Wk 6 Radiation Oncology

Question 1

What are indirect and direct effects of ionizing radiation?

Answer 1

1. indirect: damage to DNA by formation of free radicals through chain reactions -> cell damage
2. direct: damage to DNA molecule by one of the following 3 methods:
   A. direct DNA chain breakage - double or single strand by electron
   B. breakage of hydrogen bond
   C. faulty cross-linkage

Question 2

What are the 4 R’s of Fractionation in radiobiology

Answer 2

1. Repair of sublethal damage to cells b/w fractions caused by radiation
2. Repopulation/regrowth of cancer cells
3. Redistribution of cells into radiosensitive phases of cell cycle
4. Reoxygenation of hypoxic cells to make them more sensitive to radiation