Minn. R. agency 144, ch. 4731, MEDICAL USE OF RADIOACTIVE MATERIAL, pt. 4731.4469

Current through Register Vol. 49, No. 29, 2025

Part 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.

Minn. R. agency 144, ch. 4731, MEDICAL USE OF RADIOACTIVE MATERIAL, pt. 4731.4469

29 SR 755

Statutory Authority: MS s 144.1202; 144.1203