Fig. 7. (A) Hypothetical radiation survival curve of tumor cells in vivo assuming about 10% of the tumor cells are radiobiologically hypoxic. The 'a' corresponds the radiation-induced death of oxic cells and 'b' indicates the death of hypoxic cells assuming that radiation-induced cell death is due only to direct damage in DNA/chromosomes. The 'c' and 'd' show indirect and additional cell death due to vascular damages at high radiation doses. (B) The dotted line indicates decline in cell survival when radiation-induced cell death is linearly related to radiation dose. Solid line is the linear-quadratic (LQ) survival curve which bends downward at high radiation dose indicating that the LQ model overestimates cell death at high radiation doses.