Radiation Biology: Oxygen Effect and Reoxygenation Chapter 6
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Questions and Answers

What is the approximate Oxygen Enhancement Ratio (OER) for neutrons?

  • 2.0
  • 1.6 (correct)
  • 2.5
  • 1.2

    • What is the primary factor that determines the extent of radiation-induced DNA damage?

  • Phase of cell cycle
  • Linear energy transfer (LET)
  • Type of radiation (X-rays or neutrons)
  • Presence or absence of oxygen (correct)

    • What is the minimum time required for oxygen to be present after irradiation to produce the oxygen effect?

  • 1 second
  • 1 microsecond
  • 5 milliseconds (correct)
  • 1 minute

    • What is the primary mechanism by which oxygen acts to produce the oxygen effect?

    <p>Acting at the level of free radicals</p> Signup and view all the answers

    What is the characteristic of chronic hypoxia in tumors?

    <p>Results from the limited diffusion distance of oxygen through tissue</p> Signup and view all the answers

    What is the reason for the smaller OER at low doses compared to high doses in rapidly growing cells?

    <p>G1 cells are more radiosensitive than G2 cells and dominate the low-dose region</p> Signup and view all the answers

    What is the primary mechanism by which oxygen enhances the effect of radiation?

    <p>By 'fixing' the radiation-induced DNA damage</p> Signup and view all the answers

    What is the effect of hypoxia on chemoresistance?

    <p>It decreases the sensitivity of cells to chemotherapy</p> Signup and view all the answers

    What is the Oxygen Enhancement Ratio (OER) equal to?

    <p>The ratio of hypoxic to aerobic doses required to achieve the same biological effect</p> Signup and view all the answers

    Which of the following types of radiation has an OER of unity?

    <p>Alpha particle</p> Signup and view all the answers

    What is the effect of linear energy transfer on OER?

    <p>It has no effect on the OER</p> Signup and view all the answers

    Which of the following cells have a higher OER?

    <p>Radiation-resistant cells</p> Signup and view all the answers

    What is the primary reason for the development of acute hypoxia in tumors?

    <p>Malformed vasculature of the tumor</p> Signup and view all the answers

    What is the phenomenon by which hypoxic cells become oxygenated after a dose of radiation?

    <p>Reoxygenation</p> Signup and view all the answers

    What is the primary mechanism by which hypoxia cell sensitizers increase radiosensitivity of hypoxic cells?

    <p>Free-radical formation that mimics oxygen fixation of damage</p> Signup and view all the answers

    What is the primary benefit of fractionation in reducing hypoxia in tumors?

    <p>Limiting damage to normal tissue</p> Signup and view all the answers

    What is the approximate proportion of hypoxic cells in an untreated tumor, as observed by Van Putten and Kallman in mouse sarcoma?

    <p>14%</p> Signup and view all the answers

    What is the primary advantage of using hypoxia cell sensitizers over increasing oxygen delivery to tumor cells?

    <p>Sensitizers are more metabolically stable than O2</p> Signup and view all the answers

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