Current through Bulletin 2024-06, March 15, 2024
(1) Leakage Radiation. When the x-ray tube is
operated at its maximum rated tube current for the maximum kV, the leakage air
kerma rate shall not exceed the value specified at the distance specified for
that classification of therapeutic radiation machine:
(a) Systems 5-50 kV. The leakage air kerma
rate measured at a position five centimeters from the tube housing assembly
shall not exceed 1 mGy (100 mrad) in one hour.
(b) Systems greater than 50 and less than 500
kV. The leakage air kerma rate measured at a distance of one meter from the
source in every direction shall not exceed 1 cGy (1 rad) in one hour. This air
kerma rate measurement may be averaged over areas no larger than 100 square
centimeters. In addition, the air kerma rate at a distance of five centimeters
from the surface of the tube housing assembly shall not exceed 30 cGy (30 rad)
per hour.
(2) Permanent
Beam Limiting Devices. Permanent diaphragms or cones used for limiting the
useful beam shall provide at least the same degree of attenuation as required
for the tube housing assembly.
(3)
Adjustable or Removable Beam Limiting Devices.
(a) Adjustable or removable beam limiting
devices, diaphragms, cones or blocks shall not transmit more than five percent
of the useful beam for the most penetrating beam used;
(b) When adjustable beam limiting devices are
used, the position and shape of the radiation field shall be indicated by a
light beam.
(4) Filter
System. The filter system shall be so designed that:
(a) Filters can not be accidentally displaced
at every possible tube orientation;
(b) For equipment installed after the
effective date of these rules, an interlock system prevents irradiation if the
proper filter is not in place;
(c)
The air kerma rate escaping from the filter slot shall not exceed 1 cGy (1 rad)
per hour at one meter under operating conditions; and
(d) Filters shall be marked as to its
material of construction and its thickness.
(5) Tube Immobilization.
(a) The x-ray tube shall be so mounted that
it can not accidentally turn or slide with respect to the housing aperture;
and
(b) The tube housing assembly
shall be capable of being immobilized for stationary portal
treatments.
(6) Source
Marking. The tube housing assembly shall be so marked that it is possible to
determine the location of the source to within five millimeters, and the
marking shall be readily accessible for use during calibration
procedures.
(7) Beam Block. Contact
therapy tube housing assemblies shall have a removable shield of material,
equivalent in attenuation to 0.5 millimeters of lead at 100 kV, which can be
positioned over the entire useful beam exit port during periods when the beam
is not in use.
(8) Timer. A
suitable irradiation control device shall be provided to terminate the
irradiation after a pre-set time interval.
(a) A timer which has a display shall be
provided at the treatment control panel. The timer shall have a pre-set time
selector. The timer shall activate with an indication of "BEAM-ON" and retain
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 timer;
(b) For
equipment manufactured after the effective date of these rules, the timer shall
be a cumulative timer with an elapsed time indicator. Otherwise, the timer may
be a countdown timer;
(c) The timer
shall terminate irradiation when a pre-selected time has elapsed, if the dose
monitoring system present has not previously terminated irradiation;
(d) The timer shall permit pre-setting and
determination of exposure times as short as one second;
(e) The timer shall not permit an exposure if
set at zero;
(f) The timer shall
not activate until the shutter is opened when irradiation is controlled by a
shutter mechanism unless calibration includes a timer error correction to
compensate for mechanical lag; and
(g) Timer shall be accurate to within one
percent of the selected value or to within one second, whichever is
greater.
(9) Control
Panel Functions. The control panel, in addition to the displays required by
other provisions in R313-30-6, shall have:
(a) An indication of whether electrical power
is available at the control panel and if activation of the x-ray tube is
possible;
(b) An indication of
whether x-rays are being produced;
(c) Means for indicating x-ray tube potential
and current;
(d) The means for
terminating an exposure at any time;
(e) A locking device which will prevent
unauthorized use of the therapeutic radiation machine; and
(f) For therapeutic radiation machines
manufactured after the effective date of these rules, a positive display of
specific filters in the beam.
(10) Multiple Tubes. When a control panel may
energize more than one x-ray tube:
(a) It
shall be possible to activate only one x-ray tube at a time;
(b) There shall be an indication at the
control panel identifying which x-ray tube is activated; and
(c) There shall be an indication at the tube
housing assembly when that tube is energized.
