A licensee authorized to use a gamma stereotactic radiosurgery unit for medical use must perform full calibration measurements on each unit:
before the first medical use of the unit;
before medical use under the following conditions:
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;
following replacement of the sources or following reinstallations of the gamma stereotactic radiosurgery unit in a new location; and
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
at intervals not exceeding one year, except that relative helmet factors need only be determined before the first medical use of a helmet and following any damage to a helmet.
To satisfy subpart 1, full calibration measurements must include determination of:
the output within plus or minus three percent;
relative helmet factors;
timer accuracy and linearity over the range of use;
treatment table retraction mechanism, using backup battery power or hydraulic backups with the unit off;
emergency timing circuits; and
stereotactic frames and localization devices (trunnions).
A licensee must use the dosimetry system described in part 4731.4468, subpart 1, to measure the output for one set of exposure conditions. The remaining radiation measurements required under subpart 2 may be made using a dosimetry system that indicates relative dose rates.
A licensee must make full calibration measurements required under subpart 1 according to published protocols accepted by nationally recognized bodies.
A licensee must mathematically correct the outputs determined under subpart 2, item A, at intervals not exceeding one month for cobalt-60 and at intervals consistent with one percent physical decay for all other radionuclides.
Full calibration measurements required under subpart 1 and physical decay corrections required under subpart 5 must be performed by the authorized medical physicist.
29 SR 755
March 12, 2009
Official Publication of the State of Minnesota
Revisor of Statutes