Statutes, codes, and regulations
South Carolina Code of Regulations
Chapter 61 - DEPARTMENT OF HEALTH AND ENVIRONMENTAL CONTROLSubchapter 61-64 - X-Rays (Title B)
Part VI - USE OF THERAPEUTIC EQUIPMENT
Section 61-64.VI.RHB 6.5 - X-ray and Electron Therapy Systems with Energies of 1 MeV and Above

S.C. Code Regs. § § 61-64.VI.RHB 6.5

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Current through Register Vol. 48, No. 10, October 25, 2024
Section 61-64.VI.RHB 6.5 - X-ray and Electron Therapy Systems with Energies of 1 MeV and Above

These rules shall apply to facilities using therapy systems with energies 1 MeV and above. The records shall be maintained and available for review.

6.5.1 Leakage Radiation to the Patient Area. Equipment shall meet the following requirements:
6.5.1.1 For operating conditions producing maximum leakage radiation, the absorbed dose in rads (Grays) due to leakage radiation, including x-rays and electrons, at any point in a circular plane of two meters (2 m) radius centered on and perpendicular to the central axis of the beam at the isocenter or nominal treatment distance and outside the maximum useful beam size shall not exceed 0.1 percent 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 plane surface. Measurements excluding those for neutrons shall be averaged over an area up to, but not exceeding, one hundred square centimeters (100 cm2) 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, two hundred square centimeters (200 cm2).
6.5.1.2 For each system, the registrant shall determine or obtain from the manufacturer the leakage radiation existing at the positions specified in RHB 6.5.1.1 for the specified operating conditions. Records on leakage radiation measurements shall be maintained for inspection by the Department.
6.5.2 Beam-Limiting Devices. Adjustable or interchangeable beam limiting devices shall be provided and such devices shall transmit no more than two percent (2%) of the useful photon beam at the nominal treatment distance for the portion of the useful beam which is to be attenuated by the beam-limiting device. The neutron component of the useful beam shall not be included in this requirement.
6.5.3 Filters.
6.5.3.1 Each filter which 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 (if permanently mounted to the tray). If the wedge tray is damaged, the wedge transmission factor shall be redetermined.
6.5.3.2 If the absorbed dose rate data required by RHB 6.5.15 relates exclusively to operation with a field-flattening filter or beam scattering foil in place, such filter shall be removable only by the use of tools.
6.5.3.3 For equipment installed after May 25, 2001, which utilizes a system of wedge filters, interchangeable field-flattening filters, or interchangeable beam scattering foils:
6.5.3.3.1 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.
6.5.3.3.2 An interlock system shall be provided to prevent irradiation if the filter selected is not in the correct position.
6.5.3.3.3 A display shall be provided at the treatment control panel showing filters in use.
6.5.3.3.4 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.
6.5.3.4 Attenuation of wedges and compensator devices must be checked before the device is placed into service. A visual inspection of the mechanical integrity of these accessories must be done monthly.
6.5.4 Beam Quality. The registrant shall determine data sufficient to assure that the following beam quality requirements in tissue equivalent material are met:
6.5.4.1 The absorbed dose resulting from x-rays in a useful electron beam at a point on the central axis of the beam ten centimeters (10 cm) 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

6.5.4.2 Compliance with RHB 6.5.4 shall be determined using:
6.5.4.2.1 A measurement within a tissue equivalent phantom with the incident surface of the phantom at the normal treatment distance and normal to the central axis of the beam;
6.5.4.2.2 The largest field size available which does not exceed fifteen centimeters by fifteen centimeters (15 cm x 15 cm); and
6.5.4.2.3 A phantom whose cross-sectional dimensions exceed the measurement radiation field by at least five centimeters (5 cm) and whose depth is sufficient to perform the required measurement.
6.5.4.3 The measured ionization at the surface relative to maximum ionization along the central axis 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

