DEFINITION OF TERMS

 

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A

 

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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B

 

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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C

 

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 1010 disintegrations per second = 3.7 x 1010 becquerels = 2.22  X 1012 disintegrations per minute.

 

 

 

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D

 

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/cm2).

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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E

 

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/cm2).

 

 

 

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F

 

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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G

 

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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H

 

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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I

 

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                                                                                                                                                                      
1)   An atom that has too many or too few electrons, causing it to have an electrical charge, and therefore chemically
     active.                                                                                                                                      
2)   An electron that is not associated (in orbit) with a nucleus.

Ionization
The process of adding one or more electrons to, or removing one or more electrons from, atoms or molecules, thereby creating ions. High temperatures, electrical discharges, or nuclear radiations can cause ionization.

Ionization Chamber
An instrument that detects and measures ionizing radiation by measuring the electrical current that flows when radiation ionizes gas in a chamber, making the gas a conductor of electricity.

Ionizing Radiation
Any radiation capable of displacing electrons from atoms or molecules, thereby producing ions.  Some examples are alpha, beta, gamma, X-rays, neutrons. High doses of ionizing radiation may produce severe skin or tissue damage.

Isotope
One of two or more atoms with the same number of protons, but different numbers of neutrons in their nuclei. Thus, carbon-12, carbon-13, and carbon-14 are isotopes of the element carbon, the number denoting the approximate atomic weights. Isotopes have very nearly the same chemical properties, but often different physical properties (for example, carbon-12 and -13 are stable, carbon-14 is radioactive).

 

 

 

J

 

Joule
The SI unit of work and energy.  It represents the work done when a force on one (1) newton is exerted through a distance of one (1) meter.

 

 

 

K

 

K-capture
The radioactive transformation process by which one of the extra-nuclear electrons is captured by the nucleus, and unites with an intra-nuclear proton to form a neutron and emit a neutrino.

Kilo-
A prefix that multiplies a basic unit by 1,000.

 

 

 

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L

 

Lead equivalent
The thickness of lead affording the same attenuation, under specified conditions, as the material in question.

Leakage radiation
Radiation emanating from a diagnostic or therapeutic source assembly except for:
a) The useful beam and
b) Radiation produced when the exposure switch or timer is not activated.

Leakage technique factors
The technique factors associated with the diagnostic or therapeutic source assembly (i.e., tube housing and beam limiting device) which are used in measuring leakage radiation. They are defined as follows:
a)   for diagnostic source assemblies intended for capacitor energy storage equipment, the          
      maximum rated peak tube potential and the maximum rated number of exposures in an hour for
      operation at the maximum rated peak tube potential with quantity of charge per exposure being 10
      millicoulombs (mC) or the minimum obtainable from the unit, whichever is larger

b)   for diagnostic source assemblies intended for field emission equipment rated for pulsed
      operation, the maximum rated peak tube potential and the maximum rated number of x-ray
      pulses in an hour for operation at the maximum rated peak tube potential; and

c)   for all other diagnostic or therapeutic source assemblies, the maximum rated peak tube
      potential and the maximum rated continuous tube current for the maximum rated peak tube
      potential.

Lethal Dose 50/30 (LD50/30)
The dose of radiation expected to cause death within 30 days to 50% of those exposed.   Generally accepted to range from 400 to 600 rem (4-6 Gray) received over a short period of time.

License                                                                                                                                                      
Except where otherwise specified, means a license issued pursuant to Section .0300 of the North Carolina Regulations for Protection Against Radiation.

Licensee
Any person who is licensed by the agency pursuant to Section .0300 of the North Carolina Regulations for Protection Against Radiation.

Licensing state
Any state designated as such by the Conference of Radiation Control Program Directors, Inc. Unless the context clearly indicates otherwise, use of the term Agreement State in this Chapter shall be deemed to include licensing state with respect to naturally occurring and accelerator produced radioactive material (NARM).

