OAR 333-123-0025
Requirements for Therapeutic Radiation Machines

(1)

Grenz Ray. When the x-ray tube is operated at its maximum rated tube current for the maximum kV, the leakage air kerma rate must not exceed the value specified at the distance specified for that classification of therapeutic radiation machine.

(2)

For therapeutic radiation systems which operate at 5kV to 50 kV or are used for Grenz Ray application:

(a)

The leakage air kerma rate measured at any position 5 cm from the tube housing assembly must not exceed 1 mGy (100 mRad) in any 1 hour.

(b)

A timer with a display must be provided at the treatment control panel. The timer must have a pre-set time selector and an elapsed time or time remaining indicator. The timer must:

(A)

Activate with an indication of BEAM-ON and retain it’s reading after irradiation is interrupted or terminated. After irradiation is terminated and before irradiation can be reinitiated, the timer must be reset; and

(B)

Terminate irradiation when a pre-selected time has elapsed; and

(C)

Permit accurate pre-setting and determination of exposure times as short as 1 second: and

(D)

Must not permit an exposure if set at zero; and

(E)

Be accurate to within 1 percent of the selected value or 1 second, whichever is greater.

(c)

The control panel, in addition to the displays required by other provisions in these rules, must have:

(A)

An indication of whether x-rays are being produced; and

(B)

A means for indicating x-ray tube potential and current; and

(C)

A means for terminating an exposure at any time; and

(D)

A locking device which will prevent unauthorized use of the therapeutic radiation machine; or

(d)

There must be a means of determining the central axis target-to-skin distance (TSD) within 1 cm and of reproducing this measurement to within 2 mm thereafter.

(3)

Therapeutic Radiation Machines Operating At >50 Kv And <1 Mev. The leakage air kerma rate measured at a distance of 1 m from the target in any direction may not exceed 1 cGy (1 rad) in any 1 hour. This air kerma rate measurement may be averaged over areas no larger than 100 square centimeters. In addition, the air kerma rate at a distance of 5 cm from the surface of the tube housing assembly must not exceed 30 cGy (30 rad) per hour.

(a)

For each therapeutic radiation machine, the registrant must determine, or obtain from the manufacturer, the leakage radiation existing at the positions specified in this rule for the specified operating conditions. Records on leakage radiation measurements must be maintained at the installation for inspection by the Authority.

(b)

Permanent Beam Limiting Devices. Permanent diaphragms or cones used for limiting the useful beam must provide at least the same degree of attenuation as required for the tube housing assembly.

(c)

Adjustable or Removable Beam Limiting Devices. Adjustable or removable beam limiting devices, diaphragms, cones or blocks must not transmit more than 5 percent of the useful beam for the most penetrating beam used.

(d)

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

(e)

Filter System. The filter system must be so designed that:

(A)

Filters cannot be accidentally displaced at any possible tube orientation; and

(B)

For equipment installed after January 30, 2007, an interlock system prevents irradiation if the proper filter is not in place; and

(C)

The air kerma rate escaping from the filter slot does not exceed 1 cGy (1 rad) per hour at 1 m under any operating conditions; and

(D)

Each filter is be labeled to indicate the material it is constructed of and its thickness.

(f)

Tube Immobilization. The x-ray tube must be so mounted that it cannot accidentally turn or slide with respect to the housing aperture and the tube housing assembly must be capable of being immobilized for stationary portal treatments.

(g)

Source Marking. The tube housing assembly must be so marked that it is possible to determine the location of the source to within 5 mm, and such marking must be readily accessible for use during calibration procedures.

(h)

Timer. A suitable irradiation control device must be provided to terminate the irradiation after a pre-set time interval.

(i)

A timer with a display must be provided at the treatment control panel and the timer must:

(A)

Have a pre-set time selector and an elapsed time or time remaining indicator; and

(B)

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 must be necessary to reset the elapsed time indicator; and

(C)

Terminate irradiation when a pre-selected time has elapsed, if any dose monitoring system present has not previously terminated irradiation; and

(D)

Permit accurate pre-setting and determination of exposure times as short as 1 second; and

(E)

Not permit an exposure if set at zero; and

(F)

Not activate until the shutter is opened when irradiation is controlled by a shutter mechanism unless calibration includes a timer error correction to compensate for mechanical lag; and

(G)

Timer must be accurate to within 1 percent of the selected value or 1 second, whichever is greater.