Measured Ionization at surface relative to Maximum Ionization along central axis

1

0.80

2

0.70

5

0.60

15

0.50

35

0.40

50

0.20

6.5.4.4 Compliance with RHB 6.5.4.3 shall be determined by measurements made:
6.5.4.4.1 Within a tissue equivalent phantom using an instrument which will allow extrapolation to the surface absorbed dose;
6.5.4.4.2 Using a phantom whose size and placement meet the requirements of RHB 6.5.4.2;
6.5.4.4.3 After removal of all beam modifying devices which can be removed without the use of tools, except for beam scattering or beam-flattening filters; and
6.5.4.4.4 Using the largest field size available which does not exceed fifteen centimeters by fifteen centimeters (15 cm x 15 cm).
6.5.5 Beam Monitors. All therapy systems shall be provided with radiation detectors in the radiation head.
6.5.5.1 Equipment manufactured after January 1, 1994, shall be provided with at least two (2) independent radiation detectors. The detectors shall be incorporated into two (2) independent dose monitoring systems.
6.5.5.2 Equipment manufactured before January 1, 1994, shall be provided with at least one (1) radiation detector. This detector shall be incorporated into a primary dose monitoring system.
6.5.5.3 The detector and the system into which that detector is incorporated shall meet the following requirements:
6.5.5.3.1 Each detector shall be removable only with tools and shall be interlocked to prevent incorrect positioning.
6.5.5.3.2 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.
6.5.5.3.3 Each dose monitoring system shall be capable of independently monitoring, interrupting, and terminating irradiation.
6.5.5.3.4 For new equipment, the design of the dose monitoring systems shall assure that:
a) malfunctioning of one (1) system shall not affect the correct functioning of the secondary system; and
b) failure of any element common to both systems which could affect the correct function of both systems shall terminate irradiation.
6.5.5.3.5 Each dose monitoring system shall have a legible display at the treatment control panel. For new equipment, each display shall:
6.5.5.3.5.1 Maintain a reading until intentionally reset to zero (0);
6.5.5.3.5.2 Have only one (1) scale and no scale multiplying factors for each mode of operation; and
6.5.5.3.5.3 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.
6.5.5.3.6 In the event of power failure, the dose monitoring information required by RHB 6.5.5.3.5 displayed at the control panel at the time of failure shall be retrievable in at least one (1) system for a twenty (20)-minute period of time.
6.5.6 Beam Symmetry. In new equipment inherently capable of producing useful beams with unattenuated asymmetry exceeding five percent (5%), the asymmetry of the radiation beam in two (2) 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 five percent (5%) of the central axis dose rate, indication of this condition is made at the control panel; and if this difference exceeds ten percent (10%), the irradiation is terminated.
6.5.7 Selection and Display of Dose Monitor Units.
6.5.7.1 Irradiation shall not be possible until a selection of a number of dose monitor units has been made at the treatment control panel.
6.5.7.2 The preselected number of dose monitor units shall be displayed at the treatment control panel until reset manually for the next irradiation.
6.5.7.3 After termination of irradiation, it shall be necessary to manually reset the dosimeter display to zero (0) before subsequent treatment can be initiated.
6.5.7.4 For new equipment, after termination of irradiation, it shall be necessary to manually reset the preselected dose monitor units before irradiation can be initiated.
6.5.8 Termination of Irradiation by the Dose Monitoring System or Systems during Stationary Beam Therapy.
6.5.8.1 Each primary system shall terminate irradiation when the preselected number of dose monitor units has been detected by the system.
6.5.8.2 If original design of the equipment included a secondary dose monitoring system, that system shall be capable of terminating irradiation when not more than fifteen percent (15%) or forty (40) dose monitor units, whichever is smaller, above the preselected number of dose monitor units set at the control panel, has been detected by the secondary dose monitoring system.
6.5.8.3 For equipment manufactured after January 1, 1994, a secondary dose monitoring system shall be present. That system shall be capable of terminating irradiation when not more than ten percent (10%) or twenty-five (25) dose monitoring units, whichever is smaller, above the preselected number of dose monitor units set at the control panel has been detected by the secondary dose monitoring system.
6.5.8.4 For equipment manufactured after January 1, 1994, an indicator on the control panel shall show which dose monitoring system has terminated irradiation.
6.5.9 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 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.
6.5.10 Termination Switches. It shall be possible to terminate irradiation and equipment movements or go from any interruption condition to termination conditions at any time from the operator's position at the treatment control panel.
6.5.11 Timer.
6.5.11.1 A timer which has a display shall be provided at the treatment control panel. The timer shall have a preset time selector and an elapsed time indicator.
6.5.11.2 The timer shall be a cumulative timer which 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 (0).
6.5.11.3 For equipment manufactured after May 25, 2001, after termination of irradiation and before irradiation can be reinitiated, it shall be necessary to manually reset the preset time selector.
6.5.11.4 The timer shall terminate irradiation when a preselected time has elapsed if the dose monitoring systems have not previously terminated irradiation.
