Cells that are oxygenated are more susceptible to radiation damage; this describes which concept?

Cells that are oxygenated are more susceptible to radiation damage; this describes which concept?

• A. Target theory
• B. Direct effect
• C. Doubling dose
• D. Oxygen enhancement ratio

Answer: (D)

Oxygen enhances the effect of radiation by making the damage more permanent. When radiation creates free radicals inside a cell, the presence of oxygen interacts with those radicals to form reactive species that “fix” DNA damage, so it cannot be easily repaired. The measure of this effect is the oxygen enhancement ratio, which compares the dose needed to achieve a given biological effect in hypoxic tissue versus oxygenated tissue. Since oxygenated cells are more easily killed by the same radiation dose, the ratio is greater than 1 (typically around 2.5–3 for low-LET radiation). This concept is distinct from target theory, direct effect, or doubling dose, which relate to different aspects of radiation biology.

Oxygen enhances the effect of radiation by making the damage more permanent. When radiation creates free radicals inside a cell, the presence of oxygen interacts with those radicals to form reactive species that “fix” DNA damage, so it cannot be easily repaired. The measure of this effect is the oxygen enhancement ratio, which compares the dose needed to achieve a given biological effect in hypoxic tissue versus oxygenated tissue. Since oxygenated cells are more easily killed by the same radiation dose, the ratio is greater than 1 (typically around 2.5–3 for low-LET radiation). This concept is distinct from target theory, direct effect, or doubling dose, which relate to different aspects of radiation biology.