Mississippi Administrative Code, Subchapter 15, Rule 15-21-78-1.15.7 - Therapeutic Radiation Machines - Photon Therapy Systems (500 kV and Above) and Electron Therapy Systems (500 keV and Above) | Mississippi Administrative Code

1. Possession of Survey Instrument(s). A registrant authorized to use a therapeutic radiation machine in accordance with 1.15.7 shall possess 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 1 mrem (10 µSv) per hour to 1000 mrem (10 mSv) per hour. The survey instrument(s) shall be operable and calibrated in accordance with 1.15.8.

2 Leakage Radiation Outside the Maximum Useful Beam in Photon and Electron Modes.

a. The absorbed dose rate due to leakage radiation (excluding neutrons) at any point outside the maximum sized useful beam, but within a circular plane of radius 2 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 percent and an average of 0.1 percent of the absorbed dose rate on the central axis of the beam at the nominal treatment distance. Measurements shall be averaged over an area up to but not exceeding 100 square centimeters at the positions specified;

b. Except for the area defined in 1.15.7(2)(a), the absorbed dose rate in tissue (excluding that from neutrons) at I meter from the electron path between the source and the target or electron window shall not exceed 0.5 percent of the absorbed dose rate in tissue on the central axis of the beam at the nominal treatment distance. Measurements shall be averaged over an area up to but not exceeding 100 square centimeters at the positions specified;

c. The neutron absorbed dose rate outside the useful beam shall be kept as low as practicable. Measurements of the portion of the leakage radiation dose contributed by neutrons shall be averaged over an area up to but not exceeding 800 square centimeters; and d. For each therapeutic radiation machine, the registrant shall determine, or obtain from the manufacturer, the leakage radiation existing at the positions specified in 1.15.7(2)(a) through 1.15.7(2)(c) for the specified operating conditions. Records on leakage radiation measurements shall be maintained at the installation for inspection by the Agency.

3 Leakage Radiation Through Beam-Limiting Devices.

a. Photon Radiation. All adjustable or interchangeable beam-limiting devices shall attenuate the useful beam such that:

i. At the nominal treatment distance, the maximum absorbed dose anywhere in the area shielded by the beam-limiting device(s) shall not exceed 2 percent of the maximum absorbed dose on the central axis of the useful beam measured in a 10 centimeters by 10 centimeters radiation field.

ii. For fields of any size in which the maximum area shielded by the beam-limiting devices exceeds 500 square centimeters, the product of the average absorbed dose due to leakage radiation through the beam-limiting devices and the maximum area protectable by the beam-limiting devices shall not exceed one tenth (0.1) of the product of the maximum absorbed dose on the central axis of the useful beam and the area of the useful beam for a radiation field of 10 centimeters by 10 centimeters. All values of absorbed dose and area are referred to the nominal treatment distance.

b. 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 following limits apply:

i. The absorbed dose in a plane perpendicular to the central axis of the useful beam at the nominal treatment distance shall not exceed:

i. An average of 2 percent of the absorbed dose on the central axis of the useful beam at the nominal treatment distance. This limit shall apply in the area between a line 4 centimeters outside the periphery of the geometrical radiation field and the border of the maximum area protectable by the electron applicator; and

ii. A maximum of 10 percent of the absorbed dose on the central axis of the useful beam at the nominal treatment distance. This limit shall apply in the area between a line 2 centimeters outside the periphery of the geometrical radiation field and the border of the maximum area protectable by the electron applicator.

ii. For fields of any size in which the maximum area shielded by the electron applicator exceeds 1000 square centimeters, the product of the average absorbed dose due to leakage radiation through the electron applicators and the maximum area protectable by the electron applicators shall not exceed two tenths (0.2) of the product of the maximum absorbed dose on the central axis of the useful beam and the area of the useful beam for a radiation field of 10 centimeters by 10 centimeters. All values of absorbed dose and area are referred to the nominal treatment distance.

c. Measurement of Leakage Radiation.

i. 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 (2) 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, and the leakage radiation from each set shall not exceed a maximum of 2 percent anywhere in the area protectable by that beam-limiting device.

ii. 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 1 square centimeter suitably protected against radiation which has been scattered from material beyond the radiation detector. Measurements shall be made using 1 centimeter of tissue equivalent build up material.

d. When adjustable beam-limiting devices are used, the position and shape of the radiation field shall be indicated by a light field.

