| (13) Background radiation--Radiation from cosmic sources;
non‑technologically enhanced naturally occurring radioactive
material, including radon, except as a decay product of source or
special nuclear material, and including global fallout as it exists
in the environment from the testing of nuclear explosive devices or
from past nuclear accidents, such as Chernobyl, that contribute to
background radiation and are not under the control of the registrant.
"Background radiation" does not include radiation from radiation machines
regulated by the agency.
(14) Barrier--See definition for protective barrier.
(15) Beam axis--A line from the source through the
centers of the x-ray fields.
(16) Beam-limiting device--A device that provides a
means to restrict the dimensions of the x-ray field.
(17) Beam quality (diagnostic x-ray)--A term that describes
the penetrating power of the x-ray beam. This is identified numerically
by half-value layer and is influenced by kilovolt peak (kVp) and filtration.
(18) Central axis of the beam--A line passing through
the virtual source and the center of the plane figure formed by the
edge of the first beam‑limiting device.
(19) Certificate of registration--A form of permission
given by the agency to an applicant who has met the requirements for
registration set out in the Act and this chapter.
(20) 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.
(21) Commissioner--The Commissioner of the Department
of State Health Services.
(22) Committed Effective Dose Equivalent (HE,50 )--The sum of the products of the weighting
factors applicable to each of the body organs or tissues that are
irradiated and the committed dose equivalent to these organs or tissues
(HE,50 = ΣWT HT.50 ).
(23) Computed tomography (CT)--The production of a
tomogram by the acquisition and computer processing of x-ray transmission
data.
(24) Control panel--The part of the radiation machine
control upon which are mounted the switches, knobs, push buttons,
and other hardware necessary for manually setting the technique factors.
(25) CT conditions of operation--All selectable parameters
governing the operation of a CT system including, nominal tomographic
section thickness, filtration, and the technique factors as defined
in this subsection.
(26) CT gantry--The tube housing assemblies, beam-limiting
devices, detectors, and the supporting structures and frames that
hold these components.
(27) Declared pregnant woman--A woman who has voluntarily
informed the registrant, in writing, of her pregnancy and the estimated
date of conception. The declaration remains in effect until the declared
pregnant woman voluntarily withdraws the declaration in writing or
is no longer pregnant.
(28) Deep dose equivalent (Hd )
that applies to external whole-body exposure--The dose equivalent
at a tissue depth of 1 cm (1,000 milligrams per square centimeter
(mg/cm2 )).
(29) Diagnostic source assembly--The tube housing assembly
with a beam-limiting device attached.
(30) Dose--A generic term that means absorbed dose,
dose equivalent, or total effective dose equivalent. For purposes
of this section, "radiation dose" is an equivalent term.
(31) 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 sievert (Sv) and rem.
(32) Dose limits--The permissible upper bounds of radiation
doses established in accordance with this chapter. For purposes of
this section, "limits" is an equivalent term.
(33) 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 = ΣWT HT ).
(34) Embryo/fetus--The developing human organism from
conception until the time of birth.
(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.
Cont'd... |
