4731.4471 Gamma Stereotactic Radiosurgery Units; Full Calibration


Published: 2015

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4731.4471 GAMMA STEREOTACTIC RADIOSURGERY UNITS; FULL CALIBRATION.


§
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:

§
A.

before the first medical use of the unit;


§
B.

before medical use under the following conditions:

§
(1)

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;


§
(2)

following replacement of the sources or following reinstallations of the gamma stereotactic radiosurgery unit in a new location; and


§
(3)

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



§
C.

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:

§
A.

the output within plus or minus three percent;


§
B.

relative helmet factors;


§
C.

isocenter coincidence;


§
D.

timer accuracy and linearity over the range of use;


§
E.

on-off error;


§
F.

trunnion centricity;


§
G.

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


§
H.

helmet microswitches;


§
I.

emergency timing circuits; and


§
J.

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.