10 CFR 35.632, Full Calibration Measurements On Teletherapy Units
Full calibration measurements on teletherapy units
a
(a) A licensee authorized to use a teletherapy unit for medical use shall perform full calibration measurements on each teletherapy unit--
- (1) Before the first medical use of the unit; and
- (2) Before medical use under the following conditions:
- (i) Whenever spot-check measurements indicate that the output differs by more than 5 percent from the output obtained at the last full calibration corrected mathematically for radioactive decay;
- (ii) Following replacement of the source or following reinstallation of the teletherapy unit in a new location;
- (iii) Following any repair of the teletherapy unit that includes removal of the source or major repair of the components associated with the source exposure assembly; and
- (3) At intervals not exceeding 1 year.
b
(b) To satisfy the requirement of paragraph (a) of this section, full calibration measurements must include determination of--
- (1) The output within +/-3 percent for the range of field sizes and for the distance or range of distances used for medical use;
- (2) The coincidence of the radiation field and the field indicated by the light beam localizing device;
- (3) The uniformity of the radiation field and its dependence on the orientation of the useful beam;
- (4) Timer accuracy and linearity over the range of use;
- (5) On-off error; and
- (6) The accuracy of all distance measuring and localization devices in medical use.
c
(c) A licensee shall use the dosimetry system described in § 35.630(a) to measure the output for one set of exposure conditions. The remaining radiation measurements required in paragraph (b)(1) of this section may be made using a dosimetry system that indicates relative dose rates.
d
(d) A licensee shall make full calibration measurements required by paragraph (a) of this section in accordance with published protocols accepted by nationally recognized bodies.
e
(e) A licensee shall mathematically correct the outputs determined in paragraph (b)(1) of this section for physical decay for intervals not exceeding 1 month for cobalt-60, 6 months for cesium-137, or at intervals consistent with 1 percent decay for all other nuclides.
f
(f) Full calibration measurements required by paragraph (a) of this section and physical decay corrections required by paragraph (e) of this section must be performed by the authorized medical physicist.
g
(g) A licensee shall retain a record of each calibration in accordance with § 35.2632.
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