   b. win a major lawsuit against the manufacturers of the coffee and the coffee machine, enabling him to retire a millionaire.
   c. be so stimulated by the caffeine that his test score will improve by 10 points.
   d. absorb the same amount of energy as a lethal dose of ionizing radiation.
   
   
9. The difference between a 250 keV x-ray and a 250 keV alpha particle is:
   a. The x-ray has greater penetrating ability in water or soft tissue.
   b. The ionization density of the alpha particle is many thousand-fold higher than that of the x-ray.
   c. of no consequence as far as the potential for biological damage is concerned.
   d. both (a) and (b) above.
   e. all of the above.
   
   
10. Electron capture decay is:
    a. always accompanied by emission of x-rays.
    b. usually accompanied by emission of gamma rays.
    c. an alternative to positron decay for proton-rich radionuclides.
    d. all of the above.
    e. none of the above.
    
    
11. Briefly define, identify, or describe:
    a. Ionizing radiation
    b. Radioactive decay
    c. LET
    d. Marie Curie
    e. Mean free path
    f. Photoelectric effect
    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 slides 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 explanation.)
    

INTRODUCTORY RADIATION BIOLOGY
EXAM II 2002

1. A radiation worker at a reactor received a whole body dose of 360 mrem during the last quarter. The Radiation Safety Officer discovered that 160 mrem was from fast neutrons (QF=20) and 200 mrem was from gamma rays.
   a. How many mSv is 360 mrem? (show work and/or the conversion factor you used).
   b. How many mrads did this worker receive from the fast neutron exposure?
   c. How many mrads did this worker receive from the gamma-ray exposure?
   
   
2. Using the simplified double strand model for DNA used in class (i.e., a ladder type structure), pictorially show how a double strand break can be produced by two separate Low LET radiation (e.g., high energy electrons) events. Explain why that at low dose rates , the probability of causing a double strand break by this type of two hit process approaches zero.
   
   
3. Which of the following species are "Free Radicals" (there is more than one answer).
   a. OH^-
   b. H⁺
   c. H-atom
   d. H₂O₂
   
   e. a²²₁₁ Na-metal atom
   f. O^-₂
   g. e^-_aq
   h. N₂
   
4. Make a sketch of a cell survival curve (including proper labeling of the X and Y axes) that demonstrates how the semi-log plot should appear:
   a. If mammalian cells are irradiated under oxygen (Po ₂ =150 mm Hg) at a high dose rate with 4 MeV alpha particles.
   b. If mammalian cells are irradiated under oxygen at a high dose rate with 1 MeV gamma-rays.
   
   
5. a) Explain what is meant by the "Oxygen Effect".
   b)Briefly explain how the oxygen effect alters the effectiveness of treating tumors in cancer patients irradiated with a beam of high-energy electrons or with gamma rays.
   
   
6. Outline the steps in the Nucleotide Excision Repair (Cut & Patch) mechanism. Identify the enzymes (or what functions they perform) involved at the corresponding steps.
   
   
7. Briefly define or describe:
   a. At least two types of damage to double strand DNA that is NOT repairable.
   b. sub-lethal damage
   c. The Roentgen Unit
   d. Thymine-Thymine (T-T) dimmers
   e. R.B.E.
   f. TA cells
   g. Anoxia (or anoxic)
   h. repair replication
   
