§ 175.64 Therapeutic Radiation Machines of less than 500 kV.
RCNY § 175.64
This section applies to photon therapy systems not capable of operating at 500kV and above, and to electron therapy systems not capable of operating at 500 keV and above. The requirements of this section do not apply to electronic brachytherapy devices.
(a)Leakage radiation. 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, as follows: (1) for 5-50 kV Systems, the leakage air kerma rate measured at any position 5 centimeters from the tube housing assembly must not exceed 1 mGy (100 mrad) in any one hour.
(2)for >50 and <500 kV Systems, the leakage air kerma rate measured at a distance of 1 meter from the target in any direction must 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 (100 cm 2 ). In addition, the air kerma rate at a distance of 5 centimeters from the surface of the tube housing assembly must not exceed 30 cGy (30 rad) per hour.
(3)For each therapeutic radiation machine, the registrant must determine, or obtain from the manufacturer, the leakage radiation existing at the positions specified in paragraphs (1) and (2) of this subdivision for the specified operating conditions. Records on leakage radiation measurements must be maintained at the installation for inspection by the Department.
(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.
(1)All 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; (2) When adjustable beam limiting devices are used, the position and shape of the radiation field must be indicated by a light beam.
(d)Filter system. The filter system must be so designed that: (1) filters cannot be accidentally displaced at any possible tube orientation; (2) for equipment installed after August 1, 1994, an interlock system prevents irradiation if the proper filter is not in place; (3) the air kerma rate escaping from the filter slot must not exceed 1 cGy (1 rad) per hour at 1 meter under any operating conditions; and (4) each filter must be marked as to its material of construction and its thickness.
(e)Tube immobilization.
(f)Source marking. The tube housing assembly must be so marked that it is possible to determine the location of the source to within 5 millimeters and such marking must be readily accessible for use during calibration procedures.
(g)Beam block. Contact therapy tube housing assemblies must have a removable shield of material, equivalent in attenuation to 0.5 millimeters of lead at 100 kV, which can be positioned over the entire useful beam exit port during periods when the beam is not in use.
(h)Timer. A suitable irradiation control device must be provided to terminate the irradiation after a pre-set time interval.
(i)Control panel functions. The control panel, in addition to the displays required by other provisions in this section, must have: (1) an indication of whether electrical power is available at the control panel and if activation of the x-ray tube is possible; (2) an indication of whether x-rays are being produced; (3) a means for indicating x-ray tube potential and current; (4) the means for terminating an exposure at any time; (5) a locking device which will prevent unauthorized use of the therapeutic radiation machine; and (6) for therapeutic radiation machines installed after August 1, 1994, a positive display of specific filters in the beam.
(j)Multiple tubes. When a control panel may energize more than one x-ray tube: (1) it must be possible to activate only one x-ray tube at any time; (2) there must be an indication at the control panel identifying which x-ray tube is activated; and (3) there must be an indication at the tube housing assembly when that tube is energized.
(k)Target-to-Skin Distance (TSD). There must be a means of determining the central axis TSD to within 1 centimeter and of reproducing this measurement to within 2 millimeters thereafter.
(l)Shutters. 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.
(m)Low filtration x-ray tubes. Each therapeutic radiation machine equipped with a beryllium or other low-filtration window must be clearly labeled as such upon the tube housing assembly 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.
(n)Facility design requirements for therapeutic radiation machines capable of operating in the range 50 kV to 500 kV. In addition to shielding adequate to meet the requirements of 24 RCNY Health Code § 175.67, the treatment room must meet the following design requirements: (1) Aural communication. Provision must be made for continuous two-way aural communication between the patient and the operator at the control panel; (2) Viewing systems. Provision must be made to permit continuous observation of the patient during irradiation and the viewing system must be so located that 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.
(o)Additional requirements. Treatment rooms that contain a therapeutic radiation machine capable of operating above 150 kV must meet the following additional requirements: (1) all protective barriers must be fixed except for entrance doors or beam interceptors; (2) the control panel must be located outside the treatment room or in a totally enclosed booth, which has a ceiling, inside the room; (3) interlocks must be provided such that 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; and (4) when any door referred to in paragraph (3) of this subdivision 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 mGy (100 mrad) per hour.
(p)Full calibration measurements.
(iv)Notwithstanding the requirements of subparagraphs (i) – (iii) of this paragraph: (A) 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 (B) 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 against the criteria in subparagraph (iii) of this paragraph.
(q)Periodic quality assurance checks.
(10)The registrant must maintain a record of each quality assurance check required by paragraphs (1) and (7) of this subdivision for 3 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 manufacturer's name, model number and serial number for the instrument 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 (r) Operating procedures.
(4)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 kV. In such cases, the holder must wear protective gloves and apron of not less than 0.25 millimeters lead equivalency at 100 kV.
(5)A copy of the current operating and emergency procedures must be maintained at the therapeutic radiation machine control console.
(6)No individual other than the patient shall be in the treatment room during exposures from therapeutic radiation machines operating above 150 kV. At energies less than or equal to 150 kV, any individual, other than the patient, in the treatment room must be protected by a barrier sufficient to meet the requirements of this Article.
(s)Possession of survey instruments. Each facility location authorized to use a therapeutic radiation machine in accordance with this section must possess appropriately calibrated portable monitoring equipment. At a minimum, such equipment must include a portable radiation measurement survey instrument capable of measuring dose rates over the range 10 µSv (1 mrem) per hour to 10 mSv (1,000 mrem) per hour. The survey instrument must be operable and calibrated in accordance with 24 RCNY Health Code § 175.66. (Added City Record 4/24/2019, eff. 5/24/2019)