Light field
That area of the intersection of the light beam from the beam-limiting device and one of the set of planes parallel to and including the plane of the image receptor, whose perimeter is the focus of points at which the illumination is one-fourth of the maximum in the intersection.

Limits or dose limits
The permissible upper bounds of radiation doses.

Linear Energy Transfer (LET)
The measure of the linear rate of energy absorption by the absorbing medium as the ionizing radiation traversed the medium.

 

 

 

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M

 

Maximum line current
The rms (root-mean-square) current in the supply line of an x-ray machine operating at its maximum rating.

Mega-
A prefix that multiplies a basic unit by 1,000,000.

Member of the public
Any individual except when that individual is receiving an occupational dose.

Micro-
A prefix that divides a basic unit into one million parts (i.e., 1/1,000,000).

Milli-
A prefix that divides a basic unit by 1,000 (i.e., 1/1000).

Minor
An individual less than 18 years of age.

Mobile equipment
(see x-ray equipment).

Molecule
A group of atoms held together by chemical forces. A molecule is the smallest unit of a compound that can exist by itself and retain all of its chemical properties.

Monitoring ("radiation monitoring" or "radiation protection monitoring")
The measurement of radiation levels, concentrations, surface area concentrations or quantities of radioactive material and the use of the results of these measurements to evaluate potential exposures and doses.

 

 

 

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N

 

Nano
A prefix that divides a basic unit by one billion (i.e., 1/1,000,000,000).

NCSRT
North Carolina Society of Radiologic Technologists

Neutro
An uncharged elementary particle with a mass slightly greater than that of the proton, and found in the nucleus of every atom heavier than hydrogen.

NEXT
Nationwide Evaluation of X-Ray Trends

Nonstochastic effect
Health effects, the severity of which varies with the dose and for which a threshold is believed to exist. Radiation-induced cataract formation is an example of a nonstochastic effect (also called a deterministic effect).

NRC
United States Nuclear Regulatory Commission or its duly authorized representatives.

Nucleus; nuclei (plural)
The small, central positively charged region of an atom that carries essentially all the mass. Except for the nucleus of ordinary (light) hydrogen, which has a single proton, all atomic nuclei contain both protons and neutrons. The number of protons determines the total positive charge, or atomic number. This is the same for all the atomic nuclei of a given chemical element. The total number of neutrons and protons is called the mass number.

 

 

 

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O

 

Occupational dose
The dose received by an individual in the course of employment in which the individual's assigned duties involve exposure to radiation or radioactive material from licensed and unlicensed sources of radiation, whether in the possession of the licensee or registrant or other person. Occupational dose does not include dose received from background radiation, as a patient from medical practices, from exposure to individuals administered radioactive material and released in accordance with 15A NCAC 11 .0358 of this Chapter, from voluntary participation in medical research programs, or as a member of the general public.

 

 

P

 

Peak tube potential
The maximum value of the potential difference across the x-ray tube during an exposure.

Person
Any individual, corporation, partnership, firm, association, trust, estate, public or private institution, group, agency, political subdivision of this state, any other state or political subdivision or agency thereof, and any legal successor, representative, agent or agency of these entities.

Periodic training
A periodic review conducted or provided by the licensee or registrant for its employees on radiation safety aspects of radiography. The review shall include the results of internal inspections, new procedures or equipment, accidents or errors that have been observed, and opportunities for employees to ask safety questions.

Permanent radiographic installation
An enclosed shielded room, cell, or vault in which radiography is performed.

Personnel monitoring equipment
Devices, such as film badges, pocket dosimeters, and thermoluminescent dosimeters, designed to be worn or carried by an individual for the purpose of estimating the dose received by the individual.

Phototimer
A method for controlling radiation exposures to image receptors by the amount of radiation which reaches a radiation monitoring device(s). The radiation monitoring device(s) is part of an electronic circuit which controls the duration of time the tube is activated (see also "Automatic exposure control").

Physician
An individual currently licensed to practice medicine in this state.

Pico-
A prefix that divides a basic unit by one trillion (i.e., 1/1,000,000,000,000).

