 |
Virginia Administrative Code (Last Updated: January 10, 2017) |
 |
Title 12. Health |
|
Agency 5. Department of Health |
|
Chapter 481. Virginia Radiation Protection Regulations |
Section 3430. Therapeutic radiation machines - photon therapy systems (500 kV and above) and electron therapy systems (500 kV and above)
-
A. Possession of survey instruments. Each facility location authorized to use a therapeutic radiation machine in accordance with this section shall have access to appropriately calibrated portable monitoring equipment. As a minimum, such equipment shall include a portable radiation measurement survey instrument capable of measuring dose rates over the range 10 µSv (1 mrem) per hour to 10 mSv (1000 mrem) per hour. The survey instruments shall be operable and calibrated in accordance with 12VAC5-481-3440.
B. Leakage radiation outside the maximum useful beam in photon and electron modes.
1. The absorbed dose due to leakage radiation (excluding neutrons) at any point outside the maximum sized useful beam, but within a circular plane of radius two meters which is perpendicular to and centered on the central axis of the useful beam at the nominal treatment distance (i.e., patient plane), shall not exceed a maximum of 0.2% and an average of 0.1% of the absorbed dose on the central axis of the beam at the nominal treatment distance. Measurements shall be averaged over an area not exceeding 100 square centimeters at a minimum of 16 points uniformly distributed in the plane;
2. Except for the area defined in subdivision 1 of this subsection, the absorbed dose due to leakage radiation (excluding neutrons) at one meter from the electron path between the electron source and the target or electron window shall not exceed 0.5% of the absorbed dose on the central axis of the beam at the nominal treatment distance. Measurements shall be averaged over an area not exceeding 100 square centimeters;
3. For equipment manufactured after September 20, 2006, the neutron absorbed dose outside the useful beam shall be in compliance with International Electrotechnical Commission (IEC) Document 601-2-1 (most current revision); and
4. For each therapeutic radiation machine, the registrant shall determine, or obtain from the manufacturer, the leakage radiation existing at the positions specified in subdivisions 1, 2, and 3 of this subsection for the specified operating conditions. Records on leakage radiation measurements shall be maintained at the installation for inspection by the agency.
C. Leakage radiation through beam limiting devices.
1. Photon radiation. All adjustable or interchangeable beam limiting devices shall attenuate the useful beam such that at the nominal treatment distance, the maximum absorbed dose anywhere in the area shielded by the beam limiting devices shall not exceed 2.0% of the maximum absorbed dose on the central axis of the useful beam measured in a 100 square centimeter radiation field, or maximum available field size if less than 100 square centimeters;
2. Electron radiation. All adjustable or interchangeable electron applicators shall attenuate the radiation, including but not limited to photon radiation generated by electrons incident on the beam limiting device and electron applicator and other parts of the radiation head, such that the absorbed dose in a plane perpendicular to the central axis of the useful beam at the nominal treatment distance shall not exceed:
a. A maximum of 2.0% and average of 0.5% of the absorbed dose on the central axis of the useful beam at the nominal treatment distance. This limit shall apply beyond a line seven centimeters outside the periphery of the useful beam; and
b. A maximum of 10% of the absorbed dose on the central axis of the useful beam at the nominal treatment distance. This limit shall apply beyond a line two centimeters outside the periphery of the useful beam.
3. Measurement of leakage radiation.
a. Photon radiation. Measurements of leakage radiation through the beam limiting devices shall be made with the beam limiting devices closed and any residual aperture blocked by at least two tenth-value layers of suitable absorbing material. In the case of overlapping beam limiting devices, the leakage radiation through each set shall be measured independently at the depth of maximum dose. Measurements shall be made using a radiation detector of area not exceeding 10 square centimeters;
b. Electron radiation. Measurements of leakage radiation through the electron applicators shall be made with the electron beam directed into the air and using a radiation detector of area up to but not exceeding one square centimeter suitably protected against radiation which has been scattered from material beyond the radiation detector. Measurements shall be made using one centimeter of water equivalent build up material.
