1. A. Teletherapy units.

   1. 1. Licensees authorized to use a teletherapy unit for medical use shall perform full calibration measurements on each teletherapy unit:

      1. a. Before the first medical use of the unit;

      2. b. Before medical use under the following conditions:

         1. (1) Whenever spot-check measurements indicate that the output differs by more than 5.0% from the output obtained at the last full calibration corrected mathematically for radioactive decay;
         2. (2) Following replacement of the source or following reinstallation of the teletherapy unit in a new location; and
         3. (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
      3. c. At intervals not exceeding one year.

   2. 2. To satisfy the requirement of subdivision 1 of this subsection, full calibration measurements shall include determination of:

      1. a. The output within plus or minus 3.0% for the range of field sizes and for the distance or range of distances used for medical use;
      2. b. The coincidence of the radiation field and the field indicated by the light beam localizing device;
      3. c. The uniformity of the radiation field and its dependence on the orientation of the useful beam;
      4. d. Timer accuracy and linearity over the range of use;
      5. e. On-off error; and
      6. f. The accuracy of all distance measuring and localization devices in medical use.
   3. 3. Licensees shall use the dosimetry system described in 12VAC5-481-2044 to measure the output for one set of exposure conditions. The remaining radiation measurements required in subdivision 2 a of this subsection may be made using a dosimetry system that indicates relative dose rates.
   4. 4. Licensees shall make full calibration measurements required by subdivision 1 of this subsection in accordance with published protocols accepted by nationally recognized bodies.
   5. 5. Licensees shall mathematically correct the outputs determined in subdivision 2 a of this subsection for physical decay for intervals not exceeding one month for cobalt-60, six months for cesium-137, or at intervals consistent with 1.0% decay for all other nuclides.
   6. 6. Full calibration measurements required by subdivision 1 of this subsection and physical decay corrections required by subdivision 5 of this subsection shall be performed by the authorized medical physicist (AMP).

2. B. Remote afterloader units.

   1. 1. Licensees authorized to use a remote afterloader unit for medical use shall perform full calibration measurements on each unit:

      1. a. Before the first medical use of the unit;

      2. b. Before medical use under the following conditions:

         1. (1) Following replacement of the source or following reinstallation of the unit in a new location outside the facility; and
         2. (2) Following any repair of the unit that includes removal of the source or major repair of the components associated with the source exposure assembly;
      3. c. At intervals not exceeding one quarter for high dose-rate, medium dose-rate, and pulsed dose-rate remote afterloader units with sources whose half-life exceeds 75 days; and
      4. d. At intervals not exceeding one year for low dose-rate remote afterloader units.

   2. 2. To satisfy the requirement of subdivision 1 of this subsection, full calibration measurements shall include, as applicable, determination of:

      1. a. The output within plus or minus 5.0%;
      2. b. Source positioning accuracy to within plus or minus 1 millimeter;
      3. c. Source retraction with backup battery upon power failure;
      4. d. Length of the source transfer tubes;
      5. e. Timer accuracy and linearity over the typical range of use;
      6. f. Length of the applicators; and
      7. g. Function of the source transfer tubes, applicators, and transfer tube-applicator interfaces.
   3. 3. Licensees shall use the dosimetry system described in 12VAC5-481-2044 to measure the output.
   4. 4. Licensees shall make full calibration measurements required by subdivision 1 of this subsection in accordance with published protocols accepted by nationally recognized bodies.
   5. 5. In addition to the requirements for full calibrations for low dose-rate remote afterloader units in subdivision 2 of this subsection, licensees shall perform an autoradiograph of the sources to verify inventory and source arrangement at intervals not exceeding one calendar quarter.
   6. 6. For low dose-rate remote afterloader units, licensees may use measurements provided by the source manufacturer that are made in accordance with subdivisions 1 through 5 of this subsection.
   7. 7. Licensees shall mathematically correct the outputs determined in subdivision 2 a of this subsection for physical decay at intervals consistent with 1.0% physical decay.
   8. 8. Full calibration measurements required by subdivision 1 of this subsection and physical decay corrections required by subdivision 7 of this subsection shall be performed by the AMP.

3. C. Gamma stereotactic radiosurgery units.

   1. 1. Licensees authorized to use a gamma stereotactic radiosurgery unit for medical use shall perform full calibration measurements on each unit:

      1. a. Before the first medical use of the unit;

      2. b. Before medical use under the following conditions:

         1. (1) Whenever spot-check measurements indicate that the output differs by more than 5.0% from the output obtained at the last full calibration corrected mathematically for radioactive decay;
         2. (2) Following replacement of the sources or following reinstallation of the gamma stereotactic radiosurgery unit in a new location; and
         3. (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
      3. c. At intervals not exceeding one year, with the exception that relative helmet factors need only be determined before the first medical use of a helmet and following any damage to a helmet.

   2. 2. To satisfy the requirement of subdivision 1 of this subsection, full calibration measurements shall include determination of:

      1. a. The output within plus or minus 3.0%;
      2. b. Relative helmet factors;
      3. c. Isocenter coincidence;
      4. d. Timer accuracy and linearity over the range of use;
      5. e. On-off error;
      6. f. Trunnion centricity;
      7. g. Treatment table retraction mechanism, using backup battery power or hydraulic backups with the unit off;
      8. h. Helmet microswitches;
      9. i. Emergency timing circuits; and
      10. j. Stereotactic frames and localizing devices (trunnions).
   3. 3. Licensees shall use the dosimetry system described in 12VAC5-481-2044 to measure the output for one set of exposure conditions. The remaining radiation measurements required in subdivision 2 a of this subsection may be made using a dosimetry system that indicates relative dose rates.
   4. 4. Licensees shall make full calibration measurements required by subdivision 1 of this subsection in accordance with published protocols accepted by nationally recognized bodies.
   5. 5. Licensees shall mathematically correct the outputs determined in subdivision 2 a of this subsection at intervals not exceeding one month for cobalt-60 and at intervals consistent with 1.0% physical decay for all other radionuclides.
   6. 6. Full calibration measurements required by subdivision 1 of this subsection and physical decay corrections required by subdivision 5 of this subsection shall be performed by the AMP.

Statutory Authority

§ 32.1-229 of the Code of Virginia.

Historical Notes

Derived from Virginia Register Volume 32, Issue 24, eff. August 25, 2016.