A comparison of treatment duration for Cobalt-60 and Iridium-192 sources with different activities in HDR brachytherapy using tandem-ovoid applicator

The long-half-life Cobalt-60 source with high dose rate (HDR) brachytherapy is an appropriate alternative to Iridium-192 (HDR) source in the treatment of GYN patients in developing countries. This study aimed to compare HDR cervical cancer treatment duration using Cobalt-60 and Iridium-192 sources for the Tandem-ovoid applicators.

In the present study, BEBIG Cobalt-60 source model Co0.A86 and Iridium-192 source model mHDR-v2r were utilized. The treatment time required for both radionuclides was calculated using the TG-43 formalism. To calculate the treatment time for the Iridium source, the absorbed dose was used in the TG-43 formalism and treatment data. Then the dwell times were determined after repeating the calculations with Cobalt-60. Finally, the comparison was made for the treatment duration for the two sources.

According to our findings, the treatment time for the cobalt source with the activity of 2.131 Ci is somehow the same as that of the iridium source with the activity of 5.690 Ci. If the maximum treatment duration is supposed to be 16 minutes in a treatment session, the effective time window for Iridium-192 is about 160 days. This is, however, the effective time window is 2000 days for Cobalt-60.

According to the findings, the use of Cobalt-60 instead of Iridium-192 is economically beneficial for equipment selection in newly constructed departments. Changes in the activities of Cobalt-60 in comparison with Iridium-192 requires editing the total treatment time of the treatment planning system for patients. Such editing may raise errors and reduce accuracy.