D. Filters and wedges.
1. 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 permanently mounted to the tray). If the wedge or wedge tray is significantly damaged, the wedge transmission factor shall be redetermined.
2. If the absorbed dose rate information required by subsection I of this section relates exclusively to operation with a field flattening filter or beam scattering foil in place, such foil or filter shall be removable only by the use of tools.
3. For equipment manufactured after September 20, 2006, that utilizes wedge filters, interchangeable field flattening filters, or interchangeable beam scattering foils:
a. Irradiation shall not be possible until a selection of a filter or a positive selection to use "no filter" has been made at the treatment control panel, either manually or automatically;
b. An interlock system shall be provided to prevent irradiation if the filter selected is not in the correct position;
c. A display shall be provided at the treatment control panel showing the wedge filters, interchangeable field flattening filters, or interchangeable beam scattering foils in use; and
d. An interlock shall be provided to prevent irradiation if any filter or beam scattering foil selection operation carried out in the treatment room does not agree with the filter or beam scattering foil selection operation carried out at the treatment control panel.
E. Stray radiation in the useful beam. For equipment manufactured after September 20, 2006, the registrant shall determine during acceptance testing, or obtain from the manufacturer, data sufficient to ensure that x-ray stray radiation in the useful electron beam, absorbed dose at the surface during x-ray irradiation, and stray neutron radiation in the useful x-ray beam are in compliance with International Electrotechnical Commission (IEC) Document 601-2-1 (most current revision).
F. Beam monitors. All therapeutic radiation machines subject to this section shall be provided with redundant beam monitoring systems. The sensors for these systems shall be fixed in the useful beam during treatment to indicate the dose monitor unit rate.
1. Equipment manufactured after September 20, 2006, shall be provided with at least two independently powered integrating dose meters. Alternatively, common elements may be used if the production of radiation is terminated upon failure of any common element.
2. Equipment manufactured on or before September 20, 2006, shall be provided with at least one radiation detector. This detector shall be incorporated into a useful beam monitoring system.
3. The detector and the system into which that detector is incorporated shall meet the following requirements:
a. Each detector shall be removable only with tools and, if movable, shall be interlocked to prevent incorrect positioning.
b. Each detector shall form part of a beam monitoring system from whose readings in dose monitor units the absorbed dose at a reference point can be calculated.
c. Each beam monitoring system shall be capable of independently monitoring, interrupting, and terminating irradiation.
d. For equipment manufactured after September 20, 2006, the design of the beam monitoring systems shall ensure that the:
(1) Malfunctioning of one system shall not affect the correct functioning of the other systems; and
(2) Failure of either system shall terminate irradiation or prevent the initiation of radiation.
e. Each beam monitoring system shall have a legible display at the treatment control panel. For equipment manufactured after September 20, 2006, each display shall:
(1) Maintain a reading until intentionally reset;
(2) Have only one scale and no electrical or mechanical scale multiplying factors;
(3) Utilize a design such that increasing dose is displayed by increasing numbers; and
(4) In the event of power failure, the beam monitoring information required in subdivision 3 e (3) of this subsection displayed at the control panel at the time of failure shall be retrievable in at least one system for a 20-minute period of time.
G. Beam symmetry.
1. A bent-beam linear accelerator with beam flattening filter subject to this section shall be provided with an auxiliary device to monitor beam symmetry;
2. The device referenced in subdivision 1 of this subsection shall be able to detect field asymmetry greater than 10%; and
3. The device referenced in subdivision 1 of this subsection shall be configured to terminate irradiation if the specifications in subdivision 2 of this subsection cannot be maintained.
H. Selection and display of dose monitor units.
1. Irradiation shall not be possible until a new selection of a number of dose monitor units has been made at the treatment control panel;
2. The preselected number of dose monitor units shall be displayed at the treatment control panel until reset manually for the next irradiation;
3. After termination of irradiation, it shall be necessary to reset the dosimeter display before subsequent treatment can be initiated; and
4. For equipment manufactured after September 20, 2006, after termination of irradiation, it shall be necessary for the operator to reset the preselected dose monitor units before irradiation can be initiated.
