| cause a significant increase in radiation hazard.
(-b-) The registrant shall maintain a copy of the initial
survey report and all subsequent survey reports required by this subclause
in accordance with subsection (k)(2) of this section for inspection
by the agency.
(-c-) 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.
(-a-) The calibration of a therapeutic radiation system
shall be performed at intervals not to exceed one year and after any
change or replacement of components that could cause a change in the
radiation output.
(-b-) 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.
(-c-) The calibration of the therapeutic radiation
system shall include verification that the radiation therapy system
is operating in compliance with the design specifications.
(-d-) 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 for the dosimetry system shall
not exceed 24 months.
(-e-) Records of calibration measurements specified
in clause (ii) of this subparagraph shall be maintained by the registrant
in accordance with subsection (k)(2) of this section for inspection
by the agency.
(-f-) 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.
(-a-) 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.
(-b-) Records of written spot checks and any necessary
corrective actions shall be maintained by the registrant in accordance
with subsection (k)(2) 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.
(C) Therapeutic radiation machines capable of operating
at energies of 1 MeV and above.
(i) 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 percent 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 (k)(2) 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 re-determined. Equipment manufactured
after March 1, 1989, shall meet the following requirements.
(-a-) 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.
(-b-) An interlock system shall be provided to prevent
irradiation if the filter selected is not in the correct position.
(-c-) A display shall be provided at the treatment
console showing the beam quality in use.
(-d-) 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.
(-a-) 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 III. Linear interpolation
shall be used for values not stated.
Attached Graphic
(-b-) Compliance with subclause (I) of this clause
shall be determined using:
(-1-) a measurement within a tissue equivalent phantom
with the incident surface of the phantom at the normal treatment distance
and normal to the central axis of the beam;
(-2-) a field size of 10 cm by 10 cm; and
(-3-) a phantom whose cross-sectional dimensions exceed
the measurement radiation field by at least 5 cm and whose depth is
sufficient to perform the required measurement.
(-c-) The absorbed dose at a surface located at the
normal treatment distance, at the point of intersection of that surface
with the central axis of the useful beam during x-ray irradiation,
shall not exceed the limits stated in the following Table IV. Linear
interpolation shall be used for values not stated.
Attached Graphic
(-d-) Compliance with subclause (III) of this clause
shall be determined by measurements made as follows:
(-1-) within a tissue equivalent phantom using an instrument
that will allow extrapolation to the surface absorbed dose;
(-2-) using a phantom whose size and placement meet
the requirements of subclause (II) of this clause;
(-3-) after removal of all beam modifying devices that
can be removed without the use of tools, except for beam scattering
or beam-flattening filters; and
(-4-) using the largest field size available that does
not exceed 15 cm by 15 cm.
(IV) All therapeutic radiation systems shall be provided
with radiation detectors in the radiation head. These shall include
the following, as appropriate.
(-a-) Equipment manufactured after March 1, 1989, shall
be provided with at least two independent radiation detectors. The
detectors shall be incorporated into two independent dose monitoring
systems.
(-b-) Equipment manufactured on or before March 1,
1989, shall be provided with at least one radiation detector. This
detector shall be incorporated into a primary dose monitoring system.
(-c-) The detector and the system into which that detector
is incorporated shall meet the following requirements.
(-1-) Each detector shall be removable only with tools
and shall be interlocked to prevent incorrect positioning.
(-2-) Each detector shall form part of a dose monitoring
system from whose readings in dose monitor units the absorbed dose
at a reference point in the treatment volume can be calculated.
(-3-) Each dose monitoring system shall be capable
of independently monitoring, interrupting, and terminating irradiation.
(-4-) For equipment manufactured after March 1, 1989,
the design of the dose monitoring systems shall assure that the malfunctioning
of one system shall not affect the correct functioning of the secondary
system, and failure of any element common to both systems that could
affect the correct function of both systems shall terminate irradiation.
(-5-) Each dose monitoring system shall have a legible
display at the treatment console. For equipment manufactured after
March 1, 1989, each display shall maintain a reading until intentionally
reset to zero; have only one scale and no scale multiplying factors;
utilize a design such that increasing dose is displayed by increasing
numbers and shall be so designed that, in the event of an overdosage
of radiation, the absorbed dose may be accurately determined; and
each display shall retain the dose monitoring information in at least
one system for a 15-minute period of time in the Cont'd... |
