S1921
Physics - Dose prediction/calculation, optimisation and applications for photon and electron planning
ESTRO 2026
896(1):31–49, 2007[2] V.A. Semenenko, R.D. Stewart. Fast MC simulation of DNA damage by electrons and ions. Phys Med Biol, 51(7):1693, 2006.[3] W. Wang, C. Li, R. Qiu et al. Modelling cellular survival after DNA DSBs. Sci Rep, 8(1):16202, 2018.[4] S.M. Sebastián et al. MC of cell survival in proton SOBP. Phys Med Biol, 68(19):195024, 2023.[5] R. Azimi, et al. Characterization of an orthovoltage biological irradiator for radiobiological research. J Radiat Res, 56(3):485–492, 2015.[6] K. Claesson et al. RBE of α -particles from 211At for complex DNA damage and cell survival. Int J Radiat Biol, 87(4):372–384, 2011. Keywords: Monte Carlo, simulations, cell survival Reirradiation treatment planning: comparative analysis of photon and proton approaches and voxel-wise EQD2Gy background dose optimisation Louise Murray 1,2 , Christopher Thompson 3 , Esther Bär 4,5 , Finbar Slevin 1,2 , John Lilley 3 , Maria A Hawkins 4,6 , Ane L Appelt 7,2 1 Department of Clinical Oncology, Leeds Cancer Centre, Leeds, United Kingdom. 2 Leeds Institute of Medical Research, University of Leeds, Leeds, United Kingdom. 3 Department of Medical Physics, Leeds Cancer Centre, Leeds, United Kingdom. 4 Department of Medical Physics and Biomedical Engineering, Digital Poster Highlight 3194 University College London, London, United Kingdom. 5 Department of Medical Physics, University College London Hospitals, London, United Kingdom. 6 Department of Clinical Oncology, University College London Hospitals, London, United Kingdom. 7 Department of Oncology, Rigshospitalet & Technical University of Denmark, Copenhagen, Denmark Purpose/Objective: Purpose: To compare reirradiation treatment planning using (1) standard clinical photon planning, (2) proton beam therapy (PBT), and (3) photon planning incorporating robustly mapped original dose distribution as background dose with voxel-by-voxel optimisation in Equivalent Dose in 2Gy fractions (EQD2Gy)[1]. Material/Methods: Ten patients with recurrent pelvic malignancies (six
Figure 1. Reproduced geometry of the XRAD320 and the cellular target in FLUKA. Results: The integrated geometry of the XRAD320 with the cellular target was successfully reproduced in FLUKA. The predicted SF(D), acquired under simulated conditions of 125 kVp X rays filtered with 2 mm Al, showed close agreement with the experimental data [6], with a RMSE of 0.047.
Figure 2. Comparison between simulated predictions and experimental data [6]. Conclusion: The computational framework was validated against experimental data for V79, showing consistent predictive accuracy. The simulated protocol slightly differed from the one originally used, as it was chosen to match the configuration available for experimental validation in the laboratory, nevertheless, both setups are largely comparable. The main discrepancy between prediction and data is observed at 4 Gy, where the experimental data do not follow the trend of the neighboring points. This highlights the importance of having a predictive framework capable of guiding experimental measurements and optimizing data acquisition. Although the computational chain was initially developed for hadrons, the results support its applicability to photons, thus extending the model’s domain of validity. References: [1] G. Battistoni, S. Muraro, P.R. Sala et al. The FLUKA code: description and benchmarking. AIP Conf Proc,
prostate, three colorectal, one anal; GTV median:5.0cm3, range:1.2-38.3cm3; PTV
median:30.6cm3, range:7.1-87.1cm3) previously treated with pelvic radiotherapy were replanned for Stereotactic Ablative Radiotherapy, 30Gy in 5 fractions, aiming to cover ≥ 95% of the PTV with the prescription dose.Identical cumulative organ at risk (OAR) constraints were applied for all approaches. For standard photon and PBT planning, physical reirradiation plan constraints were derived from case-
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