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DEFINITION OF TERMS

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Absorbed dose The energy imparted by ionizing radiation per unit mass of irradiated material. The units of absorbed dose are the rad and the gray (Gy). Absorption The process by which the number of particles or photons entering a body of matter is reduced by interaction with matter. Also the process in which energy is absorbed from the particles or photons even if the number is not reduced. Accessible surface The external surface of the enclosure or housing provided by the manufacturer Act The North Carolina Radiation Protection Act as defined in G.S. 104E-1. Added filter The filter added to the inherent filtration. Adult An individual 18 or more years of age. Agency The North Carolina Department of Environment and Natural Resources, Division of Radiation Protection. ALARA                                                                                                                                                       Acronym for "As Low As is Reasonably Achievable."  Means making every reasonable effort to maintain exposures to radiation as far below the dose limits in 15A NCAC 11 as is practical consistent with the purpose for which the licensed or registered activity is undertaken, taking into account the state of technology, the economics of improvements in relation to benefits to the public health and safety, and other societal and socioeconomic considerations, and in relation to utilization of sources of radiation in the public interest. Alpha A positively charged particle ejected spontaneously from the nuclei of some radioactive elements. It has low penetrating power and a short range. The most energetic alpha particle will generally fail to penetrate the dead layers of cells covering the skin. Alphas are hazardous when an alpha-emitting isotope is inside the body. Aluminum equivalent The thickness of aluminum, type 1100 alloy, affording the same attenuation, under specified conditions, as the material in question. This nominal composition of type 1100 aluminum alloy is 99.00 percent minimum aluminum and 0.12 percent copper. Annually At intervals not to exceed 12 consecutive months. ANSI American National Standards Institute ARRT American Registry of Radiologic Technologists ASRT American Society of Radiologic Technologists ASNT American Society for Non-destructive Testing Associated equipment Equipment used in conjunction with a radiographic exposure device to make radiographic exposures that drives, guides or comes in contact with the sealed source or radiation machines. Atom The smallest particle of an element that cannot be divided or broken up by chemical means. It consists of a central core of protons and neutrons, called the nucleus. Electrons revolve in orbits in the region surrounding the nucleus. Atomic Energy Commission (AEC) Federal agency created in 1946 to manage the development, use, and control of nuclear energy for military and civilian application. Abolished by the Energy Reorganization Act of 1974 and succeeded by the Energy Research and Development Administration (now part of the U.S. Department of Energy) and the U.S. Nuclear Regulatory Commission Attenuation block A block or stack, having dimensions 20 cm by 20 cm by 3.8 cm, of type 1100 aluminum alloy or other materials having equivalent attenuation. Authorized representative An employee of the agency, or an individual outside the agency when the individual is specifically so designated by the agency under Rule .0112 of 15A NCAC 11. Authorized user An individual who is authorized by license or registration condition to use a source of radiation. Automatic exposure control A device, which automatically controls one or more technique factors in order to obtain, at a preselected location(s), a required quantity of radiation. Phototimer is described separately.

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Background radiation Radiation from cosmic sources; naturally occurring radioactive materials, including radon (except as a decay product of source or special nuclear material); and global fallout as it exists in the environment from the testing of nuclear explosive devices.  "Background radiation" does not include sources of radiation regulated by the agency. Beam axis A line from the source of x-rays through the centers of the x-ray fields. Beam-limiting device A device which provides a means to restrict the dimensions of the x-ray field. Becquere The SI unit of radioactivity. One becquerel is equal to one disintegration per second (s^-1). Beta A charged particle emitted from a nucleus during radioactive decay, with a mass equal to 1/1837 that of a proton. A negatively charged beta particle is identical to an electron. A positively charged beta particle is called a positron. Large amounts of beta radiation may cause skin burns, and beta emitters are harmful if they enter the body. Beta particles may be stopped by thin sheets of metal or plastic.