(11) Target-to-Skin Distance (TSD). There
shall be a means of determining the central axis TSD to within one centimeter
and of reproducing this measurement to within two millimeters
thereafter.
(12) Shutters. Unless
it is possible to bring the x-ray output to the prescribed exposure parameters
within five seconds after the x-ray "ON" switch is energized, the beam shall be
attenuated by a shutter having a lead equivalency not less than that of the
tube housing assembly. In addition, after the unit is at operating parameters,
the shutter shall be controlled electrically by the operator from the control
panel. An indication of shutter position shall appear at the control
panel.
(13) Low Filtration X-ray
Tubes. Therapeutic radiation machines equipped with a beryllium or other
low-filtration window shall have a label clearly marked on the tube housing
assembly and shall be provided with a permanent warning device on the control
panel that is activated when no additional filtration is present, to indicate
that the dose rate is very high.
(14) Facility Design Requirements for
Therapeutic Radiation Machines Capable of Operating in the Range 50 kV to 500
kV. In addition to shielding adequate to meet requirements of
R313-30-9,
the treatment room shall meet the following design requirements:
(a) Aural Communication. Provision shall be
made for continuous two-way aural communication between the patient and the
operator at the control panel;
(b)
Viewing Systems. Provision shall be made to permit continuous observation of
the patient during irradiation and the viewing system shall be so located that
the operator can observe the patient from the control panel. The therapeutic
radiation machine shall not be used for patient irradiation unless at least one
viewing system is operational.
(15) Additional Requirements. Treatment rooms
which contain a therapeutic radiation machine capable of operating above 150 kV
shall meet the following additional requirements:
(a) Protective barriers shall be fixed except
for entrance doors or beam interceptors;
(b) The control panel shall be located
outside the treatment room or in a totally enclosed booth, which has a ceiling,
inside the room;
(c) Interlocks
shall be provided so that entrance doors, including doors to interior booths,
shall be closed before treatment can be initiated or continued. If the
radiation beam is interrupted by a 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; and
(d) When a door referred to in
R313-30-6(15)(c) is opened while the x-ray tube is activated, the irradiation
shall be interrupted either electrically or by the closure of the
shutter.
(16) Full
Calibration Measurements.
(a) Full
calibration of a therapeutic radiation machine subject to R313-30-6 shall be
performed by, or under the direct supervision of, a Radiation Therapy
Physicist:
(i) Before the first medical use
following installation or reinstallation of the therapeutic radiation
machine;
(ii) Annually. The
intervals should not exceed 12 months and shall not exceed 13 months;
and
(iii) Before medical use under
the following conditions:
(A) Whenever
quality assurance check measurements indicate that the radiation output differs
by more than five percent from the value obtained at the last full calibration
and the difference cannot be reconciled; and
(B) Following a component replacement, major
repair, or modification of components that could significantly affect the
characteristics of the radiation beam.
(iv) Notwithstanding the requirements of
R313-30-6(16)(a)(iii):
(A) Full calibration
of therapeutic radiation machines with multi-energy capabilities is required
only for those modes and energies that are not within their acceptable range;
and
(B) If the repair, replacement
or modification does not affect all energies, full calibration shall be
performed on the affected energy that is in most frequent clinical use at the
facility. The remaining energies may be validated with quality assurance check
procedures against the criteria in R313-30-6(16)(a)(iii)(A).
(v) The registrant shall use the
dosimetry system described in
R313-30-8(6)(a)
to perform the full calibration required in R313-30-6(16)(b);
(b) To satisfy the requirement of
R313-30-6(16)(a), full calibration shall include measurements recommended for
annual calibration by NCRP Report 69, "Dosimetry of X-Ray and Gamma Ray Beams
for Radiation Therapy in the Energy Range 10 keV to 50 MeV," 1981 ed., which is
adopted and incorporated by reference.
(c) The registrant shall maintain a record of
calibrations for the duration of the registration. The record shall include the
date of the calibration, the manufacturer's name, model number, and serial
number for both the therapeutic radiation machine and the x-ray tube, the model
numbers and serial numbers of the instruments used to calibrate the therapeutic
radiation machine, and the signature of the Radiation Therapy Physicist
responsible for performing the calibration.
