Wis. Admin. Code Department of Health Services DHS 157.85 - Therapeutic radiation machines
(1) LEAKAGE
RADIATION.
(a) When a therapeutic radiation
machine is operated at its maximum dose rate, the leakage air kerma rate may
not exceed the value specified at the distance specified for that
classification of therapeutic radiation machine.
(b) Leakage radiation from contact therapy
systems may not exceed one mGy (103 mR) per hour at 5 centimeters from the
surface of the tube housing assembly. 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 may be positioned over the entire useful
beam exit port during periods when the beam is not in use.
(c) Leakage radiation from systems operating
at 150 kV or less may not exceed one mGy (103 mR) per hour at one meter from
the tube housing.
(d) Leakage
radiation from systems operating above 150 kV may not exceed 0.1% of the useful
beam one meter from the source housing for any of its operating
conditions.
(2)
PERMANENT BEAM-LIMITING DEVICES. Permanent, non-adjustable collimators 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) All removable beam-limiting
devices or diaphragms may not transmit more than one percent of the useful beam
for the most penetrating beam used. This paragraph does not apply to beam
shaping blocks or shaping materials.
(b) When adjustable beam-limiting devices are
used, the position and shape of the useful beam shall be indicated by a light
beam. These devices may transmit not more than 5% of the useful beam.
(4) FILTER SYSTEMS. The filter
system shall be designed to meet all of the following requirements:
(a) Accidental displacement of filters is not
possible at any tube orientation.
(b) If the proper filter is not in place, an
interlock system shall prevent irradiation.
(c) The air kerma rate escaping from the
filter placement opening slot in the tube head may not exceed 100 mGy (one rad)
per hour at one meter under any operating conditions.
(d) Each filter shall be marked as to its
material of construction and its thickness.
(e) Each wedge filter that is removable from
the system shall be clearly marked with an identification number. For removable
wedge filters, the nominal wedge angle shall appear on the wedge or wedge tray.
If the wedge or wedge tray is significantly damaged, the wedge transmission
factor shall be reestablished.
(f)
If the absorbed dose rate information relates exclusively to operation with a
field flattening filter or beam scattering foil in place, that foil or filter
shall be removable only by the use of tools.
(5) TUBE IMMOBILIZATION.
(a) An x-ray tube shall be mounted so that it
cannot accidentally turn or slide with respect to the opening in the tube
housing through which radiation is emitted.
(b) The tube housing assembly shall be
capable of being immobilized.
(6) EMERGENCY SWITCHES. At least one
emergency power cutoff switch shall be present. If more than one emergency
power cutoff switch is installed and not all switches are tested at once, each
switch shall be tested on a rotating basis. Safety quality control checks of
the emergency power cutoff switches may be conducted at the end of the
treatment day to minimize possible stability problems with the therapeutic
radiation machine.
(7) SOURCE
MARKING. An x-ray tube housing assembly shall be marked so that it is possible
to determine the location of the focal spot to within 5 millimeters and the
marking shall be readily accessible for use during calibration
procedures.
(8) TIMER.
(a) A suitable irradiation control device
shall be provided to terminate the irradiation after a preset time interval or
after a preset radiation dose has been delivered.
(b) A timer with a display shall be provided
at the treatment control panel. The timer shall have a pre-set time selector
and an elapsed time or time remaining indicator.
(c) A timer shall be a cumulative timer that
activates with an indication of "BEAM-ON" and retains its reading after
irradiation is interrupted or terminated. After irradiation is terminated and
before irradiation may be reinitiated, it shall be necessary to reset the
elapsed time indicator.
(d) A timer
shall terminate irradiation when a pre-selected time has elapsed, if any dose
monitoring system present has not previously terminated irradiation.
(e) A timer may not permit an exposure if set
at zero.
(f) A timer may not
activate until the shutter is opened when irradiation is controlled by a
shutter mechanism unless calibration includes a timer end effect correction to
compensate for mechanical lag.
(g)
A timer shall be accurate to within one percent of the selected value or one
second, whichever is greater.
(9) CONTROL PANEL INDICATORS. An x-ray unit
shall have all of the following:
(a) An
indication at the control panel of whether electrical power is on and if
activation of the x-ray tube is possible.
(b) An indication of whether x-rays are being
produced.
(c) A means for
indicating x-ray tube potential and current.
(d) A means for terminating an exposure at
any time.
(e) A locking device that
will prevent unauthorized use of the therapeutic radiation machine.
(10) TARGET TO SKIN DISTANCE.
There shall be a means of determining the central axis target to skin distance
to within 2 millimeters and of reproducing this measurement to within 2
millimeters thereafter.
(11)
SHUTTERS. Unless it is possible to bring the x-ray tube output to the
prescribed exposure parameters within 5 seconds after the x-ray "ON" switch is
energized, the beam shall be attenuated by a shutter having a shielding
equivalency not less than that of the tube housing assembly. In addition, after
the unit is at operating parameters, the shutter shall be controlled by the
operator from the control panel. An indication of shutter position shall appear
at the control panel.