4 Filters/Wedges.

a. Each filter and/or wedge which 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 damaged, the wedge transmission factor shall be redetermined;

b. If the absorbed dose rate information required by 1.15.7(9) relates exclusively to operation with a field flattening or beam scattering filter in place, such filter shall be removable only by the use of tools;

c. For equipment manufactured after the effective date of these regulations which utilize a system of wedge filters, interchangeable field flattening filters, or interchangeable beam scattering foils:

i. 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;

ii. An interlock system shall be provided to prevent irradiation if the filter selected is not in the correct position;

iii. A display shall be provided at the treatment control panel showing the wedge filter(s), interchangeable field flattening filter(s), and/or interchangeable beam scattering foil(s) in use; and

iv. An interlock shall be provided to prevent irradiation if any filter and/or beam scattering foil selection operation carried out in the treatment room does not agree with the filter and/or beam scattering foil selection operation carried out at the treatment control panel.

5 X-Ray Stray Radiation in the Useful Electron Beam. For equipment manufactured after the effective date of these regulations, 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).

6. Beam Monitors. All therapeutic radiation machines subject to 1.15.7 shall be provided with beam monitoring devices. The sensors for this device shall be fixed in the useful beam during treatment, (or interlocked) to indicate the air kerma rate or dose rate.

a. Equipment manufactured after the effective date of these regulations shall be provided with at least two independently powered integrating dose meters. Alternatively, a common power supply may be used if the production of radiation is terminated upon failure of any common element.

b. Equipment manufactured on or before the effective date of these regulations shall be provided with at least one radiation detector. This detector shall be incorporated into a primary beam monitoring system;

c. The detector and the system into which that detector is incorporated shall meet the following requirements:

i. Each detector shall be removable only with tools and, if movable, shall be interlocked to prevent incorrect positioning;

ii. Each detector shall form part of a beam monitoring system from whose readings in dose monitor units the absorbed dose at a reference point in the treatment volume can be calculated;

iii. Each beam monitoring system shall be capable of independently monitoring, interrupting, and terminating irradiation; and

iv. For equipment manufactured after the effective date of these regulations, the design of the beam monitoring systems shall ensure that the:

i. Malfunctioning of one system shall not affect the correct functioning of the secondary system; and

ii. Failure of any element common to both systems which could affect the correct function of both systems shall terminate irradiation or prevent the initiation of radiation.

v. Each beam monitoring system shall have a legible display at the treatment control panel. For equipment manufactured after the effective date of these regulations, each display shall:

i. maintain a reading until intentionally reset;

ii. have only one scale and no electrical or mechanical sc ale multiplying factors;

iii. utilize a design such that increasing dose is displayed by increasing numbers; and

iv. In the event of power failure, the beam monitoring information required in 1.15.7(6)(c)(v)(iii) 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.

7 Beam Symmetry.

a. Bent-beam linear accelerators subject to 1.15.7 shall be provided with auxiliary device(s) to monitor beam symmetry;

b. The device(s) referenced in 1.15.7(7)(a) shall be able to detect field asymmetry greater than 10 percent; and c. The device(s) referenced in 1.15.7(7)(a) shall be configured to terminate irradiation if the specifications in 1.15.7(7)(b) cannot be maintained.