I. Air kerma rate or absorbed dose rate. For equipment manufactured after September 20, 2006, a system shall be provided from whose readings the air kerma rate or absorbed dose rate at a reference point can be calculated. (The radiation detectors specified in subsection F of this section may form part of this system.) In addition:
1. The dose monitor unit rate shall be displayed at the treatment control panel;
2. If the equipment can deliver under any conditions an air kerma rate or absorbed dose rate at the nominal treatment distance more than twice the maximum value specified by the manufacturer, a device shall be provided that terminates irradiation when the air kerma rate or absorbed dose rate exceeds a value twice the specified maximum. The dose rate at which the irradiation will be terminated shall be a record maintained by the registrant;
3. If the equipment can deliver under any fault conditions an air kerma rate or absorbed dose rate at the nominal treatment distance more than 10 times the maximum value specified by the manufacturer, a device shall be provided to prevent the air kerma rate or absorbed dose rate anywhere in the radiation field from exceeding twice the specified maximum value and to terminate irradiation if the excess absorbed dose at the nominal treatment distance exceeds 4 Gy (400 rad); and
4. For each therapeutic radiation machine, the registrant shall determine, or obtain from the manufacturer, the maximum values specified in subdivisions 2 and 3 of this subsection for the specified operating conditions. Records of these maximum values shall be maintained at the installation for inspection by the agency.
J. Termination of irradiation by the beam monitoring system or systems during stationary beam radiation therapy.
1. Each primary system shall terminate irradiation when the preselected number of dose monitor units has been detected by the system;
2. If the original design of the equipment included a secondary dose monitoring system, that system shall be capable of terminating irradiation when not more than 15% or 40 dose monitor units above the preselected number of dose monitor units set at the control panel has been detected by the secondary dose monitoring system; and
3. For equipment manufactured after September 20, 2006, an indicator on the control panel shall show which monitoring system has terminated irradiation.
K. Termination of irradiation. It shall be possible to terminate irradiation and equipment movement or go from an interruption condition to termination condition at any time from the operator's position at the treatment control panel.
L. Interruption of irradiation. If a therapeutic radiation machine has an interrupt mode, it shall be possible to interrupt irradiation and equipment movements at any time from the treatment control panel. Following an 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, irradiation and equipment movements shall be automatically terminated.
M. Timer. A suitable irradiation control device shall be provided to terminate the irradiation after a pre-set time interval.
1. A timer shall be provided which has a display at the treatment control panel. The timer shall have a pre-set time selector and an elapsed time indicator;
2. The 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 can be reinitiated, it shall be necessary to reset the elapsed time indicator;
3. The timer shall terminate irradiation when a preselected time has elapsed if the dose monitoring systems have not previously terminated irradiation.
N. Selection of radiation type. Equipment capable of both x-ray therapy and electron therapy shall meet the following additional requirements:
1. Irradiation shall not be possible until a selection of radiation type (x-rays or electrons) has been made at the treatment control panel;
2. The radiation type selected shall be displayed at the treatment control panel before and during irradiation;
3. An interlock system shall be provided to ensure that the equipment can principally emit only the radiation type that has been selected;
4. An interlock system shall be provided to prevent irradiation with x-rays, except to obtain an image, when electron applicators are fitted;
5. An interlock system shall be provided to prevent irradiation with electrons when accessories specific for x-ray therapy are fitted; and
6. An interlock system shall be provided to prevent irradiation if any selected operations carried out in the treatment room do not agree with the selected operations carried out at the treatment control panel.
O. Selection of energy. Equipment capable of generating radiation beams of different energies shall meet the following requirements:
1. Irradiation shall not be possible until a selection of energy has been made at the treatment control panel;
2. The nominal energy value selected shall be displayed at the treatment control panel until reset manually for the next irradiation. After termination of irradiation, it shall be necessary to reset the nominal energy value selected before subsequent treatment can be initiated;
3. Irradiation shall not be possible until the appropriate flattening filter or scattering foil for the selected energy is in its proper location; and
4. For equipment manufactured after September 20, 2006, the selection of energy shall be in compliance with International Electrotechnical Commission (IEC) Document 601-2-1.
