In: Biology
Describe the effect of oxygen in radiotherapy and discuss the mechanism for this effect
OER :
The Oxygen Enhancement Ratio (OER) or oxygen enhancement effect in radiobiology refers to the enhancement of therapeutic or detrimental effect of ionizing radiation due to the presence of oxygen. This so-called oxygen effect is most notable when cells are exposed to an ionizing radiation dose.
The OER is traditionally defined as the ratio of radiation doses during lack of oxygen compared to no lack of oxygen for the same biological effect. This may give varying numerical values depending on the chosen biological effect. Additionally, OER may be presented in terms of hyperoxic environments and/or with altered oxygen baseline, complicating the significance of this value.
The oxygen effect is the oxygen fixation hypothesis which postulates that oxygen permanently fixes radical-induced DNA damage so it becomes permanent.
Mechanism :
Oxygen acts as the levels of the free radical.
Series of chain events occurs
1. Absorption of radiation
2. Production of fast charged particles
3. Production of ion pairs
4. Production of free radicals
5. Breakage of chemical bonds and chemical changes occurs
6. Results in biological damage
The Oxygen fixation hypothesis
Oxygen fixes the damage produced by free radicals. The formation of RO2 an organic peroxide represents a non restorable form of the target material.i.e. the reaction results in a change in the chemical composition of the material exposed to the radiation.