According to the Oxygen Enhancement Ratio concept, which statement is true?

• A. Anoxic tissue requires three times the radiation dose to achieve the same biological effect as aerobic tissue.
• B. Anoxic tissue requires one third the dose.
• C. Anoxic tissue requires the same dose as aerobic tissue.
• D. Oxygen levels do not influence anoxic tissue.

Answer: (A)

Oxygen makes radiation more effective at damaging cells because it helps fix the DNA damage caused by radiation, making those lesions permanent. The Oxygen Enhancement Ratio shows how much more dose is needed when oxygen is absent to achieve the same biological effect as with oxygen. For typical low-LET radiation, this ratio is about 3, so anoxic tissue needs roughly three times the radiation dose to reach the same level of damage as aerobic tissue. That’s why the statement about needing three times the dose is true. The other options conflict with this relationship: giving less dose without oxygen, or the same dose, or saying oxygen has no influence all contradict the established effect of oxygen on radiation response.