SECTION 252:410-11-74. Calibrations of systems of 1 MeV or more

(a)   Frequency. A system of 1 MeV or more must be calibrated before it is first used for irradiation of a patient and thereafter at least every 12 months and when any change occurs in the system which might significantly alter the calibration, spatial distribution, or other characteristics of the therapy beam.

(b)   Protocol and procedures. The calibration of systems of 1 MeV or more shall be performed using an established calibration protocol acceptable to DEQ. One acceptable calibration protocol is entitled, "AAPM's TG-51 Protocol for Clinical Reference Dosimetry of high-energy photon and electron beams.", Medical Physics 26 (9): 1847-1890, Sept. 1999. If another protocol is used, the person performing the calibration needs to record the name and methods used in the calibration report. Upon review of the report, DEQ may require a copy of the protocol for review and/or may require that calibration be performed under another protocol.

(c)   Performance. The calibration shall be performed under the direct supervision of a radiological physicist.

(d)   Dosimetry system. Full calibration radiation measurements of systems of 1 MeV or more shall be performed with a dosimetry system that has:

(1)   a calibration factor for cobalt-60 gamma rays traceable to a national standard;

(2)   been calibrated within the previous two years and after any servicing that may have affected its calibration;

(3)   been calibrated in such a fashion that an uncertainty can be stated for the radiation quantities monitored by the system; and

(4)   had constancy checks performed on the system as specified by a radiological physicist.

(e)   Precision. 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.

(f)   Outcome. The calibration of the therapy beam shall include but not be limited to:

(1)   verification that the therapeutic system is operating in compliance with the design specifications concerning the:

(A)   light localizer and back-pointer alignment with the isocenter when applicable,

(B)   variation in the axis of rotation for the table, gantry and jaw system, and

(C)   beam flatness and symmetry at the specified depth;

(2)   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 utilized with that therapy beam;

(3)   the uniformity of the radiation field to include symmetry and flatness;

(4)   dependency of beam output on gantry angle;

(5)   verification that existing isodose charts applying to the machine continue to be valid or are updated to existing machine conditions; and

(6)   verification of transmission and electron buildup factors for all accessories such as wedges, shadow trays attached to the radiation head to support auxiliary beam blocking material, and compensators.

[Source: Added at 17 Ok Reg 1136, eff 6-1-00; Amended at 29 Ok Reg 672, eff 7-1-12]