WAC 246-225-130
X-ray and electron therapy systems with
energies of one MeV and above. Chapter 246-229 WAC except WAC 246-229-100 (3) and (4) shall apply to medical facilities
using therapy systems with energies 1 MeV and above.
(1) Definitions. In addition to the definitions provided
in WAC 246-225-010, the following definitions shall be
applicable to this section.
(a) "Applicator" means a structure which indicates the
extent of the treatment field at a given distance from the
nominal source and which may or may not incorporate an
additional beam-limiting device.
(b) "Beam scattering foil" means a device which scatters
and flattens a beam of electrons.
(c) "Central axis of the beam" means a line passing
through the origin of the source and the center of the plane
figure formed by the edge of the secondary collimating jaws
when in a symmetric mode.
(d) "Dose monitoring system" means a system of devices
for the detection and display of quantities of radiation.
(e) "Dose monitor unit" means a unit from which the
absorbed dose can be calculated.
(f) "Existing equipment" means therapy systems subject to
this section which were manufactured on or before the
effective date of these regulations.
(g) "Field flattening device" means an absorber used to
homogenize the dose rate over the area of a useful beam of
X-rays.
(h) "Field size" means the dimensions of an area in a
plane perpendicular to the specified direction of the beam of
incident radiation at a maximum dose depth. Determine
dimensions by fifty percent decrement lines.
(i) "Gantry" means that part of the system supporting and
allowing possible movements of the radiation head.
(j) "Interruption of irradiation" means the stopping of
irradiation with the possibility of continuing irradiation
without resetting of the operating conditions at the control
panel.
(k) "Isocenter" means a fixed point in space located at
the intersection of the rotation axes of the principal
movements of the therapy system.
(l) "Moving beam therapy" means radiation therapy with
relative displacement of the useful beam and the patient
during irradiation.
(m) "New equipment" means systems subject to this section
which were manufactured after effective date of these
regulations.
(n) "Nominal source" means a point from which radiation
originates.
(o) "Normal treatment distance" means the distance
between the virtual source and a reference point on the
central axis of the beam. The reference is located at a
position on the central axis at a specified distance from the
nominal source.
(p) "Patient" means an individual subjected to
examination and treatment.
(q) "Phantom" means a volume of material behaving in a
manner similar to tissue with respect to the attenuation and
scattering of radiation.
(r) "Primary dose monitoring system" means a system which
will monitor the quantity of radiation produced during
irradiation and which will terminate irradiation when a
preselected number of dose monitor units have been acquired.
(s) "Radiation treatment prescription" means the absorbed
dose which is intended to be delivered to the treatment
volume.
(t) "Radiation head" means the structure from which the
useful beam emerges.
(u) "Redundant dose monitoring combination" means a
combination of two dose monitoring systems in which both
systems are arranged to terminate irradiation in accordance
with a preselected number of dose monitor units.
(v) "Secondary dose monitoring system" means a system
which will terminate irradiation in the event of failure of
the primary system.
(w) "Shadow tray" means a device attached to the
radiation head to support auxiliary beam limiting material.
(x) "Stationary beam therapy" means radiation therapy
without relative displacement of the useful beam and the
patient during irradiation.
(y) "Target" means that part of a radiation source which
intercepts a beam of accelerated particles with subsequent
emission of other radiation.
(z) "Termination of irradiation" means the stopping of
irradiation in a fashion which will not permit continuance of
irradiation without the resetting of operating conditions at
the control panel.
(aa) "Treatment field" means the cross-sectional area of
the patient's tissue which is to be irradiated.
(bb) "Treatment volume" means that portion of the
patient's body which is to be irradiated.
(2) Requirements for equipment.
(a) Leakage radiation to the patient area.
