180 Neb. Admin. Code, ch. 20, § 006

Current through September 17, 2024

Section 180-20-006 - THERAPEUTIC RADIATION MACHINES OF LESS THAN 500 KILOVOLTS (kV)

The requirements for therapeutic radiation machines of less than 500 kilovolts (kV) are as follows.

006.01LEAKAGE RADIATION. When the x-ray tube is operated at its maximum rated tube current for the maximum kilovolts (kV), the leakage air kerma rate must not exceed the value specified at the distance specified for that classification of therapeutic radiation machine as follows.

006.01(A)0-50 KILOVOLT (KV) SYSTEMS. The leakage air kerma rate measured at any position 5 centimeters from the tube housing assembly must not exceed 1 milligray (mGy) or 100 millirad (mrad) in any one hour.

006.01(B)GREATER THAN 50 AND LESS THAN 500 KILOVOLT (KV) SYSTEMS. The leakage air kerma rate measured at a distance of 1 meter from the target in any direction must not exceed 1 centigray (cGy) or 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 centimeters from the surface of the tube housing assembly must not exceed 30 centigray (cGy) or 30 rad per hour.

006.01(C)DETERMINATION OF LEAKAGE RADIATION. For each therapeutic radiation machine, the registrant must determine, or obtain from the manufacturer, the leakage radiation existing at the positions specified in 180 NAC 20-006.01(A) and 20-006.01(B) for the specified operating conditions. Records on leakage radiation measurements must be maintained at the installation for inspection by the Department.

006.02PERMANENT 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.

006.03ADJUSTABLE OR REMOVABLE BEAM LIMITING DEVICES. Adjustable or removable beam limiting devices must:

(A) Not transmit more than 5 percent of the useful beam for the most penetrating beam used for all adjustable or removable beam limiting devices, diaphragms, cones or blocks; and

(B) Indicate the position and shape of the radiation field by a light beam when adjustable beam limiting devices are used.

006.04FILTER SYSTEM. The filter system must be marked so that:

(A) Filters cannot be accidentally displaced at any possible tube orientation;

(B) An interlock system prevents irradiation if the proper filter is not in place for equipment installed after July 11, 2009;

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

(D) Each filter is marked regarding its material of construction and its thickness.

006.05TUBE IMMOBILIZATION. The x-ray tube and housing must be immobilized as follows.

006.05(A)X-RAY TUBE. The x-ray tube must be mounted so it cannot accidentally turn or slide with respect to the housing aperture.

006.05(B)TUBE HOUSING ASSEMBLY. The tube housing assembly must be capable of being immobilized for stationary portal treatments.

006.06SOURCE MARKING. The tube housing assembly must be marked so that it is possible to determine the location of the source to within 5 millimeters. That marking must be readily accessible for use during calibration procedures.

006.07BEAM BLOCK. Contact therapy tube housing assemblies must have a removable shield of material, equivalent in attenuation to 0.5 millimeters of lead at 100 kilovolts (kV) that can be positioned over the entire useful beam exit port during periods when the beam is not in use.

006.08TIMER. A suitable irradiation control device must be provided to terminate the irradiation after a pre-set time interval. The timer must:

(A) Be provided at the treatment control panel. The timer must have a display and must have a preset time selector and an elapsed time or time remaining indicator;

(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;

(C) The timer must terminate irradiation when a pre-selected time has elapsed, if any dose monitoring system present has not previously terminated irradiation;

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

(E) Not permit an exposure if the timer is set at zero;

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

006.09CONTROL PANEL FUNCTIONS. The control panel, in addition to the displays required by other provisions in 180 NAC 20-006, 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;

(B) An indication of whether x-rays are being produced;

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

(D) A means for terminating an exposure at any time;

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

(F) A positive display of specific filter or filters in the beam for therapeutic radiation machines installed after July 11, 2009.

006.10MULTIPLE TUBES. When a control panel can energize more than one x-ray tube:

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

(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.

006.11TARGET TO SKIN DISTANCE (TSD). There must be a means of determining the central axis target to skin distance (TSD) to within 1 centimeter and to reproduce this measurement to within 2 millimeters from then on.

006.12SHUTTERS. Unless it is possible to bring the x-ray output to the prescribed exposure parameters within 5 seconds 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.

