[91] This ability to disrupt chemical bonds means that ionizing radiation focuses its impact in a very small but crucial area, a bit like a karate master focusing energy to break a brick. For example after receiving a lethal dose of 10 Gy, the body temperature will only increase by 0.02 °C but the dose may lead to death of all the exposed entities. The relative biological effectiveness (RBE) or quality factor (QF) is given in Table 1 for several types of ionizing radiation—the effect of the radiation is directly proportional to the RBE. Non-ionizing radiation behaves exactly like ionizing radiation, but differs in that it has a much greater wavelength and, therefore, less energy. Absorbed dose, D, is defined as the quotient of mean energy, dε, imparted by ionising radiation in a volume element and the mass, dm, of the matter in that volume (Cember, 1969). The energy is enough to damage DNA, which can result in cell death or cancer. How does ionising radiation affect human tissue? A dose unit more closely related to effects in biological tissue is called the roentgen equivalent man or rem and is defined to be the dose in rads multiplied by the relative biological effectiveness. The potential damage from an absorbed dose depends on the type of radiation and the sensitivity of different tissues and organs. The body is made up of different cells. Ionizing radiation is more harmful than nonionizing radiation because it has enough energy to remove an electron from an atom and thereby directly damage biological material. Ionizing radiation (ionising radiation) is radiation, traveling as a particle or electromagnetic wave, that carries sufficient energy to detach electrons from atoms or molecules, thereby ionizing an atom or a molecule. The term radiation means to give off energy as waves or particles. The RBE always compares the amount of orthovoltage radiation to another type of radiation (e.g. It includes the various effects caused by different types of ionizing radiation, the tissue type into which the energy is imparted, the biological effect under investigation, and the rate at which that dose is delivered. Normal tissue responses to ionizing radiation have been a major subject for study since the discovery of X‐rays at the end of the 19th century. The relative biological effectiveness (RBE) or quality factor (QF) is given in Table 2 for several types of ionizing radiation—the effect of the radiation is directly proportional to the RBE. For example we have brain cells, muscle cells, blood cells etc. 3 • BIOLOGICAL EFFECTS OF IONIZING RADIATION INTRODUCTION This chapter deals with the effects ofionizing radiation on the body. Itdescribes the possible and probable short-termand long-termeffects produced by ionizing radiation depositing energy in living tissue. By contrast, evidence has emerged concerning “bystander” responses involving damage to nearby cells that were not themselves directly traversed by the radiation. Relative Biologic Effectiveness (RBE) 3. According to the IAEA, ionizing radiation has a direct action on the complex vital molecules (for example the DNA) within the cell by breaking the bonds between the atoms. Radiation poisoning, also called radiationsickness or a creeping dose, is a form of damage to organ tissue due to excessive exposure to ionizing radiation. Ionizing radiation and the products of the cleavage of water are able to damage all biological macromolecules, including… aging: Ionizing radiation The shortening of life caused by ionizing radiation (e.g., X-rays) has been determined for many species, including mice, … For example, alpha particle radiation absorbed in tissue is considered to be about 20 times more effective as a carcinogen than the same dose of gamma rays. This is because the living tissue can more easily repair damage from radiation that is spread over a large area than that which is concentrated in a small area. A central tenet in understanding the biological effects of ionizing radiation has been that the initially affected cells were directly damaged by the radiation. - LET increases, the potential to produce biological harm increases) 2. a variety of ways, such as by chemical, biological and physical agents or by ionising radiation. In short, the biological damage from high-LET radiation (alpha particles, protons or neutrons) is much greater than that from low-LET radiation . Charged Particle Interactions . What’s RF – Ionizing RF Radiation – non- Ionizing RF “Ionization” is a process by which electrons are stripped from atoms and molecules. Health effects of ionizing radiation. Anyone who has received a sunburn knows that ultraviolet light can damage skin cells. This includes the processes through which radiation interacts with tissue and how these interactions affect biological systems. All exposures to ionizing radiation carry a risk of biological damage, although this risk decreases as the exposure decreases. Finally, damage produced by different types of radiation will be discussed. Most of these biological effects are stimulated by nuclear DNA (nucDNA) damage. The biological effect of this radiation depends not only on the amount of the absorbed dose but also on the intensity of the ionization in the living cells caused by different types of radiation. Either way admits that ionizing radiation can hurt cells and that the body is capable of repairing some of the damage but not all of the damage. It is the genes within a cell that determine how a cell functions. Different types of radiation differ somewhat in biological effectiveness per unit of dose. For example, a