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Radiation Biology: Oxygen Effect and Reoxygenation Chapter 6

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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?

Acting at the level of free radicals Signup and view all the answers

What is the characteristic of chronic hypoxia in tumors?

Results from the limited diffusion distance of oxygen through tissue 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?

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

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

By 'fixing' the radiation-induced DNA damage Signup and view all the answers

What is the effect of hypoxia on chemoresistance?

It decreases the sensitivity of cells to chemotherapy Signup and view all the answers

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

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

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

Alpha particle Signup and view all the answers

What is the effect of linear energy transfer on OER?

It has no effect on the OER Signup and view all the answers

Which of the following cells have a higher OER?

Radiation-resistant cells Signup and view all the answers

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

Malformed vasculature of the tumor Signup and view all the answers

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

Reoxygenation Signup and view all the answers

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

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

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

Limiting damage to normal tissue 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?

14% Signup and view all the answers

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

Sensitizers are more metabolically stable than O2 Signup and view all the answers