   
8. TRUE-FALSE
   ___ a. Molecular oxygen (O₂ ) is considered to be a free radical.
   ___ b. In general, as the LET decreases, the extrapolation number on cell survival curves decreases when the cells are irradiated under oxygen at a high dose rate.
   ___ c. After your visit to MURR, all individuals leaving the facility must pass through a portal monitor (to check for radioactivity contamination) before reentering the lobby of MURR.
   ___ d. RBE increases with LET of radiation to a maximum of approximately 100 KeV/µm.
   ___ e. Alpha particle radiation produces about 65% of its damage to living cells by the "indirect effect".
   ___ f. High energy alpha particles were used to irradiate human lung cells in culture that were fully oxygenated (i.e., Po ₂ =150 mm Hg) at a high dose rate. You would expect the OER will be approximately 1.0.
   ___ g. UV light produces damage to DNA in our cells primarily by promoting the bases (i.e., A, T, C, G) to an excited state and not by ionizing these bases.
   ___ h. Cell survival curves, using a high energy proton beam, were generated by irradiating human kidney cells and human thyroid cells in culture. The D₀ measured for the kidney cells was 70 rads and the D₀ measured for the thyroid cells was 300 rads. This data shows that the thyroid cells are more sensitive to proton beam irradiation than the kidney cells.
   ___ i. In the "Linear-quadratic" model, the "quadratic" term for cell killing dominates (relative to the linear term) for cells irradiated with X-rays in the low total dose (i.e., <5 rads) region of the curve.
   ___ j. The Quality Factor (QF) is an experimentally determined value while the RBE is an LET derived "estimate" of the QF.
   ___ k. A fast neutron will lose a larger fraction of its energy when it collides head-on with the nucleus of a C-atom, compared to a head-on collision of the fast neutron with the nucleus of an H-atom (i.e., a proton).
   

NE 328 Radiation Biology - Exam 3
November 14, 2002 Dr. Lattimer
Please select the one best answer for each question. Some answers may be partly true. Variable credit. Negative credit is possible.

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 most likely to result in permanent or lethal injury to the cell?
   A. The nuclear DNA
   B. The nuclear RNA
   C. The mitochondrial DNA
   D. The cytoplasmic messenger DNA
   E. The nucleus
   
   
2. 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. Ionization of the disulfide crosslink bonds
   B. Ionization of carbon hydrogen bonds
   C. Ionization of water
   D. Ionization of carbon phosphorous bonds
   E. Ionization of peroxide molecules
   
   
3. When radiation damage occurs in DNA the damage must be made permanent or normal enzymatic processes will repair the injury. What is the principal way in which radiation derived injury to the DNA is "fixed".
   A. By reduction by hydrogen
   B. The injury cannot be repaired by the cell
   C. Inappropriate replacement of atoms in the damaged area by repair enzymes.
   D. Carbon to carbon fusion reaction
   E. Oxidation by cellular oxygen
   
   
4. The term "cell cycle" refers to the life cycle of cells. All cells go through this cycle if they are replicating cells. Each of the stages of the cell cycle has different functional attributes. Which of the following is the stage of the cell cycle where the actual "work" that the cell is designed to perform is done.
   A. G ₁
   B. S
   C. G ₂
   D. M
   E. G ₀
   
   
5. In radiation biology, the death of the cell can occur at various points along the cell cycle depending on the dose and the cell type. Which of the follow represents the two principal sites at which cell death occurs.
   A. S-phase and M-phase
   B. G₂-phase an M-phase
   C. G₁ phase and M-phase
   D. G₁-S interface and M-G₁ interface
   E. S-G₂ interface and G₁-S interface
   
   
6. Cells which are damaged my be removed from the circulating pool of cells by a process whereby certain genes recognize the damaged cell and cause it to die. This is the process of ?
   A. Apoptosis
   B. Mitotic Linked Death
   C. Interphase death
   D. Prophase death
   E. Osmosis
   
   
7. 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. That the cells accrue injury at a faster rate as the dose goes up.
   B. That there are two mechanisms of killing taking place.
   C. That there are multiple targets being affected with more affected at higher doses.
   D. That the cells have some ability to repair injury. Especially at low doses.
   E. That there are multiple killing mechanisms present and that some damage is repaired.
   
