La. Admin. Code tit. 33 § XV-609

Current through Register Vol. 50, No. 11, November 20, 2024

Section XV-609 - X-Ray and Electron Therapy Systems with Energies of 1 MeV and Above

A. LAC 33:XV.Chapter 9, except LAC 33:XV.911.C and D, shall apply to medical facilities using therapy systems with energies of 1 MeV and above.

B. In addition to the definitions provided in LAC 33:XV.602, the following definitions shall be applicable to LAC 33:XV.609:

Applicator- a structure that determines the extent of the treatment field at a given distance from the virtual source.

Beam-Scattering Filter- a filter used to scatter a beam of electrons.

Central Axis of the Beam- a line passing through the virtual source and the center of the plane figure formed by the edge of the first beam-limiting device.

Dose Monitor Unit- a unit response from the dose-monitoring system from which the absorbed dose can be calculated.

Dose-Monitoring System- a system of devices for the detection, measurement, and display of quantities of radiation.

Existing Equipment- therapy systems subject to LAC 33:XV.609 that were manufactured on or before January 1, 1985.

Field-Flattening Filter- a filter used to provide dose uniformity over the area of a useful beam of X-rays at a specified depth.

Field Size- the dimensions along the major axes of an area in a plane perpendicular to the specified direction of the beam of incident radiation at the normal treatment distance and defined by the intersection of the major axes and the 50 percent isodose line.

Gantry- that part of the system supporting and allowing possible movements of the radiation head.

Interruption of Irradiation- the stopping of irradiation with the possibility of continuing irradiation without resetting of operating conditions at the control panel.

Isocenter- a fixed point in space located at the center of the smallest sphere through which the central axis of the beam passes in all conditions. The sphere is described by the intersection of the axes of rotation of the gantry, the collimator, and the couch.

Moving Beam Therapy- radiation therapy with relative displacement of the useful beam and the patient during irradiation. It includes arc therapy, skip therapy, and rotational therapy.

New Equipment- systems subject to LAC 33:XV.609 that were manufactured after January 1, 1985.

Nominal Treatment Distance-

a. for electron irradiation, the nominal source-to-surface distance along the central axis of the useful beam as specified by the manufacturer for the applicator;

b. for X-ray irradiation, the nominal source-to-isocenter distance along the central axis of the useful beam. For non-isocentric equipment, this distance shall be that specified by the manufacturer.

Radiation Head- the structure from which the useful beam emerges.

Shadow Tray- a device attached to the radiation head to support auxiliary beam limiting material.

Stationary Beam Therapy- radiation therapy without relative displacement of the useful beam and the patient during irradiation.

Target- that part of a radiation head that by design intercepts a beam of accelerated particles with subsequent emission of other radiation.

Virtual Source- a point from which radiation appears to originate.

C. Requirements for Equipment

1. Leakage Radiation to the Patient Area. Requirements are as follows:

a. new equipment and existing equipment manufactured or installed after April 20, 1977, shall meet the following requirements:

i. for operating conditions producing maximum leakage radiation, the absorbed dose in rads (centigrays) due to leakage radiation, including X-rays, electrons, and neutrons, at any point in a circular plane of 2 meters radius centered on and perpendicular to the central axis of the beam at the isocenter or normal treatment distance and outside the maximum useful beam size, shall not exceed 0.1 percent of the maximum absorbed dose in rads (centigrays) of the unattenuated useful beam measured at the point of intersection of the central axis of the beam and the plane surface. Measurements excluding those for neutrons shall be averaged over an area up to but not exceeding 100 square centimeters at the positions specified. Measurements of the portion of the leakage radiation dose contributed by neutrons shall be averaged over an area up to but not exceeding 200 square centimeters; and

ii. for each system, the registrant or licensee shall determine or obtain from the manufacturer the leakage radiation existing at the positions specified in LAC 33:XV.609.C.1.a.i for the specified operating conditions. Records on leakage radiation measurements shall be maintained for inspection by the department; and

b. existing equipment shall meet the following requirements:

i. for operating conditions producing maximum leakage radiation, the absorbed dose in rads (centigrays) due to leakage radiation excluding neutrons at any point in a circular plane of 2 meters radius centered on a perpendicular to the central axis of the beam 1 meter from the nominal source, and outside the maximum size useful beam, shall not exceed 0.1 percent of the maximum absorbed dose in rads (centigrays) of the unattenuated useful beam measured at the point of intersection of the central axis of the beam and the surface of the circular plane. Measurements shall be averaged over an area up to but not exceeding 100 square centimeters at the positions specified; and

ii. for each system, the registrant or licensee shall determine or obtain from the manufacturer the leakage radiation existing at the positions specified in LAC 33:XV.609.C.1.b.i for the specified operating conditions. Records on radiation leakage shall be maintained for inspection by the department.