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Cabinet radiography using radiation machines Industrial radiography using radiation machines, which is conducted in an enclosed, interlocked cabinet, such that the radiation machine will not operate unless all openings are securely closed, and which cabinet is so shielded that every location on the exterior meets conditions for an unrestricted area as specified in Rule .1611 of the North Carolina Regulations for Protection Against Radiation. Calibration The adjustment, as necessary, of a measuring device such that it responds within the required range and accuracy to known values of input. Cephalometric device A device intended for the radiographic visualization and measurement of the dimensions of the human head. Changeable filters Any added filter which can be removed from the useful x-ray beam through any electronic, mechanical or physical process. Charged Particle An ion. An elementary particle carrying a positive or negative electric charge. Collective dose The sum of the individual doses received in a given period of time by a specified population from exposure to a specified source of radiation. Collimator A device used to limit the size, shape, and direction of the primary radiation beam. Commission The North Carolina Radiation Protection Commission. Contact therapy system That the x-ray tubes target is put within five centimeters of the surface being treated. Control device The control cable, the protective sheath and control drive mechanism used to move the sealed source from the shielded position in the radiographic device or camera to an unshielded position outside the device for the purpose of making a radiographic exposure.   Commonly called a crank-out. Control panel That part of the x-ray control upon which are mounted the switches, knobs, pushbuttons and other hardware necessary for manually setting the techniques factors. Controlled area An area, outside of a restricted area but inside the site boundary, access to which can be limited by the licensee or registrant for any reason. Cooling curve The graphical relationship between heat units stored and cooling time. Cosmic Radiation Penetrating ionizing radiation, both particulate and electromagnetic, originating in outer space. Secondary cosmic rays, formed by interactions in the earth's atmosphere, account for about 45 to 50 millirems of the 360 millirems background radiation that an average individual receives in a year. CRCPD Conference of Radiation Control Program Directors. Curie The special unit of radioactivity. One curie is equal to 3.7 x 10^10 disintegrations per second = 3.7 x 10^10 becquerels = 2.22  X 10^12 disintegrations per minute.

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Dead-man switch A switch so constructed that a circuit closing contact can be maintained only by continuous pressure on the switch by the operator. Declared pregnant woman A woman who has voluntarily informed her employer, in writing, of her pregnancy and the estimated date of conception. Deep-dose equivalent (Hd) As it applies to external whole-body exposure, is the dose equivalent at a tissue depth of one cm (1000 mg/cm^2). Department The North Carolina Department of Environment and Natural Resources. Diagnostic source assembly The tube housing assembly with a device attached. Diagnostic-type protective tube housing A tube housing so constructed that the leakage radiation measured at a distance of one meter from the source does not exceed 100 mR in one hour when the tube is operated at its leakage technique factors. Diagnostic x-ray system An x-ray system designed for irradiation of any part of the human body for the purpose of diagnosis or visualization. Direct scattered radiation Radiation which has been deviated in direction by materials irradiated by the useful beam. (See also scattered radiation). DOE (United States) Department of Energy Dose (or radiation dose) A generic term that means absorbed dose, dose equivalent, effective dose equivalent, committed dose equivalent, effective dose equivalent, or total effective dose equivalent, as defined in other areas in the North Carolina Regulations for Protection Against Radiation. Dose equivalent (HT) The product of the absorbed dose in tissue, quality factor, and all other necessary modifying factors at the location of interest. The units of dose equivalent are the rem and sievert (Sv). Dose limits (see "Limits" defined below). Dosimeter A portable instrument for measuring and registering the total accumulated dose to ionizing radiation Dosimetry processor An individual or an organization that processes and evaluates individual monitoring equipment in order to determine the radiation dose delivered to the equipment.

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Effective dose equivalent(HE) The sum of the products of the dose equivalent to the organ or tissue (HT) and the weighting factors (wT) applicable to each of the body organs or tissues that are irradiated (HE = wTHT). Electromagnetic Radiation A traveling wave motion resulting from changing electric or magnetic fields. Familiar electromagnetic radiation range from X-rays (and gamma rays) of short wavelength, through the ultraviolet, visible, and infrared regions, to radar and radio waves of relatively long wavelength. All electromagnetic radiations travel in a vacuum with the velocity of light. Electron An elementary particle with a negative charge and a mass 1/1837 that of the proton. Electrons surround the positively charged nucleus and determine the chemical properties of the atom. Embryo/fetus The developing human organism from conception until the time of birth. Entrance (or access) point Any location through which an individual could gain access to radiation areas or to a source of radiation. This includes entry or exit portals of sufficient size to permit human entry, irrespective of their intended use. Equipment services The selling, installation, rebuilding, conversion, repair, inspection, testing, survey or calibration of equipment which can affect compliance with 15A NCAC 11 by a licensee or registrant. Exposure The quotient of dQ by dm where "dQ" is the absolute value of the total charge of the ions of one sign produced in air when all the electrons, negatrons and positrons, liberated by photons in a volume element of air having mass "dm" are completely stopped in air. The special unit of exposure is the roentgen.  Being exposed to ionizing radiation or to radioactive material. Exposure rate The exposure per unit of time, such as R/min and mR/h. External dose That portion of the dose equivalent received from radiation sources outside the body. Extremity Hand, elbow, arm, arm below the elbow, foot, knee, or leg below the knee. Eye Dose Equivalent Applies to the external exposure of the lens of the eye and is taken as the dose equivalent at a tissue depth of 0.3 centimeter (300 mg/cm^2).