typical ionization releases six to seven times the energy needed to break the chemical bond between two carbon atoms. Exposure to ionizing radiation (IR) causes various biological effects on organ-forming cells. Ionizing Radiation • Ionizing radiation − Composed of particles that individually carry enough kinetic energy to liberate an electron from an atom or molecule − Kinetic energy > 12.4 eV Biological Radiation Effects 3 Non-ionizing radiation Ionizing radiation Ionization energy of soft tissue 12.4 eV or 100 nm Biological damage from radiation begins with this ionizing effect. The other acknowledges that any radiation hit will injure cells and eventually it will accumulate damage enough to make itself known as a cancer or precancer. Although this non-ionizing radiation does not have the energy to create ion pairs, some of these waves can cause personal injury. Alpha particles do not penetrate very far into matter, whereas γ rays penetrate more deeply. One characteristic of ionizing radiation on human body is that the energy absorbed is low but the biological effects are serious. For example, neutron, proton and alpha radiation can cause 5-20 times more harm than the same amount of the absorbed dose of beta or gamma radiation. Ionizing radiation gives off energy by knocking electrons off atoms, which causes the atoms to have a charge. We first need to understand a little bit about the structure of DNA. Ionizing radiation produces many different possible clusters of spatially adjacent damage, and analysis of track structures from different types of radiation has shown that clustered DNA damage of complexity greater than double-strand breaks can occur at biologically relevant frequencies with all types of ionizing radiation, at any dose (Brenner & Ward, 1992; Goodhead, 1994). Radiation, Biological Damage ABDEL HAKIM BEN NASR BRIAN HOYLE The nuclear explosions at Hiroshima and Nagasaki, Japan on August 6 and 9, 1945, demonstrated the immense power of the nuclear bomb.The effects of the explosion were immediate. Certain anti-oxidents can help repair damage. Another term for a charged particle is an ion. For example, the risk associated with natural background radiation is very small, although elevated levels of naturally occurring radon increase the risk of lung cancer. This is known as the equivalent dose. The absorbed dose quantifies the energy imparted per unit mass absorbing medium, but does not relate this value to radiation damage induced in cells or tissue. These aggregates can swell and make the shield mechanically unsound. Shortly thereafter, time–dose relationships were established for some normal tissue endpoints that led to investigations into how the size of dose per fraction and the quality of radiation affected outcome. The effects of the damage from ionising radiation can be short-term or long-term depending on the means and severity of the exposure. Ionizing Radiation Definition. A dose unit more closely related to effects in biological tissue is called the roentgen equivalent man or rem and is defined to be the dose in rads multiplied by the relative biological effectiveness. The relative biological effectiveness (RBE) or quality factor (QF) is given in for several types of ionizing radiation—the effect of the radiation is directly proportional to the RBE. DNA is a very long molecule that stores our genetic information. This process can produce molecular changes that can lead to damage in biological tissue, including effects on DNA,genetic material.This process requires interaction with high levels of electromagnetic energy. The most important long-term effect of radiation exposure is an increased chance of getting cancer. Ionizing radiation is relatively high in energy, and when it collides with an atom, it can completely remove an electron to form a positively charged ion that can damage biological tissues. Why does radiation damage the body? Radiation damage is the effect of ionizing radiation on physical objects. ... For instance, the biological shield of the reactor is frequently composed of Portland cement, where dense aggregates are added in order to decrease the radiation flux through the shield. To understand how ionizing can affect or even damage the cells in our bodies. Exposure of mammalian cells to 1 gray (Gy) of acute γ-irradiation is estimated to generate ~50 nucDNA DSBs Among the various types of DNA damage, the DNA double-strand breaks (DSBs) are the most severe. It lies curled up inside the nucleus of a cell. The genetic material of the cell is found in the nucleus in the form of genes which are in turn combined into strand-like structures called chromosomes. Ionizing radiation is powerful enough to do this. The charges on the atomic particles make ionizing radiation unstable and reactive. 2 Ionizin g Radiation Effects on Cells, Organe lles and Tissues on Proteome L ev el 45 The label-free approach enables the quantita- ti ve measurement of radiation-induced alterations The radiation that was released by the explosions, however, caused the deaths of many people weeks, months, and even years later. Radiation damage to tissue and/or organs depends on the dose of radiation received, or the absorbed dose which is expressed in a unit called the gray (Gy). Because acute as well as late effects of ionizing radiation such as cancer arise at the cellular level of biological organization, absorbed doses to cell-equivalent micromasses may reveal more than does the absorbed dose to whole tissue, especially under conditions of low-dose exposure. 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