8 Selection and Display of Dose Monitor Units.

a. Irradiation shall not be possible until a selection of a number of dose monitor units has been made at the treatment control panel;

b. The preselected number of dose monitor units shall be displayed at the treatment control panel until reset manually for the next irradiation;

c. After termination of irradiation, it shall be necessary to reset the dosimeter display before subsequent treatment can be initiated; and

d. For equipment manufactured after the effective date of these regulations, after termination of irradiation, it shall be necessary for the operator to reset the preselected dose monitor units before irradiation can be initiated.

9. Air Kerma Rate/Absorbed Dose Rate. For equipment manufactured after the effective date of these regulations, a system shall be provided whose readings the air kerma rate or absorbed dose rate at a reference point in the treatment volume can be calculated. [The radiation detectors specified in 1.15.7(6) may form part of this system.] In addition:

a. The dose monitor unit dose rate shall be displayed at the treatment control panel;

b. 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 which 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; and

c. For equipment manufactured after the effective date of these regulations, if the equipment can deliver under any conditions an air kerma rate or absorbed dose rate at the nominal treatment distance more than ten (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 400 rad (4 Gy).

10 Termination of Irradiation by the Beam Monitoring System or Systems During Stationary Beam Radiation Therapy.

a. Each primary system shall terminate irradiation when the preselected number of dose monitor units has been detected by the system;

b. If original design of the equipment included a secondary dose monitoring system, that system shall be capable of terminating irradiation when not more than 15 percent 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

c. For equipment manufactured after the effective date of these regulations, an indicator on the control panel shall show which monitoring system has terminated irradiation.

11. Termination Switches. 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.

12. Interruption Switches. 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.

13. Timer. A suitable irradiation control device shall be provided to terminate the irradiation after a preset time interval.

a. A timer shall be provided which has a display at the treatment control panel. The timer shall have a preset time selector and an elapsed time indicator;

b. The timer shall be a cumulative timer which 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;

c. For equipment manufactured after the effective date of these regulations, after termination of irradiation and before irradiation can be reinitiated, it shall be necessary for the operator to reset the preset time selector; and d. The timer shall terminate irradiation when a preselected time has elapsed, if the dose monitoring systems have not previously terminated irradiation.

14. Selection of Radiation Type. Equipment capable of both x-ray therapy and electron therapy shall meet the following additional requirements: a. Irradiation shall not be possible until a selection of radiation type (x-rays or electrons) has been made at the treatment control panel;

b. The radiation type selected shall be displayed at the treatment control panel before and during irradiation;

c. An interlock system shall be provided to ensure that the equipment can principally emit only the radiation type which has been selected;

d. An interlock system shall be provided to prevent irradiation with x-rays except to obtain a verification film, when electron applicators are fitted;

e. An interlock system shall be provided to prevent irradiation with electrons when accessories specific for x-ray therapy are fitted; and

f 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.

15. Selection of Energy. Equipment capable of generating radiation beams of different energies shall meet the following requirements:

a. Irradiation shall not be possible until a selection of energy has been made at the treatment control panel;

b. The measured energy value selected shall be displayed (MV for photons and MeV for electrons) at the treatment control panel before and during irradiation; and

c. Irradiation shall not be possible until the appropriate flattening filter or scattering foil for the selected energy is in its proper location.

16 Selection of Stationary Beam Radiation Therapy or Rotational Arc Radiation Therapy. Therapeutic radiation machines capable of both stationary beam radiation therapy and rotational arc radiation therapy shall meet the following requirement:

a. Irradiation shall not be possible until a selection of stationary beam radiation therapy or rotational arc radiation therapy has been made at the treatment control panel;

b. The mode of operation shall be displayed at the treatment control panel;

c. An interlock system shall be provided to ensure that the equipment can operate only in the mode which has been selected;

d. 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;

e. Rotational arc radiation therapy shall be controlled to obtain the selected relationships between incremental dose monitor units and incremental angle of movement:

i. For equipment manufactured after the effective date of these regulations, an interlock system shall be provided to terminate irradiation if the number of dose monitor units delivered in any 15 degrees of arc differs by more than 20 percent from the selected value;

