• Absorbed dose - The quantity of energy imparted by ionising radiation to unit mass of matter. Unit gray (Gy). 1 Gy = 1 joule per kg
  • Activity - Attribute of the amount of a radionuclide. The rate at which a radionuclide transforms. Unit becquerel (Bq). 1 Bq = 1 disintegration per second
  • Alpha particle - A particle comprised of two protons and two neutrons emitted from a radionuclide
  • Annual limit of intake (ALI) - One ALI is the maximum permissible exposure each year for occupational exposure, without detectable health risk. One ALI corresponds to a committed effective dose equivalent of 0.05 Sv, or a committed effective dose equivalent of 0.5 Sv to any individual organ or tissue, whichever is the more limiting
  • Becquerel - The unit of activity. Symbol Bq
  • Beta particle - An electron emitted by the nucleus of a radionuclide
  • Biodosimetry - The measurement of radiation induced biological or physical effects within the body to assess the radiation dose to an individual
  • Biokinetics - The study of movement (of radionuclides) within organisms
  • Biological half-life - The time for half the amount of a substance to be eliminated from the body following absorption.
  • Chromosomes - Genetic material seen as rod-shaped bodies found in the nucleus of cells at metaphase. Humans have 23 pairs of chromosomes
  • Cloudshine - The external dose received from radioactive material that is still suspended in the atmosphere
  • Committed effective dose equivalent - The calculated dose over 50 years from internal contamination is the committed effective dose equivalent (CEDE)
  • Contamination - The deposition of radioactive material on skin, clothing, or in the body or environment.
  • Cosmic radiation - High energy ionising radiations from outer space
  • Curie - An older unit of activity. Symbol Ci. 1 Ci = 37 GBq (3.7 x 102 Bq)
  • Cytogenetics - The study of cell structure and functions, especially the chromosomes
  • Decay - The process of spontaneous transformation of a radionuclide. The decrease in the activity of a radioactive substance
  • Decorporation - Treatment to displace incorporated radionuclides from tissues
  • Desquamation - Peeling of skintop of page
  • Deterministic effects - Dose-related, acute health effects caused by exposure to high levels of radiation that cause large numbers of cells to die or lose their ability to replicate
  • Dicentrics - During repair of DNA strand breaks in cells affected by radiation, misrepair of two chromosomes and abnormal replication during cell division may result in the formation of a chromosome with two centromeres, a dicentric.
  • Dirty bomb - Conventional explosive material combined with a radioactive substance
  • DNA - Deoxyribonucleic acid, genetic material
  • Dose - A general term for quantity of ionising radiation. See absorbed dose, equivalent dose, effective dose and collective dose. Frequently used for effective dose
  • Effective dose - The quantity obtained by multiplying the equivalent dose to various tissues by a weighting factor appropriate to each and summing the products. Unit sievert (Sv). Frequently abbreviated to dose
  • Effective half-life - The time taken for the radiological effect of the substance absorbed into the body to be reduced by half by biological elimination and radioactive decay.
  • Electron - An elementary particle with low mass, 1/1836 that of a proton, and unit negative charge
  • Electron volt - An electron volt is a unit of energy equal to the energy gained by an electron in passing through a potential difference of 1 volt. Symbol eV. 1 eV = 1.6 x 10-19 joule approximately
  • Epilation - Hair loss
  • Equivalent dose - The quantity obtained by multiplying the absorbed dose by a factor to allow for the different effectiveness of the various ionising radiations in causing harm to tissue. Unit sievert (Sv)
  • Fission - A process in which the nucleus splits into two or more nuclei and energy is released
  • Fractionated dose - (Radiation) administered in divided doses
  • Free radical - A grouping of atoms that normally exists in combination with other atoms but can sometimes exist independently. Generally very reactive in a chemical sense
  • Gamma ray - A discrete quantity of electromagnetic energy without mass or charge. Emitted by a radionuclide.
