§ 228.75. Calibrations.
(a) The calibration of systems subject to this subchapter shall be performed in accordance with an established calibration protocol. The calibration protocol published by the American Association of Physicists in Medicine is accepted as an established protocol. Other protocols which are equivalent will be accepted, but the user shall submit that protocol to the Department for concurrence that the protocol is equivalent. The calibration shall be performed as follows:
(1) Before the system is first used for irradiation of a patient and, at time intervals which do not exceed 1 year.
(2) After a change which alters the calibration, spatial distribution or other characteristics of the therapy beam.
(b) The calibration shall be performed by, or under the direct supervision of, a qualified expert for radiation therapy calibrations.
(c) Calibration radiation measurements required by subsection (a) shall be performed using a dosimetry system meeting the following specifications:
(1) The system has an exposure calibration factor appropriate to the beam energy measured and traceable to a National standard.
(2) The system has been calibrated within the previous 2 years and after servicing that may have affected its calibration.
(3) The system has been calibrated so that an uncertainty can be stated for the radiation quantities monitored by the system.
(4) The system has had constancy checks performed on the system as specified by a qualified expert for radiation therapy calibrations.
(d) Calibrations made under this section shall be made so that the dose at a reference point in soft tissue may be calculated as accurately as possible but with an uncertainty of no greater than 5%.
(e) The calibration of the therapy beam shall include, but is not limited to, the following determinations:
(1) Verification that the equipment is operating in compliance with the design specifications concerning the light localizer, the side light and back-pointer alignment with the isocenter when applicable, variation in the axis of rotation for the table, gantry and beam limiting device (collimator) system.
(2) The absorbed dose rate at various depths (depth dose) and beam profile measured in water and the beam flatness and symmetry for the range of field sizes used, for each beam energy, and if applicable, for each flattening filter free mode.
(3) The uniformity of the radiation field and a dependency upon the direction of the useful beam.
(4) Verification of depth-dose data and isodose curves applicable to the specific machine.
(5) Verification of the applicability of transmission factors of accessories such as wedges, shadow trays, compensators and their effects on electron buildup.
(6) The dose per monitor unit, end effect, linearity and dose rate dependence of the dose monitor systems.
(7) For photon beams, the congruence of the light field and the radiation field.
(8) For electron beams, the validity of commissioning data for virtual source distances or effective source-to-skin distances is to be verified at a single electron energy with a beam restriction device. When the replacement of a beam restriction device occurs, the determination will be required for each electron energy.
(f) Records of calibration measurements under subsection (a) and dosimetry system calibrations under subsection (c) shall be preserved for 5 years.
(g) A copy of the latest calibration performed under subsection (a) shall be available at the facility.
Source The provisions of this § 228.75 adopted October 2, 1998, effective October 3, 1998, 28 Pa.B. 4894; amended July 16, 2004, effective July 17, 2004, 34 Pa.B. 3823; amended October 26, 2018, effective January 24, 2019, 48 Pa.B. 6791. Immediately preceding text appears at serial pages (304594) to (304596).
Cross References This section cited in 25 Pa. Code § 228.76 (relating to spot checks).
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