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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 oxygen effect is quantified by measuring the radiation sensitivity or Oxygen Enhancement Ratio (OER) of a particular biological effect (e.g., cell death or DNA damage), [14] which is the ratio of doses under pure oxygen and anoxic conditions.
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]
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 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.
Tumor cells typically have a lower oxygen content than normal tissue. This medical condition is known as tumor hypoxia and therefore the oxygen effect acts to decrease the sensitivity of tumor tissue. [9] The oxygen effect may be quantitatively described by the Oxygen Enhancement Ratio (OER).
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.
Intraoperative radiation therapy (IORT) is radiation therapy that is administered during surgery directly in the operating room (hence intraoperative).. Usually therapeutic levels of radiation are delivered to the tumor bed while the area is exposed during surgery.