   
8. 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. Hepatocytes
   B. Small circulating lymphocytes
   C. Intestinal smooth muscle cells
   D. Endothelial cells
   E. Erythrocytes
   
   
9. Which of the following best describes the principal put forth in the "Law of Bergonie' and Tribondeau"?
   A. Tissues composed mainly of slowly cycling cell exhibit radiation injury first.
   B. Cell lines which are rapidly cycling will recover from radiation injury first.
   C. Cell lines which have long cell cycle times but are continously cycling are radiation resistant.
   D. Tissues composed mainly of non-cycling cells are more radiation resistant.
   E. Critical cell lines are responsible for tissue death.
   
   
10. The concept of cellular differentiation as an indicator of tissue radiation sensitivity is well established in radiation biology. This principal is described by which of the following.
    A. The more specialized a cell function is the more radiation sensitive it is.
    B. The more specialized a cell function is the more radiation resistant it is.
    C. The more specialized a cell' structure is the more radiation sensitive it is.
    D. The more specialized a cell's structure is the more radiation resistant it is.
    E. The more specialized a cell's structure is the less likely it is to undergo division.
    
    
11. Rubin and Casarett classified cells according to their division kinetics. According to this classification which of the follow type of cells is the most likely to demonstrate evidence of radiation injury shortly after the radiation injury occurs?
    A. Fixed Post Mitotic cells
    B. Reverting Post Mitotic cells
    C. Multipotential Connective Tissue cells
    D. Differentiating Intermitotic Cells
    E. Vegetative Intermitotic Cells
    
    
12. 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. The ability of cells in a given cell line to survive radiation injury.
    B. The ability of cells in a given cell line to reproduce after radiation injury.
    C. The ability of a tissue to survive the a radiation dose to a given cell line.
    D. The ability of cells in a given cell line to repair radiation injury.
    E. The ability of cells in a given cell line to function after radiation injury.
    
    
13. 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. The functional reserve of the organ.
    B. The repair capacity of the cells in that organ.
    C. The length of the cell cycle time of the cells in that organ.
    D. The amount of hypoxic tissue in that organ.
    E. The degree of tissue differentiation in that tissue.
    
    
14. In the low dose ranges (1-2 Grey) there are at least two factors which can dramatically influence whether or not a tissue can recover from radiation injury. Which of the follow best reflects these factors.
    A. The repair capacity and cell loss fraction within the tissue cell population
    B. The repair capacity, cell loss fraction and oxygenation of the tissue cells.
    C. The repair capacity, cell growth fraction and oxygenation of the tissue cells
    D. The repair capacity, cell growth fraction and cell loss fraction of the tissue cells
    E. The cell growth fraction, cell loss fraction and oxygenation of the tissue cells.
    
    
15. Following radiation injury there is a period of time which passes before the radiation injury is manifest in the tissue or at the clinical level. Tissues roughly break down into tissues that manifest injury soon after irradiation and tissues which manifest changes slowly over time. Loss of intestinal epithelium after irradiation of the abdomen is and example of ?
    A. An acute change in a late responding tissue
    B. A chronic change in an early responding tissue
    C. An acute change in an early responding tissue
    D. A chronic change in a late responding tissue.
    E. Cellular regeneration in a late responding tissue.
    
    
16. Which of the following represents an acute radiation change.
    A. Atrophy
    B. Depigmentation
    C. Edema
    D. Fibrosis
    E. Regeneration
    
    
17. Regeneration potential is an important characteristic of a tissue which may determine whether or not a patient ultimately survives irradiation of that tissue. Which of the follow tissue cell types is most likely to regenerate following radiation injury?
    A. Fixed Post Mitotic cells
    B. Reverting Post Mitotic cells
    C. Multipotential Connective Tissue cells
    D. Differentiating Intermitotic Cells
    E. Vegetative Intermitotic Cells
    
    
18. The hemopoietic system is the system in the body which is responsible for the creation of the blood and lymphatic cells within the body and as such is very necessary to life. Which of the following cell types in this system is considered to be the most sensitive?
    A. The Erythroblast
    B. The Lymphoblast
    C. The Macrophage
    D. The Thrombocyte
    E. The Erythrocyte
    
    
19. The skin is actually made up of a large number of cell types which have different functions. Which of the following components of the skin cell population is considered most radiation resistant.
    A. Basal cells of the skin
    B. Mature surface layer epithelium
    C. The fibroblasts in the skin
    D. The endothelial cells of the blood vessels
    E. The melanocytes.
    