6.5.12 Selection of Radiation Type. Equipment capable of both x-ray therapy and electron therapy shall meet the following additional requirements:
6.5.12.1 Irradiation shall not be possible until a selection of radiation type has been made at the treatment control panel.
6.5.12.2 An interlock system shall be provided to ensure that the equipment can emit only the radiation type which has been selected.
6.5.12.3 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 at the treatment control panel.
6.5.12.4 An interlock system shall be provided to prevent irradiation with x-ray except to obtain a port film when electron applicators are fitted.
6.5.12.5 An interlock system shall be provided to prevent irradiation with electrons when accessories specific for x-ray therapy are fitted.
6.5.12.6 The radiation type selected shall be displayed at the treatment control panel before and during irradiation.
6.5.13 Selection of Energy. Equipment capable of generating radiation beams of different energies shall meet the following requirements:
6.5.13.1 Irradiation shall not be possible until a selection of energy has been made at the treatment control panel.
6.5.13.2 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.
6.5.13.3 The nominal energy value selected shall be displayed at the treatment control panel before and during irradiation.
6.5.13.4 For new equipment, an interlock system utilizing monitoring of the bending magnet current shall be provided to terminate irradiation if the energy of the electrons striking the target or electron window deviates by more than twenty percent (20%) or three megaelectron volt (3 MeV), whichever is smaller, from the selected nominal energy.
6.5.14 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:
6.5.14.1 Irradiation shall not be possible until a selection of stationary beam therapy or moving beam therapy has been made at the treatment control panel.
6.5.14.2 An interlock system shall be provided to ensure that the equipment can operate only in the mode which has been selected.
6.5.14.3 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.
6.5.14.4 The mode of operation shall be displayed at the treatment control panel.
6.5.14.5 An interlock system shall be provided to terminate irradiation if movement of the gantry:
6.5.14.5.1 Occurs during stationary beam therapy; or
6.5.14.5.2 Stops during moving beam therapy unless such stoppage is a preplanned function.
6.5.14.6 Moving beam therapy shall be controlled to obtain the selected relationships between incremental dose monitor units and incremental angle of movement:
6.5.14.6.1 An interlock system shall be provided to terminate irradiation if the number of dose monitor units delivered in any ten (10) degrees of arc differs by more than twenty percent (20%) from the selected value.
6.5.14.6.2 Where gantry angle terminates the irradiation in arc therapy, the dose monitor units shall differ by less than five percent (5%) from the value calculated from the absorbed dose per unit angle relationship.
6.5.14.7 Where the dose monitor system terminates the irradiation in moving beam therapy, the termination of irradiation shall be as required in RHB 6.5.8.
6.5.15 Absorbed Dose Rate. 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 in RHB 6.5.5 may form part of this system. In addition:
6.5.15.1 The dose monitor rate shall be displayed at the treatment control panel.
6.5.15.2 If the equipment can deliver under any conditions an absorbed dose rate at the nominal treatment distance more than twice the maximum value specified by the manufacturer for any machine parameter utilized, a device shall be provided which terminates irradiation when the absorbed dose rate exceeds a value twice the specified maximum. The dose rate at which the irradiation will be terminated shall be in a record maintained by the registrant.
6.5.16 Location of Virtual Source and Beam Orientation. The registrant shall determine, or obtain from the manufacturer, the location with reference to an accessible point on the radiation head of:
6.5.16.1 The x-ray target or the virtual source of x-rays; and
6.5.16.2 The electron window or the virtual source of electrons if the system has electron beam capabilities.
6.5.17 System Checking. Capabilities shall be provided so that all radiation safety interlocks can be checked for operation.
6.5.18 Facility and Shielding Requirements. In addition to RHB 6.2 of these rules, the following design requirements shall apply:
6.5.18.1 Protective Barriers. All protective barriers shall be fixed except for entrance doors or beam interceptors.
6.5.18.2 Control Panel. The control panel shall be located outside the treatment room.
6.5.18.3 Viewing Systems.
6.5.18.3.1 Windows, mirrors, closed-circuit television, or an equivalent 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 control panel.
6.5.18.3.2 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.
6.5.19 Aural Communications. Provision shall be made for continuous two-way aural communication between the patient and the operator at the control panel independent of the particle accelerator. However, where excessive noise levels or treatment requirements make aural communication impractical, other methods of communication shall be used. When this is the case, a description of the alternate method shall be submitted to and approved by the Department.
6.5.20 Room Entrances. Treatment room entrances shall be provided with warning lights in readily observable positions near the outside of all accessible doors to indicate when the useful beam is "on" and "off."
6.5.21 Entrance Interlocks. 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.

S.C. Code Regs. § 61-64.VI.RHB 6.5

Replaced and amended by State Register Volume 40, Issue No. 06, eff. 6/24/2016; State Register Volume 47, Issue No. 05, eff. 5/26/2023.