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Subpart 1.

Calibration required.

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.

Subp. 2.

Required determinations.

To satisfy subpart 1, full calibration measurements must include determination of:


the output within plus or minus three percent;


relative helmet factors;


isocenter coincidence;


timer accuracy and linearity over the range of use;


on-off error;


trunnion centricity;


treatment table retraction mechanism, using backup battery power or hydraulic backups with the unit off;


helmet microswitches;


emergency timing circuits; and


stereotactic frames and localization devices (trunnions).

Subp. 3.

Required system.

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.

Subp. 4.

Required protocols.

A licensee must make full calibration measurements required under subpart 1 according to published protocols accepted by nationally recognized bodies.

Subp. 5.

Required corrections.

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.

Subp. 6.

Authorized medical physicist.

Full calibration measurements required under subpart 1 and physical decay corrections required under subpart 5 must be performed by the authorized medical physicist.

Subp. 7.

Record retention.

A licensee must retain a record of each calibration according to part 4731.4518.

Statutory Authority:

MS s 144.1202; 144.1203


29 SR 755

Published Electronically:

March 12, 2009

Official Publication of the State of Minnesota
Revisor of Statutes