Dictionary
Mario P. Iturralde in Dictionary and Handbook of Nuclear Medicine and Clinical Imaging, 1990
Nuclides are distinguished by their atomic mass and number as well as by energy state. Nuclides are distinct nuclear species, isotopes are nuclides of the same element. In some nuclides various energy states of the nucleus with finite lifetimes are possible. These states are called isomers of the nuclide. Isomeric nuclides have the same number of protons and neutrons and differ only in their energy content and thus their lifetime. The nature of a nuclide is indicated unambiguously by the chemical symbol of the element and the number of nucleons (sum of the protons [Z] and neutrons [N] = A, mass number) shown as an upper index to the left of the element symbol (e.g., 12C, 32P). Additionally, the number of protons (Z atomic number) can be given as a lower index on the left. Isomers in an excited, metastable state are indicated by a right upper index “m†(e.g., 99mTc). Approximately 1250 different nuclides are recognized at present each being a distinct species of nucleus with its own characteristic nuclear properties. Of these, 280 are naturally occurring stable nuclides, while the remainder (radionuclides) undergo spontaneous radioactive decay with half-lives which vary from a fraction of a second to greater than 1012 years. The only radionuclides which occur in nature are those with half-lives of the order of the age of the earth (or greater), or which are constantly being generated by natural nuclear processes.
Short-Lived Positron Emitting Radionuclides
Frank Helus, Lelio G. Colombetti in Radionuclides Production, 2019
Radionuclides are applicated in many different areas including medicine. In medicine they are used for therapy as well as for diagnosis. In therapy the destructive effect of radiation of the radionuclides administered to the patient is used. For diagnosis, however, information must be obtained as accurately as is clinically necessary and this destructive effect minimized. If for medical application a radioactive compound is used in vivo, it is called a radiopharmaceutical, which is defined by its chemical and by its radioactive properties. The chemical structure determines the mode of localization of the material in the patient, or the way it is involved in metabolism. The type of radiation emitted by the radiopharmaceutical is dependent upon the nuclear properties of the radioactive label. For in vivo measurement it is necessary that the radiation can be detected outside the body of the patient; the radiation must be externally detectable. Many diagnostic in vivo methods are based on scintigraphic techniques. These are techniques by which an image of the tissue distribution of the radio-activity administered to the patient is obtained. When positron emitting radionuclides in combination with computerized tomographic systems are used, the distribution of the radioactivity can be obtained at different levels of the body and the distribution can be quantitated.
Radiotherapy Physics
Debbie Peet, Emma Chung in Practical Medical Physics, 2021
It is the role of the Clinical Scientist to have a detailed knowledge of the risks posed by radionuclides used for treatment and the safety measures required. They also ensure compliance related to the legislation surrounding holding, using and disposing of sources. Dependent on the activity and concentration of the sources, it may be necessary to gain a permit from the EA, under the Environmental Permitting Regulations (EPR 2016) and notify, register with or obtain consent from the Health and Safety Executive (HSE) under IRMER (2017) before they can be held and used. A permit specifies the operator, the source (including the isotope, the number of sources and their activity), what the source may be used for, how sources may be stored and disposed of and a map showing the site where the source may be utilised.
Radiological risk assessment of the Hunters Point Naval Shipyard (HPNS)
Published in Critical Reviews in Toxicology, 2022
Dennis J. Paustenbach, Robert D. Gibbons
Pu-239 has a radioactive half-life of 24,110 years and is produced when uranium absorbs a neutron. Small amounts of plutonium occur naturally, but large quantities have been produced in nuclear reactions or released from atmospheric nuclear weapons tests. Pu-239 transitions by alpha decay. Its decay products emit alpha, beta, and gamma radiation depending upon which radionuclide is being evaluated and can pose both an internal and external radiation hazard. Pu-239 is present in most soils in the United States at various concentrations (ICRP 2008; Johnson et al. 2012). The potential for Pu-239 to be present on ships returning from nuclear weapons tests in the Pacific and Pu-239 use in calibrating radiation detection equipment were primary reasons it was identified as an ROC at HPNS (USN 2004).
Looking for the phoenix: the current research on radiation countermeasures
Published in International Journal of Radiation Biology, 2023
Vojtěch Chmil, Alžběta Filipová, Aleš Tichý
In the case of the use of nuclear weapons and dirty bombs, but also during major accidents at nuclear power plants, various radionuclides are released into the environment, leading to contamination of water, food, and the atmosphere. During these events, a relatively large area is affected and residents have only limited options to protect themselves. Radionuclides thus enter the human body, where they cause radiation damage in addition to chemical toxicity. Decorporation therapy can be used to accelerate the excretion of radionuclides from the body, and to prevent their internalization. Decorporation agents can be divided into several groups according to the mechanism of action, such as blocking, binding (ion exchange), chelation, isotopic dilution, displacement, and mobilization. Laxatives, diuretics, and emetics can also be used to accelerate the elimination of radionuclides from the body (IAEA 2018). Four decorporating drugs have been FDA approved so far, and others are used off-label or do not need approval. Agents that may be used for decorporation treatment recommended by IAEA (2018) are summarized in Table 6.
Main radiation pathways in the landscape of Armenia
Published in International Journal of Radiation Biology, 2023
V. B. Arakelyan, G. E. Khachatryan, A. G. Nalbandyan-Schwarz, C. E. Mothersill, C. B. Seymour, V. L. Korogodina
Table 3 shows the sources and places of accumulation of radionuclides, their impact on human and non-human biotas. Radiation effects include not only a direct effect on cells and organisms, but also cause their regulatory changes (Mothersill and Seymour 2022). In the soil, radiation exposure is chronic and leads either to extinction or to an increase in radioresistance and to reproduction. Outside the soil, radiation exposure can vary and induce variability in cells and organisms (Korogodina et al. 2016). Cosmic radiation, climate changes can give rise to a variety of species in mountain landscape due to stress effects. Mines, rocks, fossil ores, stones are a permanent source of radiation and constantly affect human and non-human biotas. The consequences of nuclear weapons tests, accidents at nuclear power plants are of a prolonged nature and can lead to cancer. Dust and emissions from industries lead to diseases and accumulate in plants.
Related Knowledge Centers
- Alpha Particle
- Beta Particle
- Cyclotron
- Gamma Ray
- Ionizing Radiation
- Particle Accelerator
- Radioactive Decay
- Internal Conversion
- Half-Life
- Radionuclide Generator