(j)

Control Panel Functions. The control panel, in addition to the displays required by other provisions in this rule, must have:

(A)

An indication of whether electrical power is available at the control panel and if activation of the x-ray tube is possible; and

(B)

An indication of whether x-rays are being produced; and

(C)

A means for indicating x-ray tube potential and current; and

(D)

The means for terminating an exposure at any time; and

(E)

A locking device which will prevent unauthorized use of the therapeutic radiation machine; and

(F)

For therapeutic radiation machines manufactured after January 30, 2007, a positive display of specific filter(s) in the beam.

(k)

Multiple Tubes. When a control panel may energize more than one x-ray tube:

(A)

It must be possible to activate only one x-ray tube at any time; and

(B)

There must be an indication at the control panel identifying which x-ray tube is activated; and

(C)

There must be an indication at the tube housing assembly when that tube is energized.

(l)

Target-To-Skin Distance (TSD). There must be a means of determining the central axis TSD to within 1 cm and of reproducing this measurement to within 2 mm thereafter.

(m)

Shutters. Unless it is possible to bring the x-ray output to the prescribed exposure parameters within 5 seconds (sec) after the x-ray ON switch is energized, the beam must be attenuated by a shutter having a lead equivalency not less than that of the tube housing assembly. In addition, after the unit is at operating parameters, the shutter must be controlled by the operator from the control panel. An indication of shutter position must appear at the control panel.

(4)

Photon And Electron Beam Therapeutic Radiation Machines 1 Mv And Above.

(a)

Leakage Radiation Outside The Maximum Useful Beam In Photon And Electron Modes. 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 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), must not exceed a maximum of 0.2 percent and an average of 0.1 percent of the absorbed dose on the central axis of the beam at the nominal treatment distance. Measurements must be averaged over an area not exceeding 100 square centimeters at a minimum of 16 points uniformly distributed in the plane; and

(b)

Except for the area defined in section (3)(a) of this rule, the absorbed dose due to leakage radiation (excluding neutrons) at 1 m from the electron path between the electron source and the target or electron window, must not exceed 0.5 percent of the absorbed dose on the central axis of the beam at the nominal treatment distance. Measurements must be averaged over an area not exceeding 100 square centimeters; and

(c)

For equipment manufactured after January 30, 2007, the neutron absorbed dose outside the useful beam must be in compliance with International Electrotechnical Commission (IEC) Document 60601-2-1 dated June 30, 1998; and

(d)

For each therapeutic radiation machine, the registrant must determine, or obtain from the manufacturer, the leakage radiation existing at the positions specified in sections (3)(a) through (c) of this rule for the specified operating conditions. Records on leakage radiation measurements must be maintained at the installation for inspection by the Authority.

(e)

Leakage Radiation Through Beam Limiting Devices. The attenuation of leakage radiation through a beam-limiting device must meet the following requirements:

(A)

Photon Radiation. All adjustable or interchangeable beam limiting devices must attenuate the useful beam such that at the nominal treatment distance and the maximum absorbed dose anywhere in the area shielded by the beam limiting device(s) must not exceed 2 percent (or the amount specified by the manufacturer), of the maximum absorbed dose on the central axis of the useful beam measured in a 100 square centimeters radiation field, or maximum available field size if less than 100 square centimeters; and

(B)

Electron Radiation. All adjustable or interchangeable electron applicators must 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 must not exceed: and

(C)

A maximum of 2 percent and average of 0.5 percent of the absorbed dose on the central axis of the useful beam at the nominal treatment distance. This limit must apply beyond a line 7 cm outside the periphery of the useful beam; and

(D)

A maximum of 10 percent of the absorbed dose on the central axis of the useful beam at the nominal treatment distance. This limit must apply beyond a line 2 cm outside the periphery of the useful beam.

