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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 [ 1 ] is most notable when cells are exposed to an ionizing radiation dose .
The best known explanation of the oxygen effect is the oxygen fixation hypothesis developed by Alexander in 1962, [9] which posited that radiation-induced non-restorable or "fixed" nuclear DNA lesions are lethal to cells in the presence of diatomic oxygen. [10] [11] Recent hypotheses include one based on oxygen-enhanced damage from first ...
As ions' damage is direct, OER (Oxygen Enhancement Ratio) is 1, so the effect of oxygen it is not important. An important approach of hypoxia-related treatment interventions is a procedure called dose painting, in which a higher radiation dose is targeted to hypoxic subvolumes of tumor. [37]
The relative biological effectiveness for radiation of type R on a tissue is defined as the ratio R B E = D X D R {\displaystyle RBE={\frac {D_{X}}{D_{R}}}} where D X is a reference absorbed dose of radiation of a standard type X , and D R is the absorbed dose of radiation of type R that causes the same amount of biological damage.
Oxygen enhancement ratio, effect magnitude of ionizing radiation due to the presence of oxygen Oxygen Evolution Reaction , the formation of oxygen by electrochemical reduction of water Owner’s Equivalent Rent, an economic metric for housing prices often used in the calculation of market baskets
The rationale is that tumours containing hypoxic cells (cells with enough oxygen concentration to be viable, yet not enough to be X-ray-radiosensitive) and cells deficient in oxygen are resistant to killing by X-rays. Thus, the lower Oxygen Enhancement Ratio (OER) of neutrons confers an advantage.
Multiple studies have investigated this possibility, one being Jin. et al., 2020, where it was observed that circulating blood cells experienced a significantly lower impact during FLASH-RT, resulting in the killing of only 5-10% of cells, in contrast, CONV-RT exhibited a much more substantial effect, leading to the death of 90-100% of cells. [14]
The number of oxygen vacancies is frequently measured by using X-ray photoelectron spectroscopy to compare the ratio of Ce 3+ to Ce 4+. The loss of oxygen continues into the molten liquid state where the local Ce-O coordination number drops to predominantly 6-fold, compared to 8-fold in the stoichiometric fluorite structure.