Washington Administrative Code
Title 246 - Health, Department of
RADIATION
Chapter 246-225 - Radiation protection - X rays in the healing arts
Section 246-225-130 - X-ray and electron therapy systems with energies of one MeV and above
Universal Citation: WA Admin Code 246-225-130
Current through Register Vol. 24-18, September 15, 2024
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. |
Statutory Authority: RCW 70.98.050 and 70.98.080. 91-15-083 (Order 183), § 246-225-130, filed 7/23/91, effective 8/23/91. Statutory Authority: RCW 43.70.040. 91-02-049 (Order 121), recodified as § 246-225-130, filed 12/27/90, effective 1/31/91. Statutory Authority: RCW 70.98.080. 87-01-031 (Order 2450), § 402-28-101, filed 12/11/86. Statutory Authority: RCW 70.98.050. 81-01-011 (Order 1570), § 402-28-101, filed 12/8/80.
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