Dosimetric characterization of Flexisource HDR 192Ir brachytherapy source using GATE/GEANT4 Monte Carlo code

Abstract

Author(s): A. Oustous, Z. Airouss, Y. El Attaoui, Y.Raoui, M. Khalis, R. Sebihi

Aim: The aim of this study is to validate the dosimetric parameters of High Dose Rate ¹⁹²Ir Flexi-source (mHDR v1 model) using GATE (version 9.1) Geant4-based Monte Carlo code, which is widely used in clinical applications for brachytherapy. This validation serves as a preliminary step toward investigating the issues related to tissue heterogeneities in brachytherapy dosimetry.

Methods: In this study, the geometry of the ¹⁹²Ir Flexi-source mHDR-v1 was simulated within a water sphere using GATE Monte Carlo code. The dosimetric parameters, including air kerma strength Sk, dose rate constant λ, radial dose function g(r), and anisotropy function F (r, θ), were computed in accordance with the TG- 43U1 and ESTRO guidelines, and the results were compared with available literature and clinical data for validation.

Results: The dose rate constant obtained was 1.078 cGy h⁻¹ U⁻¹ ± 0.012 cGy h⁻¹ U⁻¹, showing a relative difference of 2.79% compared to the reference value. The radial dose function, starting from 0.25 cm to 15 cm, showed excellent agreement with a maximum of 3.43% at 15 cm. For the anisotropy function F (r, θ), the agreements were within 4.45% for 5<θ<175, and within 13.29% for all θ values.

Conclusion: Results from this study demonstrate that the validation of the Flexi-source HDR ¹⁹²Ir source is achievable using the GATE based Monte Carlo simulation. Consequently, the GATE code can be employed to explore challenges associated with tissue heterogeneities in brachytherapy dosimetry for ¹⁹²Ir Flexi-source.

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