2. Leakage Radiation Outside the Patient Area for New Equipment. Requirements are as follows:

a. the absorbed dose in rads (centigrays) due to leakage radiation except in the area specified in LAC 33:XV.609.C.1.a.i when measured at any point 1 meter from the path of the charged particle, before the charged particle strikes the target window, shall not exceed 0.1 percent for X-ray leakage nor 0.05 percent for neutron leakage of the maximum absorbed dose in rads (grays) of the unattenuated useful beam measured at the point of intersection of the central axis of the beam and the circular plan specified in LAC 33:XV.609.C.1.a.i; and

b. the registrant or licensee shall determine or obtain from the manufacturer the actual leakage radiation existing at the positions specified in LAC 33:XV.609.C.2.a for specified operating conditions. Radiation measurements excluding neutrons shall be averaged over an area up to but not exceeding 100 square centimeters. Neutron measurements shall be averaged over an area up to but not exceeding 200 square centimeters.

3. Reserved.

4. Beam-Limiting Devices. Adjustable or interchangeable beam-limiting devices shall be provided, and such devices shall transmit no more than 2 percent of the useful beam at the normal treatment distance for the portion of the useful beam that is to be attenuated by the beam-limiting device. The neutron component of the useful beam shall not be included in this requirement.

5. Filters. Filters shall meet the following requirements:

a. each filter that is removable from the system shall be clearly marked with an identification number. Documentation available at the control panel shall contain a description of the filter. For wedge filters, the wedge angle shall appear on the wedge or wedge tray;

b. if the absorbed dose rate data required by LAC 33:XV.609.C.16 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; and

c. for new equipment that utilizes a system of wedge filters, interchangeable field-flattening filters, or interchangeable beam-scattering filters:

i. irradiation shall not be possible until a selection of a filter has been made at the treatment control panel;

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 filter(s) in use; and

iv. an interlock shall be provided to prevent irradiation if any filter selection operation carried out in the treatment room does not agree with the filter selection operation carried out at the treatment control panel.

6. Beam Quality. The registrant or licensee shall determine, or obtain from the manufacturer, data sufficient to assure that the following beam quality requirements are met:

a. the absorbed dose resulting from X-rays in a useful electron beam at the point on the central axis of the beam 10 centimeters greater than the practical range of the electrons shall not exceed the values stated in Table 2. Linear interpolation shall be used for values not stated.

Table 2
Maximum Energy of Electron Beam in MeV	X-Ray Absorbed Dose as a Fraction of Maximum Absorbed Dose
1	0.03
15	0.05
35	0.10
50	0.20

b. compliance with LAC 33:XV.609.C.6.a shall be determined using:

i. a measurement within a phantom with the incident surface of the phantom at the normal treatment distance and normal to the central axis of the beam;

ii. the largest field size available that does not exceed 15 by 15 centimeters; and

iii. a phantom whose cross-sectional dimensions exceed the measurement radiation field by at least 5 centimeters and whose depth is sufficient to perform the required measurement;

c. the absorbed dose at a surface located at the normal treatment distance, at the point of intersection of that surface with the central axis of the useful beam during X-ray irradiation, shall not exceed the limits stated in Table 3. Linear interpolation shall be used for values not stated.

Table 3
Maximum Photon Energy in MeV	Absorbed Dose at the Surface as a Fraction of the Maximum Absorbed Dose
1	0.80
2	0.70
5	0.60
15	0.50
35	0.40
50	0.20

d. compliance with LAC 33:XV.609.C.6.c shall be determined by measurements made:

i. within a phantom using an instrument that will allow extrapolation to the surface absorbed dose;

ii. using a phantom whose size and placement meet the requirements of LAC 33:XV.609.C.6.b;

iii. after removal of all beam modifying devices that can be removed without the use of tools, except for beam-scattering or field-flattening filters; and

iv. using the largest field size available that does not exceed 15 by 15 centimeters; and

e. the registrant or licensee shall determine, or obtain from the manufacturer, the maximum percentage absorbed dose in the useful beam due to neutrons, excluding stray neutron radiation, for specified operating conditions.

