Current through Register Vol. 48, No. 9, September 27, 2024
These rules shall apply to facilities using therapy systems
with energies 1 MeV and above. The records shall be maintained and available
for review.
6.5.1 Leakage Radiation to
the Patient Area. Equipment shall meet the following requirements:
6.5.1.1 For operating conditions producing
maximum leakage radiation, the absorbed dose in rads (Grays) due to leakage
radiation, including x-rays and electrons, at any point in a circular plane of
two meters (2 m) radius centered on and perpendicular to the central axis of
the beam at the isocenter or nominal treatment distance and outside the maximum
useful beam size shall not exceed 0.1 percent of the maximum absorbed dose in
rads (Grays) of the unattenuated useful beam measured at the point of
intersection of the central axis of the beam and plane surface. Measurements
excluding those for neutrons shall be averaged over an area up to, but not
exceeding, one hundred square centimeters (100 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, two hundred square centimeters (200
cm2).
6.5.1.2 For each system, the registrant shall
determine or obtain from the manufacturer the leakage radiation existing at the
positions specified in
RHB 6.5.1.1 for the
specified operating conditions. Records on leakage radiation measurements shall
be maintained for inspection by the Department.
6.5.2 Beam-Limiting Devices. Adjustable or
interchangeable beam limiting devices shall be provided and such devices shall
transmit no more than two percent (2%) of the useful photon beam at the nominal
treatment distance for the portion of the useful beam which is to be attenuated
by the beam-limiting device. The neutron component of the useful beam shall not
be included in this requirement.
6.5.3 Filters.
6.5.3.1 Each filter which 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. For
wedge filters, 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.
6.5.3.2 If the absorbed dose rate data
required by
RHB 6.5.15 relates
exclusively to operation with a field-flattening filter or beam scattering foil
in place, such filter shall be removable only by the use of tools.
6.5.3.3 For equipment installed after May 25,
2001, which utilizes a system of wedge filters, interchangeable
field-flattening filters, or interchangeable beam scattering foils:
6.5.3.3.1 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 control panel, either manually or
automatically.
6.5.3.3.2 An
interlock system shall be provided to prevent irradiation if the filter
selected is not in the correct position.
6.5.3.3.3 A display shall be provided at the
treatment control panel showing filters in use.
6.5.3.3.4 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 control panel.
6.5.3.4 Attenuation of wedges and compensator
devices must be checked before the device is placed into service. A visual
inspection of the mechanical integrity of these accessories must be done
monthly.
6.5.4 Beam
Quality. The registrant shall determine data sufficient to assure that the
following beam quality requirements in tissue equivalent material are met:
6.5.4.1 The absorbed dose resulting from
x-rays in a useful electron beam at a point on the central axis of the beam ten
centimeters (10 cm) greater than the practical range of the electrons shall not
exceed the values stated in Table 2. Linear interpolation shall be used for
values not stated.
Table 2
|
Maximum Energy of Electron Beam in MeV
|
X-ray Absorbed Dose As a Fraction of Maximum
Absorbed Dose
|
|
1
|
0.03
|
|
15
|
0.05
|
|
35
|
0.10
|
|
50
|
0.20
|
6.5.4.2 Compliance with
RHB 6.5.4 shall be determined
using:
6.5.4.2.1 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;
6.5.4.2.2 The largest field size available
which does not exceed fifteen centimeters by fifteen centimeters (15 cm x 15
cm); and
6.5.4.2.3 A phantom whose
cross-sectional dimensions exceed the measurement radiation field by at least
five centimeters (5 cm) and whose depth is sufficient to perform the required
measurement.
6.5.4.3 The
measured ionization at the surface relative to maximum ionization along the
central axis shall not exceed the limits stated in Table 3. Linear
interpolation shall be used for values not stated.
