Comparison the treatment duration for Cobalt-60, and Iridium-192 sources with different activities in HDR brachytherapy using tandem-ovoid applicator

Introduction: The long-half-life Cobalt-60 high dose rate (HDR) brachytherapy source is an appropriate alternative for Iridium-192 (HDR) source for treatment of GYN patients in developing countries. The aim of this study is to compare the treatment duration for HDR cervical cancer treatments using Cobalt-60 and Iridium-192 sources using Tandem and ovoid applicators. Materials and Methods: In this study, Iridium-192 source model mHDR-v2r, and BEBIG 60Co source model Co0.A86 were used. The TG-43 formalism was used to calculate the treatment time required for both radionuclides. The treatment data provided us with the exact dwell positions, and times of the source, and positions of the dosimetry points. The treatment time for Iridium source was calculated by using absorbed dose in treatment data and the TG-43 formalism. Then, the calculations were repeated with Cobalt-60 to determine the dwell times. Finally, the treatment duration obtained for the two sources were compared with each other. Results: The results of this study indicate that the treatment time for cobalt source with the activity of 2.131 Ci is almost the same as the treatment time for iridium source with the activity of 5.690 Ci. If we consider the maximum treatment duration is 16 minutes in one treatment session, the effective time window for Iridium-192 is about 160 days, while for Cobalt-60 this effective time window becomes 2000 days. Conclusion: According to the results obtained in this study, using Cobalt-60 instead of Iridium-192 will be economically beneficial in newly constructed departments where the selection of the equipment is still in progress. Changes the activities of the Iridium-192 versus Cobalt-60 require editing treatment planning system for a patient in total treatment time. These editing of treatment planning can cause errors and reduce accuracy.