7. Beam Monitors. All therapy systems shall be provided with radiation detectors in the radiation head. The following requirements apply:

a. new equipment shall be provided with at least two radiation detectors. The detectors shall be incorporated into two separate dose-monitoring systems;

b. existing equipment shall be provided with at least one radiation detector. This detector shall be incorporated into a primary dose-monitoring system; and

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 shall be interlocked to prevent incorrect positioning;

ii. each detector shall form part of a dose-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 dose-monitoring system shall be capable of independently monitoring, interrupting, and terminating irradiation;

iv. for new equipment, the design of the dose-monitoring systems shall assure that:

(a). the malfunctioning of one system shall not affect the correct functioning of the second system; and

(b). the failure of any element common to both systems that could affect the correct function of both systems shall terminate irradiation; and

v. each dose-monitoring system shall have a legible display at the treatment control panel. For new equipment, each display shall:

(a). maintain a reading until intentionally reset to zero;

(b). have only one scale and no scale multiplying factors;

(c). utilize a design such that increasing dose is displayed by increasing numbers and shall be so designed that, in the event of an overdosage of radiation, the absorbed dose may be accurately determined; and

(d). in the event of power failure, the dose-monitoring information required by LAC 33:XV.609.C.7.c.v 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.

8. Beam Symmetry. In new equipment inherently capable of producing useful beams with asymmetry exceeding 5 percent, the asymmetry of the radiation beam in two orthogonal directions shall be monitored before the beam passes through the beam-limiting device. Facilities shall be provided so that, if the difference in dose rate between one region and another region symmetrically displaced from the central axis of the beam exceeds 5 percent of the central axis dose rate, indication of this condition is made at the control panel, and if this difference exceeds 10 percent, the irradiation is terminated.

9. Selection and Display of Dose Monitor Units. The following requirements shall be met:

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

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

d. for new equipment, after termination of irradiation, it shall be necessary to manually reset the preselected dose monitor units before irradiation can be initiated.

10. Termination of Irradiation by the Dose-Monitoring System or Systems during Stationary Beam Therapy. The following requirements shall be met:

a. if the original design of the equipment included a second 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 have been detected by the second dose-monitoring system;

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

c. for new equipment, a second dose-monitoring system shall be present. That system shall be capable of terminating irradiation when not more than 10 percent or 25 dose monitor units above the preselected number of dose monitor units set at the control panel have been detected by the second dose-monitoring system; and

d. for new equipment, an indicator on the control panel shall show which dose-monitoring system has terminated irradiation.

11. Interruption Switches. It shall be possible to interrupt irradiation and equipment movements at any time from the operator's position at 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.

12. Termination Switches. It shall be possible to terminate irradiation and equipment movements, or go from an interruption condition to termination conditions, at any time from the operator's position at the treatment control panel.

13. Timer. Requirements for timers are as follows:

a. a timer that has a display shall be provided 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 that activates with the production of radiation 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 to zero;

c. the timer shall terminate irradiation when a preselected time has elapsed if the dose-monitoring systems have not previously terminated irradiation; and

d. for new equipment, after termination of irradiation and before irradiation can be reinitiated, it shall be necessary to manually reset the preset time selector.

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 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 emit only the radiation type selected;

d. 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;

e. an interlock system shall be provided to prevent irradiation with X-rays except to obtain a port film when electron applicators are fitted; and

f. an interlock system shall be provided to prevent irradiation with electrons when accessories specific for X-ray therapy are fitted.

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 nominal energy value selected shall be displayed at the treatment control panel before and during irradiation;

c. 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; and

d. for new equipment, an interlock system shall be provided to terminate irradiation if the energy of the electrons striking the X-ray target or electron window deviates by more than 20 percent or 3 MeV, whichever is smaller, from the selected nominal energy.

