Introduction: The use of radionuclides in telecobalt and brachytherapy machines demands safe handling of the equipment and accurate measurement of source activity to ensure safety of the patients, workers and public. This paper reports dosimetric consistency of few Quality Assurance parameters of Theratron Phoenix Telecobalt and micro Selectron HDR Brachytherapy machines performed for a period of thirteen years from 2007 to 2019.

Materials and Method: The output of the telecobalt unit for both SSD and SAD techniques and the source strength of the HDR Brachytherapy unit in terms of RAKR were measured as per national and international guidelines. The percentage variations between measured and theoretically calculated values were obtained for the thirteen years period. Timer error, error in Timer linearity and variations in TPS vs. manually calculated treatment times were calculated for the HDR unit after each source replacements.

Results: The results obtained from the measurements done all over the thirteen years period were found to be well within the stipulated values specified by competent authority. The results were shown in graphical and tabulated form.

Conclusion: The results show that the parameters measured were well within tolerance limits for a long period of thirteen years. Hence, this study establishes the consistency and accuracy in the dosimetric parameters of the Theratron Phoenix and micro Selectron HDR Brachytherapy machines.

Keywords:  Telecobalt, Brachytherapy, Reference Air Kerma Rate, Timer Error and Linearity, Dosimetric Consistency, TPS.

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Pranjal Goswami, MSc., DRP

Medical Physicist, Dept. of Radiation Oncology, Dr. B. Borooah Cancer Institute, Guwahati, Assam