| (25) Electronic brachytherapy device--The system used
to produce and deliver therapeutic radiation including the x-ray tube,
the control mechanism, the cooling system, and the power source.
(26) Electronic brachytherapy source--The x-ray tube
component used in an electronic brachytherapy device.
(27) External beam radiation therapy--Therapeutic irradiation
in which the source of radiation is at a distance from the body.
(28) Field-flattening filter--A filter used to homogenize
the absorbed dose rate over the radiation field.
(29) 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% isodose
line.
(30) Filter--Material placed in the useful beam to
change beam quality in therapeutic radiation machines subject to subsection
(h) of this section.
(31) Focal spot--The area projected on the anode of
the x-ray tube that is bombarded by the electrons accelerated from
the cathode and from which the useful beam originates.
(32) Gantry--That part of the radiation therapy system
supporting and allowing possible movements of the radiation head about
the center of rotation.
(33) Gray (Gy)--For purposes of this section, the SI
unit of absorbed dose, kerma, and specific energy imparted equal to
1 joule per kilogram. For purposes of this section the previous unit
of absorbed dose (rad) is being replaced by the gray (1 Gy = 100 rad).
(34) Half-value layer (HVL)--The thickness of a specified
material which attenuates x-radiation or gamma radiation to an extent
such that the exposure rate (air kerma rate), or absorbed dose rate
is reduced to one-half of the value measured without the material
at the same point.
(35) Healing arts--Any treatment, operation, diagnosis,
prescription, or practice for the ascertainment, cure, relief, palliation,
adjustment, or correction of any human disease, ailment, deformity,
injury, or unhealthy or abnormal physical or mental condition.
(36) Image receptor--Any device, such as a fluorescent
screen or radiographic film, 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.
(37) Institutional Review Board (IRB)--Any board, committee,
or other group formally designated by an institution to review, approve
the initiation of, and conduct periodic review of biomedical research
involving human subjects.
(38) Interlock--A device preventing the start or continued
operation of equipment unless certain predetermined conditions prevail.
(39) Interruption of irradiation--The stopping of irradiation
with the possibility of continuing irradiation without resetting of
operating conditions at the control panel.
(40) Irradiation--The exposure of a living being or
matter to ionizing radiation.
(41) Isocenter--The center of the sphere through which
the useful beam axis passes while the gantry moves through its full
range of motions.
(42) Kilovolt (kV) (kilo electron volt (keV))--The
energy equal to that acquired by a particle with one electron charge
in passing through a potential difference of one thousand volts in
a vacuum. (Note: current convention is to use kV for photons and keV
for electrons.)
(43) Kilovolt peak--kVp (See definition for peak tube
potential).
(44) Lead equivalent--The thickness of lead affording
the same attenuation, under specified conditions, as the material
in question.
(45) Leakage radiation--Radiation emanating from the
source(s) assembly except for the useful beam and radiation produced
when the exposure switch or timer is not activated.
(46) Leakage technique factors--The technique factors
associated with the source assembly that is used in measuring leakage
radiation.
(47) Licensed medical physicist--An individual holding
a current Texas license under the Medical Physics Practice Act, Texas
Occupations Code, Chapter 602, with a specialty in therapeutic radiological
physics.
(48) Light field--The area illuminated by light, simulating
the radiation field.
(49) mA--Milliampere.
(50) Medical event--An event that meets the criteria
specified in subsection (i) of this section.
(51) Megavolt (MV) (megaelectron volt (MeV))--The energy
equal to that acquired by a particle with one electron charge in passing
through a potential difference of one million volts in a vacuum.
(52) Mobile electronic brachytherapy device--An electronic
brachytherapy device that is transported from one address to be used
at another address.
(53) Moving beam radiation therapy--Radiation therapy
with any planned displacement of radiation field or patient relative
to each other, or with any planned change of absorbed dose distribution.
It includes arc, skip, conformal, intensity modulation and rotational
therapy.
(54) Nominal treatment distance--The following nominal
treatment distances shall apply.
(A) For electron irradiation, the distance from the
scattering foil, virtual source, or exit window of the electron beam
to the entrance surface of the irradiated object along the central
axis of the useful beam, as specified by the manufacturer.
(B) For x-ray irradiation, the virtual source or target
to isocenter distance along the central axis of the useful beam to
the isocenter. For non-isocentric equipment, this distance shall be
that specified by the manufacturer.
(55) Output--The exposure rate (air kerma rate), dose
rate, or a quantity related to these rates from a therapeutic radiation
machine.
(56) Peak tube potential--The maximum value of the
potential difference in kilovolts across the x-ray tube during an
exposure.
(57) Phantom--An object behaving in essentially the
same manner as tissue, with respect to absorption or scattering of
the ionizing radiation in question.
(58) Physician--An individual licensed by the Texas
Medical Board.
(59) Port film--An x-ray exposure made with a radiation
therapy system to visualize a patient's treatment area using radiographic
film.
(60) Portable shielding--Moveable shielding that can
be placed in the primary or secondary beam to reduce the radiation
exposure to the patient, occupational worker or a member of the public.
The shielding can be easily moved to position with use of mobility
devices or by hand.
(61) Prescribed dose--The total dose and dose per fraction
as documented in the written directive. The prescribed dose is an
estimation from measured data from a specified therapeutic machine
using assumptions that are clinically acceptable for the treatment
technique and historically consistent with the clinical calculations
previously used for patients treated with the same clinical technique.
(62) Primary dose monitoring system--A system that
will monitor the useful beam during irradiation and that will terminate
irradiation when a preselected number of dose monitor units have been
delivered.
(63) Primary protective barrier--(See definition for
protective barrier).
(64) Protective apron--An apron made of radiation absorbing
materials used to reduce radiation exposure.
(65) 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--A barrier sufficient
to attenuate the useful beam to the required degree.
(B) secondary protective barrier--A barrier sufficient
to attenuate the stray radiation to the required degree.
(66) Protective glove--A glove made of radiation absorbing
materials used to reduce radiation exposure.
(67) Radiation detector--A device which, in the presence
of radiation provides, by either direct or indirect means, a signal
or other indication suitable for use in measuring 1 or more quantities
of incident radiation.
(68) Radiation field--(See definition for useful beam).
(69) Radiation head--The structure from which the useful
beam emerges.
(70) Radiation oncologist--A physician with a specialty
in radiation therapy.
(71) Radiation therapy simulation system (simulator)--An
x-ray system intended for localizing and confirming the volume to
be irradiated during radiation treatment and confirming the position
and size of the therapeutic irradiation field.
(72) Radiation therapy system--An x-ray system that
utilizes prescribed doses of ionizing radiation for treatment.
Cont'd... |