ii. For equipment manufactured after the effective date of these regulations, where gantry angle terminates the irradiation in rotational arc radiation therapy, the dose monitor units shall differ by less than 5 percent from the value calculated from the absorbed dose per unit angle and total angle relationship;

iii. For equipment manufactured after the effective date of these regulations, an interlock shall be provided to prevent the gantry moving more than 5 degrees beyond the selected angular limits during rotational arc radiation therapy; and

iv. For equipment manufactured after the effective date of these regulations, an interlock shall be provided to require that a selection of direction be made at the treatment control panel in all units which are capable of both clockwise and counter-clockwise rotational arc radiation therapy.

f. Where the beam monitor system terminates the irradiation in rotational arc radiation therapy, the termination of irradiation shall be as required by 1.15.7(10); and

g. For equipment manufactured after the effective date of these regulations, an interlock system shall be provided to terminate irradiation if movement of the gantry:

i. occurs during stationary beam radiation therapy; or

ii. stops during rotational arc radiation therapy unless such stoppage is a preplanned function.

17 Facility Design Requirements for Therapeutic Radiation Machines Operating above 500 kV. In addition to shielding adequate to meet requirements of 1.15.9, the following design requirements are made:

a. Protective Barriers. All protective barriers shall be fixed, except for access doors to the treatment room or movable beam interceptors;

b. Control Panel. In addition to other requirements specified in Subchapter 15, the control panel shall also:

i. Be located outside the treatment room;

ii. Provide an indication of whether electrical power is available at the control panel and if activation of the radiation is possible;

iii. Provide an indication of whether radiation is being produced; and

iv. Include an access control (locking) device which will prevent unauthorized use of the therapeutic radiation machine;

c. 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;

d. 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;

e. 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";

f. Entrance Interlocks. Interlocks shall be provided such that all entra nce doors must be closed before treatment can be initiated or continued. If the radiation beam is interrupted by any 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;

g. Beam Interceptor Interlocks. If the shielding material in any protective barrier requires the presence of a beam interceptor to ensure compliance with 1.4.14(1), and 1.4.14(2) of these regulations, 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(s);

h. Emergency Cutoff Switches. At least one (1) "scram button" or other 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 1.15.7(11). 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;

i. 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

j. 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.

18 Radiation Therapy Physicist Support.

a. The services of a Radiation Therapy Physicist shall be utilized in facilities having therapeutic radiation machines with energies of 500 kV and above. The Radiation Therapy Physicist shall be responsible for:

i. Full calibration(s) required by 1.15.7(20) and protection surveys required by 1.15.4(1);

ii. Supervision and review of dosimetry;

iii. Beam data acquisition and storage for computerized dosimetry, and supervision of its use;

iv. Quality assurance, including quality assurance check review required by 1.15.7(21)(e) of these regulations;

v. Consultation with the authorized user in treatment planning , as needed; and

vi. Perform calculations/assessments regarding misadministrations.

b. If the Radiation Therapy Physicist is not a full-time employee of the registrant, the operating procedures required by 1.15.7(19) shall also specifically address how the Radiation Therapy Physicist is to be contacted for problems or emergencies, as well as the specific actions, if any, to be taken until the Radiation Therapy Physicist can be contacted.

19 Operating Procedures.

a. No individual other than the patient shall be in the treatment room during treatment of a patient or during any irradiation for testing or calibration purposes;

b. Therapeutic radiation machines shall not be made available for medical use unless the requirements of 1.15.4(1), 1.15.7(20), and 1.15.7(21) have been met;

c. Therapeutic radiation machines, when not in operation, shall be secured to prevent unauthorized use;

d. If a patient must be held in position during treatment, mechanical supporting or restraining devices shall be used; and

e. A copy of the current operating and emergency procedures shall be maintained at the therapeutic radiation machine control console.