006.13LOW FILTRATION X-RAY TUBES. Each therapeutic radiation machine equipped with a beryllium or other low filtration window must have the tube housing assembly clearly labeled and must be provided with a permanent warning device on the control panel that is activated when no additional filtration is present, to indicate that the dose rate is very high.

006.14FACILITY DESIGN REQUIREMENTS FOR THERAPEUTIC RADIATION MACHINES CAPABLE OF OPERATING IN THE RANGE 50 KILOVOLTS (KV) TO 500 KILOVOLTS (KV). In addition to shielding adequate to meet requirements of 180 NAC 20-009, the treatment room must meet the following design requirements.

006.14(A)AURAL COMMUNICATION. Provision must be made for continuous two way aural communication between the patient and the operator at the control panel.

006.14(B)VIEWING SYSTEMS. Provision must be made to permit continuous observation of the patient during irradiation. The viewing system must be located so the operator can observe the patient from the control panel. The therapeutic radiation machine must not be used for patient irradiation unless at least one viewing system is operational.

006.15ADDITIONAL REQUIREMENTS. Treatment rooms that contain a therapeutic radiation machine capable of operating above 150 kilovolts (kV) must meet the following additional requirements.

006.15(A)FIXED PROTECTIVE BARRIERS. All protective barriers must be fixed except for entrance doors or beam interceptors.

006.15(B)CONTROL PANEL. The control panel must be located outside the treatment room or in a totally enclosed booth, which has a ceiling, inside the room.

006.15(C)INTERLOCKS. Interlocks must be provided so all entrance doors, including doors to any interior booths, must be closed before treatment can be initiated or continued. If the radiation beam is interrupted by any door opening, it must not be possible to restore the machine to operation without closing the door and reinitiating irradiation by manual action at the control panel.

006.15(D)DOOR. When any door referred to in 180 NAC 20-006.15, item (C) is opened while the x-ray tube is activated, the air kerma rate at a distance of 1 meter from the source must be reduced to less than 1 milligray (mGy) or 100 millirad (mrad) per hour.

006.16FULL CALIBRATION MEASUREMENTS. Full calibration measurements must be performed as follows.

006.16(A)FREQUENCY. Full calibration of a therapeutic radiation machine subject to 180 NAC 20-006 must be performed by, or under the direct supervision of, a radiological medical physicist:

(i) Before the first medical use following installation or reinstallation of the therapeutic radiation machine;

(ii) At intervals not exceeding one year; and

(iii) Before medical use under the following conditions:

(1) 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 reconciled; and

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

(iv) Apart from the requirements of 180 NAC 20-006.16(A)(iii):

(1) Full calibration of therapeutic radiation machines with multi energy capabilities is required only for those modes or energies that are not within their acceptable range; and

(2) If the repair, replacement or modification does not affect all energies, full calibration must be performed on the affected energy that is in most frequent clinical use at the facility. The remaining energies may be validated with quality assurance check procedures compared to the criteria in 180 NAC 20-006.16(A), item (iii)(1).

006.16(B)REQUIRED MEASUREMENTS. To satisfy the requirement of 180 NAC 20-006.16(A), full calibration must include all measurements recommended for annual calibration by the National Council on Radiation Protection and Measurements (NCRP) Report 69, "Dosimetry of X-ray and Gamma Ray Beams for Radiation Therapy in the Energy Range 10 keV to 50 MeV" (1981). This document is available for viewing at the Department of Health and Human Services, Division of Public Health, Office of Radiological Health, 301 Centennial Mall South, 3rd Floor, Lincoln, Nebraska 68509.

006.16(C)CALIBRATION RECORDS. The registrant must maintain a record of each calibration for the duration of the registration. The record must include:

(i) The date of the calibration;

(ii) The manufacturer's name;

(iii) Model number and serial number for the therapeutic radiation machine if applicable;

(iv) The model numbers and serial numbers of the instruments used to calibrate the therapeutic radiation machine; and

(v) The signature of the radiological medical physicist responsible for performing the calibration.

006.17PERIODIC QUALITY ASSURANCE CHECKS. The requirements for periodic quality assurance checks are as follows.

006.17(A)APPLICABILITY. Periodic quality assurance checks must be performed on therapeutic radiation machines subject to 180 NAC 20-006 that are capable of operation at greater than or equal to 50 kilovolts (kV).