Table 3
|
Maximum Photon Energy in MeV
|
Measured Ionization at surface relative to Maximum
Ionization along central axis
|
|
1
|
0.80
|
|
2
|
0.70
|
|
5
|
0.60
|
|
15
|
0.50
|
|
35
|
0.40
|
|
50
|
0.20
|
6.5.4.4 Compliance with
RHB 6.5.4.3 shall be
determined by measurements made:
6.5.4.4.1
Within a tissue equivalent phantom using an instrument which will allow
extrapolation to the surface absorbed dose;
6.5.4.4.2 Using a phantom whose size and
placement meet the requirements of
RHB 6.5.4.2;
6.5.4.4.3 After removal of all beam modifying
devices which can be removed without the use of tools, except for beam
scattering or beam-flattening filters; and
6.5.4.4.4 Using the largest field size
available which does not exceed fifteen centimeters by fifteen centimeters (15
cm x 15 cm).
6.5.5 Beam Monitors. All therapy systems
shall be provided with radiation detectors in the radiation head.
6.5.5.1 Equipment manufactured after January
1, 1994, shall be provided with at least two (2) independent radiation
detectors. The detectors shall be incorporated into two (2) independent dose
monitoring systems.
6.5.5.2
Equipment manufactured before January 1, 1994, shall be provided with at least
one (1) radiation detector. This detector shall be incorporated into a primary
dose monitoring system.
6.5.5.3 The
detector and the system into which that detector is incorporated shall meet the
following requirements:
6.5.5.3.1 Each
detector shall be removable only with tools and shall be interlocked to prevent
incorrect positioning.
6.5.5.3.2
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.
6.5.5.3.3
Each dose monitoring system shall be capable of independently monitoring,
interrupting, and terminating irradiation.
6.5.5.3.4 For new equipment, the design of
the dose monitoring systems shall assure that:
a) malfunctioning of one (1) system shall not
affect the correct functioning of the secondary system; and
b) failure of any element common to both
systems which could affect the correct function of both systems shall terminate
irradiation.
6.5.5.3.5
Each dose monitoring system shall have a legible display at the treatment
control panel. For new equipment, each display shall:
6.5.5.3.5.1 Maintain a reading until
intentionally reset to zero (0);
6.5.5.3.5.2 Have only one (1) scale and no
scale multiplying factors for each mode of operation; and
6.5.5.3.5.3 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.
6.5.5.3.6 In the event of power failure, the
dose monitoring information required by
RHB 6.5.5.3.5 displayed
at the control panel at the time of failure shall be retrievable in at least
one (1) system for a twenty (20)-minute period of time.
6.5.6 Beam Symmetry. In new
equipment inherently capable of producing useful beams with unattenuated
asymmetry exceeding five percent (5%), the asymmetry of the radiation beam in
two (2) orthogonal directions shall be monitored before the beam passes through
the beam-limiting device. Facilities shall be provided so that, if the
difference in dose rate between one region and another region symmetrically
displaced from the central axis of the beam exceeds five percent (5%) of the
central axis dose rate, indication of this condition is made at the control
panel; and if this difference exceeds ten percent (10%), the irradiation is
terminated.
6.5.7 Selection and
Display of Dose Monitor Units.
6.5.7.1
Irradiation shall not be possible until a selection of a number of dose monitor
units has been made at the treatment control panel.
6.5.7.2 The preselected number of dose
monitor units shall be displayed at the treatment control panel until reset
manually for the next irradiation.
6.5.7.3 After termination of irradiation, it
shall be necessary to manually reset the dosimeter display to zero (0) before
subsequent treatment can be initiated.
6.5.7.4 For new equipment, after termination
of irradiation, it shall be necessary to manually reset the preselected dose
monitor units before irradiation can be initiated.
6.5.8 Termination of Irradiation by the Dose
Monitoring System or Systems during Stationary Beam Therapy.
6.5.8.1 Each primary system shall terminate
irradiation when the preselected number of dose monitor units has been detected
by the system.