(f)

Measurement Of Leakage Radiation. Measurement of leakage radiation shall be done after installation and before clinical usage and must include:

(A)

Photon Radiation. Measurements of leakage radiation through the beam limiting devices must be made with the beam limiting devices closed and any residual aperture blocked by at least 2 tenth value layers of suitable absorbing material. In the case of overlapping beam-limiting devices, the leakage radiation through each set must be measured independently at the depth of maximum dose. Measurements must be made using a radiation detector of area not exceeding 10 square centimeters; and

(B)

Electron Radiation. Measurements of leakage radiation through the electron applicators must be made with the electron beam directed into the air and using a radiation detector of area up to but not exceeding 1 square centimeters suitably protected against radiation, which has been scattered from material beyond the radiation detector. Measurements must be made using 1 cm of tissue/water equivalent material for build up.

(g)

Filters/Wedges. Each wedge filter that is removable from the system must be clearly marked with an identification number. For removable wedge filters, the nominal wedge angle must 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 must be re-measured; and

(A)

For equipment manufactured after January 30, 2007 which utilizes wedge filters, interchangeable field flattening filters, or interchangeable beam scattering foils; and

(B)

Irradiation must 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; and

(C)

An interlock system must be provided to prevent irradiation if the wedge, flattening filter or scattering foil selected is not in the correct position; and

(D)

A display must be provided at the treatment control panel showing the wedge or beam modifying filter(s) in use; and

(E)

An interlock must be provided to prevent irradiation if any filter and/or beam scattering foil selection operation does not agree with the energy/mode selected by the operator at the control panel.

(h)

Stray Radiation in the Useful Beam. For equipment manufactured after January 30, 2007, the registrant must determine during acceptance testing, or obtain from the manufacturer, stray x-ray radiation, and absorbed dose at the surface and neutron data. This data must be sufficient to ensure compliance with International Electrotechnical Commission (IEC) Document 60601-2-1 dated June 30, 1998.

(i)

Beam Monitors. All therapeutic radiation machines subject to these rules must be provided with redundant beam monitoring systems. The sensors for these systems must be fixed in the useful beam during treatment to indicate the dose monitor unit rate.

(j)

Equipment manufactured after January 30, 2007 must be provided with at least 2 independently powered integrating dose meters. Alternatively, common elements may be used if the production of radiation is terminated upon failure of any common element.

(k)

Equipment manufactured on or before January 30, 2007 must be provided with at least 1 radiation detector. This detector must be incorporated into a useful beam monitoring system; and

(l)

The detector and the system into which that detector is incorporated must meet the following requirements:

(A)

Each detector must form part of a beam monitoring system from whose readings in dose monitor units the absorbed dose at a reference point can be calculated; and

(B)

Each beam monitoring system must be capable of independently monitoring, interrupting, and terminating irradiation; and

(m)

For equipment manufactured after January 30, 2007, the design of the beam monitoring systems must ensure that the:

(A)

Malfunctioning of one beam monitoring system must not affect the correct functioning of the other system(s); and

(B)

Failure of either system must terminate irradiation or prevent the initiation of radiation.

(n)

Each beam monitoring system must have a legible display at the treatment control panel. For equipment manufactured after January 30, 2007, each display must:

(A)

Maintain a display of the patient treatment parameters until intentionally reset;

(B)

Have only one scale and no electrical or mechanical scale multiplying factors;

(C)

Utilize a design such that increasing dose is displayed by increasing numbers; and

(D)

In the event of power failure the beam monitoring information required in section (3)(k) of this rule must be displayed at the control panel, and at the time of failure, must be retrievable in at least one system for a 20 minute period of time.

(o)

Beam Symmetry. A bent-beam linear accelerator with beam flattening filter(s) subject to this rule must be provided with auxiliary device(s) to monitor beam symmetry;

(A)

The integrating dose meters referenced in section (3)(k) of this rule must be able to detect field asymmetry greater than 10 percent; and

(B)

The integrating dose meters referenced in section (3)(k) of this rule must be configured to terminate irradiation if the specifications in section (3)(o)(A) of this rule cannot be maintained.

(p)

Selection And Display Of Dose Monitor Units. Irradiation must not be possible until a new selection of a number of dose monitor units has been made at the treatment control panel; and

(A)

The pre-selected number of dose monitor units must be displayed at the treatment control panel until reset manually for the next irradiation; and

(B)

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

(C)

For equipment manufactured after January 30, 2007, after termination of irradiation, it must be necessary for the operator to reset the pre-selected dose monitor units before irradiation can be initiated.

