Low dose rate caesium-137 implant time of intracavitary brachytherapy source of a selected oncology center in Ghana

Background: The treatment time taken for a radioactive source is found to be very important in intracavitary brachytherapy treatment. The duration of the treatment time depends on the prescribed dose requested to a reference point and the calculated dose rate to the same point. The duration of the treatment time of source is found to depend on the tumour stage. In this work, the treatment time of implant has been calculated for a Caesium-137 low dose rate brachytherapy source at an oncology facility in Ghana. Objective: The objective was to determine how the treatment time of tumours depends on the dose rate to the reference point prescribed by the Oncologists and the dose rate determined by the dosimetrists at the facility. Materials and Method: Depending upon the stage of the cancer, the Oncologist determines the type of treatment modality, source configuration for the cancer patient and positions of both tandem and ovoids in the cervix. Depending also on the tumour stage, two orthogonal radiographic X-ray films are taken using a simulator machine. The treatment machine used in the study is AMRA-Curietron. The maximum activity of the source was 259GBq. It has five channels which is a manual remote afterloader. In clinical practice, the treatment time t is very short(only some few days) for such low dose rate brachytherapy source like Cs-137 which lasts only for some few days in comparison with the half life of the Cs-137 source. The mathematical equation for the calculation of treatment time is written as t=D/D. Hence t is the treatment time of the radioactive source of patients undergoing intracavitary brachytherapy treatment, D is prescribed dose to a reference point and D is the dose rate to the same reference point. Results: The calculated treatment time of the Cs-137 brachytherapy source for different source arrangements or channels used in clinical practice at the brachytherapy Centre have been determined. Also provided, are the prescribed doses to the reference point and the calculated dose rate to the same point. The source arrangements in the channels are (1-2-5), (1-3-5), (1-4-5) and (1-5) respectively. Conclusion: The treatment time of Cs-137 low dose rate radioactive source for intracavitary brachytherapy treatment has been determined using the Manchester System. The results show that the treatment time depends on the dose prescribed to a reference point, which is usually set up by the oncologist at the Oncology center and the dose rate to the same point, which is determined by the dosimetrists using the Treatment Planning System (TPS) at the facility. The treatment time for advanced stages of the tumors were found to be much higher than the early stages of tumours.