20 Full Calibration Measurements.

a. Full calibration of a therapeutic radiation machine subject to 1.15.7 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. At intervals not exceeding 1 year; and

iii. Before medical use under the following conditions:

i. Whenever quality assurance check measurements indicate that the radiation output differs by more than 5 percent from the value obtained at the last full calibration and the difference cannot be easily discerned; and

ii. Following any component replacement, major repair, or modification of components that could significantly affect the characteristics of the radiation beam.

iv. Notwithstanding the requirements of 1.15.7(20)(a)(iii):

i. Full calibration of therapeutic radiation machines with multi-energy and/or multi-mode capabilities is required only for those modes and/or energies that are not within their acceptable range; and

ii. If the repair, replacement or modification does not affect all modes and/or energies, full calibration shall be performed on the affected mode/energy that is in most frequent clinical use at the facility. The remaining energies/modes may be validated with quality assurance check procedures against the criteria in 1.15.7(20)(a)(iii)(i).

b. To satisfy the requirement of 1.15.7(1)(a), full calibration shall include all measurements required for annual calibration by American Association of Physicists in Medicine (AAPM) Report 13, "Physical Aspects of Quality Assurance in Radiation Therapy";

c. The registrant shall use the dosimetry system described in 1.15.4(3) to measure the radiation output for one set of exposure conditions. The remaining radiation measurements required in 1.15.7(20)(b) may then be made using a dosimetry system that indicates relative dose rates; and

d. The registrant shall maintain a record of each calibration 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 Radiation Therapy Physicist responsible for performing the calibration.

21 Periodic Quality Assurance Checks.

a. Periodic quality assurance checks shall be performed on all therapeutic radiation machines subject to 1.15.7 at intervals not to exceed 1 week;

b. To satisfy the requirement of 1.15.7(21)(a), quality assurance checks shall include determination of all parameters for periodic quality assurance checks contained in American Association of Physicists in Medicine (AAPM) Report 13, "Physical Aspects of Quality Assurance in Radiation Therapy";

c. The registrant shall use a dosimetry system which has been intercompa red within the previous 6 months with the dosimetry system described in 1.15.4(3) to make the periodic quality assurance checks required in 1.15.7(21)(b);

d. The registrant shall perform periodic quality assurance checks required by 1.15.7(21)(a) in accordance with procedures established by the Radiation Therapy Physicist;

e. The registrant shall review the results of each periodic radiation output check according to the following procedures:

i. The authorized user and Radiation Therapy Physicist shall be immediately notified if any parameter is not within its acceptable range. The therapeutic radiation machine shall not be made available for subsequent medical use until the Radiation Therapy Physicist has determined that all parameters are within their acceptable range;

ii. If all quality assurance check parameters appear to be within their acceptable range, the quality assurance check shall be reviewed and signed by either the authorized user or Radiation Therapy Physicist within 3 treatment days; and

iii. The Radiation Therapy Physicist shall review and sign the results of each radiation output quality assurance check at intervals not to exceed 1 month;

f. Therapeutic radiation machines subject to 1.15.7 shall have safety quality assurance checks of each radiation therapy facility performed at intervals not to exceed 1 week;

g. To satisfy the requirement of 1.15.7(21)(f), safety quality assurance checks shall ensure proper operation of:

i. Electrical interlocks at each external beam radiation therapy room entrance;

ii. Proper operation of the "BEAM-ON", interrupt and termination switches;

iii. Beam condition indicator lights on the access doors, control console, and in the radiation therapy room;

iv. Viewing systems;

v. Electrically operated treatment room door(s) from inside and outside the treatment room; and

vi. 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.

h. The registrant shall promptly repair any system identified in 1.15.7(21)(g) that is not operating properly; and

i. A registrant shall maintain a record of each quality assurance check required by 1.15.7(21)(a) and 1.15.7(21)(g) for 3 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 instrument(s) used to measure the radiation output of the therapeutic radiation machine, and the signature of the individual who performed the periodic quality assurance check.