Planned special exposure
An infrequent exposure to radiation, separate from and in addition to the annual dose limits.

Portable equipment
(see x-ray equipment).

Position indication device (PID)
A device on dental x-ray equipment used to indicate the beam position and to establish a definite source-skin distance. It may or may not incorporate or serve as a beam-limiting device.

Positron
A particle with the same mass as an ordinary electron.  It has a positive electrical charge of exactly the same amount as an electron.  Positrons are created either by radioactive decay of certain unstable nuclei, or in collisions between photons of greater than 1 MeV and electrically charged particles or photons.  A positron does not decay, but rather will collide with an ordinary electron and in this collision, the positron-electron pair is annihilated.  This results in the coincident emission of two photons, each with an energy of 0.511 MeV.  These photons are are emitted 180 apart, making spatial localization possible.

Primary protective barrier
The material, excluding filters, placed in the useful beam, for radiation protection purposes, to reduce the radiation exposure.

Protective apron
An apron made of radiation attenuating materials used to reduce radiation exposure.

Protective barrier
A barrier of radiation attenuating material(s) used to reduce radiation exposure. Types of protective barriers are defined in other items of the Rule.

Protective glove
A glove made of radiation attenuating materials used to reduce radiation exposure.

Proton
An elementary nuclear particle with a positive electric charge and a mass slightly less than that of a neutron but about 1836 times greater than that of an electron,   located in the nucleus of an atom.

Public dose
The dose received by a member of the public from exposure to radiation or radioactive material released by a licensee or registrant, or to another source of radiation within a licensee's or registrant's control. It does not include occupational dose or doses received from background radiation, as a patient from medical practices, from exposure to individuals administered radioactive material and released in accordance with Rule .0358 of this Chapter, or from voluntary participation in medical research programs.

 

 

 

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Q

 

Qualified expert
An individual who is registered pursuant to Rule .0205 of this Chapter.

Quality factor (Q)
The modifying factor that is used to derive dose equivalent from absorbed dose. Quality factors are provided in the definition of rem below.

Quarter
A period of time equal to one-fourth of the year observed by the licensee or registrant (approximately 13 consecutive weeks), providing that the beginning of the first quarter in a year coincides with the starting date of the year and that no day is omitted or duplicated in consecutive quarters.

 

 

 

R

 

Rad
The special unit of absorbed dose. One rad is equal to an absorbed dose of 100 ergs/gram or 0.01 joule/kilogram (0.01 gray).

Radiation (ionizing radiation)
Except as otherwise defined in 15A NCAC 11 .1400 of the North Carolina Regulations for Protection Against Radiation, means alpha particles, beta particles, gamma rays, x-rays, neutrons, high-speed electrons, high-speed protons, and other particles capable of producing ions.

Radiation area
An area, accessible to individuals, in which radiation levels could result in an individual receiving a dose equivalent in excess of 0.005 rem (0.05 mSv) in one hour at 30 centimeters from the radiation source or from any surface that the radiation penetrates.

Radiation dose
Refers to dose.

Radiation machine
Any device capable of producing radiation except devices which produce radiation only from radioactive material.

Radiation safety officer
One who has the knowledge and responsibility to apply appropriate radiation protection rules.

Radiation Safety Officer (for Radiography)
An individual named by the licensee or registrant who has knowledge of, responsibility for, and authority to ensure compliance with appropriate radiation protection rules, standards, and practices on behalf of the licensee or registrant and who meets the requirements of 15A NCAC 11 .0510(g) of this the North Carolina Regulations for Protection Against Radiation.

Radiation Sickness (syndrome)
The complex of symptoms characterizing the disease known as radiation injury, resulting from excessive exposure of the whole body (or large part) to ionizing radiation. The earliest of these symptoms are nausea, fatigue, vomiting, and diarrhea, which may be followed by loss of hair (epilation), hemorrhage, inflammation of the mouth and throat, and general loss of energy. In severe cases, where the radiation exposure has been relatively large, death may occur within two to four weeks. Those who survive six weeks after the receipt of a single large dose of radiation may generally be expected to recover.

