How is oxygen enhancement ratio calculated?

The oxygen enhancement ratio (OER) is given by the dose in hypoxia divided by the dose in air to achieve the same survival level, and at high dose levels the value of OER for most cell types is in the range of about 2.53.0.

What is RBE and OER?

RBE is a measure of the damage that will occur in comparison with x-rays for the same radiation dose, and high LET radiation will have high RBE. Oxygen enhancement ratio (OER) is the ratio of the radiation dose needed to cause the same biological damage when there is oxygen absent to when there is oxygen present.

What is the oxygen effect?

In biochemistry, the oxygen effect refers to a tendency for increased radiosensitivity of free living cells and organisms in the presence of oxygen than in anoxic or hypoxic conditions, where the oxygen tension is less than 1% of atmospheric pressure (i.e., <1% of 101.3 kPa, 760 mmHg or 760 torr).

How does radiation affect oxygen?

Ionizing radiation damages DNA through generation of free radicals. In the presence of oxygen these lesions are chemically modified, and thus harder to repair while hypoxia protects cells from radiation (Oxygen enhancement ratio (OER)).

What does a high oxygen enhancement ratio mean?

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. … Radiation with higher LET and higher relative biological effectiveness (RBE) have a lower OER in mammalian cell tissues.

What is RBE in radiology?

RBE is the ratio of the dose of a reference radiation (usually high energy or x rays) and the dose of a test radiation type, to give the same level of biological effect.

How are RBE and LET related?

When biological response is defined in terms of the Relative Biologic Effectiveness (RBE) and different radiation type is characterized by Linear Energy Transfer (LET), the plot of the RBE versus LET (RBE-LET) curve shows RBE to increase with increasing LET, to reach a maximum, and to decrease with further increasing …

What is high LET radiation?

High LET radiation includes particles with substantial mass and charge such as alpha particles. Low energy neutrons, which carry no electrical charge, are also a high-LET radiation. The distribution of energy in cells has a marked influence on the amount of biological damage done by a fixed amount of radiation.

When should I raise my RBE?

LET, linear energy transfer; RBE, relative biological effectiveness. As particle energy increases, LET decreases. As particle charge and atomic number increases, LET increases. As LET increases, relative biological effectiveness (RBE) increases and maximizes around 100 KeV/m, and then RBE decreases with LET.

Is too much oxygen bad for humans?

An oxygen level of 60 mmHg or lower indicates the need for supplemental oxygen. Too much oxygen can be dangerous as well, and can damage the cells in your lungs. Your oxygen level should not go above 110 mmHg.

Does acidification lead to oxygen loss?

During decomposition, microorganisms (e.g. bacteria) consume oxygen through respiration, a process that reduces the amount of oxygen available for other aquatic organisms. … Hypoxia and acidification often co-occur because microbial decomposition depletes oxygen and releases carbon dioxide.

Does oxygen increase radiosensitivity?

Nearly all the biological materials studied have shown that, as oxygen concentration is increased from anoxia to that of air, there is a sharp, approximately threefold, increase in radiosensitivity; but sensitivity is little enhanced, if at all, with higher concentrations.

Does radiation reduce oxygen?

Radiotherapy can cause changes in the oxygen supply to tissues in the treated area. This is because radiotherapy affects normal cells and blood vessels, as well as cancer cells. The small blood vessels in the treated area can be damaged by radiotherapy. This can reduce the amount of blood supplied to that area.

Does radiation cause lack of oxygen?

a side effect of chemotherapy or radiation (which may reduce lung capacity) anemia, meaning your lungs don’t have enough red blood cells to deliver oxygen throughout your body.

Are oxygenated cells sensitive to radiation?

cells are less sensitive to radiation than well oxygenated cells, they may gain enhanced radiation sensitivity following reoxygenation.

What is the law of Bergonie and Tribondeau?

The law of Bergonie and Tribondeau is that the radiosensitivity of a biological tissue is directly proportional to the mitotic activity and inversely proportional to the degree of differentiation of its cells.

How does age affect the radiosensitivity of tissue?

It is widely believed that human radiosensitivity increases with age due to an increase of oxidative stress, telomere attrition, a decline in DNA damage response efficiency and inflammatory response [1, 2]. Especially DNA double stand break repair seems to be affected.

What does oxygen fixation do?

The oxygen effect is most commonly explained by the oxygen fixation hypothesis, which postulates that radical-induced DNA damage can be permanently ‘fixed’ by molecular oxygen, rendering DNA damage irreparable.

What does RBE mean?

relative biological effectiveness The relative biological effectiveness (RBE) is defined as the ratio of the doses required by two radiations to cause the same level of effect.

What is the RBE formula?

RBE is calculated as a ratio of the reference radiation dose to the dose of the test radiation (ICRP, 2003): 3. However, the value of RBE varies depending on the level of effect being considered (Fig 1). The ratio D High/Dn High may be different from D Low/Dn Low.

Why RBE blood test is done?

RBE is a complex concept to compare a test radiation with reference radiation in a comprehensive way. RBE depends on dose, dose rate, LET, expose conditions, cell type and endpoint (10) and is used for radiation treatment planning and radiation protection.

Does the RBE stay constant for different ISO effects?

It follows that RBE cannot be a constant value when taken in the context of the complexities of different tissues within the human body, the heterogeneity of cancer types, and the wide variety of doses used as well as the degree to which Bragg peaks are shifted or mixed with lower LET regions.

Does the presence of oxygen increase or decrease radiation damage?

Oxygen presence (aerated cells) increases radiation effectiveness for cell killing.

Why RBE is different for different cell or tissue types?

The RBE is an empirical value that varies depending on the type of ionizing radiation, the energies involved, the biological effects being considered such as cell death, and the oxygen tension of the tissues or so-called oxygen effect.

Which type of cell is most sensitive to radiation?

Lymphocytes (white blood cells) and cells which produce blood are constantly regenerating, and are, therefore, the most sensitive. Reproductive and gastrointestinal cells are not regenerating as quickly and are less sensitive. The nerve and muscle cells are the slowest to regenerate and are the least sensitive cells.

What is water radiolysis?

Water radiolysis is the decomposition of water molecules due to ionizing radiation. Usually, this ionizing radiation stems from the decay of radioactive nuclei, beams of accelerated charged particles (electrons, protons) and from X-ray radiation (with a photon energy greater than 50100 eV).

Why is let always less than stopping power?

It is identical to the retarding force acting on a charged ionizing particle travelling through the matter. By definition, LET is a positive quantity. LET depends on the nature of the radiation as well as on the material traversed. … Hence nuclear stopping power is not contained in LET.