Current through Register Vol. 47, No. 52, December 29, 2023
In addition to the provisions of Sections
360.10 through
360.30
of this Part, the requirements of this Section apply to x-ray therapy systems
and associated facilities operating at energies less than 1 MeV.
a) Facility Design
1) A therapeutic radiological physicist shall
be consulted in the design of an x-ray therapy installation.
2) Shielding requirements
A) Each x-ray therapy installation shall be
provided with such primary and secondary barriers as are necessary to assure
compliance with 32 Ill. Adm. Code 340.
B) For all x-ray therapy systems capable of
operating above 150 kVp installed after October 15, 1993, facility design
information shall be submitted to the Agency for review prior to installation
of the x-ray therapy system. Information submitted to the Agency shall include,
but need not be limited to, the following:
i)
Name and address of the planned installation.
ii) Name, address and telephone number of the
therapeutic radiological physicist who was consulted in the design of the
installation.
iii) A scale drawing
that includes the location of the therapy system, control panel and doors to
the room.
iv) The structural
composition and thickness of all walls, doors, partitions, floor and ceiling of
the installation.
v) The occupancy
of areas adjacent to the installation.
vi) Calculations that demonstrate the
adequacy of the amount of shielding specified for each primary and secondary
protective barrier.
vii) Projected
weekly dose rates in areas adjacent to the installation.
3) Interlock. X-ray therapy
systems operating at greater than 150 kVp shall have an interlock installed on
each door of the therapy room. The interlock shall be wired into the electrical
circuit in such a manner that when the door is opened, for any reason, the
generation of x-rays will automatically be terminated and irradiation can be
resumed only by manually resetting the controls on the control panel after the
door is closed.
4) Doors. The doors
to the therapy room shall be designed and installed to allow opening from the
inside at all times and shall be capable of being opened manually.
5) Warning Lights. X-ray therapy systems
operating above 150 kVp, and all therapy rooms to which access is possible
through more than one entrance shall be provided with warning lights in a
readily observable position near the outside of all access doors. The warning
lights shall indicate when the useful beam is on.
6) Operator and control position
A) X-ray Therapy Systems Operating at 150 kVp
and Below. The control panel and operator shall be located either outside the
therapy room or behind a protective barrier within the room.
B) X-ray Therapy Systems Operating Above 150
kVp. The control panel and operator shall be located outside the therapy
room.
7) Viewing System.
Windows, mirrors, closed-circuit television or an equivalent system shall be
provided to permit continuous visual observation of the patient during
irradiation and shall be located so that the operator can observe the patient
from the control panel.
8)
Communication. The facility design shall permit two-way aural communications
between the patient and the operator at the control panel.
9) Signs required by 32 Ill. Adm. Code
340.920
shall be posted in the facility.
b) Equipment Requirements
1) Leakage Radiation. When the tube is
operated at its maximum rated continuous current for the maximum rated tube
potential, the leakage radiation shall not exceed the value specified in the
table below at the distance specified in the table for the classification of
that x-ray system. Radiation measurements shall be averaged over an area up to,
but not exceeding, 100 square centimeters.
X-Ray System
|
Leakage Limit
|
Measurement Location
|
Contact Therapy
|
25.8 microC/kg (0.1 R) per hour
|
5 centimeters from the tube housing
|
0 - 499 kVp
|
258 microC/kg (1 R) per hour
|
1 meter from the source
|
500 kVp - 999 kVp
|
0.1 percent of useful beam or 258 microC/kg (1 R) per
hour, whichever is greater
|
1 meter from the source
|
2)
Beam-Limiting Devices
A) Permanent fixed
diaphragms or cones used for limiting the useful beam shall provide the same or
a higher degree of protection as required for the tube housing
assembly.
B) Removable
beam-limiting devices shall, for the portion of the useful beam to be blocked
by these devices, transmit not more than one percent of the useful beam at the
maximum kilovoltage and maximum treatment filter. This requirement does not
apply to auxiliary blocks or materials placed in the useful beam to shape the
useful beam to the individual patient.
C) Adjustable beam-limiting devices installed
after October 15, 1993 shall meet the requirements of subsection (b)(2)(B) of
this Section.
D) Adjustable
beam-limiting devices installed on or before October 15, 1993 shall, for the
portion of the x-ray beam to be blocked by these devices, transmit not more
than five percent of the useful beam at the maximum kilovoltage and maximum
treatment filter.