Radioactive material
Any material, solid, liquid, or gas, which emits radiation spontaneously.

Radioactivity
The disintegration of unstable atomic nuclei by emission of radiation.

Radiograph
An image receptor on which the image has been created directly or indirectly by an x-ray pattern and results in a permanent record.

Radiographer
Any individual who performs or who, in attendance at the site where sources of radiation are being used, personally supervises industrial radiographic operations and who is responsible to the licensee or registrant for assuring compliance with the requirements of the North Carolina Regulations for Protection Against Radiation and all license or registration conditions.

Radiographer's assistant
Any individual who, under the personal supervision of a radiographer, uses sources of radiation, related handling tools, or survey instruments in industrial radiography.

Radiographic exposure device
Any instrument containing a sealed source fastened or contained therein, in which the sealed source or shielding thereof may be moved, or otherwise changed, from a shielded to unshielded position for purposes of making a radiographic exposure.  Commonly called a camera or projector.

Radiographic imaging system
Any system whereby a permanent or semi-permanent image is recorded on an image receptor by the action of ionizing radiation.

Rating
The operating limits as specified by the component manufacturer.

Recording
Producing a permanent form of an image resulting from x-ray photons such as film and video tape.

Reference man
A hypothetical aggregation of human physical and physiological characteristics arrived at by international consensus as published by the International Commission on Radiological Protection. These characteristics may be used by researchers and public health workers to standardize results of experiments and to relate biological insult to a common base.

Registrant
As used in this Section, means any person who owns or possesses and administratively controls an x-ray system which is used to deliberately expose humans or animals to the useful beam of the system and is required by the provisions contained in Sections .0100 and .0200 of this Chapter to register with the agency.

Registration
Registration with the agency in accordance with the North Carolina Regulations for Protection Against Radiation.

Rem
The special unit of any of the quantities expressed as dose equivalent. The dose equivalent in rems is equal to the absorbed dose in rads multiplied by the quality factor (1 rem = 0.01 sievert). As used in this Chapter, the quality factors for converting absorbed dose to dose equivalent are as follows:

QUALITY FACTORS AND ABSORBED DOSE EQUIVALENCIES

TYPE OF RADIATION

Quality Factor
Q

Absorbed Dose Equal to a Unit Dose Equivalenta

X-, gamma, or beta radiation

1

1

Alpha particles, multiple-charged particles, fission fragments and heavy particles of unknown energy

20

0.05

Neutrons of unknown energy

10

0.1

High-energy protons

10

0.1

aAbsorbed dose in rad equal to one rem or the absorbed dose in gray equal to one sievert.

If it is more convenient to measure the neutron fluence rate than to determine the neutron dose equivalent rate in rems per hour or sieverts per hour, one rem (0.01 Sv) of neutron radiation of unknown energies may, for purposes of the rules in 15A NCAC 11, be assumed to result from a total fluence of 25 million neutrons per square centimeter incident upon the body.

If sufficient information exists to estimate the approximate energy distribution of the neutrons, the licensee or registrant may use the fluence rate per unit dose equivalent or the appropriate Q value from the following table to convert a measured tissue dose in rads to dose equivalent in rems:

MEAN QUALITY FACTORS, Q, AND FLUENCE PER UNIT DOSE EQUIVALENT FOR MONOENERGETIC NEUTRONS

 

Neutron Energy (MeV)

Quality Factora (Q)

Fluence per Unit Dose Equivalentb (neutrons cm-2 rem-1)

thermal

2.5 x 10-8

2

980 x 106

 

1 x 10-7

2

980 x 106

 

1 x 10-6

2

810 x 106

 

1 x 10-5

2

810 x 106

 

1 x 10-4

2

840 x 106

 

1 x 10-3

2

980 x 106

 

1 x 10-2

2.5

1010 x 106

 

1 x 10-1

7.5

170 x 106

 

