Section 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 removeable 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.

(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.

3. The output within 2% of the expected value, if applicable, or determination of the output if there is no expected value.

4. Evaluation that the relative dose distribution about the source is within 5% of the expected value.

5. Source position accuracy to within 1 millimeter within the applicator.

6. Determination of the proper length of source transfer tubes and applicators.

7. 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 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.

(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.

(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.

(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 than 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 and operator shall be physically present during the initiation and course of patient 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.

CR 01-108 : cr. Register July 2002 No. 559 , eff. 8-1-02; CR 09-062 : cr. (13) (em), (14) (fm), (g) 6., (gm) and (16) (g), am. (14) (e) and (g) 4. Register April 2010 No. 652 , eff. 5-1-10.

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 . Microsoft Windows NT 6.1.7601 Service Pack 1 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. Microsoft Windows NT 6.1.7601 Service Pack 1 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 . Microsoft Windows NT 6.1.7601 Service Pack 1