Term
| (LET) Linear Energy Transfer |
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Definition
| LET is the average energy deposited per unit length of track by ionizing radiation as it passes through of track by ionizing radiation as it passes through and interacts with a medium along its path. |
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Term
| (RBE) Relative biologic effectiveness |
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Definition
| is defined as the ratio of a dose of standard radiation to the dose of test radiation to produce the same biological effects |
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Term
| (OER) Oxygen enhanced ratio |
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Definition
| (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 2.5–3.0 |
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Term
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Definition
| Biologic damage that occurs as a result of ionization of atoms on essential molecules produced by straight interaction with the incident radiation |
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Term
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Definition
| The formation of covalent bonds which hold portions of several polymer chains together is called cross-linking. Extensive cross-linking results in a random three-dimensional network of interconnected chains, as shown in the figure |
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Term
| Radiation weighting factor |
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Definition
| The factor by which the absorbed dose (rad or gray) must be multiplied to obtain a quantity that expresses, on a common scale for all ionizing radiation, the biological damage (rem or sievert) to the exposed tissue. |
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Term
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Definition
| the changing of the structure of a gene, resulting in a variant form that may be transmitted to subsequent generations, caused by the alteration of single base units in DNA, or the deletion, insertion, or rearrangement of larger sections of genes or chromosomes. |
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Term
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Definition
| Cell-survival curves are used to describe the relationship between radiation dose and the proportion of cells that survive. Usually mathematical models are used to describe cell survival data. Survival of normal cells is an important consideration in radiation therapy. |
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Term
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Definition
| A multistage process that first involves the production of reactive free radicals that are created by the interaction of radiation with water molecules. |
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Term
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Definition
| the death of cells which occurs as a normal and controlled part of an organism's growth or development. |
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Term
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Definition
| Chromosome aberrations include changes in chromosome number (gains and losses) and changes in structure (deletions, inversions, and exchanges). Chromosomes can be viewed by standard light microscopy and many of these aberration types can be observed. |
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Term
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Definition
| is one of the essential concepts for understanding radiation biology. Although many complex interpretations of target theory have been developed, its fundamental principle is that 'inactivation of the target(s) inside an organism by radiation results in the organism's death'. |
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Term
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Definition
| When breaks are induced at stages in the cell cycle during or after DNA synthesis, chromatid aberrations occur in which chromatids rather than whole chromosomes are seen to be involved in exchanges. Many structural chromosome rearrangements do not result in gain or loss of DNA. |
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Term
| Law of Bergonie and Tribondeau |
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Definition
| 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. The more it differs from healthy tissue, the greater its radiosensitivity will be. |
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Term
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Definition
| Free radicals are unstable atoms that can damage cells, causing illness and aging. Free radicals are linked to aging and a host of diseases, but little is known about their role in human health, or how to prevent them from making people sick. |
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Term
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Definition
| Mitotic catastrophe refers to a mechanism of delayed mitosis-linked cell death, a sequence of events resulting from premature or inappropriate entry of cells into mitosis that can be caused by chemical or physical stresses. |
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Term
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Definition
| Chromosomal breakage syndromes are a group of genetic disorders that are typically transmitted in an autosomal recessive mode of inheritance. In culture, cells from affected individuals exhibit elevated rates of chromosomal breakage or instability, leading to chromosomal rearrangements. |
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Term
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Definition
| Aging at the molecular level is characterized by the progressive accumulation of molecular damage. The sources of damage act randomly through environmental and metabolically generated free radicals, through spontaneous errors in biochemical reactions, and through nutritional components. |
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Term
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Definition
| a cell containing half the number of chromosomes of a somatic cell and able to unite with one from the opposite sex to form a new individual; a gamete. |
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Term
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Definition
| a mutation affecting only one or very few nucleotides in a gene sequence. |
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