A peer-reviewed journal published by K. N. Toosi University of Technology

Comparative GEANT4-based Monte Carlo dosimetry of I-125 and Pd-103 in soft tissue, blood, and adipose tissue

Document Type : Research Article

Authors

1 Department Physics, Shahed University, Tehran, Iran

2 Department of Biomedical Engineering, Islamic Azad University, Science and Research Branch, Tehran, Iran.

Abstract
This study presents a GEANT4-based Monte Carlo dosimetry comparison of clinically realistic I-125 (Amersham OncoSeed 6702) and Pd-103 (BEBIG IsoSeed) brachytherapy sources in adipose tissue, soft tissue, and blood. The simulation model was rigorously validated against AAPM TG-43 consensus data, showing excellent agreement in dose rate constants and radial dose functions. The model was thoroughly tested and validated to ensure its robustness and accuracy. Results demonstrated that tissue composition significantly alters dose distributions compared to water. Adipose tissue permitted the deepest penetration, while blood showed the strongest attenuation. The results indicated that I-125, align with its lower average energy, produced a broader dose distribution than Pd-103. Conversely, 103Pd exhibited a steeper dose gradient, confining energy closer to the source. These findings underscore the critical importance of incorporating both tissue-specific composition and the full photon energy spectrum into brachytherapy treatment planning to optimize dose delivery for personalized patient care ultimately optimizing clinical outcomes.

Highlights

  • Comparative Monte Carlo dosimetry of I-125 and Pd-103 sources were performed in biological tissues.
  • Dose attenuation varied significantly among soft tissue, blood, and adipose tissue.
  • Pd-103 showed a steeper dose gradient than I-125 due to lower photon energy.
  • Simulation results were validated against TG-43 reference data with good agreement.
  • The findings highlight the impact of tissue composition on the accuracy of brachytherapy dosimetry.

Keywords


Copyright
RPE is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0).

Conflict of Interest
The authors declare no potential conflict of interest regarding the publication of this work‎.

Funding
‎The authors declare that no funds‎, ‎grants‎, ‎or other financial support were received during the preparation of this manuscript‎.

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Volume 7, Issue 1
Winter 2026
Pages 1-10

  • Receive Date 01 October 2025
  • Revise Date 08 November 2025
  • Accept Date 16 November 2025