16. Selection of Stationary Beam Therapy or Moving Beam Therapy. Equipment capable of both stationary beam therapy and moving beam therapy shall meet the following requirements:

a. irradiation shall not be possible until a selection of stationary beam therapy or moving beam therapy has been made at the treatment control panel;

b. an interlock system shall be provided to ensure that the equipment can operate only in the mode selected;

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

e. for new equipment, an interlock system shall be provided to terminate irradiation if:

i. movement of the gantry occurs during stationary beam therapy; or

ii. movement of the gantry stops during moving beam therapy unless such stoppage is a preplanned function;

f. moving beam therapy shall be controlled to obtain the selected relationships between incremental dose monitor units and incremental angle of movement:

i. for new equipment, an interlock system shall be provided to terminate irradiation if the number of dose monitor units delivered in any 10 degrees of arc differs by more than 20 percent from the selected value; and

ii. for new equipment, where gantry angle terminates the irradiation in arc therapy, the dose monitor units shall differ by less than 5 percent from the value calculated from the absorbed dose per unit angle relationship; and

g. where the dose-monitoring system terminates the irradiation in arc therapy, the termination of irradiation shall be as required by LAC 33:XV.609.C.9.

17. Absorbed Dose Rate. For new equipment, a system shall be provided from whose readings the absorbed dose rate at a reference point in the treatment volume can be calculated. The radiation detectors specified may form part of this system. In addition:

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

b. if the equipment can deliver under any conditions an absorbed dose rate at the normal treatment distance more than twice the maximum value specified by the manufacturer for any machine parameters utilized, a device shall be provided that terminates irradiation when the absorbed dose rate exceeds a value twice the specified maximum. The value at which the irradiation will be terminated shall be in a record maintained by the registrant or licensee.

18. Location of Virtual Source and Beam Orientation. The registrant or licensee shall determine, or obtain from the manufacturer, the location with reference to an accessible point on the radiation head of:

a. the X-ray target or the virtual source of X-rays; and

b. the electron window or the virtual source of electrons if the system has electron beam capabilities.

19. System-Checking Facilities. Capabilities shall be provided so that all radiation safety interlocks can be checked for correct operation. When preselection of any of the operating conditions requires action in the treatment room and at the treatment control panel, selection at one location shall not give a display at the other location until the requisite selected operations in both locations have been completed.

D. Facility and Shielding Requirements. In addition to LAC 33:XV.Chapter 4, the following design requirements shall apply.

1. Protective Barriers. All protective barriers shall be fixed except for entrance doors or beam interceptors.

2. Control Panel. The control panel shall be located outside the treatment room.

3. Viewing Systems. Provisions shall be made as follows:

a. windows, mirrors, closed-circuit television, or an equivalent system shall be provided to permit continuous observation of the patient during irradiation and shall be so located that the operator can observe the patient from the control panel; and

b. when the primary viewing system is by electronic means, an alternate viewing system, which may be electronic, shall be available for use in the event of failure of the primary viewing system.

4. Aural Communications. Provision shall be made for two-way aural communication between the patient and the operator at the control panel. However, where excessive noise levels or treatment requirements makes aural communication impractical, other methods of communication shall be used.

5. Room Entrances. Treatment room entrances shall be provided with warning lights in readily observable positions near the outside of all access doors to indicate when the useful beam is "on."

6. Entrance interlocks shall be provided such that all entrance 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.

E. Surveys, Calibrations, Spot Checks, and Operating Procedures

1. Survey requirements are as follows:

a. all new facilities, and existing facilities not previously surveyed, shall have a survey made by, or under the direction of, a qualified expert. In addition, such surveys shall be done after any change in the facility or equipment that might cause a significant increase in radiation hazard;

b. the registrant or licensee shall obtain a written report of the survey from the qualified expert, and a copy of the report shall be transmitted by the registrant or licensee to the Office of Environmental Compliance within 30 days of receipt of the report; and

c. the survey and report shall indicate all instances in which the installation, in the opinion of the qualified expert, is in violation of applicable regulations.