3)
Filter System. The filter system shall be designed so that:
A) The filters are securely positioned and
will not become dislodged when the machine is positioned at any possible
orientation;
B) The radiation dose
at one meter from the filter insertion slot opening does not exceed 258 mC/kg
(1 R) per hour when the machine is operated at its maximum current and maximum
tube potential;
C) Each filter is
labeled with its composition and thickness (for wedge filters, the wedge angle
and maximum design field size shall appear on the wedge or wedge
tray);
D) If the x-ray therapy
system uses changeable filters, there is a filter indication system which
permits recognition of any added filter in place and indicates from the control
panel the presence of a particular filter or absence of any filter;
and
E) For x-ray therapy systems
installed after October15, 1993, an interlock prevents irradiation if the
selected filter is not installed.
4) Tube/Aperture Alignment. The x-ray tube
shall be mounted so that it cannot turn or slide with respect to the housing
aperture.
5) Tube Housing
Stability. The tube housing shall remain stable during treatment unless tube
housing movement is a designed function of the system.
6) Source-Skin Distance (SSD) Indication
A) Means shall be provided to indicate the
SSD.
B) The SSD shall be indicated
in centimeters and/or inches and the measured SSD shall correspond to the
indicated value to within 0.5 percent.
7) Timer. A timer, which has a display at the
control panel, shall be provided and shall meet the following requirements:
A) The timer shall be activated with the
production of radiation;
B) For
systems equipped with a shutter mechanism to control irradiation, the timer
shall be activated when the shutter is opened;
C) The timer shall terminate irradiation when
a preselected time has elapsed;
D)
The timer shall permit presetting and determination of exposure times at least
as short as 1 second; and
E) The
timer shall not permit an exposure if the operator has not selected a time for
the exposure.
8) Control
Panel Functions. The control panel, in addition to the displays required in
other provisions of this Section, shall have:
A) An indication of whether x-rays are being
produced;
B) A means for indicating
x-ray tube potential and current; and
C) A means for terminating an exposure at any
time.
9) Shutters.
Equipment that is provided with shutters shall meet the following requirements:
A) The shutters shall have a lead equivalency
not less than that of the tube housing assembly;
B) The shutter shall be controlled
electrically by the operator at the control panel; and
C) An indication of shutter position shall
appear at the control panel.
10) Multiple Tubes. Control panels capable of
energizing more than one x-ray tube shall meet the following requirements:
A) It shall be possible to energize only one
x-ray tube at any time;
B) There
shall be an indication at the control panel identifying which x-ray tube is
energized; and
C) There shall be an
indication at the tube housing assembly when that tube is energized.
11) Low-Filtration X-Ray Tubes.
Each x-ray therapy system equipped with a beryllium window shall be clearly
labeled as such upon the tube housing assembly and at the control
panel.
c) Radiation
Protection Survey. A radiation protection survey shall be performed by a
therapeutic radiological physicist on each x-ray therapy system. The registrant
shall maintain at the facility a copy of the most recent radiation protection
survey report for review by the Agency. Radiation protection surveys shall meet
the following additional requirements:
1)
X-ray therapy systems installed after October 15, 1993 shall have a radiation
protection survey performed by a physicist before the therapy system is first
used for irradiation of a patient.
2) For all x-ray therapy systems, a radiation
protection survey shall be performed by a physicist after any change in the
x-ray therapy system or facility that might produce a radiation hazard. The
survey shall be performed before the therapy system is used to treat
patients.
3) Survey reports shall
include, but need not be limited to, the following:
A) A diagram of the facility that details
building structures and the position of the control panel, x-ray therapy system
and associated equipment;
B) A
description of the x-ray therapy system, including the manufacturer, model
number and range of kilovolt potential;
C) A description of the instrumentation used
to determine radiation measurements, including the date and source of the most
recent calibration for each instrument used;
D) Conditions under which radiation
measurements were taken; and
E)
Survey data including:
i) Projected weekly
dose equivalent in areas adjacent to the therapy room; and
ii) A description of workload, use and
occupancy factors employed in determining the projected weekly dose
equivalent.
4) The registrant shall retain a copy of the
radiation protection survey report and a copy of the report shall be provided
to the Agency within 30 days after completion of the survey.
5) Any deficiencies detected during the
radiation protection survey that would constitute or result in a violation of
32 Ill. Adm. Code 340 shall be corrected prior to using the machine for
treatment of patients.
