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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
1010 disintegrations per second = 3.7 x 1010 becquerels = 2.22 X 1012
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/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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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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(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
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).
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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.
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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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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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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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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
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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.
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P
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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 180º 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
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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.
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R
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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:
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QUALITY FACTORS AND
ABSORBED DOSE EQUIVALENCIES
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TYPE
OF RADIATION
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Quality
Factor
Q
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Absorbed
Dose Equal to a Unit Dose Equivalenta
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X-, gamma, or beta radiation
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1
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1
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Alpha particles, multiple-charged particles, fission fragments
and heavy particles of unknown energy
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20
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0.05
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Neutrons of unknown energy
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10
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0.1
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High-energy protons
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10
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0.1
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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:
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MEAN QUALITY FACTORS,
Q, AND FLUENCE PER UNIT DOSE EQUIVALENT FOR MONOENERGETIC NEUTRONS
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Neutron Energy (MeV)
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Quality Factora
(Q)
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Fluence per Unit Dose Equivalentb
(neutrons cm-2 rem-1)
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thermal
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2.5 x 10-8
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2
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980 x 106
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1 x 10-7
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2
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980 x 106
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1 x 10-6
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2
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810 x 106
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1 x 10-5
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2
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810 x 106
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1 x 10-4
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2
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840 x 106
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1 x 10-3
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2
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980 x 106
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1 x 10-2
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2.5
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1010 x 106
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1 x 10-1
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7.5
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170 x 106
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5 x 10-1
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11
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39 x 106
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1
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11
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27 x 106
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2.5
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9
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29 x 106
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5
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8
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23 x 106
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7
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7
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24 x 106
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10
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6.5
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24 x 106
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14
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7.5
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17 x 106
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20
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8
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16 x 106
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40
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7
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14 x 106
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60
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5.5
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16 x 106
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1 x 102
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4
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20 x 106
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2 x 102
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3.5
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19 x 106
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3 x 102
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3.5
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16 x 106
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4 x 102
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3.5
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14 x 106
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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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S
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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
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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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U
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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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V
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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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W
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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
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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.
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Y
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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.
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Z
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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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