| (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.
(73) Scan--The complete process of collecting x-ray
transmission data for the production of a tomogram. Data can be collected
simultaneously during a single scan for the production of one or more
tomograms.
(74) Scan increment--The amount of relative displacement
of the patient with respect to the CT x-ray system between successive
scans measured along the direction of such displacement.
(75) Scan sequence--A preselected set of 2 or more
scans performed consecutively under preselected CT conditions of operation.
(76) Scan time--The period of time between the beginning
and end of x-ray transmission data accumulation for a single scan.
(77) Scattered radiation--Radiation that has been deviated
in direction during passage through matter.
(78) Secondary dose monitoring system--A system which
will terminate irradiation in the event of failure of the primary
dose monitoring system.
(79) Secondary protective barrier (See definition for
protective barrier).
(80) Shutter--A device attached to the tube housing
assembly which can totally intercept the useful beam and which has
a lead equivalency not less than that of the tube housing assembly.
(81) Source-to-skin distance (SSD)--The distance from
the source to the skin of the patient.
(82) Spot check--Those tests and analyses performed
at specified intervals for the purpose of verifying the consistent
output of radiation equipment.
(83) Stationary beam therapy--Radiation therapy without
displacement of one or more mechanical axes relative to the patient
during irradiation.
(84) Supervision--The delegating of the task of applying
radiation in accordance with this section to persons not licensed
in the healing arts or veterinary medicine, who provide services under
the physician's control. The physician or veterinarian assumes full
responsibility for these tasks and shall assure that the tasks will
be administered correctly.
(85) Target--That part of an x-ray tube or accelerator
onto which a beam of accelerated particles is directed to produce
ionizing radiation or other particles.
(86) Termination of irradiation--The stopping of irradiation
in a fashion which will not permit continuance of irradiation without
the resetting of operating conditions at the control panel.
(87) Therapeutic radiation machine--X ray or electron
producing equipment designed and used for external beam radiation
therapy.
(88) Traceable to a national standard--This indicates
that a quantity or a measurement has been compared to a national standard,
for example, National Institute of Standards and Technology, directly
or indirectly through one or more intermediate steps and that all
comparisons have been documented.
(89) Tube housing assembly--The tube housing with tube
installed. It includes high-voltage and/or filament transformers and
other appropriate elements when such are contained within the tube
housing.
(90) Useful beam--Radiation that passes through the
window, aperture, cone, or other collimating device of the source
housing. Also referred to as the primary beam.
(91) Veterinarian--An individual licensed by the Texas
Board of Veterinary Medical Examiners.
(92) Virtual source--A point from which radiation appears
to originate.
(93) Wedge filter--An added filter effecting continuous
progressive attenuation on all or part of the useful beam.
(94) Written directive--An order in writing for the
administration of radiation to a specific patient as specified in
subsection (h)(1)(F)(ii) of this section.
(f) Accelerators used for research and development
and industrial operations.
(1) Registration. Each person possessing an accelerator
for non-human use, shall apply for and receive a certificate of registration
from the agency before beginning use of the accelerator. A person
may energize the accelerator for purposes of installation and acceptance
testing before receiving a certificate of registration from the agency
in accordance with §289.226(i)(1) of this title.
(2) Facility requirements.
(A) Each accelerator facility shall be provided with
primary and/or secondary barriers as are necessary to assure compliance
with §289.231(m) and (o) of this title.
Cont'd... |