    
20. In the digestive system the epithelial cells are rapidly lost following radiation injury and may recover relatively rapidly following the radiation injury. However, late effects in the intestinal tract can be quite profound. Which of the following late effects would you expect to cause clinical problems in the intestine.
    A. Edema
    B. Muscle atrophy
    C. Fibrosis
    D. Mucosal thinning
    E Depigmentation
    
    
21. Many 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. The lung is able to regenerate it's epithelium readily
    B. The radiation dose to the lung is less than to the tumor due to the air in the lung.
    C. The lung is a late responding tissue and is able to repair injury well.
    D. The lung has a very large functional reserve.
    E. I lied. The lung is very radioresistant
    
    
22. Under most circumstance irradiation (particularly with therapy beams) of the eyes is avoided if at all possible. Why?
    A. The retina is very sensitive to radiation injury.
    B. The lens of the eye is very sensitive to radiation injury
    C. The eyes are very close to the brain, which should be avoided.
    D. The vascular supply to the cornea of the eye is very tenuous and easily depleted.
    E. The supporting epithelium of the lens is very sensitive and does not regenerate.
    
    
23. Radiation injury to the skeleton from a moderate dose (6-10 grey acute single dose) is most likely to occur under which of the following circumstances?
    A. When a joint is in the radiation field.
    B. When the vertebral column (spine) is irradiated.
    C. When the animal is skeletally quite immature
    D. When the radiation dose is delivered just before surgery.
    E. When a tourniquet is on the limb at the time of irradiation.
    
    
24. Irradiation of the reproductive organs is of great concern even at low doses (less than 1 grey). Why?
    A. In women there is always the possibility of an early pregnancy which might be lost from such a radiation dose.
    B There is always the possibility of mutations which could be passed on to offspring
    C. The reproductive organs will be sterilized even at these low doses.
    D. The hormonal output of the ovaries and testes will be reduced and cause numerous clinical problems.
    E. Loss of function in these organs will cause significant psychological problems.
    
    
25. 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 2 grey?
    A. Transient decreased ability to respond to disease challenge
    B. Bone marrow syndrome
    C. Sterility
    D GI syndrome
    E. Central Nervous System syndrome.
    
    
26. 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. Early embryonic death or no effect
    B. Early embryonic death or severe birth defects.
    C. Early embryonic death or mental retardation
    D. Early embryonic death or severe permanent immunological deficiency
    E. No effect on an embryo at this dose.
    
    
27. 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 major difference between tumors and normal tissues.
    A. Tumors have no blood supply.
    B. Tumors often have a phenotypically very heterogenous cell population
    C. Tumors usually have about the same cell cycle time as the cells in the tissue of origin.
    D. Tumors often have a phenotypically very homogenous cell population.
    E. Tumors have excessively developed blood supplies.
    
    
28. 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 difficult?
    A. Hypoxic cells cannot be killed with radiation.
    B. The hypoxia prevents the cellular repair mechanisms from repairing injury.
    C. Hypoxic cells may require more than twice the dose of radiation to kill them that oxic cells require.
    D. Hypoxic cells can reproduce better than normal cells
    E. Hypoxic cells are not cycling a part of the tumor cell cycle.
    
    
29. 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. The cell growth fraction.
    B. The cell death fraction
    C. The hypoxic cell fraction
    D. The cell cycle time
    E. The cell loss fraction.
    
    
30. Radiation therapy practice usually dictates that a tumor be treated with fractionated protocols (many small dose of radiation rather than a single large one.) Why is this done?
    A. Numerous small fractions maximize the repair of late responding normal tissues and minimize the survival of early responding tissues. (tumors)
    B. Multiple small fractions promote regeneration of normal tissues.
    C. Multiple small fractions promote the reoxygenation of hypoxic cells
    D. Multiple small fractions are easier to administer than a single large one
    E. Multiple small fractions promote an immune response by the body to the tumor.
    