(q)

Air Kerma Rate/Absorbed Dose Rate. For equipment manufactured after January 30, 2007, a system must be provided from which readings the air kerma rate or absorbed dose rate at a reference point can be calculated. [The radiation detectors specified in section (3)(k) of this rule may form part of this system]. In addition:

(A)

The dose monitor unit rate must be displayed at the treatment control panel; and

(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 must 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 irradiation is terminated at must be maintained in a record by the registrant.

(r)

If the equipment can deliver, under any fault condition(s), an air kerma rate or absorbed dose rate at the nominal treatment distance of more than 10 times the maximum value specified by the manufacturer:

(A)

A device must 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

(B)

Terminate irradiation if the excess absorbed dose at the nominal treatment distance exceeds 4 Gy (400 rad); and

(C)

For each therapeutic radiation machine, the registrant must determine, or obtain from the manufacturer, the maximum value(s) specified in section (3)(p) of this rule for the specified operating conditions. Records of these maximum value(s) must be maintained at the facility for 5 years or until inspected by the Authority.

(s)

Termination or Interruption of Irradiation by the Beam Monitoring System or Systems During Stationary Beam Radiation Therapy. Each primary system must terminate irradiation when the pre-selected number of dose monitor units has been detected by the system; and

(A)

If the original design of the equipment included a secondary dose monitoring system, that system must be capable of terminating irradiation when not more than 15 percent or 40 dose monitor units above the pre-selected number of dose monitor units set at the control panel has been detected by the secondary dose monitoring system; and

(B)

For equipment manufactured after January 30, 2007, an indicator on the control panel must show which monitoring system has terminated irradiation; and

(C)

It must be possible to terminate irradiation and equipment movement or go from an interruption condition to termination condition at any time from the operator’s protected position at the treatment control panel; and

(D)

Interruption Of Radiation. If a therapeutic radiation machine has an interrupt mode, it must be possible to interrupt irradiation and equipment movements at any time from the treatment control panel. Following an interruption it must be possible to restart irradiation by operator action without any reselection of operating conditions. If any change is made of a pre-selected value during an interruption, irradiation and equipment movements must be automatically terminated.

(t)

Timer. A suitable irradiation control device must be provided to terminate the irradiation after a pre-set time interval; and

(A)

The timer must be provided with a display at the treatment control panel. The timer must have a pre-set time selector and an elapsed time indicator; and

(B)

The timer must 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 must be necessary to reset the elapsed time indicator; and

(C)

The timer must terminate irradiation when a pre-selected time has elapsed, if the dose monitoring systems have not previously terminated irradiation.

(u)

Selection Of Radiation Type. Equipment capable of both x-ray therapy and electron therapy must meet the following additional requirements:

(A)

Irradiation must not be possible until a selection of radiation type (x-rays or electrons) has been made at the treatment control panel and the patient’s chart has been checked to verify that the selected radiation type is the one specified in the chart; and

(B)

The radiation type selected must be displayed at the treatment control panel before and during irradiation.
(v)
Interlocks must be provided to:

(A)

Ensure that the equipment can principally emit only the radiation type that has been selected; and

(B)

Prevent irradiation with x-rays, except to obtain an image, when electron applicators are fitted; and

(C)

Prevent irradiation with electrons when accessories specific for x-ray therapy are fitted; and

(D)

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.

(w)

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

(A)

Irradiation must not be possible until a selection of the appropriate energy has been made at the treatment control panel and the patient’s chart has been checked to verify that the selected energy is that which is specified in the patient’s chart; and

(B)

The nominal energy value selected must be displayed at the treatment control panel until reset manually for the next irradiation. After termination of irradiation, it must be necessary to reset the nominal energy value selected before subsequent treatment can be initiated; and

(C)

Irradiation must not be possible until the appropriate flattening filter or scattering foil for the selected energy is in its proper location and the patient’s chart has been checked to verify that the flattening filter or scattering foil is that which is specified in the chart; and

(D)

For equipment manufactured after January 30, 2007, the selection of energy must comply with International Electrotechnical Commission (IEC) Document 60601-2-1 dated June 30, 1998.
(x)
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 must meet the following requirements:

(A)

Irradiation must not be possible until a selection of stationary beam radiation therapy or moving beam radiation therapy has been made at the treatment control panel and the patient’s chart has been checked to verify that the selection of stationary or moving beam radiation is that which is specified in the patient’s chart; and

(B)

The mode of operation must be displayed at the treatment control panel and interlocks must be provided to:

(C)

Ensure that the equipment can operate only in the mode that has been selected; and

(D)

Prevent irradiation if any selected parameter in the treatment room does not agree with the selected parameter at the treatment control panel.