(i) New equipment shall meet the following requirements:
(A) For all operating conditions, the dose equivalent in
rem due to leakage radiation, including X-ray and electrons,
but excluding neutrons, at any point in a circular plane of
two meters radius centered on and perpendicular to the central
axis of the beam at the normal treatment distance and outside
the maximum useful beam, shall not exceed 0.1 percent of the
maximum dose equivalent in rem of the unattenuated useful beam
measured at the point of intersection of the central axis of
the beam and the plane surface. Measurements shall be
averaged over an area up to but not exceeding one hundred
square centimeters at the positions specified; and
(B) For each system the registrant shall determine, or
obtain from the manufacturer, the leakage radiation existing
at the positions specified in (a)(i)(A) of this subsection for
specified operating conditions. Records for leakage radiation
shall be maintained at the installation for inspection by the
department.
(ii) Existing equipment (that installed prior to the
effective date of the regulations) shall meet the following
requirements:
(A) The leakage radiation, excluding neutrons, at any
point in the area specified by (a)(i)(A) of this subsection,
where such area intercepts the central axis of the beam one
meter from the nominal source, shall not exceed 0.1 percent of
the maximum dose equivalent in rems of the unattenuated useful
beam measured at the point of intersection of the central axis
of the beam and the surface of the reference circular plane. Measurements shall be averaged over an area up to but not
exceeding one hundred square centimeters at the positions
specified.
(B) For each system, the registrant shall determine, or
obtain from the manufacturer, the leakage radiation existing
at the positions specified in (a)(ii)(A) of this subsection
for specified operating conditions. Records for radiation
leakage shall be maintained at the installation for inspection
by the department.
(b) Leakage radiation outside the patient area.
(i) The dose equivalent in rem due to leakage radiation,
except in the area specified in (a) of this subsection, when
measured at any point one meter from the path of the charged
particle, before the charged particle strikes the target or
window, shall not exceed 0.1 percent for X-ray leakage of the
maximum dose equivalent in rems of the unattenuated useful
beam measured at the point of intersection of the central axis
of the beam and the circular plane specified in (a) of this
subsection.
(ii) The registrant shall determine, or obtain from the
manufacturer, the actual leakage radiation existing at the
positions specified in (a) of this subsection for specified
operating conditions. Measurements shall be averaged over an
area up to but not exceeding one hundred square centimeters at
the positions specified.
(c) Beam-limiting devices. Secondary beam-limiting
devices shall be provided and such devices shall transmit no
more than two percent of the useful beam for the portion of
the useful beam attenuated by the beam-limiting device. The
neutron component of the useful beam shall not be included in
this requirement.
(d) Beam-modifying devices.
(i) When the absorbed dose rate information required by
subsection (2)(q) of this section is dependent on operation
with a beam-flattening or beam-scattering device in place, the
device shall be removable from the machine only by the use of
tools.
(ii) In systems using interchangable beam-flattening
devices or beam-scattering foils:
(A) Irradiation shall not be possible until a selection
of beam-modifying device is made and verified at the treatment
control panel;
(B) An interlock system shall be provided to prevent
irradiation when the beam-modifying device selected is not in
the correct position; and
(C) A display at the control panel shall indicate what
beam-modifying device is selected.
(e) Wedges.
(i) Presence of wedges in the beam shall be indicated at
the control panel, by direct observation or by electronic
means.
(ii) Each wedge removable from the system shall be
clearly identified as to that wedge's material of
construction, thickness, and wedge angle.
(iii) An interlock shall be provided to prevent
irradiation when a wedge selection carried out in the
treatment room does not agree with the wedge selection
indicated at the control panel.
(f) Beam quality. The registrant shall obtain from the
therapy X-ray system manufacturer, and have available, the
following information:
(i) At various beam energies, the X-ray absorbed dose
expressed as a fraction of maximum absorbed dose;
(ii) At various beam energies, the absorbed dose at the
surface of the skin as a fraction of the maximum absorbed
dose; and
(iii) The maximum percentage absorbed dose due to stray
neutrons in the useful beam at specified operating conditions.
(g) Beam monitors. Therapy systems shall be provided
with radiation detectors in the radiation head.
(i) New equipment shall be provided with two or more
radiation detectors. The detectors shall be incorporated into
two monitoring systems arranged either as a primary/primary
combination or as a primary/secondary combination.