    
31. Much of the modern theory and practice of radiation therapy hinges around the 4 R's of radiation biology . Which of the following is not part of the original 4 R's.
    A. Recruitment
    B. Reoxygenation
    C. Repair
    D. Repopulation
    E. Reassortment.
    
    
32. 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. Oxic tumor cells killed by radiation are replaced by hypoxic cells which then become oxic.
    B. The tumor vasculature releases a spasm and more blood flows into a hypoxic area.
    C. Surgical removal of the bulk of the tumor mass..
    D. Giving the patient pure oxygen to breath for a few minutes before the treatment.
    E. Shedding of hypoxic cells into the blood stream.
    
    
33. Other than the effect on hypoxic cells, fractionation has some other positive attributes. Which of the following is reduced by fractionation.
    A. The total dose of radiation given to the tumor is reduced.
    B. Fractionation decreases repair in late responding normal tissues.
    C Fractionation decreases repair in tumor tissues
    D. Fractionation decreases acute effects in early responding tissues
    E. Fraction decreases chronic changes in late responding normal tissues.
    
    
34. Repair is an important component of a normal tissue's response to a radiation insult. Which of the following is true about intracellular radiation repair in normal tissues.
    A. It is promoted by the presence of oxygen in the cell
    B. It is typically complete by 2 hours after the radiation injury occurs.
    C. It is greatest at low doses of less than 2 Grey.
    D. Repair is greater and occurs more quickly in tumor tissues than in normal tissues
    E. Repair and regeneration mean essentially the same thing.
    
    
35. In tumor biology it is a well know phenomenon that the apparent aggressiveness of a tumor increases as the size of the tumor increases. Following radiation therapy it is sometimes noted that if a tumor recurs it is more aggressive and rapid growing than the original tumor. Which of the following would be an explanation for this?
    A. The radiation treatment would tend to select for more clonogenic cells which could reestablish the population after the radiation treatment.
    B. Radiation therapy is less likely to kill more anaplastic (primitive) cells
    C. Radiation therapy tends to be more lethal for rapidly dividing cells.
    D. Radiation therapy kills the oxygenated cells and the remaining hypoxic cells are more aggressive when they become reoxygenated.
    E. Some of the cells in the tumor population have very slow cell cycle times and the radiation therapy will spare these cells which then reestablish the tumor because they repair injury.
    
    
36. When designing a radiation therapy protocol fractionation is usually a part of it for low LET radiation. The principal reason for this is?
    A. The fractionation results in fewer acute responses in early responding tissues
    B. The fractionation results in fewer chronic responses in early responding tissues.
    C. The fractionation results in fewer acute responses in late responding tissues
    D. The fractionation results in fewer chronic responses in late responding tissues.
    E. The fractionation results in greater overall dose to the tumor and fewer chronic changes in late responding tissues.
    
    
37. 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. The electrons are high LET at the end of the tract and deliver increased dose there
    B. The electrons are absorbed over a narrow range and there is little dose beyond the tumor. C. The electrons deposit the dose only in the tumor
    D. Electrons are high LET particles and therefore do not require fractionation so the number of treatments is reduced.
    E. Because they are charged particles there is less surface dose that with high energy photons.
    