P. Selection of stationary beam radiation therapy or moving beam radiation therapy. Therapeutic radiation machines capable of both stationary beam radiation therapy and moving beam radiation therapy shall meet the following requirements:
1. Irradiation shall not be possible until a selection of stationary beam radiation therapy or moving beam radiation therapy has been made at the treatment control panel;
2. The mode of operation shall be displayed at the treatment control panel;
3. An interlock system shall be provided to ensure that the equipment can operate only in the mode that has been selected;
4. An interlock system shall be provided to prevent irradiation if any selected parameter in the treatment room does not agree with the selected parameter at the treatment control panel;
5. Moving beam radiation therapy shall be controlled to obtain the selected relationships between incremental dose monitor units and incremental movement. For equipment manufactured after September 20, 2006:
a. An interlock system shall be provided to terminate irradiation if the number of dose monitor units delivered in any 10 degrees of rotation or one centimeter of linear motion differs by more than 20% from the selected value;
b. Where angle terminates the irradiation in moving beam radiation therapy, the dose monitor units delivered shall differ by less than 5.0% from the dose monitor unit value selected;
c. An interlock shall be provided to prevent motion of more than five degrees or one centimeter beyond the selected limits during moving beam radiation therapy;
d. An interlock shall be provided to require that a selection of direction be made at the treatment control panel in all units that are capable of both clockwise and counter-clockwise moving beam radiation therapy;
e. Moving beam radiation therapy shall be controlled with both primary position sensors and secondary position sensors to obtain the selected relationships between incremental dose monitor units and incremental movement;
6. Where the beam monitor system terminates the irradiation in moving beam radiation therapy, the termination of irradiation shall be as required by subsection J of this section; and
7. For equipment manufactured after September 20, 2006, an interlock system shall be provided to terminate irradiation if movement:
a. Occurs during stationary beam radiation therapy; or
b. Does not start or stops during moving beam radiation therapy unless such stoppage is a pre-planned function.
Q. Facility design requirements for therapeutic radiation machines operating above 500 kV. In addition to shielding adequate to meet requirements of 12VAC5-481-3450, the following design requirements are made:
1. Protective barriers. All protective barriers shall be fixed, except for access doors to the treatment room or movable beam interceptors;
2. Control panel. In addition to other requirements specified in Part XV (12VAC5-481-3380 et seq.) of this chapter, the control panel shall also:
a. Be located outside the treatment room;
b. Provide an indication of whether electrical power is available at the control panel and if activation of the radiation is possible;
c. Provide an indication of whether radiation is being produced; and
d. Include an access control (locking) device that will prevent unauthorized use of the therapeutic radiation machine;
3. Viewing systems. Windows, mirrors, closed-circuit television or an equivalent viewing system shall be provided to permit continuous observation of the patient following positioning and during irradiation and shall be so located that the operator may observe the patient from the treatment control panel. The therapeutic radiation machine shall not be used for patient irradiation unless at least one viewing system is operational;
4. Aural communications. Provision shall be made for continuous two-way aural communication between the patient and the operator at the control panel. The therapeutic radiation machine shall not be used for irradiation of patients unless continuous two-way aural communication is possible;
5. Room entrances. Treatment room entrances shall be provided with warning lights in a readily observable position near the outside of all access doors, which will indicate when the useful beam is "ON" and when it is "OFF";
6. Entrance interlocks. Interlocks shall be provided such that all access controls are activated before treatment can be initiated or continued. If the radiation beam is interrupted by any access control, it shall not be possible to restore the machine to operation without resetting the access control and reinitiating irradiation by manual action at the control panel;
7. Beam interceptor interlocks. If the shielding material in any protective barrier requires the presence of a beam interceptor to ensure compliance with 12VAC5-481-720, interlocks shall be provided to prevent the production of radiation, unless the beam interceptor is in place, whenever the useful beam is directed at the designated barrier;
8. Emergency cutoff switches. At least one emergency power cutoff switch shall be located in the radiation therapy room and shall terminate all equipment electrical power including radiation and mechanical motion. This switch is in addition to the termination switch required by subsection K of this section. All emergency power cutoff switches shall include a manual reset so that the therapeutic radiation machine cannot be restarted from the unit's control console without resetting the emergency cutoff switch;
9. Safety interlocks. All safety interlocks shall be designed so that any defect or component failure in the safety interlock system prevents or terminates operation of the therapeutic radiation machine; and
10. Surveys for residual radiation. Surveys for residual activity shall be conducted on all therapeutic radiation machines capable of generating photon and electron energies above 10 MV prior to machining, removing, or working on therapeutic radiation machine components which may have become activated due to photo-neutron production.