(12) LOW
FILTRATION MACHINES. Each therapeutic radiation machine equipped with a
beryllium or other low filtration window shall be clearly labeled 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.
(13) FULL CALIBRATION MEASUREMENTS.
(a) Full calibration of a therapeutic
radiation machine shall be performed by or under the direct supervision of a
medical physicist under all of the following conditions:
1. Before the first medical use following
installation or reinstallation of the therapeutic radiation machine.
2. At intervals not exceeding 12
months.
3. Before medical use under
all of the following conditions:
a. Whenever
quality control check measurements indicate that the radiation output differs
by more than 5% from the value obtained at the last full calibration and the
difference cannot be reconciled.
b.
Following any component replacement, major repair or modification of components
that could significantly affect the characteristics of the radiation beam.
(b) Full
calibration of therapeutic radiation machines with multi-energy capabilities is
required only for those operational modes or radiation energies that are not
within their acceptable range.
(c)
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 control check procedures.
(d) Full calibration shall include all
measurements recommended for annual calibration by protocols approved by
recognized national or international organizations. An acceptable protocol is
the "Protocol for clinical reference dosimetry of high-energy photon and
electron beams" as stated in AAPM Report No. 67, American Association of
Physicists in Medicine, 1999.
Note: Report No. 67 "Protocol for Clinical Reference Dosimetry of High-Energy Photon and Electron Beams," was published in Medical Physics, 26 (9), September 1999, pp. 1847-70. The report may also be obtained from: Medical Physics Publishing, 4531 Vernon Blvd., Madison WI 53705-4964 or ordered from their website: www.medicalphysics.org.
(e) A registrant shall maintain a
record of each calibration for the duration of the registration. The record
shall include all of the following:
1. The
date of the calibration.
2. The
manufacturer's name, model and serial number for both the therapeutic radiation
machine and the x-ray tube.
3. The
model and serial numbers of the instruments used to calibrate the therapeutic
radiation machine.
4. The signature
of the medical physicist responsible for performing the calibration.
(em) Full calibration for
electronic brachytherapy units shall include all of the following:
1. Timer accuracy and linearity over the
typical range of use.
2. Proper
operation of back-up exposure control devices. External testing protocol is
acceptable as long as the back-up exposure control is tested per the
manufacturer's scheduled calibration cycle.
3. The output within the manufacturer's
specified tolerance of the expected value, if applicable, or the calculated
output if there is no expected value.
4. Evaluation that the relative dose
distribution about the source is within the manufacturer's specified tolerance
of the expected value.
5. For
electronic brachytherapy systems where the source is moveable, the source
position accuracy shall be within 1 millimeter within the applicator. Fixed
x-ray source systems shall meet the manufacturer's tolerances for source
location and shape within the applicator.
6. For systems with transfer tubes and
applicators, determination of the proper length of source transfer tubes and
applicators.
7. For systems with
transfer tubes and applicators, determination of the operability of the source
transfer tubes, applicators and transfer tube-applicator interfaces.
(14) QUALITY CONTROL
CHECKS.
(a) Quality control checks shall be
performed on therapeutic radiation machines.
(b) Quality control checks shall meet all of
the following requirements:
1. A registrant
shall perform quality control checks using written procedures established by a
medical physicist.
2. The quality
control check procedures shall specify all of the following:
a. The frequency at which tests or
measurements are to be performed.
b. Which quality control checks are to be
performed during calibration.
c.
The acceptable tolerance for each parameter measured in the quality control
check when compared to the value for that parameter.
(c) The cause for a parameter
exceeding a tolerance set by the medical physicist shall be investigated and
corrected before the system is used for patient irradiation.
(d) Whenever a quality control check
indicates a significant change in the operating characteristics of a system, as
specified in the medical physicist's quality control check procedures, the
system shall be recalibrated.
(e) A
registrant shall have the medical physicist review and sign the results of each
radiation output quality control check and notify the registrant of results
within 10 working days of the date that the check was performed.
(f) A registrant shall ensure that daily
safety quality control checks of therapeutic radiation machines are performed.
(fm) If the results of the quality
control checks indicate malfunction of any system, the registrant shall prevent
clinical use of the system until repaired.
(g) Safety quality control checks shall be
performed prior to the first treatment of the day to ensure proper operation of
all of the following:
1. Electrical interlocks
at each external beam radiation therapy room entrance.
2. The "BEAM-ON" and termination
switches.
3. Beam status indicator
lights on the access doors, control console and in the radiation therapy
room.
4. Viewing and intercom
systems, if applicable.
5. If
applicable, electrically operated treatment room doors from inside and outside
the treatment room.
6. If
applicable, the integrity of all cables, catheters or parts of the device that
carry high voltages.
(gm)
Daily quality control checks for adjustable source electronic brachytherapy
shall include all the following:
1. The output
of the x-ray source falls within 3% of expected values, which includes output
as a function of time or output as a function of setting on a monitor
chamber.
2. Verification of the
consistency of the dose distribution to within 3% of that found during
calibration.