    
38. Hypothermia is a means of sensitizing tissue to radiation. The combination of the two is more effective than either alone. Which of the following is not a mechanism of heating which is synergistic with radiation.
    A. The S-phase cells are more sensitive to thermal injury than other phases of the cell cycle.
    B. The hypoxic cells are preferentially damaged by heat
    C. The cells at low pH are preferentially killed by heat.
    D. The heat increases the blood flow to the tumor.
    E. Thermal injury inhibits repair
    
    
39. Implantation of radiation sources into the tumor has many advantages. Which of the following is one of those advantages.
    A. The radiation dose is concentrated in the tumor
    B. Multiple isotopes can be used to increase the spectrum of the radiation to the tumor.
    C. Isotope implantation is essentially the same as a single large dose to the tumor.
    D. The radiation from the implant is of less danger to the person giving the treatment
    E. The dosimetry of this type of treatment is simpler than for external beam therapy
    
    
40. The use of multiple fields to treat a tumor deep within the body is a commonly used technique to reduce the dose to the normal tissues. Which of the following is true.
    A. The use of multiple fields reduces the overall amount of radiation used.
    B. The use of multiple fields usually reduces the dose you can give to the tumor
    C. The use of multiple fields does not eliminate the risk of carcinogenesis
    D. The use of multiple fields does not allow the tumor to be treated homogenously
    E. The use of multiple fields reduces the number of treatment fractions needed.
    
    
41. 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. The cell growth fraction.
    B. The cell death fraction
    C. The length of the cell cycle of the irradiated cells.
    D. The level of cellular oxygenation.
    E. The extent of damage to the DNA.
    1. _____ 21 _____
    2. _____ 22 _____
    3. _____ 23 _____
    4. _____ 24 _____
    5. _____ 25 _____
    6. _____ 26. _____
    7. _____ 27. _____
    8, _____ 28. _____
    9. _____ 29. _____
    10. _____ 30. _____
    11. _____ 31. _____
    12. _____ 32. _____
    13. _____ 33. _____
    14, _____ 34. _____
    15. _____ 35. _____
    16. _____ 36. _____
    17. _____ 37. _____
    18. _____ 38. _____
    19. _____ 39. _____
    20. _____ 40. _____
    41. _____
    
    

Introductory Radiation Biology
Final Exam, 2002

1. Which type of cancer is ¹⁵³Sm-EDTMP capable of treating in humans
   a. liver cancer
   b. stomach cancer
   c. skin cancer
   d. bone cancer
   
   
2. ¹³¹I is a radioisotope used in Nuclear Medicine and for other applications. Which one of the statements below is correct?
   a. ¹³¹I emits both beta particles and gamma rays
   b. ¹³¹I emits alpha particles and gamma rays
   c. ¹³¹I emits beta particles but no gamma rays
   d. ¹³¹I emits only alpha particles
   
   
3. If ¹³¹I-sodium iodide is administered to patients, it will concentrate in the thyroid gland with high specificity.
   a. Briefly explain (no more than 3 sentences) the reason ¹³¹I-iodide concentrates in the thyroid gland.
   b. Briefly explain the reason ¹³¹Iworks well as a therapeutic agent for the cure of well differentiated thyroid cancer.
   
   
4. PET is an abbreviation for ___________ __________________ __________.
   
   
5. 18 FDG is a radioactive analogue of which one of the following molecules
   a. glutamic acid
   b. dextran
   c. glucose
   d. DNA
   
   
6. Briefly (in 2 or 3 sentences) explain why epidemiologists demonstrate statistically demonstratable increased levels of radiation induced thyroid cancers in lower dose ranges (i.e., at 10-20 rad levels) while a statistically significant increase in breast cancer incidence could only be demonstrated at higher doses (i.e., 50-200 rads).
   
   
7. Briefly describe (in 1 sentence) why a statistically significant radiation-induced increase in the incidence of most other cancers (e.g., skin cancer, liver cancers, etc.) cannot be demonstrated at a whole body dose of 50 rads.
   
   
8. A population of 100,000 people received a whole body dose of 10 rads each, according to the risk factor discussed in class that is based on the BEIR V report, the total number of cancer deaths produced in this 100,000 population is estimated to be:
   a. 100
   b. 500
   c. 5,000
   d. 20,000
   
   
9. 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 __________%.
   
