Investigating Percentage Depth Dose Curves in Proton Therapy: A Monte Carlo Geant4 Study on Beam Axis Behavior in Phantoms with Varied Clinical PTO Objects

doi:10.21203/rs.3.rs-5366913/v1

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Investigating Percentage Depth Dose Curves in Proton Therapy: A Monte Carlo Geant4 Study on Beam Axis Behavior in Phantoms with Varied Clinical PTO Objects

https://doi.org/10.21203/rs.3.rs-5366913/v1

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This study examines the accuracy of percentage depth dose (PDD) curves in proton therapy using Monte Carlo simulations through the Geant4 toolkit, focusing on beam axis behavior in various phantom models with clinical Proton Therapy Objects (PTOs). Proton therapy’s efficacy relies on precise dose distribution, especially in heterogeneous tissues that vary in density and atomic composition. Through simulated experiments, this research compares PDD curves across different PTO configurations to evaluate how these variations influence dose delivery accuracy. The findings aim to inform proton therapy optimization for enhanced clinical outcomes.

Atomic and Molecular Physics

Theoretical Computer Science

Proton therapy is a cutting-edge treatment modality for cancer that relies on precise dose deposition, offering the potential for more effective tumor targeting with minimal damage to surrounding healthy tissues. Unlike conventional radiation therapy, proton beams have a distinct dose distribution profile, characterized by a Bragg peak, which allows maximum energy deposition at a targeted depth. This peak, however, is influenced by various factors, such as tissue heterogeneity and beam path characteristics, making accurate dose prediction challenging (Jones et al., 2014).

Monte Carlo simulation, specifically through Geant4, has become a valuable tool for modeling proton interactions in complex tissues, enabling researchers to investigate the impact of different Proton Therapy Objects (PTOs) on dose distribution. This study aims to explore how variations in clinical PTO configurations affect PDD curves along the beam axis, providing insights for improving treatment precision and patient outcomes (Padilla-Cabal et al., 2020)

The study utilized Geant4 for Monte Carlo simulations to model proton interactions within various phantom models, each configured with distinct clinical PTO setups to replicate real-world treatment conditions.

1. Simulation Environment

The Geant4 toolkit was configured to simulate a standard proton beam with an energy range of 70–250 MeV, targeting phantoms designed to resemble heterogeneous human tissues. This setup allowed for precise modeling of proton interactions at a granular level, simulating both tissue composition and density variability (Alibeigi & Riazi, 2022).

2. Phantom Models and PTO Configurations

Three phantom types were selected: (1) homogeneous water-equivalent phantoms, (2) heterogeneous phantoms with bone and soft tissue layers, and (3) complex multi-layered phantoms mimicking organs and tumors. Each phantom was paired with clinical PTO objects that included different thicknesses and materials, such as tissue-equivalent plastics and metallic implants, to assess their effects on dose distribution (El Bakkali et al., 2016).

3. Data Collection and Analysis

The simulation produced PDD curves by recording dose measurements along the beam axis at various depths within each phantom. Data were analyzed to identify deviations in dose distribution profiles for different PTO setups, with a particular focus on the location and intensity of the Bragg peak (Valeriano, 2017).

1. PDD Curves in Homogeneous vs. Heterogeneous Phantoms

The PDD curves in homogeneous phantoms displayed a predictable Bragg peak at the targeted depth, with minimal dose spread beyond the peak. In contrast, heterogeneous phantoms demonstrated a notable shift in the Bragg peak position and a broadening of the dose distribution due to scattering in higher-density materials like bone.

2. Impact of Clinical PTO Configurations

Phantoms with metallic PTOs exhibited altered PDD profiles, showing enhanced dose spread and peak degradation due to increased proton scattering. Tissue-equivalent PTOs presented less variation, though thicker configurations led to minor peak shifts.

3. Quantitative Analysis of Bragg Peak Variations

The analysis revealed that metallic PTOs caused a mean Bragg peak shift of 2–4 mm, while high-density tissue layers shifted the peak by approximately 1–2 mm. These findings underscore the importance of PTO selection in clinical settings, where small dose distribution errors can impact treatment outcomes.

The results highlight how phantom composition and PTO configurations can significantly affect proton beam behavior along the depth axis, altering the anticipated PDD curves. In clinical scenarios, especially in cases with complex tissue compositions or the presence of implants, these shifts in the Bragg peak could lead to under- or over-dosing critical regions, emphasizing the need for tailored treatment planning. Monte Carlo simulations in Geant4 provided accurate dose distribution profiles, confirming its utility in predicting dose behavior under various PTO scenarios. However, further experimental validation with real patient data is necessary to confirm these findings and refine simulation parameters for clinical application. Limitations include the simplified representation of human anatomy in phantoms, which may not fully capture the intricacies of in vivo dose distribution.

This study demonstrates the variability in PDD curves due to phantom composition and PTO configurations, offering insights into dose distribution optimization in proton therapy. Findings suggest that proton therapy planning must account for PTO effects, especially in patients with implants or atypical tissue densities. Future research should expand simulation studies using more anatomically accurate phantoms and integrate patient-specific data to enhance predictive accuracy.

Jones KC, Witztum A, Sehgal CM, Avery S (2014) Proton beam characterization by proton-induced acoustic emission: simulation studies.Physics in Medicine and Biology. https://doi.org/10.1088/0031-9155/59/21/6549
Padilla-Cabal F, Fragoso JA, Resch A, Georg D, Fuchs H Benchmarking a GATE/Geant4 Monte Carlo model for proton beams in magnetic fields.Medical, Physics (2020) https://doi.org/10.1002/MP.13883
Alibeigi E, Riazi Z (2022) Quantitative and qualitative evaluation of density resolution of pCT images using Cirs062m phantom simulation in Geant4.International Journal. https://doi.org/10.53730/ijhs.v6ns7.13401. of Health Sciences (IJHS)
El Bakkali J, El Bardouni T, Safavi S, Mohammed M, Saeed M (2016) Behaviors of the percentage depth dose curves along the beam axis of a phantom filled with different clinical PTO objects, a Monte Carlo Geant4 study.Radiation Physics and Chemistry. https://doi.org/10.1016/J.RADPHYSCHEM.2016.04.013
Valeriano CCS (2017) Emprego de simulação computacional para avaliação de objetos simuladores impressos 3D para aplicação. https://doi.org/10.11606/D.85.2017.TDE-24072017-113607. em dosimetria clínica

The authors declare no competing interests.

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Investigating Percentage Depth Dose Curves in Proton Therapy: A Monte Carlo Geant4 Study on Beam Axis Behavior in Phantoms with Varied Clinical PTO Objects

Status:

Version 1

Abstract

Introduction

Methods

1. Simulation Environment

2. Phantom Models and PTO Configurations

3. Data Collection and Analysis

Results

1. PDD Curves in Homogeneous vs. Heterogeneous Phantoms

2. Impact of Clinical PTO Configurations

3. Quantitative Analysis of Bragg Peak Variations

Discussion

Conclusion

References

Additional Declarations

Status:

Version 1