006.17(B)QUALITY ASSURANCE CHECK CONTENT. To satisfy the requirements of 180 NAC 20-006.17(A), quality assurance checks must meet the following requirements:

(i) Quality assurance checks must be performed according to written procedures established by the radiological medical physicist; and

(ii) The quality assurance check procedures must specify the frequency the tests or measurements are to be performed. The quality assurance check procedures must specify that the quality assurance check will be performed during the calibration specified in 180 NAC 20-006.16(A). The acceptable tolerance for each parameter measured in the quality assurance check, when compared to the value for that parameter established in the calibration specified in 180 NAC 20-006.16(A), must be specified.

006.17(C)PARAMETER EXCEEDING TOLERANCE. The cause for a parameter exceeding a tolerance set by the radiological medical physicist must be investigated and corrected before the system is used for patient irradiation.

006.17(D)CHANGE IN OPERATING CHARACTERISTICS. Whenever a quality assurance check indicates a significant change in the operating characteristics of a system, as specified in the radiological medical physicist's quality assurance check procedures, the system must be recalibrated as required in 180 NAC 20-006.16(A).

006.17(E)DOSIMETRY SYSTEM. The registrant must use the dosimetry system described in 180 NAC 20-004.03(B), to make the quality assurance check required in 180 NAC 20-006.17(B).

006.17(F)RADIOLOGICAL MEDICAL PHYSICIST REVIEW. The registrant must have the radiological medical physicist review and sign the results of each radiation output quality assurance check within 1 month of the date that the check was performed.

006.17(G)REQUIRED INTERVALS. The registrant must ensure that quality assurance checks of therapeutic radiation machines subject to 180 NAC 20-006 are performed at intervals not to exceed 1 month.

006.17(H)PROHIBITION. Despite the requirements of 180 NAC 20-006.17(F) and (G), the registrant must ensure that no therapeutic radiation machine is used to administer radiation to humans unless the quality assurance checks required by 180 NAC 20-006.17(F) and (G) have been performed within the 30 day period immediately prior to that administration.

006.17(I)PROPER OPERATION. To satisfy the requirement of 180 NAC 20-006.17(B), safety quality assurance checks must ensure proper operation of:

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

(ii) The "BEAM-ON" and termination switches;

(iii) Beam condition indicator lights on the access door or doors, control console, and in the radiation therapy room;

(iv) Viewing systems; and

(v) If applicable, electrically operated treatment room doors from inside and outside the treatment room.

006.17(J)RECORD MAINTENANCE. The registrant must maintain a record of each quality assurance check required by 180 NAC 20-006.17(A) and (G) for three years. The record must include:

(i) The date of the quality assurance check;

(ii) The manufacturer's name, model number, and serial number of the therapeutic radiation machine;

(iii) The manufacture's name, model number and serial number for the instrument or instruments used to measure the radiation output of the therapeutic radiation machine; and

(iv) The signature of the individual who performed the periodic quality assurance check.

006.18OPERATING PROCEDURES. The requirements for operation procedures are as follows.

006.18(A)PROHIBITION. The therapeutic radiation machine must not be used for irradiation of patients unless the requirements of 180 NAC 20-006.16 and 20-006.17 have been met.

006.18(B)SECURED IF UNATTENDED. Therapeutic radiation machines must not be left unattended unless secured according to 180 NAC 20-006.09, item(E).

006.18(C)MECHANICAL SUPPORT OR RESTRAINT. When a patient must be held in position for radiation therapy, mechanical supporting or restraining devices must be used.

006.18(D)HOLDER PROTECTION. The tube housing assembly must not be held by an individual during operation unless the assembly is designed to require such holding and the peak tube potential of the system does not exceed 50 kilovolts (kV). In those cases, the holder must wear protective gloves and a protective apron of not less than 0.5 millimeters lead equivalency at 100 kilovolts (kV).

006.18(E)OPERATING AND EMERGENCY PROCEDURES. A copy of the current operating and emergency procedures must be maintained at the therapeutic radiation machine control console.

006.18(F)INDIVIDUALS OTHER THAN THE PATIENT. No individual other than the patient must be in the treatment room during exposures from therapeutic radiation machines operating above 150 kilovolts (kV). At energies less than or equal to 150 kilovolts (kV), any individual, other than the patient, in the treatment room must be protected by a barrier sufficient to meet the requirements of 180 NAC 4-005.

180 Neb. Admin. Code, ch. 20, § 006

Amended effective 11/21/2020