| (i) Each installation shall be provided with primary
and/or secondary barriers as are necessary to assure compliance with
§289.231(m) and (o) of this title. All protective barriers shall
be fixed except for entrance doors or beam interceptors.
(ii) The control panel shall be located outside the
treatment room or in an enclosed booth inside the room.
(iii) Interlocks shall be provided such that all entrance
doors shall be closed, including doors to any interior booths, before
treatment can be initiated or continued. If the radiation beam is
interrupted by any door opening, it shall not be possible to restore
the machine to operation without closing the door and reinitiating
irradiation by manual action at the control panel. When any door is
opened while the x-ray tube is activated, the exposure at a distance
of 1 m from the source shall be reduced to less than 100 mR/hr (1
mGy/hr).
(D) Surveys, calibrations, and spot checks.
(i) Surveys shall be performed as follows.
(I) All new and existing facilities not previously
surveyed shall have an initial survey made by a licensed medical physicist
with a specialty in therapeutic radiological physics, who shall provide
a written report of the survey to the registrant. Additional surveys
shall be done after any change in the facility, facility design, or
equipment that might cause a significant increase in radiation hazard.
(II) The registrant shall maintain a copy of the initial
survey report and all subsequent survey reports required by subclause
(I) of this clause in accordance with subsection (l) of this section
for inspection by the agency.
(III) The survey report shall indicate all instances
where the installation is in violation of applicable requirements
of this chapter.
(ii) Calibrations shall be performed as follows.
(I) The calibration of a therapeutic radiation system
shall be performed at intervals not to exceed 1 year and after any
change or replacement of components that could cause a change in the
radiation output. The calibrations shall be such that the dose at
a reference point in a water or plastic phantom can be calculated
to within an uncertainty of 5.0%.
(II) The calibration of the radiation output of the
therapeutic radiation system shall be performed by a licensed medical
physicist with a specialty in therapeutic radiological physics who
is physically present at the facility during such calibration.
(III) The calibration of the therapeutic radiation
system shall include, but not be limited to, the following determinations:
(-a-) verification that the radiation therapy system
is operating in compliance with the design specifications;
(-b-) HVL for each kV setting and filter combination
used;
(-c-) the exposure rates (air kerma rates) as a function
of field size, technique factors, filter, and treatment distance used;
and
(-d-) the degree of congruence between the radiation
field and the field indicated by the localizing device, if such device
is present, which shall be within 5 mm for any field edge.
(IV) Calibration of the radiation output of a therapeutic
radiation system shall be performed with a calibrated dosimetry system.
The dosimetry system calibration shall be traceable to a national
standard. The calibration interval shall not exceed 24 months.
(V) Records of calibration measurements specified in
clause (ii) of this subparagraph shall be maintained by the registrant
in accordance with subsection (l) of this section for inspection by
the agency.
(VI) A copy of the latest calibrated absorbed dose
rate measured on a particular therapeutic radiation system shall be
available at a designated area within the therapy facility housing
that therapeutic radiation system.
(iii) Spot checks shall be performed on therapeutic
radiation systems capable of operation at greater than 150 kVp. Such
measurements shall meet the following requirements.
(I) The spot check procedures shall be in writing,
or documented in an electronic reporting system, and shall have been
developed by a licensed medical physicist with a specialty in therapeutic
radiological physics.
(II) If a licensed medical physicist does not perform
the spot check measurements, the results of the spot check measurements
shall be reviewed by a licensed medical physicist with a specialty
in therapeutic radiological physics within 5 treatment days and a
record made of the review. If the output varies by more than 5.0%
from the expected value, a licensed medical physicist with a specialty
in therapeutic radiological physics shall be notified immediately.
(III) The written spot check procedures shall specify
the frequency that tests or measurements are to be performed and that
the spot check shall be performed during the calibration specified
in clause (ii) of this subparagraph. The acceptable tolerance for
each parameter measured when compared to the value for that parameter
determined in the calibration specified in clause (ii) of this subparagraph
shall be stated.
(IV) The written spot check procedures shall include
special operating instructions that shall be carried out whenever
a parameter in subclause (III) of this clause exceeds an acceptable
tolerance.
(V) Whenever a spot check indicates a significant change
in the operating characteristics of a system, as specified in the
procedures, the system shall be recalibrated, as required in clause
(ii) of this subparagraph.
(VI) Records of written spot checks and any necessary
corrective actions shall be maintained by the registrant in accordance
with subsection (l) of this section for inspection by the agency.
A copy of the most recent spot check shall be available at a designated
area within the therapy facility housing that therapeutic radiation
system.
(VII) Spot checks shall be obtained using a system
satisfying the requirements of clause (ii)(IV) of this subparagraph.
(3) Therapeutic radiation machines capable of operating
at energies of 1 MeV and above.
(A) Equipment requirements.
(i) For operating conditions producing maximum leakage
radiation, the absorbed dose in rads (mGy) due to leakage radiation,
including x rays, electrons, and neutrons, at any point in a circular
plane of 2 m radius centered on and perpendicular to the central axis
of the beam at the isocenter or normal treatment distance and outside
the maximum useful beam size shall not exceed 0.1% of the maximum
absorbed dose in rads (mGy) of the unattenuated useful beam measured
at the point of intersection of the central axis of the beam and the
plane surface. Measurements excluding those for neutrons shall be
averaged over an area up to, but not exceeding, 100 square centimeters
(cm2 ) at the positions specified. Measurements
of the portion of the leakage radiation dose contributed by neutrons
shall be averaged over an area up to, but not exceeding, 200 cm2 . For each system, the registrant shall determine
or obtain from the manufacturer the leakage radiation existing at
the positions specified for the specified operating conditions. Records
on leakage radiation measurements shall be maintained in accordance
with subsection (l) of this section for inspection by the agency.
(ii) Each wedge filter that is removable from the system
shall be clearly marked with an identification number. Documentation
available at the control panel shall contain a description of the
filter. The wedge angle shall appear on the wedge or wedge tray (if
permanently mounted to the tray). If the wedge tray is damaged, the
wedge transmission factor shall be redetermined. Equipment manufactured
after March 1, 1989, shall meet the following requirements.
(I) Irradiation shall not be possible until a selection
of a filter or a positive selection to use "no filter" has been made
at the treatment console, either manually or automatically.
(II) An interlock system shall be provided to prevent
irradiation if the filter selected is not in the correct position.
(III) A display shall be provided at the treatment
console showing the beam quality in use.
(IV) An interlock shall be provided to prevent irradiation
if any filter selection operation carried out in the treatment room
does not agree with the filter selection operation carried out at
the treatment console.
(iii) The registrant shall determine data sufficient
to assure that the following beam quality requirements in tissue equivalent
material are met.
(I) The absorbed dose resulting from x rays in a useful
electron beam at a point on the central axis of the beam 10 cm greater
than the practical range of the electrons shall not exceed the values
stated in the following Table II. Linear interpolation shall be used
for values not stated.
Attached Graphic
(II) Compliance with subclause (I) of this clause shall
be determined using:
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