Monte Carlo characterization of the VariSource VS2000 HDR Iridium brachytherapy source

Abstract

The dosimetry calculation in High Dose Rate (HDR) brachytherapy with TPS treatment planning systems, based on the TG-43U1 dosimetric formalism data of the used source, presents an essential element in the successful clinical treatment of cancers aiming to achieve the maximum dose in the in targeted tumor volumes, and minimizing the risks of unwanted exposure to organs at risk (OAR) contouring in DICOM CT images. The purpose of this investigation was to obtain and optimize the TG-43U1 dosimetric parameters data of a VS2000 high dose rate iridium source installed in the center of a water phantom using GATE_8.2 version Monte Carlo simulation, taking into account the geometrical and physical characteristics of the HDR brachytherapy source, and also respecting the “High Energy Brachytherapy Source Dosimetry (HEBD)” working group recommendations. The findings achieved in this Monte Carlo investigation mainly the air kerma strength per unit activity S<inf>K</inf>/A = 10.31x10⁻⁸ U Bq⁻¹ the dose rate constant ∧ = 1.105 cGy h⁻¹ U⁻¹, and the radial dose function gL(r) have proved to be in favorable agreement with reference data, in particular Angelopoulos et al and Casado et al using respectively a customized MC and PENELOPE Monte Carlo simulation codes.