(ii) Existing equipment shall be provided with one or
more radiation detectors. The detector shall be incorporated
into a primary system.
(iii) The detectors and system where the detector is
incorporated shall meet the following requirements:
(A) Each primary system shall have a detector which is a
transmission full-beam detector placed on the patient side of
beam-modifying devices;
(B) The detectors shall be removable only with tools and
shall be interlocked to prevent incorrect positioning;
(C) Each detector shall be capable of independently
monitoring and controlling the useful beam;
(D) 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;
(E) For new equipment, the design of the dose-monitoring
systems of subsection (2)(i) of this section shall assure the
malfunctioning of one system shall not affect the correct
functioning of the second system. In addition, the failure of
an element common to both systems shall terminate irradiation.
(F) Each dose monitoring system shall have a legible
display at the treatment control panel. Each display shall:
(I) Maintain a reading until intentionally reset to zero;
(II) Have only one scale and no scale multiplying factors
in new equipment; and
(III) Utilize a design so increasing dose is displayed by
increasing numbers and shall be designed so, in the event of
an overdosage of radiation, the absorbed dose may be
accurately determined under normal conditions of use or
foreseeable failures.
(G) In the event of power failure, the dose-monitoring
information required in subsection (2)(i) of this section
displayed at the control panel at the time of failure shall be
retrievable in one or more systems.
(h) Beam symmetry.
(i) A therapy machine installed after the effective date
of these regulations shall have the capability of comparing
the dose rates in each of the four quadrants of the central
eighty percent of the useful beam.
(ii) Beam symmetry information shall be displayed at the
treatment control panel making possible the following
differential between quadrants:
(A) Five percent for straight-through accelerators; and
(B) Three percent for bending-magnet accelerators.
(iii) Beam asymmetry in excess of a ten percent quadrant
differential shall cause treatment to terminate, or shall
prevent irradiation.
(i) Selection and display of dose monitor units.
(i) Irradiation shall not be possible until a selection
of a number of dose monitor units is made at the treatment
control panel.
(ii) After useful beam termination, it shall be necessary
manually to reset the preselected dose monitor units before
treatment is reinitiated.
(iii) The preselected number of dose monitor units shall
be displayed at the treatment control panel until reset
manually for the next irradiation.
(j) Termination of irradiation by the dose monitoring
system.
(i) Each of the required monitoring systems shall be
capable of independently terminating an irradiation. Provision shall be made to test the correct operation of each
system.
(ii) Each primary system shall terminate irradiation when
the preselected number of dose monitor units is detected by
the system.
(iii) Each secondary system shall terminate irradiation
when a maximum of the preselected number of dose monitor units
plus forty is detected by the system.
(iv) For new equipment, indicators on the control panel
shall show which monitoring system terminated the beam.
(k) 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 any interruption, it shall be possible to restart
irradiation by operator action without any reselection of
operating conditions. If any change is made of a preselected
value during an interruption, the equipment shall go to
termination condition.
(l) Termination switches. It shall be possible to
terminate irradiation and equipment movements, or go from an
interruption condition to termination conditions, at any time
from the operator's position at the treatment control panel.
(m) Timer.
(i) A timer shall be provided which has a display at the
treatment control panel. The timer shall be graduated in
minutes and decimals of minutes. The timer shall have a
preset time selector and an elapsed time indicator.
(ii) The timer shall be a cumulative timer which switches
on and off with the radiation and retains its reading after
irradiation is interrupted or terminated. It shall be
necessary to zero and subsequently reset the elapsed time
indicator and the preset time selector after irradiation is
terminated before irradiation shall again be possible.
(iii) The timer shall terminate irradiation when a
preselected time has elapsed if the dose monitoring systems
fail to terminate irradiation.