5 x 10-1

11

39 x 106

 

1

11

27 x 106

 

2.5

9

29 x 106

 

5

8

23 x 106

 

7

7

24 x 106

 

10

6.5

24 x 106

 

14

7.5

17 x 106

 

20

8

16 x 106

 

40

7

14 x 106

 

60

5.5

16 x 106

 

1 x 102

4

20 x 106

 

2 x 102

3.5

19 x 106

 

3 x 102

3.5

16 x 106

 

4 x 102

3.5

14 x 106

a Value of quality factor (Q) at the point where the dose equivalent is maximum in a 30-cm diameter cylinder tissue-equivalent phantom.

b Monoenergetic neutrons incident normally on a 30-cm diameter cylinder tissue-equivalent phantom.

 

Research and development means:                                                                                                            
a)  theoretical analysis, exploration, or experimentation; or
b)  the extension of investigative findings and theories of a scientific or technical nature into practical application for
     experimental and demonstration purposes, including the experimental production and testing of  models,
     devices, equipment, materials, and processes. Research and development does not include the internal or
     external administration of radiation or radioactive material to human beings.

Response time
The time required for an instrument system to reach 90 percent of its final reading when the radiation-sensitive volume of the instrument system is exposed to a step change in radiation flux from zero sufficient to provide a steady state mid-scale reading.

Restricted area
An area, access to which is controlled by the licensee or registrant for purposes of protecting individuals against undue risks from exposure to radiation and radioactive materials. Restricted area does not include areas used as residential quarters, but separate rooms in a residential building may be set apart as a restricted area.

Roentgen (R)
The special unit of exposure. One roentgen equals 2.58 x 10-4 coulombs/kilogram of air.

 

 

 

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Scattered radiation
Radiation that, during passage through matter, has been deviated in direction. (See also "direct scattered radiation").

Scintillation Detector
The combination of phosphor, photomultiplier tube and associated electronic circuits used to count light emissions produced in the phosphor by ionizing radiation.

Secondary protective barrier
A barrier sufficient to attenuate the stray radiation to the required degree.

Shallow-dose equivalent (Hs)
As applies to the external exposure of the skin or an extremity, is taken as the dose equivalent at a tissue depth of 0.007 centimeter (7 mg/cm2) averaged over an area of one square centimeter.

SI unit
A unit of measure from the International System of Units as established by the General Conference of Weights and Measures.

SID
Source-image receptor distance.

Sievert
The SI unit of any of the quantities expressed as dose equivalent. The dose equivalent in sieverts is equal to the absorbed dose in grays multiplied by the quality factor (1 Sv = 100 rems).

Site boundary
That line beyond which the land or property is not owned, leased, or otherwise controlled by the licensee or registrant.

Source
The focal spot of the x-ray tube.

Source-image receptor distance (SID)
The distance from the source to the center of the input surface of the image receptor.

Source of radiation
Any radioactive material, or any device or equipment emitting or capable of producing radiation.

Spot film
A radiograph which is made during a fluoroscopic examination to permanently record conditions which exist during that fluoroscopic procedure.

State
The State of North Carolina.

Stationary equipment
(see x-ray equipment).

Stochastic effects
Health effects that occur randomly and for which the probability of the effect occurring, rather than its severity, is assumed to be a linear function of dose without threshold. Hereditary effects and cancer incidence are examples of stochastic effects.

Stray radiation
The sum of leakage and scattered radiation.

Survey
An evaluation of the radiological conditions and potential hazards incident to the production, use, transfer, release, disposal, or presence of sources of radiation. When appropriate, such an evaluation includes a physical survey of the location of sources of radiation and measurements or calculations of levels of radiation, or concentrations or quantities of radioactive material present.

 

 

 

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T

 

Technique factors
The conditions of operation. They are specified as follow
A.  for capacitor energy storage equipment, peak tube potential in kV and quantity of charge in
     mAs
B.  for field emission equipment rated for pulsed operation, peak tube potential in kV and number of
     x-ray pulses; and
C.  for all other equipment, peak tube potential in kV and either tube current in mA and exposure
     time in seconds, or the product of tube current and exposure time in mAs.