(17) Periodic Quality Assurance Checks.
(a) Periodic quality assurance checks shall
be performed on therapeutic radiation machines subject to R313-30-6, which are
capable of operation at greater than 50 kV.
(b) To satisfy the requirement of
R313-30-6(17)(a), quality assurance checks shall meet the following
requirements:
(i) The registrant shall
perform quality assurance checks in accordance with written procedures
established by the Radiation Therapy Physicist; and
(ii) The quality assurance check procedures
shall specify the frequency at which tests or measurements are to be performed.
The quality assurance check procedures shall specify that the quality assurance
check shall be performed during the calibration specified in R313-30-6(16)(a).
The acceptable tolerance for parameters measured in the quality assurance
check, when compared to the value for that parameter determined in the
calibration specified in R313-30-6(16)(a), shall be stated.
(c) The cause for a parameter
exceeding a tolerance set by the Radiation Therapy Physicist shall be
investigated and corrected before the system is used for patient
irradiation;
(d) Whenever a quality
assurance check indicates a significant change in the operating characteristics
of a system, as specified in the Radiation Therapy Physicist's quality
assurance check procedures, the system shall be recalibrated as required in
R313-30-6(16)(a);
(e) The
registrant shall use the dosimetry system described in
R313-30-8(6)(b)
to make the quality assurance check required in R313-30-6(17)(b);
(f) The registrant shall have the Radiation
Therapy Physicist review and sign the results of radiation output quality
assurance checks monthly. The interval should not exceed 30 days and shall not
exceed 40 days;
(g) Therapeutic
radiation machines subject to R313-30-6 shall have safety quality assurance
checks of external beam radiation therapy facilities performed monthly. The
interval should not exceed 30 days and shall not exceed 40 days;
(h) Notwithstanding the requirements of
R313-30-6(17)(f) and R313-30-6(17)(g), the registrant shall ensure that no
therapeutic radiation machine is used to administer radiation to humans unless
the quality assurance checks required by R313-30-6(17)(f) and R313-30-6(17)(g)
have been performed within the required interval immediately prior to the
administration;
(i) To satisfy the
requirement of R313-30-6(17)(g), safety quality assurance checks shall ensure
proper operation of:
(i) Electrical
interlocks at external beam radiation therapy room entrances;
(ii) Proper operation of the "BEAM-ON" and
termination switches;
(iii) Beam
condition indicator lights on the access doors, control console, and in the
radiation therapy room;
(iv)
Viewing systems;
(v) If applicable,
electrically operated treatment room doors from inside and outside the
treatment room;
(j) The
registrant shall maintain a record of quality assurance checks required by
R313-30-6(17)(a) and R313-30-6(17)(g) for three years. The record shall include
the date of the quality assurance check, the manufacturer's name, model number,
and serial number for the therapeutic radiation machine, the manufacturer's
name, model number and serial number of the instruments used to measure the
radiation output of the therapeutic radiation machine, and the signature of the
individual who performed the periodic quality assurance check.
(18) Operating Procedures.
(a) The therapeutic radiation machine shall
not be used for irradiation of patients unless the requirements of
R313-30-6(16) and R313-30-6(17) have been met;
(b) Therapeutic radiation machines shall not
be left unattended unless secured pursuant to R313-30-6(9)(e);
(c) When a patient must be held in position
for radiation therapy, mechanical supporting or restraining devices shall be
used;
(d) The tube housing assembly
shall not be held by an individual during operation unless the assembly is
designed to require holding and the peak tube potential of the system does not
exceed 50 kV. In these cases, the holder shall wear protective gloves and apron
of not less than 0.5 millimeters lead equivalency at 100 kV;
(e) A copy of the current operating and
emergency procedures shall be maintained at the therapeutic radiation machine
control console; and
(f) No
individual other than the patient shall be in the treatment room during
exposures from therapeutic radiation machines operating above 150 kV. At
energies less than or equal to 150 kV, individuals, other than the patient, in
the treatment room shall be protected by a barrier sufficient to meet the
requirements of
R313-15-201
of these rules.