2. Calibrations shall be performed as follows:

a. the calibration of systems subject to this Section shall be performed in accordance with an established calibration protocol acceptable to the department before the system is first used for irradiation of a patient and thereafter at intervals that do not exceed 12 months, and after any change that might significantly alter the calibration, spatial distribution, or other characteristics of the therapy beam. The calibration protocol published by the American Association of Physicists in Medicine is accepted as an established protocol. For other protocols, the user shall submit that protocol to the Office of Environmental Compliance for written concurrence that the protocol is acceptable;

b. the calibration shall be performed under the direct supervision of a radiological physicist who is physically present at the facility during the calibration;

c. calibration radiation measurements required by LAC 33:XV.609.E.2.a shall be performed using a dosimetry system:

i. that has a calibration factor for cobalt-60 gamma rays traceable to a national standard;

ii. that has been calibrated within the previous two years and after any servicing that may have affected its calibration;

iii. that has been calibrated in such a fashion that an uncertainty can be stated for the radiation quantities monitored by the system; and

iv. that has had constancy checks performed on the system as specified by a radiological physicist;

d. calibrations shall be in sufficient detail that the dose at a reference point in soft tissue may be calculated to within an uncertainty of 5 percent;

e. the calibration of the therapy beam shall include but not be limited to the following determinations:

i. verification that the equipment is operating in compliance with the design specifications concerning the light localizer, side light, and back-pointer alignment with the isocenter when applicable; variation in the axis of rotation for the table, gantry, and jaw system; and beam flatness and symmetry at the specified depth;

ii. the absorbed dose rate at various depths of water for the range of field sizes used, for each effective energy, that will verify the accuracy of the dosimetry of all therapy procedures used with that therapy beam;

iii. the uniformity of the radiation field and any dependency upon the direction of the useful beam;

iv. verification that existing depth-dose data and isodose charts applicable to the specific machine continue to be valid or are updated to existing machine conditions; and

v. verification of transmission and electron buildup factors for all accessories such as wedges, shadow trays, and compensators;

f. records of calibration measurements under LAC 33:XV.609.E.2.a and dosimetry system calibrations under LAC 33:XV.609.E.2.c shall be maintained for five years after completion of the full calibration at the facility of use; and

g. a copy of the latest calibration performed pursuant to LAC 33:XV.609.E.2.a shall be available in the area of the control panel.

3. Spot checks shall be performed on systems subject to LAC 33:XV.609 during calibrations and thereafter at intervals not to exceed one month. Such spot checks shall meet the following requirements:

a. the spot-check procedures shall be in writing and shall have been developed by a radiological physicist. A copy of the procedure shall be submitted to the Office of Environmental Compliance prior to its implementation;

b. if a radiological physicist does not perform the spot-check measurements, the results of the spot-check measurements shall be reviewed by a radiological physicist within 15 days;

c. the spot-check procedures shall specify the frequency at which tests or measurements are to be performed and the acceptable tolerance for each parameter measured in the spot check compared to the value for that parameter determined in the calibration;

d. at intervals not to exceed one week, spot checks shall be made of absorbed dose measurements at a minimum of one depth in a phantom;

e. where a system has built-in devices that provide a measurement of any parameter during irradiation, such measurement shall not be utilized as a spot-check measurement;

f. the cause for a parameter exceeding a tolerance set by the radiological physicist shall be investigated and corrected before the system is used for patient irradiation;

g. wherever a spot check indicates a significant change in the operating characteristics of a system, as specified in the radiological physicist's spot-check procedures, the system shall be recalibrated as required in LAC 33:XV.609.E.2;

h. records of spot-check measurements shall be maintained by the registrant or licensee for a period of two years after completion of the spot-check measurements and any necessary corrective actions at the facility of use; and

i. where a spot check involves a radiation measurement, such measurement shall be obtained using a system that satisfies the requirements of LAC 33:XV.609.E.2.c or that has been intercompared with a system meeting those requirements within the previous year.

4. Operating procedures shall include the following:

a. no individual other than the patient shall be in the treatment room during treatment of a patient;

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

c. the system shall not be used in the administration of radiation therapy unless the requirements of LAC 33:XV.609.E.1, 2, and 3 have been met.

La. Admin. Code tit. 33, § XV-609

Promulgated by the Department of Environmental Quality, Nuclear Energy Division, LR 13:569 (October 1987), amended by the Office of Air Quality and Radiation Protection, Radiation Protection Division, LR 19:1421 (November 1993), amended by the Office of Environmental Assessment, Environmental Planning Division, LR 26:2586 (November 2000), amended by the Office of the Secretary, Legal Affairs Division, LR 31:2532 (October 2005), LR 34:1902 (September 2008).

AUTHORITY NOTE: Promulgated in accordance with R.S. 30:2001 et seq.