R. Qualified medical physicist support.
1. The services of a qualified medical physicist shall be required in facilities having therapeutic radiation machines with energies of 500 kV and above. The qualified medical physicist shall be responsible for:
a. Full calibrations required by subsection T of this section and protection surveys required by 12VAC5-481-3400 A;
b. Supervision and review of dosimetry;
c. Beam data acquisition and transfer for computerized dosimetry, and supervision of its use;
d. Quality assurance, including quality assurance check review required by subdivision U 5 of this section;
e. Consultation with the authorized user in treatment planning, as needed; and
f. Performance of calculations or assessments regarding misadministrations.
2. If the qualified medical physicist is not a full-time employee of the registrant, the operating procedures required by subsection S of this section shall also specifically address how the qualified medical physicist is to be contacted for problems or emergencies, as well as the specific actions, if any, to be taken until the qualified medical physicist can be contacted.
S. Operating procedures.
1. No individual, other than the patient, shall be in the treatment room during treatment or during any irradiation for testing or calibration purposes;
2. Therapeutic radiation machines shall not be made available for medical use unless the requirements of 12VAC5-481-3400 A, and subsections T and U of this section have been met;
3. Therapeutic radiation machines, when not in operation, shall be secured to prevent unauthorized use;
4. When adjustable beam limiting devices are used, the position and shape of the radiation field shall be indicated by a light field;
5. If a patient must be held in position during treatment, mechanical supporting or restraining devices shall be used; and
6. A copy of the current operating and emergency procedures shall be maintained at the therapeutic radiation machine control console.
T. Acceptance testing, commissioning, and full calibration measurements.
1. Acceptance testing, commissioning and full calibration of a therapeutic radiation machine subject to this section shall be performed by, or under the direct supervision of, a qualified medical physicist.
2. Acceptance testing and commissioning shall be performed in accordance with the American Association of Physicists in Medicine (AAPM) AAPM Code of Practice for Radiotherapy Accelerators: AAPM Report Number 47," prepared by Radiation Therapy Task Group 45 and the manufacturer's contractual specifications. Acceptance testing and commissioning shall be conducted before the first medical use following installation or reinstallation of the therapeutic radiation machine.
3. Full calibration shall include measurement of all parameters required by Table II of "Comprehensive QA for Radiation Oncology: Report of AAPM Radiation Therapy: AAPM Report No. 46," prepared by Committee Task Group 40 and shall be performed in accordance with "AAPM Code of Practice for Radiotherapy Accelerators: AAPM Report No. 47" prepared by Radiation Therapy Task Group 45. Although it shall not be necessary to complete all elements of a full calibration at the same time, all parameters (for all energies) shall be completed at intervals not exceeding 12 calendar months, unless a more frequent interval is required in Table II.
4. The qualified medical physicist shall perform all elements of a full calibration necessary to determine that all parameters are within acceptable limits:
a. Whenever quality assurance check measurements indicate that the radiation output differs by more than 5.0% from the value obtained at the last full calibration and the difference cannot be reconciled. Therapeutic radiation machines with multienergy or multimode capabilities shall only require measurements for those modes or energies that are not within their acceptable range; and
b. Following any component replacement, major repair, or modification of components that could significantly affect the characteristics of the radiation beam. If the repair, replacement or modification does not affect all modes or energies, measurements shall be performed on the effected mode or energy that is in most frequent clinical use at the facility. The remaining energies or modes may be validated with quality assurance check procedures against the criteria in subdivision 4 a of this subsection.