6) The
facility shall be operated in compliance with any limitations indicated by the
therapeutic radiological physicist as a result of the radiation protection
survey required by the Agency.
d) Calibrations and Quality Assurance Checks.
1) Each x-ray therapy system installed after
October 15, 1993 shall be calibrated by a therapeutic radiological physicist
before the therapy system is first used for irradiation of a patient. The
calibration of the x-ray therapy system shall include, but need not be limited
to, determination of the following:
A) The
radiation output, expressed as exposure rate in air or dose rate in tissue, as
a function of distance, field size, x-ray tube potential and current, filters
and treatment applicators used;
B)
The half-value layer for each kilovoltage setting and filter combination
used;
C) The degree of congruence
between the radiation field and the field indicated by each beam-limiting
device; and
D) An evaluation of the
uniformity of the radiation field.
2) Quality assurance checks shall be made by
a therapeutic radiological physicist at intervals not to exceed 1 year. Quality
assurance checks shall include, but need not be limited to, determination of
the following:
A) The radiation output for a
set of operating conditions specified by the therapeutic radiological
physicist;
B) The coincidence of
the radiation field and the field indicated by the beam-limiting device, except
for systems equipped with fixed diaphragms or cones; and
C) The therapeutic radiological physicist
shall establish criteria for quality assurance check measurements and shall
determine corrective actions to be implemented if the criteria are exceeded.
AGENCY NOTE: Quality assurance checks should be performed at a
frequency which is appropriate for the particular therapy system, as determined
by the therapeutic radiological physicist and based on the history of stability
of the radiation output of the machine. A suggested frequency is one that would
result in a quality assurance check being performed at least once during a
typical patient's course of treatment.
3) Whenever service or maintenance is
performed on the therapy system, a therapeutic radiological physicist shall be
notified and shall determine whether a calibration or quality assurance check
is necessary to verify the characteristics of the beam.
4) Measurements of the radiation output of
the x-ray therapy system shall be performed using a dosimetry system that has
been calibrated by a calibration laboratory accredited by the American
Association of Physicists in Medicine (AAPM). Calibration of the dosimetry
system shall have been performed using a radiation beam of comparable
half-value layer to the x-ray system to be calibrated. The dosimetry system
shall meet one of the two conditions below:
A)
The calibration of the dosimetry system shall have been performed within the
previous 2 years and after any servicing that may have affected the calibration
of the dosimetry system; or
B) The
dosimetry system shall have been calibrated within the previous 4 years and
shall have been subjected to a protocol which provides for checks of dosimetry
constancy and provides for corrective action when results deviate by more than
two percent from the expected values.
5) The registrant shall maintain at the
facility records of machine calibrations, quality assurance checks and
instrument calibrations for inspection by the Agency for a period of 5 years.
Records to be maintained by the registrant shall include, but need not be
limited to, the following:
A) Records of
machine calibrations and quality assurance checks shall include identification
of the x-ray therapy system, radiation measurements, the date the measurements
were performed and the signature of the therapeutic radiological physicist who
performed the measurements.
B)
Instrument calibration records shall include the date of the last calibration
and identity of the calibration laboratory. If a dosimetry system has been
subjected to a protocol as described in subsection (d)(4)(B) of this Section,
records shall be maintained that show the date and results of each constancy
check performed on the system.
e) Operating Procedures
1) No x-ray therapy system shall be left
unattended unless the system is secured against unauthorized use.
2) When a patient must be held in position
for radiation therapy, mechanical supporting or restraining devices shall be
used.
3) Other than the patient, no
individual shall be in the therapy room unless such individual is protected by
a barrier sufficient to meet the requirements of 32 Ill. Adm. Code
340.
4) Other than the patient, no
individual shall be in the therapy room during exposures from x-ray therapy
systems operating above 150 kVp.
5)
The x-ray therapy system shall not be used for treatment of patients unless the
operator can maintain visual observation of the patient and audible
communication with the patient.
6)
On contact therapy systems, a shield of at least 0.5 millimeter lead
equivalency at 100 kVp shall be positioned over the entire useful beam exit
port during periods when the tube is energized and the beam is not being
used.
7) The tube housing assembly
shall not be held by hand during operating unless the x-ray therapy system is
designed to require such holding and the peak tube potential of the system does
not exceed 50 kilovolts. In such cases, the person holding the tube shall wear
protective gloves and apron of not less than 0.5 millimeter lead equivalency at
100 kVp.
Amended at 32 Ill. Reg. 3693, effective February 29,
2008