3. Validation of the
operation of positioning methods to assure that the treatment dose exposes the
intended location to within 1 mm.
4. Inspection of all treatment components on
the day of use.
(gr)
Daily quality control checks for fixed source electronic brachytherapy shall
include all the following:
1. The probe shall
be checked and adjusted for mechanical straightness to be less than or equal to
0.02 cm deflection.
2. After the
mechanical straightness of the probe is adjusted or checked, the beam itself
shall be dynamically adjusted to be straight within the probe. This will center
the beam to within 0.07mm upon the target.
3. The beam shall be checked and adjusted for
isotropy to within 12%.
4. The dose
output shall be checked with an ion chamber and compared to the manufacturer's
dose value.
5. If dose output
exceeds ± 5% of manufacturer's dose value, the physicist shall
investigate why; if the output exceeds ± 10% of manufacturer's value the
treatment shall not occur until the unit is brought within the manufacturer's
tolerance of 5%.
(h) A
registrant shall maintain a record of each quality control check for 3 years.
The record shall include all of the following:
1. The date of the quality control
check.
2. The manufacturer's name,
model and serial number of the therapeutic radiation machine.
3. The manufacturer's name, model number and
serial number for the instruments used to measure the radiation output of the
therapeutic radiation machine.
4.
The signature of the person who performed the periodic quality control
check.
(15)
QUALITY CONTROL CHECKS FOR ACCELERATORS.
(a)
Periodic quality control checks shall be performed on all therapeutic radiation
machines at intervals recommended by the manufacturer or by recognized national
or international organizations.
Note: An acceptable reference is " Comprehensive QA for Radiation Oncology: Report of AAPM Radiation Therapy Committee Task Group 40," AAPM Report No. 46, American Association of Physicists in Medicine, April, 1994.
(b) Quality control checks shall include
determination of central axis radiation output and a representative sampling of
periodic quality control checks according to recommendations of national or
international organizations. Representative sampling shall include all
referenced periodic quality control checks in an interval not to exceed 14
consecutive calendar months.
Note: An acceptable reference is " Comprehensive QA for Radiation Oncology: Report of AAPM Radiation Therapy Committee Task Group 40," AAPM Report No. 46, American Association of Physicists in Medicine, April, 1994. The publication may be consulted at the Department of Health Services, Radiation Protection Section, 1 West Wilson St, Room 150, Madison WI 53702-0007. AAPM reports may be obtained from Medical Physics Publishing, 4513 Vernon Blvd., Madison WI 53705-4964 or ordered from their website: www.medicalphysics.org.
(16) OPERATING PROCEDURES.
(a) A therapeutic radiation machine may not
be left unattended unless secured.
(b) When a patient must be held in position
for radiation therapy, mechanical supporting or restraining devices or other
means recommended by a physician shall be used.
(c) An x-ray tube housing assembly may not be
held by a person 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 tha
n 0.5 millimeters lead equivalency at 100 kV.
(d) A copy of the current operating and
emergency procedures shall be maintained at the therapeutic radiation machine
control console.
(e) No person
other than the patient may be in the treatment room during exposures from
therapeutic radiation machines operating above 150 kV. At energies less than or
equal to 150 kV, any person, other than the patient, in the treatment room
shall be protected by a barrier sufficient to meet the requirements of s.
DHS 157.22(1).
(f) A registrant shall promptly repair any
system that is not operating properly.
(g) A registrant for electronic brachytherapy
shall do all of the following:
1. Ensure the
electronic brachytherapy unit is inoperable, either by hardware or password,
when unattended by qualified staff or service personnel.
2. Secure the unit, console, console keys and
the treatment room when unattended or not in use.
3. Prevent dual operation of more than one
radiation producing device in a treatment room, if applicable.
4. Create a written procedure for safe
operation of each device.
5.
Develop, implement and maintain written procedures for responding to an
abnormal situation. The procedure shall include all the following:
a. Instructions for responding to equipment
failures and the names of the persons responsible for implementing corrective
actions.
b. The names and telephone
numbers of the licensed practitioner, the medical physicist, the radiation
safety officer and the manufacturer to be contacted if the unit or console
operates abnormally.
6.
Maintain a copy of the procedures required by subds. 4. and 5. at the unit
console.
7. Ensure all of the
following are done during treatment:
a. Only
individuals approved by the authorized user, radiation safety officer or
medical physicist may be present in the treatment room.
b. Protective shielding shall be available
for persons in the treatment room.
c. A radiation survey is performed when the
unit and/or shielding is portable to verify proper shielding placement
immediately upon initiation of treatment.
d. A medical physicist, oncologist, or
operator shall be present and at the controls throughout the course of the
patient's treatment. A medical physicist and oncologist shall remain available
during treatment.
e. A medical
physicist or operator shall monitor the position of all persons in the
treatment room to prevent unshielded exposure.
f. A medical physicist or operator shall
monitor all entrances to prevent entering individuals from unshielded
exposure.
g. Only mechanical
supporting or restraining devices may be used to hold a patient in position,
when applicable.
Notes
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No prior version found.