Modeling of dose and linear energy transfer homogeneity in cell nuclei exposed to alpha particles under various setup conditions

Abstract

Purpose

Different alpha exposure setups are often used to study the relation between biological responses and LET. This study aimed to estimate the dose heterogeneity and uncertainty in four exposure setups using Geant4 and PARTRAC codes. The importance of the irradiation system characteristics was shown in the context of reporting experimental results, especially in radiobiological studies at the molecular level.

Materials and methods

Geant4 was used to estimate the dose distributions in cells grown on a disk exposed to alpha particles penetrating from above and below. The latter setup was simulated without and with a collimator. PARTRAC was used for the validation of Geant4 simulations based on distributions of the number of alpha particles penetrating a round nucleus and the deposited energy.

Results

The LET distributions obtained for simulated setups excluding the collimator were wide and non-Gaussian. Using a collimator resulted in a Gaussian LET distribution, but strongly reduced dose rate and dose homogeneity. Comparison between PARTRAC and Geant4 calculations for the cell nucleus exposed to alpha radiation showed an excellent agreement.

Conclusions

The interpretation of results from radiobiological experiments with alpha particles should always cover the characteristics of the experimental setup, which can be done precisely with computational methods.

Keywords:

• Alpha radiation
• high LET
• dose homogeneity
• Monte Carlo modeling
• PARTRAC vs. Geant4

Acknowledgements

The authors thank Werner Friedland for providing the PARTRAC codes and valuable discussions. The resources of the Świerk Computing Centre (CIŚ) financed by the EU and the Polish Ministry of Science and Higher Education (project No. POIG.02.03.00-00-013/09) were used to carry out this work.

Disclosure statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Additional information

Funding

MF, AT, MP and BB were supported by the Polish Funds for Science. AW was supported by the Swedish Radiation Safety Authority (SSM).

Notes on contributors

Adrianna Tartas

Adrianna Tartas is a PhD student at the Biomedical Physics Division at Faculty of Physics, University of Warsaw. She is focused on the application of live imaging to study the temporal dynamics of repair foci formed in cells exposed to ionizing radiation.

Mateusz Filipek

Mateusz Filipek is a PhD Student in the field of medical physics at the Biomedical Physics Division at Faculty of Physics, University of Warsaw. Filipek focuses on radiation sources dosimetry and studies of cellular response on differences types of ionizing radiation.

Marcin Pietrzak

Marcin Pietrzak is the Head of the Laboratory of Medical Physics and Nanodosimetry. His primary interest is computational (Geant4-DNA and PTra codes) and experimental (Jet Counter nanodosemeter) work on radiation quality studies of heavily charged particles. He is also a member of EURADOS and the Polish Society of Medical Physics.

Andrzej Wojcik

Andrzej Wojcik, PhD, is a professor of radiation biology at the Stockholm University and Jan Kochanowski University in Kielce. Wojcik focuses on studying the cellular effects of radiation, with a special focus on combined exposure to radiations of different qualities.

Beata Brzozowska

Beata Brzozowska is a researcher at the Biomedical Physics Division at Faculty of Physics, University of Warsaw, and her scientific interests concern medical physics and radiobiology with a special focus on modeling DNA damage and repair in cells exposed to ionizing radiation.