  • Germ cell - The gametes of any organism that reproduces sexually, i.e. ova and sperm
  • Germinal layer - The basal layer of skin, composed of proliferating and non-proliferating cells
  • Gray - The unit of quantity of energy imparted by ionising radiation to unit mass of matter. 1 Gy = 1 joule per kg
  • Groundshine - The external dose received from radioactive material deposited on the ground
  • Half-life - The time taken for the activity of a radionuclide to lose half its value by decay
  • Hospital health physicist - A hospital-based, non-medical, health professional working in the areas of radiology, nuclear medicine, or radiotherapy
    • qualified in the application of physics of therapeutic or diagnostic uses of ionising radiation,
    • able to perform the dosimetric calculations, radiation measurements and monitoring relevant to their area of expertise
  • Incorporation - Uptake of radioactive material by cells, tissues and target organstop of page
  • Internal contamination - Intake of radioactive material via breathing, ingestion or through contamination of wounds
  • Ionisation - The process by which a neutral atom or molecule acquires or loses an electric charge. The production of ions
  • Ionising radiation - Radiation that produces ionisation in matter. Examples are alpha particles, beta particles, gamma rays, x-rays and neutrons. When these radiations pass through the tissues of the body, they have sufficient energy to damage DNA
  • Irradiation - Exposure to penetrating radiation from an external source. It does not make the irradiated person radioactive
  • Isotope - Nuclides with the same number of protons but different numbers of neutrons
  • Justification - A radiation protection principle which states that human activities that cause exposure to radiation may be permitted only if they do more good than harm
  • keV - Equal to 1000 eV
  • Linear energy transfer - The measure of energy transferred to tissues as a result of ionising radiation passing through it
  • Medical health physicist - A non-medical, health professional working in the areas of radiology, nuclear medicine, or radiotherapy
    • qualified in the application of physics of therapeutic or diagnostic uses of ionising radiation,
    • able to perform the dosimetric calculations, radiation measurements and monitoring relevant to their area of expertise
  • Myelosuppression - Bone marrow suppression
  • Neutron - An elementary particle with unit atomic mass approximately and no electric charge
  • Nuclear medicine physician - A registered medical practitioner with specialist qualifications in nuclear medicine
  • Nuclear reactor - A device in which nuclear fission can be sustained in a self-supporting chain reaction involving neutrons.
  • Nucleus - The core of an atom, occupying little of the volume, containing most of the mass, and bearing a positive charge
  • Nucleus of a cell - The controlling centre of the basic unit of tissues. Contains DNA
  • Nuclide - A species of atom characterised by the number of protons and neutrons
  • Optimisation - A radiation protection principle which states that exposure to radiation from justified activities should be kept as low as reasonably achievable, social and economic factors being taken into account
  • Penetrating radiation - Refers to the properties of different types of ionising radiation to travel through tissue. For example, alpha particles are generally considered unable to penetrate intact skin, but gamma radiation travels many centimetres through tissues
  • Photon - Quantity of electromagnetic radiation
  • Physical half-life - The time for half the amount of a substance to undergo radioactive decay.
  • Probability - The mathematical chance that a given event will occur
  • Proton - An elementary particle with unit atomic mass and unit positive chargetop of page
  • Pulmonary lavage - Bronchopulmonary lavage is a procedure for washing out the lungs
  • Radiation - The process of emitting energy as waves or particles. Frequently used to mean ionising radiation, except when it is necessary to avoid confusion with non-ionising radiation
  • Radiation oncologist - A registered medical practitioner with specialist qualifications in the therapeutic use of radiation in cancer treatment
  • Radiation Safety Officer - A member of the diagnostic radiology department or occupational health and safety unit responsible for safe operations in everyday use of radiation and, in a radiological emergency, assisting staff to ensure their doses are as low as reasonably achievable, and providing technical support and documentation
  • Radioactive - Possessing the property of radioactivity
  • Radioactivity - The property of radionuclides spontaneously emitting ionising radiation
  • Radiological protection - The science and practice of limiting harm to human beings from radiation
  • Radiologist - A registered medical practitioner with specialist qualifications in diagnostic and/or interventional radiology
  • Radiomimetic effect - Inducing effects comparable to the biological effects of ionising radiation
  • Radionuclide - An unstable nuclide that emits ionising radiation
  • Radiotherapy - The use of radiation beams for treating disease
  • Risk - The probability of injury, harm or disease
  • Risk factor - The probability of cancer, leukaemia or hereditary damage per unit equivalent dose. Usually refers to fatal malignant diseases and serious hereditary damage. Unit Sv-1
  • Sievert - The unit defined by the quantity obtained by multiplying the equivalent dose to various tissues by a weighting factor appropriate to each and summing the products. Symbol Sv
  • Stochastic effects - Doses below the thresholds for deterministic effects may cause cellular damage, with effects that are probabilistic (occurring by chance) or ‘stochastic’ in nature. Stochastic effects are believed to result from damaged cells not dying but surviving in a modified form. These effects usually appear many years after the exposure, although they do not occur in every exposed individual, the likelihood of a cancer or hereditary effect occurring after exposure is assumed to be proportional to the level of exposure
  • Stratum corneum - The outermost layer of the skin, comprising dead cells
  • Total effective dose equivalent - The sum of the committed effective dose equivalent and any external dose received is the total effective dose equivalent (TEDE)
  • Tritiated water - Water molecules incorporating tritium (3H)
  • Unstable - An isotope or nuclide is considered to be unstable if it has a half-life less than the age of the universe i.e. less than about 13.7 billion years
  • X-ray - A discrete quantity of electromagnetic energy without mass or charge. Emitted by an x-ray machine

Reference: ARPANSA. Radiation basics – glossary of terms. Available from ARPANSA website.

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