   
10. A radiation worker received a whole body dose of 100 mrem this year from gamma rays and 50 mrem from fast neutrons. The QF for fast neutrons is 20. Calculate the total equivalent dose (in mrem units) this person received this past year. Convert this person's dose to mSv units.
    
    
11. Human kidney cells were irradiated with a beam of X-rays at a high dose rate in the presence of oxygen.
    a. You would expect that the extrapolation number (n) on the cell survival curve would be:
    i) One
    ii) less than one
    iii) more than one
    iv) higher than D₀
    b. The degree of "Elkind Repair" in the surviving kidney cells after they received a dose of 500 rads would be:
    i) more than if the cells received a 500 rad dose from a beam of MeV alpha
    particles.
    ii) About the same as if the cells received a 500 rad dose of 4 MeV alpha
    particles.
    iii) Less than if the cells received a 500 rad dose of 4 MeV alpha particles.
    
    
12. Naturally occurring background radiation exposure to all humans (and animals) comes from which of the following sources.
    a. cosmic radiation
    b. radiation from radioisotopes present in soil and building materials (e.g., rocks)
    c. radiation from radioisotopes present in our bodies
    d. all of the above Briefly define or explain.
    a. oxygen effect
    b. free radical
    c. quality factor (QF)
    d. Identify three potential radiation induced effects that can result from in utero irradiation of an embryo and/or fetus within the first 10 weeks after conception.
    
    
13. TRUE/FALSE
    ___ a. Technetium-99m ( ^99m Tc) is a radioisotope that is normally used to prepare radiopharmaceuticals for therapeutic treatment of cancerous tumors.
    ___ b. Samarium-153 ( ¹⁵³Sm) is a radioisotope that is produced at MURR.
    ___ c. Studies to assess the risk of radiation induced genetic effects from the A-bomb survivor population has been performed. Results from examining the first generation offspring of the A-bomb survivors were unable to
    demonstrate a significant increase in radiation-induced genetic effects in the first generation population.
    ___ d. Studies to assess populations living for generations in areas of the world where they are exposed to high levels of natural background radiation (e.g., 500 mrem/year) have been unable to statistically demonstrate a radiation-induced increase of cancer incidence in these populations.
    ___ e. If a tissue in the body received a dose of 125 Gy, the dose this tissue received when expressed in rad units, would be lower.
    ___ f. The OER for 4 MeV alpha particle irradiation of mammalian cells will be approximately 1.0.
    ___ g. Radiation induced single strand breaks on DNA are likely to be a form of damage that is more irreparable than double strand breaks.
    ____ h. The fetus has the greatest sensitivity to in utero ionizing radiation exposure during the third trimester (relative to the first and second trimester).
    

INTRODUCTORY RADIATION BIOLOGY 328
FINAL EXAM QUESTIONS 2002-Michael R. Lewis, Ph.D.

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. 6 MeV alpha particle
   b. 62 keV x-ray
   c. 1.33 MeV gamma ray
   d. 15 MeV electron
   
   
2. Fluorine-18 ( ¹⁸₉F) decays by positron emission in 97% of all events to give oxygen (O). Its half-life is 109.77 min.
   a. Sketch a decay scheme that is consistent with this information.
   b. The Z of the daughter is _____, and the A is _____.
   c. In the other 3% of radioactive events, ¹⁸F decays by _______________________.
   d. True or False (circle one): ¹⁸F is a neutron-rich radionuclide.
   e. 18 F is most often used to synthesize [¹⁸F] fluorodeoxyglucose (FDG), which is FDA-approved for diagnosis, staging, and restaging of six types of human cancer. Typically, an injected dose of ^15mCi is required to image an oncology patient by positron emission tomography. If the last patient of the day is scanned at 4 pm, and the FDG is prepared in the cyclotron facility 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. Alpha particle (a)
   b. LET
   c. Henri Becquerel
   d. Ionizing radiation
   e. The energy given off by interaction of a positron with an electron in a nearby atom, when the positron nears or reaches the end of its path.
   
   
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.