An inter-comparison between radiobiological characteristics of a commercial low-energy IORT system by Geant4-DNA and MCDS Monte Carlo codes

Abstract

Introduction

The need for accurate relative biological effectiveness (RBE) estimation for low energy therapeutic X-rays (corresponding to 50 kV nominal energy of a commercial low-energy IORT system (INTRABEAM)) is a crucial issue due to increased radiobiological effects, respect to high energy photons. Modeling of radiation-induced DNA damage through Monte Carlo (MC) simulation approaches can give useful information. Hence, this study aimed to evaluate and compare RBE of low energy therapeutic X-rays using Geant4-DNA toolkit and Monte Carlo damage simulation (MCDS) code.

Materials and methods

RBE calculations were performed considering the emitted secondary electron spectra through interactions of low energy X-rays inside the medium. In Geant4-DNA, the DNA strand breaks were obtained by employing a B-DNA model in physical stage with 10.79 eV energy-threshold and the probability of hydroxyl radical’s chemical reactions of about 0.13%. Furthermore, RBE estimations by MCDS code were performed under fully aerobic conditions.

Results

Acquired results by two considered MC codes showed that the same trend is found for RBE_DSB and RBE_SSB variations. Totally, a reasonable agreement between the calculated RBE values (both RBE_SSB and RBE_DSB) existed between the two considered MC codes. The mean differences of 9.2% and 1.8% were obtained between the estimated RBE_SSB and RBE_DSB values by two codes, respectively.

Conclusion

Based on the obtained results, it can be concluded that a tolerable accordance is found between the calculated RBE_DSB values through MCDS and Geant4-DNA, a fact which appropriates both codes for RBE evaluations of low energy therapeutic X-rays, especially in the case of RBE_DSB where lethal damages are regarded.

Keywords:

• Low energy X-rays
• DNA damage
• rBE
• monte carlo simulation
• Geant4-DNA
• mCDS

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Data available on reasonable request from the authors.

Additional information

Funding

None declared.

Notes on contributors

Reza Shamsabadi

Reza Shamsabadi: Ph.D., Physics department, Hakim Sabzevari University, Sabzevar, Iran.

Hamid Reza Baghani

Hamid Reza Baghani: Ph.D., he is an Associate Professor at physics department of Hakim Sabzevari University, Sabzevar, Iran.