Monte Carlo dosimetry for BEBIG Cobalt-60 brachytherapy source with gynecological applicator in the presence of inhomogeneities

Introduction: High-dose-rate (HDR) Co-60 brachytherapy necessitates accurate dose calculations to minimize normal tissue toxicity and late malignancy risks. Conventionally, the American Association of Physicists in Medicine (AAPM) Task Group 43 (TG-43) formalism, utilizing table-based dose superposition, has been employed for dose calculations, overlooking tissue inhomogeneity effects. Material and methods: This study focuses on characterizing the high-dose-rate BEBIG Co-60 brachytherapy source, in combination with a gynecological applicator, using Monte Carlo simulations. The investigation is based on the model of the modified BEBIG Co-60 source (Co0.A86) implemented at the University of Malaya Medical Center. Dosimetric properties are evaluated according to AAPM TG-43 formalism, with validation against existing published data. Results: Our investigation presents comprehensive MC dosimetric properties of the high-dose-rate BEBIG Co-60 brachytherapy source, highlighting its accuracy in dose calculations compared to established data. The study also examined the impact of the applicator on depth dose calculations within a Krieger phantom and explored the influence of various tissue inhomogeneities on the depth dose. Conclusions: Our findings revealed that the applicator had a relatively minimal effect on the delivered dose, with only marginal differences observed. Furthermore, we investigated the depth doses along the central axis of the applicator, within a segment characterized by various tissue inhomogeneities where dose differences of up to 12% were observed, with the lowest and highest doses recorded within bone and adipose tissues, respectively. This study underscores the valuable role of MC simulations in estimating doses at locations where physical measurements are unfeasible, such as the intra-uterine tube surface, as well as in scenarios featuring tissue inhomogeneities.