Monte Carlo simulation of a gynecological brachytherapy applicator in a pelvis phantom and benchmarking with dosimetry and comparison with a treatment planning system

Gynecological brachytherapy requires highly precise dose delivery to optimize therapeutic effects while minimizing risks to surrounding tissues. This study uses Monte Carlo simulations to evaluate a high-dose-rate (HDR) 192Ir brachytherapy applicator for gynecological treatment within a custom-designed pelvic PMMA phantom, benchmarked against dosimetric measurements and a clinical treatment planning system (TPS), Flexiplan. Thermoluminescent dosimeters (TLD-100H) were employed to measure absorbed doses at various points near the applicator, and these values were compared with Monte Carlo (MCNP) calculated doses and TPS-based predictions. The MCNP simulations incorporated the full source geometry and applicator details for dose distribution nuances near high-gradient regions. Results demonstrated a high level of agreement among TLD, MCNP, and Flexiplan dose values, with nominal differences well within recommended tolerances as outlined by TG-40 and TG-138 reports. Statistical errors were below 1% for MCNP and under 3% for TLD readings, indicating reliability and clinical accuracy. This benchmarking approach underscores the importance of integrating Monte Carlo methods for quality assurance in brachytherapy, confirming Flexiplan's accuracy in calculating complex dose distributions in gynecological applications.