Dosimetric comparison of different allocations of I-125 Source for Brain Tumor Brachytherapy: A Comprehensive Simulation Study Using MCNP and TLD evaluation

Abstract

Author(s): Hadi Nasrollahi, Mohsen Hasani, Hasan Ali Nedaei, Hamideh Naderi

Introduction: Brachytherapy has proven to be an effective method for the treatment of brain tumours. Given the presence of sensitive organs in the brain that control vital bodily functions, it becomes paramount to optimize the dose distribution of these radiation sources. This study aims to evaluate the dose distribution characteristics of different implantation of I-125 sources using Monte Carlo simulations for the treatment of brain tumours. Materials and Methods: In this study, we first calibrated GR-207A TLDs using an orthovoltage machine operating at 100 keV energy, deriving the calibration curve. Subsequently, I-125 (Model IR-Seed2) source manufactured by Iran was exposed to TLDs within a Perspex phantom for 48 hours, and absorbed doses were determined in the perpendicular direction to the source's longitudinal axis at various distances. Next, patient head simulations were conducted in the MCNPX code using DICOM CT images and the Scan2MCNP program to assess different number of I-125 sources implantation. The simulation accuracy was evaluated using the third type Mesh Tally method and data obtained from TLD measurements. Results: The dose distribution achieved with the implantation of four I-125 sources within the tumour exhibited a superior response compared to configurations involving one or two sources for the treatment of brain tumours. Additionally, this approach significantly reduced the required source implantation time. Conclusion: Using one or two sources within the tumour is not suitable for brain tumour treatment due to significant damage and the risk of necrosis. In contrast, using four sources provides a better dose distribution and is a superior approach for brain tumour treatment.

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