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. 2025 Apr 11;15(1):12431.
doi: 10.1038/s41598-025-97522-1.

Shielding disc backscatter calculations in intraoperative radiotherapy using a Monte Carlo simulation based on the method of energy spectra reconstruction

Adam Ryczkowski  1   2 , Marta Kruszyna-Mochalska  1   2 , Bartosz Pawałowski  2 , Grzegorz Bielęda  1   2 , Agata Jodda  2 , Przemysław Adrich  3 , Tomasz Piotrowski  4   5   6
Affiliations

Shielding disc backscatter calculations in intraoperative radiotherapy using a Monte Carlo simulation based on the method of energy spectra reconstruction

Adam Ryczkowski et al. Sci Rep. .

Abstract

The study focuses on validating and applying a Monte Carlo (MC) simulation model to backscatter calculations from the shielding discs used during intraoperative electron radiotherapy (IOERT), particularly in breast cancer treatments. The MC model is developed based on dosimetric data collected under reference conditions and validated by measurements with EBT4 Gafchromic films in a water phantom. The study investigates the dose distributions for 6, 9, and 12 MeV electron beams formed by a mobile AQURE accelerator, comparing scenarios with and without a surgical stainless steel shielding disc. While the shielding disc effectively reduces radiation doses behind it, the backscatter significantly increases doses in tissues immediately in front of the disc. Specifically, the dose at 1 mm in front of the disc increases by 19.8%, 18.4%, and 17.5% were observed for 6, 9, and 12 MeV beams, respectively. The validated MC model provides an accurate tool for predicting dose distributions in complex geometries, enabling improved treatment planning and safety in IOERT applications. The findings underscore the need to consider backscatter effects when shielding discs are used in IOERT. The study suggests further optimization of shielding disc design, potentially incorporating biocompatible, low-Z materials to mitigate backscatter.

Keywords: 3-D printing; Dose modelling; EBT4; IOERT; Monte Carlo.

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Conflict of interest statement

Declarations. Competing interests: The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
(a) Shielding disc (steel circle) and the holder elements: grey for gafchromic film and shielding disc fixation and purple for fixing the applicator, (b) The setup of the holder with the shielding disc in the phantom, (c) Measurement geometry without the shielding disc, (d) Measurement geometry with the shielding disc.
Fig. 2
Fig. 2
The geometry of the beam-forming system and the phantom with the location of the detectors used for MC simulations and the shielding disc.
Fig. 3
Fig. 3
The comparisons of the simulated (line) and measured (dots) percentage dose distributions for the geometry scenarios without the shielding disc (a) and with the shielding disc (c) with particular emphasis on the results of the gamma analysis performed in a global mode (b and d). The gamma analysis criteria are 2%/2 mm.
Fig. 4
Fig. 4
(a) The graphical comparison of the doses simulated for two geometric scenarios, i.e. with (line) and without (dots) shielding disc, and (b) The dose differences between these scenarios.
See this image and copyright information in PMC

References

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