Tera-
A prefix that multiplies a basic unit by 1,000,000,000,000 (1x1012).

"Therapeutic-type protective tube housing"
The tube housing with tube installed, and it includes high voltage and filament transformers and other appropriate elements when they are contained within that housing.

Thermoluminescent Dosimeter (TLD)
A device used to measure radiation by measuring the amount of visible light emitted from a crystal in the detector when exposed to radiation.

These Rule
Chapter 11 of the North Carolina Regulations for Protection Against Radiation.

Total effective dose equivalent (TEDE)
The sum of the deep-dose equivalent (for external exposures) and the committed effective dose equivalent (for internal exposures).

Transportation equipment
X-ray equipment which is installed in a vehicle or trailer.

Tube
An x-ray tube, unless otherwise specified.

Tube housing assembly
The tube housing with tube installed. It includes high-voltage and filament transformers and other appropriate elements when they are contained within the tube housing.

Tube rating chart
The set of curves which specify the rated limits of operation of the tube in terms of the technique factors.

 

 

 

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Unrestricted area
An area, access to which is neither limited nor controlled by the licensee or registrant.

Useful beam
The radiation which passes through the tube housing port and the aperture of the beam-limiting device when the exposure switch or timer is activated.

 

 

 

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Variable-aperture beam-limiting device
A beam-limiting device which has capacity for stepless adjustment of the x-ray field size at the given SID.

Very high radiation area
An area, accessible to individuals, in which radiation levels could result in an individual receiving an absorbed dose in excess of 500 rads (5 grays) in one hour at one meter from a radiation source or from any surface that the radiation penetrates. At very high doses received at high dose rates, units of absorbed dose (e.g., rads and grays) are appropriate, rather than units of dose equivalent (e.g., rems and sieverts).

Visible area
That portion of the input surface of the image receptor over which incident x-ray photons produce a visible image.

 

 

 

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Whole body
For purposes of external exposure, whole body means the head, trunk (including male gonads), arms above the elbow, or legs above the knee.

Worker
An individual engaged in work under a license or registration issued by the agency and controlled by a licensee or registrant, but does not include the licensee or registrant.

 

 

 

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X-ray
Penetrating electromagnetic radiation (photon) having a wavelength that is much shorter than that of visible light. These rays are usually produced by excitation of the electron field around certain nuclei. In nuclear reactions, it is customary to refer to photons originating in the nucleus as gamma rays, and to those originating in the electron field of the atom as X-rays. These rays are sometimes called roentgen rays after their discoverer, W.K. Roentgen.

X-ray diffraction
The primary beam from the target of the x-ray tube passes through a collimator and strikes the sample, which diffracts it in a characteristic manner.  This diffraction pattern in measured with a photographic film or a radiation counter.  Primarily used in analytical work.

X-ray equipment
An x-ray system, subsystem or component thereof
a)  Mobile equipment
     
X-ray equipment mounted on a permanent base with wheels or casters for moving while completely
     assembled.

b)  Portable equipment
     X-ray equipment designed to be hand-carried.

c)  Stationary equipment
     X-ray equipment which is installed in a fixed location.

 

 

 

Y

 

Year
The period of time beginning in January used to determine compliance with the provisions of Section .1600 of the North Carolina Regulations for Protection Against Radiation. The licensee or registrant may change the starting date of the year used to determine compliance by the licensee or registrant provided that the change is made at the beginning of the year and that no day is omitted or duplicated in consecutive years.

 

 

 

Z

 

Zinc Sulfide Scintillator
One of the older inorganic scintillators, its main use is in the detection of alpha particle and heavy ion detection.  This type of instrument played a key role in Rutherford's experiments, in which alpha particle interactions on a scintillation screen were visually observed through a low power microscope.

 

 

 

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                                                                                                                                                     Revised  5/07/12

 

 

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