10-144-220 Me. Code R. § G-H-635

Current through 2024-51, December 18, 2024

Section 144-220-G-H-635 - Full calibration measurements on gamma stereotactic radiosurgery units

A. A licensee authorized to use a gamma stereotactic radiosurgery unit for medical use shall perform full calibration measurements on each unit:

(1) Before the first medical use of the unit;

(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 sources or following reinstallation of the gamma stereotactic radiosurgery unit in a new location; and

(c) Following any repair of the gamma stereotactic radiosurgery unit that includes removal of the sources or major repair of the components associated with the source assembly; and

(3) At intervals not exceeding one year, with the exception that relative helmet factors need only be determined before the first medical use of a helmet and following any damage to a helmet.

B. To satisfy the requirement of G.635.A, full calibration measurements must include determination of:

(1) The output within +/-3 percent;

(2) Relative helmet factors;

(3) Isocenter coincidence;

(4) Timer accuracy and linearity over the range of use;

(5) On-off error;

(6) Trunnion centricity;

(7) Treatment table retraction mechanism, using backup battery power or hydraulic backups with the unit off;

(8) Helmet microswitches;

(9) Emergency timing circuits; and

(10) Stereotactic frames and localizing devices (trunnions).

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.635.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.635.A in accordance with published protocols accepted by nationally recognized bodies.

E. A licensee shall mathematically correct the outputs determined in G.635.B.(1) at intervals not exceeding one month for cobalt-60 and at intervals consistent with 1 percent physical decay for all other radionuclides.

F. Full calibration measurements required by G.635.A and physical decay corrections required by G.635.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-635