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FDA (United States) Food and Drug Administration FEM Federal Emergency Management Administration Field emission equipment                                                                                         Equipment which uses as x-ray tube in which electron emission from the cathode is due solely to the action of an electric field. Field examination A demonstration of practical application of principles learned in the classroom that shall include use of all appropriate equipment and procedures. Film Badge A pack of photographic film used for measurement of radiation exposure for personnel monitoring purposes. The badge may contain two or three films of differing sensitivities, and it may contain a filter that shields part of the film from certain types of radiation. Filter Material placed in the useful beam to preferentially attenuate selected radiations. Fluoroscopic imaging assembly A subsystem in which x-ray photons produce a fluoroscopic image. It includes the image receptor(s) such as the image intensifier and spot-film device, electrical interlocks and structural material providing linkage between the image receptor and the diagnostic source assembly.

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Gamma Ray High-energy, short wavelength, electromagnetic radiation (a packet of energy) emitted from the nucleus. Gamma radiation frequently accompanies alpha and beta emissions and always accompanies fission. Gamma rays are very penetrating and are best stopped or shielded by dense materials, such as lead or uranium. Gamma rays are similar to X-rays. General purpose radiographic x-ray system Any radiographic x-ray system, which by design, is not limited to radiographic examination of specific anatomical regions. Generally applicable environmental radiation standards Standards issued by the U.S. Environmental Protection Agency (EPA) under the authority of the Atomic Energy Act of 1954 (42 U.S.C. 2D11 et seq;), as amended, that impose limits on radiation exposures or levels, or concentrations or quantities of radioactive material, in the general environment outside the boundaries of locations under the control of persons possessing or using sources of radiation. Geiger-Mueller Counter A radiation detection and measuring instrument. It consists of a gas-filled tube containing electrodes, between which there is an electrical voltage, but no current flowing. When ionizing radiation passes through the tube, a short, intense pulse of current passes from the negative electrode to the positive electrode and is measured or counted. The number of pulses per second measures the intensity of the radiation field. It was named for Hans Geiger and W. Mueller, who invented it in the 1920's. It is sometimes called simply a Geiger counter or a G-M counter. Giga- A prefix that multiplies a basic unit by 1,000,000,000 (one billion). Gonad shield Protective barrier used to reduce exposure to the testes or ovaries. Gray (Gy) The SI unit of absorbed dose. One gray is equal to an absorbed dose of one joule/kilogram (100 rads).

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Half-value layer (HVL) The thickness of specified material which attenuates the beam of radiation to an extent such that the exposure rate is reduced to one-half of its original value. In this definition the contribution of all scattered radiation, other than any which might be present initially in the beam concerned, is deemed to be excluded. Healing arts mass screening The examination of human beings using x-rays for the detection or evaluation of health indications when such tests are not specifically and individually ordered by a licensed practitioner of the healing arts who is legally authorized to prescribe such x-ray tests for the purpose of diagnosis or treatment. It does not include the use of x-ray tests as a requirement for hospital admission or as a condition of employment. Half-value, layer The thickness of any given absorber that will reduce the intensity of a beam of radiation to one half of its initial value. Health Physics The science concerned with recognition, evaluation, and control of health hazards from ionizing radiation. Health Physicist A person who works in the area of environmental health engineering that deals with the protection of the individual and population groups against the harmful effects of ionizing and non-ionizing radiation. The health physicist is responsible for the safety aspects in the design of processes, equipment, and facilities utilizing radiation sources, so that radiation exposure to personnel will be minimized, and will at all times be within acceptable limits. High radiation area An area, accessible to individuals, in which radiation levels could result in an individual receiving a dose equivalent in excess of 0.1 rem (1 mSv) in one hour at 30 centimeters from the radiation source or from any surface that the radiation penetrates. Hospital A facility that provides as its primary functions diagnostic services and intensive medical and nursing care in the treatment of acute stages of illness. Human use The internal or external administration of radiation or radioactive materials to human beings.

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Individual Any human being. Individual monitoring: a)   the assessment of dose equivalent by the use of devices designed to be worn by an individual, or b)   the assessment of committed effective dose equivalent by bioassay or by determination of the time-weighted      air concentrations to which an individual has been exposed, or                                                                        c)   the assessment of dose equivalent by the use of survey data. Individual monitoring devices or individual monitoring equipment Devices designed to be worn by a single individual for the assessment of dose equivalent such as film badges, thermoluminescent dosimeters (TLDs), pocket ionization chambers, and personal ("lapel") air sampling devices. Industrial radiography The examination of materials by nondestructive methods utilizing sources of radiation. Inherent filtration The filtration permanently in the useful beam; it includes the window of the x-ray tube and any permanent tube or source enclosure. Inspection An official examination or observation to determine compliance with rules, orders, requirements and conditions of the agency or the Commission. Installation The act of physical movement of a radiographic system from one location to another in conjunction with a change of ownership. Ion