Radiation Physics and Engineering
A peer-reviewed journal published by K. N. Toosi University of Technology

Monte Carlo simulation of the effects of high-‎‎Z‎‎ elemental impurities on proton therapy dose distribution

Articles in Press

Document Type : Research Article

Authors

Behshad Valizadeh 1
Elham Saniei 2
Armin Mosayebi 1
Seyed Pezhman Shirmardi 1
Hamideh Daneshvar 1
Babak Sepehri 2

1 Radiation Processing and Dosimetry Research Group, Radiation Application Research Institute, Nuclear Science and Technology Research Institute, Tehran, ‎Iran

2 Department of Medical Radiation Engineering, CT. C., Islamic Azad University, Tehran, Iran

https://doi.org/10.22034/rpe.2026.596655.1422
Abstract
Proton therapy utilizes the Bragg peak to deliver highly localized radiation doses while minimizing exposure to surrounding healthy tissues. However, tissue heterogeneities and the presence of high-atomic-number (high-Z) impurities may alter proton transport and dose deposition. In this study, Monte Carlo simulations using the MCNPX code were performed to investigate the effects of proton beam parameters, tissue heterogeneities, and high-Z impurities on proton dose distributions and Bragg peak characteristics. The influence of proton energy, beam radius, heterogeneity position, and embedded gold, lead, and uranium impurities was evaluated through analyses of penetration depth, deposited energy, and depth–dose profiles. The results showed that increasing proton energy enhanced penetration depth while reducing the maximum deposited energy, whereas beam radius mainly affected peak intensity. Tissue heterogeneities produced noticeable shifts and distortions in Bragg peak profiles depending on their density and location. Furthermore, the introduction of high-Z impurities reduced proton penetration depth from 5.07 cm to 5.01–5.03 cm and decreased deposited energy from 1.64 to 1.59-1.61 MeV.cm-3. These findings demonstrate that both tissue heterogeneities and trace high-Z impurities can significantly modify proton beam behavior and dose distributions. Accurate modeling of such effects is therefore essential for improving dosimetric accuracy and optimizing proton therapy treatment planning.

Keywords

Proton therapy
Dose Distribution
Monte Carlo Simulation
High-Z Materials
Impurities
Bragg Peak
Subjects

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.

Radiation Physics and Engineering

Articles in Press, Accepted Manuscript
Available Online from 02 October 2026

  • Receive Date 11 August 2026
  • Revise Date 07 September 2026
  • Accept Date 01 October 2026

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