5. The registrant shall maintain a record of each calibration in an auditable form 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 the therapeutic radiation machine; the model numbers and serial numbers of the instruments used to calibrate the therapeutic radiation machine; and the signature of the qualified medical physicist responsible for performing the calibration.
U. Periodic quality assurance checks.
1. Periodic quality assurance checks shall be performed on all therapeutic radiation machines subject to this section at intervals not to exceed those specified in "Comprehensive QA for Radiation Oncology: AAPM Report No. 46," prepared by AAPM Radiation Therapy Committee Task Group 40;
2. To satisfy the requirement of subdivision 1 of this subsection, quality assurance checks shall include determination of central axis radiation output and a representative sampling of periodic quality assurance checks contained in "Comprehensive QA for Radiation Oncology: AAPM Report No. 46" prepared by AAPM Radiation Therapy Committee Task Group 40. Representative sampling shall include all referenced periodic quality assurance checks in an interval not to exceed 12 consecutive calendar months;
3. The registrant shall use a dosimetry system that has been inter-compared within the previous 12 months with the dosimetry system described in 12VAC5-481-3400 C 1 to make the periodic quality assurance checks required in subdivision 2 of this subsection;
4. The registrant shall perform periodic quality assurance checks required by subdivision 1 of this subsection in accordance with procedures established by the qualified medical physicist;
5. The registrant shall review the results of each periodic radiation output check according to the following procedures:
a. The authorized user and qualified medical physicist shall be immediately notified if any parameter is not within its acceptable tolerance. The therapeutic radiation machine shall not be made available for subsequent medical use until the qualified medical physicist has determined that all parameters are within their acceptable tolerances;
b. If all quality assurance check parameters appear to be within their acceptable ranges, the quality assurance check shall be reviewed and signed by either the authorized user or qualified medical physicist within three treatment days; and
c. The qualified medical physicist shall review and sign the results of each radiation output quality assurance check at intervals not to exceed 30 days.
6. Therapeutic radiation machines subject to this section shall have applicable safety quality assurance checks listed in "Comprehensive QA for Radiation Oncology: AAPM Report No. 46," prepared by AAPM Radiation Therapy Committee Task Group 40 performed at intervals not to exceed one week;
7. To satisfy the requirement of subdivision 6 of this subsection, safety quality assurance checks shall ensure proper operation of:
a. Electrical interlocks at each external beam radiation therapy room entrance;
b. Proper operation of the "BEAM-ON," interrupt, and termination switches;
c. Beam condition indicator lights on the access doors, control console, and in the radiation therapy room;
d. Viewing systems;
e. Electrically operated treatment room doors from inside and outside the treatment room;
f. At least one emergency power cutoff switch. 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 assurance checks of the emergency power cutoff switches may be conducted at the end of the treatment day in order to minimize possible stability problems with the therapeutic radiation machine.
8. The registrant shall promptly repair any system identified in subdivision 7 of this subsection that is not operating properly; and
9. The registrant shall maintain a record of each quality assurance check required by subdivisions 1 and 7 of this subsection for three years. The record shall include: the date of the quality assurance check; the manufacturer's name, model number, and serial number of the therapeutic radiation machine; the manufacturer's name, model number and serial number for 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.
V. Quality assurance checks for intensity modulated radiation therapy (IMRT) shall:
1. Include commissioning and testing of the treatment planning and delivery systems, routine quality assurance of the delivery system, and patient-specific validation of treatment plans;
2. Be performed in accordance with "Guidance document on delivery, treatment planning, and clinical implementation of IMRT: Report of the IMRT subcommittee of the AAPM radiation therapy committee: AAPM Report No. 82"; and
3. Be performed in accordance with the manufacturer's contractual specifications.
Historical Notes
Derived from Volume 22, Issue 25, eff. September 20, 2006; amended, Virginia Register Volume 24, Issue 18, eff. June 12, 2008; Volume 32, Issue 17, eff. June 5, 2016.