ESTRO 2025 - Abstract Book

S2879

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2025

survey was carried out to identify the types of accelerators, TPS and methodology (description of the ballistic parameters, use of the virtual bolus, robust optimization or not, renormalisation, etc.).

Results: Thirty plans were produced by the 21 participating centers. The types of accelerators were: Halcyon TM (16/30), TrueBeam TM (6/30), TomoTherapy ® (2/30), Proteus ® ONE (2/30), Clinac iX TM (1/30), Synergy TM (1/30), Infinity TM (1/30), Agility TM (1/30). The TPS used were: Eclipse ® (17/30), Raystation ® (9/30), Precision ® (2/30), Pinnacle ® (2/30). For PTVs, minimum and maximum D mean , D 95% and D 2% were respectively: breast (49.6-51.3 Gy, 46.5-49.2 Gy, 51.4-54.0 Gy), all lymphe nodes (49.2-51.1 Gy, 44.8-49.0 Gy, 50.9-53.2 Gy) and IMN (49.0-51.1 Gy, 41.1-48.4 Gy, 51.2-53.5 Gy, Fig. 1). For the following organs at risk (OAR), minimum and maximum D mean were: heart (0.8-5.8 Gy, Fig. 1), right breast (0.4-5.9 Gy, Fig. 1), left lung (6.8-17.8 Gy), right lung (0.2-5.6 Gy), oesophagus (2.7-8.2 Gy), thyroid gland (13.9-22.8 Gy). The minimum and maximum doses specific to certain organs were: V 5Gy_Heart (4.4-54.7%), D mean_InterVentricular_Anterior (6.5-28 Gy), D 2%_Right_Breast (2.3-21.5 Gy), V 5Gy_Left_Lung (11.8-33.2%), V 5Gy_Right_Lung (0.3-47.9%), V 20Gy_Oesophagus (0-18.3%), D 2%_Spinal_Cord (0.8-14.4 Gy). Principal component analysis helped identify the centers and treatment techniques that both covered the target volumes well and provided the best protection for the OAR. Although less widespread in France, proton therapy was, as expected, the optimal technique. However, very acceptable results were also observed for VMAT and tomotherapy techniques in certain configurations.

Conclusion: This study revealed heterogeneous practices depending on the irradiation techniques, ballistics and experience of the centers, as well as the great interest of multicentre studies for the most complex dosimetries to promote exchanges between professionals.

Keywords: Multicentre study, VMAT, Protons, Tomotherapy

3614

Digital Poster Chemistry simulations following radiolysis with consideration of interaction potentials Robin Erdmann 1 , Larissa Derksen 1,2 , David Weishaar 1 , Uli Weber 1 , Kilian-Simon Baumann 1,2,3

1 Institute of Medical Physics and Radiation Protection, University of Applied Sciences, Giessen, Germany. 2 Marburg Ion-Beam Therapy Center (MIT), Department of Radiotherapy and Radiation Oncology, Marburg University Hospital, Marburg, Germany. 3 Department of Radiotherapy and Radiation Oncology, Marburg University Hospital, Marburg, Germany

Purpose/Objective: Modelling radiation chemistry is a fundamental part of radiobiological simulations that aim to predict indirect DNA