| (35) Entrance exposure (Entrance air kerma)--The exposure
in air expressed in roentgens (R) or the dose in air (air kerma) expressed
in Gy, measured at the point where the center of the useful beam enters
the animal.
(36) Equipment performance evaluations (EPE)--Required
testing performed by a registered service provider at a specified
interval to ensure radiation machines operate in compliance with this
chapter.
(37) 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 SI unit of exposure is the coulomb per kilogram
(C/kg). The roentgen is the special unit of exposure. For purposes
of this section, this term is used as a noun.
(38) Exposure rate (air kerma rate)--The exposure per
unit of time. For purposes of this section "air kerma rate" is an
equivalent term.
(39) External dose--That portion of the dose equivalent
received from any source of radiation outside the body.
(40) Extremity--Hand, elbow, arm below the elbow, foot,
knee, and leg below the knee. The arm above the elbow and the leg
above the knee are considered part of the whole body.
(41) Field emission equipment--Equipment that uses
an x-ray tube in which electron emission from the cathode is due solely
to the action of an electric field.
(42) Field size--The dimensions along the major axes
of an area in a plane perpendicular to the central axis of the beam
at the normal treatment or examination source to image distance and
defined by the intersection of the major axes and the 50 percent isodose
line.
(43) Filter--Material placed in the useful beam to
preferentially absorb selected radiation.
(44) Fluoroscopic imaging assembly--A subsystem in
which x-ray photons produce a fluoroscopic image. It includes the
image receptors, such as the image intensifier and spot-film device,
electrical interlocks, if any, and structural material providing linkage
between the image receptor and diagnostic source assembly.
(45) Focal spot--The area projected on the anode of
the x-ray tube bombarded by the electrons accelerated from the cathode
and from which the useful beam originates.
(46) Gray (Gy)--The SI unit of absorbed dose. One Gy
is equal to an absorbed dose of 1 joule per kilogram (J/kg) or 100
rad.
(47) Half-value layer--The thickness of a specified
material that attenuates the beam of radiation to an extent such that
the air kerma rate is reduced to one-half of its original value.
(48) High radiation area--An area, accessible to individuals,
in which radiation levels external to the body could result in an
individual receiving a dose equivalent in excess of 0.1 rem (1 millisievert
(mSv)) in one hour at 30 cm from any source of radiation or from any
surface that the radiation penetrates.
(49) Image intensifier--A device, installed in its
housing, that instantaneously converts an x-ray pattern into a corresponding
light image of higher energy density.
(50) Image receptor--Any device, such as a fluorescent
screen, radiographic film, or digital sensor that transforms incident
x-ray photons either into a visible image or into another form that
can be made into a visible image by further transformations.
(51) Individual--A human being.
(52) Individual monitoring--The assessment of dose
equivalent to an individual by the use of:
(A) individual monitoring devices; or
(B) survey data.
(53) Individual monitoring devices--Devices designed
to be worn by a single individual for the assessment of dose equivalent.
For purposes of this section, "personnel dosimeter," "dosimeter,"
and "personnel monitoring equipment" are equivalent terms. Examples
of individual monitoring devices include film badges, thermoluminescence
dosimeters, optically stimulated luminescence dosimeters, pocket ionization
chambers (pocket dosimeters), and electronic personal dosimeters.
(54) Inspection--An examination or observation, including
records, tests, surveys, and monitoring to determine compliance with
the Act and requirements of this section, orders, and conditions of
the agency.
(55) Ionizing radiation--Any electromagnetic or particulate
radiation capable of producing ions, directly or indirectly, in its
passage through matter. Ionizing radiation includes gamma rays and
x-rays, alpha and beta particles, high speed electrons, neutrons,
and other nuclear particles.
(56) Irradiation--The exposure of matter to ionizing
radiation.
(57) kV--Kilovolt.
(58) kVp--Kilovolt peak (See definition for peak tube
potential).
(59) Lead equivalent--The thickness of lead affording
the same attenuation, under specified conditions, as the material
in question.
(60) Lens dose equivalent--The external dose equivalent
to the lens of the eye at a tissue depth of 0.3 cm (300 mg/cm2 ).
(61) Licensing state--Any state with rules equivalent
to the Suggested State Regulations for Control of Radiation relating
to, and having an effective program for, the regulatory control of
naturally occurring or accelerator-produced radioactive material.
(62) mA--Milliampere.
(63) mAs--Milliampere-second.
(64) Medical research--The investigation of various
health risks and diseases as it pertains to veterinary practices.
(65) Member of the public--Any individual, except when
that individual is receiving an occupational dose.
(66) Minor--An individual who is under 18 years of
age.
(67) Mobile service operation--The provision of radiation
machines and personnel at temporary sites for limited time periods.
The radiation machines may be fixed inside a motorized vehicle or
may be a portable radiation machine that may be removed from the vehicle
and taken into a facility for use.
(68) Monitoring--The measurement of radiation and the
use of the results of these measurements to evaluate potential exposures
and doses. For purposes of this section, "radiation monitoring" and
"radiation protection monitoring" are equivalent terms.
(69) Occupational dose--The dose received by an individual
during the course of employment in which the individual's assigned
duties involve exposure to sources of radiation from licensed/registered
and unlicensed/unregistered sources of radiation, whether in the possession
of the licensee/registrant or other person. Occupational dose does
not include dose received from background radiation, from any medical
administration the individual has received, from exposure to individuals
administered radioactive material and released in accordance with
this section, from voluntary participation in medical research programs,
or as a member of the public.
(70) Peak tube potential--The maximum value of the
potential difference in kilovolts across the x-ray tube during an
exposure.
(71) Person--Any individual, corporation, partnership,
firm, association, trust, estate, public or private institution, group,
agency, local government, any other state or political subdivision
or agency thereof, or any other legal entity, and any legal successor,
representative, agent, or agency of the foregoing, other than the
NRC and other federal government agencies licensed or exempted by
the NRC.
(72) Personnel monitoring equipment--See definition
for individual monitoring devices.
(73) Phototimer--A method for controlling exposures
to image receptors by the amount of radiation that reaches a radiation
detection device. The radiation detection device is part of an electronic
circuit that controls the duration of time the tube is activated (See
definition for automatic exposure control).
(74) Primary protective barrier--See definition for
protective barrier.
(75) Protective apron--An apron made of radiation absorbing
materials used to reduce radiation exposure.
(76) Protective barrier--A barrier of radiation absorbing
materials used to reduce radiation exposure. The types of protective
barriers are as follows:
(A) primary protective barrier, which is a barrier
sufficient to attenuate the useful beam to the required degree; or
(B) secondary protective barrier, which is a barrier
sufficient to attenuate the stray radiation to the required degree.
Cont'd... |
