Full Calibration Measurement
(1)A licensee authorized to use a teletherapy unit for medical use must perform full calibration measurements on each teletherapy unit:
(a)Before the first medical use of the unit; and
(b)Before medical use under the following conditions:
(A)Whenever spot-check measurements indicate that the output differs by more than five percent from the output obtained at the last full calibration corrected mathematically for radioactive decay;
(B)Following replacement of the radioactive source or following reinstallation of the teletherapy unit in a new location;
(C)Following any repair of the teletherapy unit that includes removal of the radioactive source or major repair of the components associated with the source exposure assembly; and
(c)At intervals not exceeding one year.
(2)To satisfy the requirement of section (1) of this rule, full calibration measurements must include determination of:
(a)The output within three percent for the range of field sizes and for the distance or range of distances used for medical use;
(b)The coincidence of the radiation field and the field indicated by the light beam localizing device;
(c)The uniformity of the radiation field and its dependence on the orientation of the useful beam;
(d)Timer accuracy, constancy, and linearity;
(e)On-off error; and
(f)The accuracy of all distance measuring and localization devices in medical use.
(3)A licensee must use the dosimetry system described in OAR 333-116-0560 (Dosimetry Equipment)(1) to measure the output for one set of exposure conditions. The remaining radiation measurements required in subsection (2)(a) of this rule may then be made using a dosimetry system that indicates relative dose rates.
(4)A licensee must make full calibration measurements required by section (1) of this rule in accordance with published protocols accepted by nationally recognized bodies.
(5)A licensee must correct mathematically the outputs determined in subsection (2)(a) of this rule for physical decay for intervals not exceeding one month for cobalt-60 and intervals not exceeding six months for cesium-137, or at intervals consistent with one percent decay for all other nuclides.
(6)Full calibration measurements required by section (1) of this rule and physical decay corrections required by section (5) of this rule must be performed by a teletherapy or medical physicist certified to perform such measurements and named on the licensee’s license or authorized by a license issued by the Nuclear Regulatory Commission or an Agreement State to perform such services.
(7)A licensee must retain a record of each calibration in accordance with OAR 333-100-0057 (Maintenance of Records). The record must include the date of the calibration, the manufacturer’s name, model number, and serial number for both the teletherapy unit and the source, the model numbers and serial numbers of the instruments used to calibrate the teletherapy unit, tables that describe the output of the unit over the range of field sizes and for the range of distances used in radiation therapy, a determination of the coincidence of the radiation field and the field indicated by the light beam localizing device, the measured timer accuracy for a typical treatment time, the calculated on-off error, the estimated accuracy of each distance measuring or localization device and the signature of the teletherapy physicist.
Rule 333-116-0570 — Full Calibration Measurement,