(y)

Moving beam radiation therapy must be controlled to obtain the selected relationships between incremental dose monitor units and incremental movement. For equipment manufactured after January 30, 2007:

(A)

An interlock system must be provided to terminate irradiation if the number of dose monitor units delivered in any 10° of rotation or 1 cm of linear motion differs by more than 20 percent from the selected value; and

(B)

Where incident radiation beam angle terminates the irradiation in moving beam radiation therapy, the dose monitor units delivered must differ by less than 5 percent from the dose monitor unit value selected; and

(C)

An interlock must be provided to prevent motion of more than 5° or 1 cm beyond the selected limits during moving beam radiation therapy; and

(D)

An interlock must 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 moving beam radiation therapy; and

(E)

Moving beam radiation therapy must be controlled with both primary position sensors and secondary position sensors to obtain the selected relationships between incremental dose monitor units and incremental movement; and

(F)

Where the beam monitor system terminates the irradiation in moving beam radiation therapy, the termination of irradiation must be as required by section (3)(y)(A) of this rule; and

(G)

An interlock system must be provided to terminate irradiation if movement; and

(H)

Interruption occurs during stationary beam radiation therapy; or

(I)

Treatment does not start or stop during moving beam radiation therapy unless such stoppage is a pre-planned function.

Source: Rule 333-123-0025 — Requirements for Therapeutic Radiation Machines, .

333‑123‑0001
Purpose and Scope 333‑123‑0005
Definitions 333‑123‑0010
General Requirements, Operating Procedures, Surveys, Dosimetry, and Instrument Calibration for Facilities Using Therapeutic Radiation Machines 333‑123‑0015
Training and Qualification Requirements for Individuals in the External Beam Radiation Therapy Area 333‑123‑0020
Reports and Notifications of Unplanned Medical Treatment 333‑123‑0025
Requirements for Therapeutic Radiation Machines 333‑123‑0030
Facility Design Requirements for Therapeutic Radiation Machines 333‑123‑0035
Calibration, Acceptance Testing and Commissioning of Therapeutic Radiation Machines 333‑123‑0040
Quality Assurance And Safety Checks 333‑123‑0045
Quality Assurance Program 333‑123‑0050
Qualified Medical Physicist Support in Facilities Having Therapeutic Radiation Machines with Energies of 1 Mv and Above 333‑123‑0055
Electronic Brachytherapy 333‑123‑0060
Facility Design Requirements for Electronic Brachytherapy Devices 333‑123‑0065
Electrical Safety for Electronic Brachytherapy Devices 333‑123‑0070
Control Panel Functions 333‑123‑0075
Timer 333‑123‑0080
Medical Physicist 333‑123‑0085
Operating Procedures 333‑123‑0090
Safety Precautions for Electronic Brachytherapy Devices 333‑123‑0095
Electronic Brachytherapy Source Calibration Measurements 333‑123‑0100
Periodic and Day-of-Use Quality Assurance Checks for Electronic Brachytherapy Devices 333‑123‑0105
Therapy Related Computer Systems 333‑123‑0110
Training 333‑123‑0115
Mobile Electronic Brachytherapy Service 333‑123‑0120
Superficial Electronic Brachytherapy 333‑123‑0125
Superficial Electronic Brachytherapy Personnel Requirements 333‑123‑0130
Superficial Electronic Brachytherapy: Refresher Training 333‑123‑0135
Superficial Electronic Brachytherapy: Activation of the Superficial Electronic Brachytherapy X-ray Tube 333‑123‑0140
Superficial Electronic Brachytherapy: Facility Design Requirements 333‑123‑0145
Superficial Electronic Brachytherapy: Calibration, Acceptance Testing and Commissioning 333‑123‑0150
Superficial Electronic Brachytherapy: Quality Assurance Checks 333‑123‑0155
Superficial Electronic Brachytherapy: Operating Procedures
Last Updated

Jun. 8, 2021

Rule 333-123-0025’s source at