6.5.8.2 If original
design of the equipment included a secondary dose monitoring system, that
system shall be capable of terminating irradiation when not more than fifteen
percent (15%) or forty (40) dose monitor units, whichever is smaller, above the
preselected number of dose monitor units set at the control panel, has been
detected by the secondary dose monitoring system.
6.5.8.3 For equipment manufactured after
January 1, 1994, a secondary dose monitoring system shall be present. That
system shall be capable of terminating irradiation when not more than ten
percent (10%) or twenty-five (25) dose monitoring units, whichever is smaller,
above the preselected number of dose monitor units set at the control panel has
been detected by the secondary dose monitoring system.
6.5.8.4 For equipment manufactured after
January 1, 1994, an indicator on the control panel shall show which dose
monitoring system has terminated irradiation.
6.5.9 Interruption Switches. It shall be
possible to interrupt irradiation and equipment movements at any time from the
operator's position at the treatment control panel. Following an interruption,
it shall be possible to restart irradiation without any reselection of
operating conditions. If any change is made of a preselected value during an
interruption, irradiation and equipment movements shall be automatically
terminated.
6.5.10 Termination
Switches. It shall be possible to terminate irradiation and equipment movements
or go from any interruption condition to termination conditions at any time
from the operator's position at the treatment control panel.
6.5.11 Timer.
6.5.11.1 A timer which has a display shall be
provided at the treatment control panel. The timer shall have a preset time
selector and an elapsed time indicator.
6.5.11.2 The timer shall be a cumulative
timer which activates with the production of radiation and retains its reading
after irradiation is interrupted or terminated. After irradiation is terminated
and before irradiation can be reinitiated, it shall be necessary to reset the
elapsed time indicator to zero (0).
6.5.11.3 For equipment manufactured after May
25, 2001, after termination of irradiation and before irradiation can be
reinitiated, it shall be necessary to manually reset the preset time
selector.
6.5.11.4 The timer shall
terminate irradiation when a preselected time has elapsed if the dose
monitoring systems have not previously terminated irradiation.
6.5.12 Selection of Radiation
Type. Equipment capable of both x-ray therapy and electron therapy shall meet
the following additional requirements:
6.5.12.1 Irradiation shall not be possible
until a selection of radiation type has been made at the treatment control
panel.
6.5.12.2 An interlock system
shall be provided to ensure that the equipment can emit only the radiation type
which has been selected.
6.5.12.3
An interlock system shall be provided to prevent irradiation if any selected
operations carried out in the treatment room do not agree with the selected
operations at the treatment control panel.
6.5.12.4 An interlock system shall be
provided to prevent irradiation with x-ray except to obtain a port film when
electron applicators are fitted.
6.5.12.5 An interlock system shall be
provided to prevent irradiation with electrons when accessories specific for
x-ray therapy are fitted.
6.5.12.6
The radiation type selected shall be displayed at the treatment control panel
before and during irradiation.
6.5.13 Selection of Energy. Equipment capable
of generating radiation beams of different energies shall meet the following
requirements:
6.5.13.1 Irradiation shall not
be possible until a selection of energy has been made at the treatment control
panel.
6.5.13.2 An interlock system
shall be provided to prevent irradiation if any selected operations carried out
in the treatment room do not agree with the selected operations carried out at
the treatment control panel.
6.5.13.3 The nominal energy value selected
shall be displayed at the treatment control panel before and during
irradiation.
6.5.13.4 For new
equipment, an interlock system utilizing monitoring of the bending magnet
current shall be provided to terminate irradiation if the energy of the
electrons striking the target or electron window deviates by more than twenty
percent (20%) or three megaelectron volt (3 MeV), whichever is smaller, from
the selected nominal energy.
6.5.14 Selection of Stationary Beam Therapy
or Moving Beam Therapy. Equipment capable of both stationary beam therapy and
moving beam therapy shall meet the following requirements:
6.5.14.1 Irradiation shall not be possible
until a selection of stationary beam therapy or moving beam therapy has been
made at the treatment control panel.