(n) Selection of radiation type. Equipment capable of
both X-ray therapy and electron therapy shall meet the
following requirements:
(i) Irradiation shall not be possible until a selection
of radiation type is made at the treatment control panel;
(ii) An interlock system shall be provided to insure that
the equipment can emit only the selected radiation type;
(iii) An interlock system shall be provided to prevent
irradiation if selected operations carried out in the
treatment room do not agree with the selected operations
carried out in the treatment control panel;
(iv) With the exception of a specified number of dose
monitor units for the purpose of portal film exposures, an
interlock system shall be provided to prevent irradiation with
X-rays when electron applicators are in place and to prevent
irradiation with electrons when accessories for X-ray therapy
are in place; and
(v) The radiation type selected shall be displayed at the
treatment control panel before and during irradiation.
(o) Selection of energy. Equipment capable of generating
radiation beams of different energies shall meet the following
requirements:
(i) Irradiation shall not be possible until a selection
of energy is made at the treatment control panel;
(ii) An interlock system shall be provided to insure the
equipment can emit only the energy of selected radiation;
(iii) An interlock system shall be provided to prevent
irradiation if selected operations carried out in the
treatment room do not agree with the selected operations
carried out at the treatment control panel; and
(iv) The energy selected shall be displayed at the
treatment control panel before and during irradiation.
(p) 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:
(i) Irradiation shall not be possible until a selection
of stationary beam therapy or moving beam therapy is made at
the treatment control panel;
(ii) An interlock system shall be provided to insure the
equipment can operate only in the selected mode;
(iii) An interlock system shall be provided to prevent
irradiation when any selected operations carried out in the
treatment room do not agree with the selected operations
carried out at the treatment control panel;
(iv) An interlock system shall be provided to terminate
irradiation when the movement stops during moving beam
therapy;
(v) Moving beam therapy shall be controlled so the
required relationship between the number of dose monitor units
and movement is obtained; and
(vi) The mode of operation shall be displayed at the
treatment control panel.
(q) Absorbed dose rate. For new equipment, a system
shall be provided from whose readings the absorbed dose rate
at a reference point in the treatment volume can be
calculated.3 In addition:
(i) The quotient of the number of dose monitor units by
time shall be displayed at the treatment control panel; and
(ii) If the equipment can deliver, under any conditions,
an absorbed dose rate at the normal treatment distance more
than twice the maximum value specified by the manufacturer's
anticipated dose rate for any machine parameters utilized, a
device shall be provided which terminates irradiation when the
absorbed dose rate exceeds a value twice the specified
maximum. The value at which the irradiation is terminated
shall be in a registrant-maintained record.
(r) Location of focal spot 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:
(i) The X-ray target or the virtual source of X-rays;
(ii) The electron window or the scattering foil;
(iii) All possible orientations of the useful beam.
(s) System interlock checks. Capabilities shall be
provided to check radiation safety interlocks. When
preselection of operating conditions requires action in the
treatment room and at the treatment control panel, selection
at one location shall not give a display at the other location
until the requisite selected operations in both locations are
completed.
(t) Facility and shielding requirements. In addition to
chapter 246-221 WAC, the following design requirements shall
apply:
(i) Except for entrance doors or beam interceptors,
required barriers shall be fixed barriers;
(ii) The treatment control panel shall be located outside
the treatment room;
(iii) Windows, mirrors, closed-circuit television, or
other equivalent viewing systems shall be provided to permit
continuous observation of the patient during irradiation and
shall be located so the operator may observe the patient from
the treatment control panel. When the viewing system is by
electronic means, for example, by television, an alternate
viewing system shall be provided for use in the event of the
primary system failure, or, alternatively, treatments shall be
discontinued until the viewing system is again functional;
(iv) Provision shall be made for two-way aural
communication between the patient and the operator at the
treatment control panel. However, where excessive noise
levels make aural communications impractical, other methods of
communication shall be used;
(v) Treatment rooms to which access is possible through
two entrances or more shall be provided with warning lights
and shall indicate when the useful beam is "on" in a readily
observable position near the outside of all access doors; and
(vi) Interlocks shall be provided so entrance doors shall
be closed before treatment is initiated or continued. When
the radiation beam is interrupted by any door opening, it
shall be possible to restore the machine to operation only by
closing the door and reinitiating exposure by manual action at
the control panel.
