Minnesota Administrative Rules

4731.4469 TELETHERAPY UNITS; FULL CALIBRATION.

Subpart 1.

Calibration required.

A licensee authorized to use a teletherapy unit for medical use must perform full calibration measurements on each teletherapy 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 source or following reinstallation of the teletherapy unit in a new location; and

(3)

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

C.

at intervals not exceeding one year.

Subp. 2.

Required determinations.

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

A.

the output within plus or minus three percent for the range of field sizes and for the distance or range of distances used for medical use;

B.

the coincidence of the radiation field and the field indicated by the light beam localizing device;

C.

the uniformity of the radiation field and its dependence on the orientation of the useful beam;

D.

timer accuracy and linearity over the range of use;

E.

on-off error; and

F.

the accuracy of all distance-measuring and localization devices in medical use.

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 in subpart 2, item A, for physical decay for intervals not exceeding one month for cobalt-60, six months for cesium-137, or at intervals consistent with one percent decay for all other nuclides.

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

History:

29 SR 755

Published Electronically:

March 12, 2009