10-144-220 Me. Code R. § G-H-632

Current through 2025-03, January 15, 2025

Section 144-220-G-H-632 - Full calibration measurements on teletherapy units

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:

(a) 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;

(b) Following replacement of the 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 source or major repair of the components associated with the source exposure assembly; and

(3) At intervals not exceeding one year.

B. To satisfy the requirement of G.632.A, 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. A licensee shall use the dosimetry system described in G.630.A to measure the output for one set of exposure conditions. The remaining radiation measurements required in G.630.B.(1) may be made using a dosimetry system that indicates relative dose rates.

D. A licensee shall make full calibration measurements required by G.632.A in accordance with published protocols accepted by nationally recognized bodies.

E. A licensee shall mathematically correct the outputs determined in G.632.B.(1) for physical decay for intervals not exceeding one month for cobalt-60, six months for cesium-137, or at intervals consistent with 1 percent decay for all other nuclides..

F. Full calibration measurements required by G.632.A and physical decay corrections required by G.632.E must be performed by the authorized medical physicist.

G. A licensee shall retain a record of each calibration in accordance with G.2632.

10-144 C.M.R. ch. 220, § G-H-632