(u) Surveys, calibrations, spot checks and operating
procedures.
(i) Survey.
(A) New facilities, and existing facilities not
previously surveyed, shall have a survey made by, or under the
direction of, a qualified expert. Such surveys shall also be
done after a change in the facility or equipment causing a
significant increase in radiation hazard.
(B) The registrant shall obtain a written report of the
survey from the qualified expert and the registrant shall
transmit a copy of the report to the department.
(C) The report shall indicate instances where the
installation, in the opinion of the qualified expert, is in
violation of applicable regulations and shall cite the section
violated.
(ii) Calibrations.
(A) The calibration of systems subject to this section
shall be performed before the system is first used for
irradiation of patient and thereafter at time intervals which
do not exceed twelve months and after any change which
significantly alters the calibration, spatial distribution, or
other characteristics of the therapy beam.
(B) The calibration shall be performed by a qualified
expert.
(C) Calibration of the dose equivalent of the therapy
beam shall be performed with a measurement instrument of which
the calibration is traceable to national standards of exposure
or absorbed dose and which shall have been calibrated within
the preceding two years.
(D) Calibrations made under subsection (2)(u)(ii) of this
section shall require the dose at a reference point in soft
tissue be calculated within ± 5 percent.
(E) The calibration of the therapy beam shall include,
but not be limited to, the following determinations:
(I) Verification that the equipment is operating in
compliance with the design specifications concerning the light
localizer, the side light and back-pointer alignment with the
isocenter, when applicable, variation in the axis of rotation
for the table, gantry and jaw system, and beam flatness and
symmetry at specified depths;
(II) The output factors in terms of dose per monitor unit
or dose per minute at a specific depth in a phantom for the
range of field sizes used, for each effective energy, and for
each treatment distance used for radiation therapy;
(III) The congruence between the radiation field and the
field indicated by the localizing device; and
(IV) The uniformity of the radiation field and its
dependency upon the direction of the useful beam.
(F) Records of the calibration performed under subsection
(2)(u)(ii) of this section shall be maintained by the
registrant for two years after completion of the calibration.
(G) A copy of the latest calibration performed under
subsection (2)(u)(ii) of this section shall be available for
operator use.
(iii) Spot checks. Spot checks shall be performed on the
system subject to this section. Such spot checks shall meet
the following requirements:
(A) A qualified expert shall develop, in writing, spot
check procedures;
(B) The measurements taken during spot checks shall
demonstrate the degree of consistency of the operating
characteristics affecting the radiation output of the system
or the radiation delivered to a patient during a therapy
procedure;
(C) The spot check procedures shall specify the frequency
of tests or measurements performed;
(D) For systems where beam quality can vary
significantly, spot checks shall include quality checks;
(E) Where a system has built-in devices which provide a
self-check of any parameter during irradiation, the spot check
procedures shall require the parameter be independently
verified at specific time intervals;
(F) Erratic spot checks or inconsistent spot checks of
calibration data shall be promptly investigated and corrected
before the system is used for patient irradiation;
(G) When a spot check indicates a significant change in
the operating characteristics of a system, as specified in the
qualified expert's spot check procedures, the system shall be
recalibrated as required under subsection (2)(u)(ii) of this
section;
(H) Records of spot check measurements performed under
subsection (2)(u)(iii) of this section shall be maintained by
the registrant for a period of one year or for twice as long
as the spot check cycle, whichever is greater;
(I) Operating procedures.
(I) No individual other than the patient shall be in the
treatment room during treatment of a patient.
(II) If a patient must be held in position during
treatment, mechanical supporting or restraining devices shall
be used.
(III) The system shall not be used in the administration
of radiation therapy unless subsection (2)(u)(i), (ii), and
(iii) of this section are met.
3The radiation detectors specified under subsection (2)(g) of this section may form part of this system.