6.5.14.2 An interlock system shall be
provided to ensure that the equipment can operate only in the mode which has
been selected.
6.5.14.3 An
interlock system shall be provided to prevent irradiation if any selected
operations carried out in the treatment room do not agree with the selected
operations carried out at the treatment control panel.
6.5.14.4 The mode of operation shall be
displayed at the treatment control panel.
6.5.14.5 An interlock system shall be
provided to terminate irradiation if movement of the gantry:
6.5.14.5.1 Occurs during stationary beam
therapy; or
6.5.14.5.2 Stops during
moving beam therapy unless such stoppage is a preplanned function.
6.5.14.6 Moving beam therapy shall
be controlled to obtain the selected relationships between incremental dose
monitor units and incremental angle of movement:
6.5.14.6.1 An interlock system shall be
provided to terminate irradiation if the number of dose monitor units delivered
in any ten (10) degrees of arc differs by more than twenty percent (20%) from
the selected value.
6.5.14.6.2
Where gantry angle terminates the irradiation in arc therapy, the dose monitor
units shall differ by less than five percent (5%) from the value calculated
from the absorbed dose per unit angle relationship.
6.5.14.7 Where the dose monitor system
terminates the irradiation in moving beam therapy, the termination of
irradiation shall be as required in
RHB 6.5.8.
6.5.15 Absorbed Dose Rate. A
system shall be provided from whose readings the absorbed dose rate at a
reference point in the treatment volume can be calculated. The radiation
detectors specified in
RHB 6.5.5 may form part of
this system. In addition:
6.5.15.1 The dose
monitor rate shall be displayed at the treatment control panel.
6.5.15.2 If the equipment can deliver under
any conditions an absorbed dose rate at the nominal treatment distance more
than twice the maximum value specified by the manufacturer for any machine
parameter utilized, a device shall be provided which terminates irradiation
when the absorbed dose rate exceeds a value twice the specified maximum. The
dose rate at which the irradiation will be terminated shall be in a record
maintained by the registrant.
6.5.16 Location of Virtual Source and Beam
Orientation. The registrant shall determine, or obtain from the manufacturer,
the location with reference to an accessible point on the radiation head of:
6.5.16.1 The x-ray target or the virtual
source of x-rays; and
6.5.16.2 The
electron window or the virtual source of electrons if the system has electron
beam capabilities.
6.5.17 System Checking. Capabilities shall be
provided so that all radiation safety interlocks can be checked for
operation.
6.5.18 Facility and
Shielding Requirements. In addition to
RHB 6.2 of these rules, the
following design requirements shall apply:
6.5.18.1 Protective Barriers. All protective
barriers shall be fixed except for entrance doors or beam
interceptors.
6.5.18.2 Control
Panel. The control panel shall be located outside the treatment room.
6.5.18.3 Viewing Systems.
6.5.18.3.1 Windows, mirrors, closed-circuit
television, or an equivalent system shall be provided to permit continuous
observation of the patient following positioning and during irradiation and
shall be so located that the operator may observe the patient from the control
panel.
6.5.18.3.2 When the primary
viewing system is by electronic means, an alternate viewing system, which may
be electronic, shall be available for use in the event of failure of the
primary viewing system.
6.5.19 Aural Communications. Provision shall
be made for continuous two-way aural communication between the patient and the
operator at the control panel independent of the particle accelerator. However,
where excessive noise levels or treatment requirements make aural communication
impractical, other methods of communication shall be used. When this is the
case, a description of the alternate method shall be submitted to and approved
by the Department.
6.5.20 Room
Entrances. Treatment room entrances shall be provided with warning lights in
readily observable positions near the outside of all accessible doors to
indicate when the useful beam is "on" and "off."
6.5.21 Entrance Interlocks. Interlocks shall
be provided such that all entrance doors must be closed 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.
