180 NAC 7-073. FULL CALIBRATION MEASUREMENTS ON TELETHERAPY UNITS

073. FULL CALIBRATION MEASUREMENTS ON TELETHERAPY UNITS. 073.01 FREQUENCY. 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: (i) Whenever spot-check measurements indicate that the output differs by more than 5% from the output obtained at the last full calibration corrected mathematically for radioactive decay;(ii) Following replacement of the source or following reinstallation of the teletherapy unit in a new location; and(iii) 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. 073.02 DETERMINANTS. To satisfy the requirement of 180 NAC 7-073.01, full calibration measurements must include determination of: (A) The output within plus or minus 3% 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. 073.03 DOSIMETRY SYSTEM USAGE. A licensee must use the dosimetry system described in 180 NAC 7-072.01 to measure the output for one set of exposure conditions. The remaining radiation measurements required by 7-073.02(A) may then be made using a dosimetry system that indicates relative dose rates. 073.04 PROTOCOLS. A licensee must make full calibration measurements required by 180 NAC 7-073.01 according to published protocols accepted by nationally recognized bodies. 073.05 MATHEMATICAL CORRECTION OF OUTPUTS. A licensee must mathematically correct the outputs determined in 180 NAC 7-073.02, (A), for physical decay for intervals not exceeding one month for cobalt-60, six months for cesium-137, or at intervals consistent with 1% decay for all other nuclides. 073.06 CALIBRATION MEASUREMENT AND DECAY CORRECTIONS. Full calibration measurements required by 180 NAC 7-073.01 and physical decay corrections required by 180 NAC 7-073.05 must be performed by an authorized medical physicist. 073.07 RECORDS. A licensee must maintain a record of each calibration according to 180 NAC 7-108.