ESTRO 2025 - Abstract Book

S3538

Physics - Optimisation, algorithms and applications for ion beam treatment planning

ESTRO 2025

Differences between the Vmin and the scenario doses increased. A V95% of 98% or higher was consistently achieved in scenario dose distributions for the 9, 18 and 27 beam plans (Figure 2).

Similar results were found for the near maximum dose, which was higher in the Vmax than in the scenario dose distributions. A systematically smaller difference between the McNamara and RBE 1.1. dose distributions was found for the PAT plans compared to the clinical plans with median differences of 9.1 Gy(E) and 6.5 Gy(E) in the clinical and 18-beam PAT plans respectively. For the optic chiasm, the median difference was 9.7Gy(E), 8.1Gy(E), 7.6Gy(E) an 7.4Gy(E) for clinical, 9, 18 and 9 with RS, respectively. Smaller differences were found in PAT plans with a RS. Conclusion: PAT plans showed reduced robustness in Vmin/Vmax evaluations, while scenario-based evaluations remained robust, indicating the need for an alternative evaluation. PAT plans showed smaller differences between the RBE 1.1. and Macnamare RBE-weighted dose, suggesting potential benefits in reducing high LET/RBE in OARs. LET optimization could enhance this even further.

Keywords: proton arc, robustness, RBE-weighted dose

3582

Digital Poster incorporation of cell line radiosensitivity into microdosimetric kinetic model in carbon therapy Honghu Song, Ming Chen, Xiaoyan Huang Radiotherapy, Sun Yat-sen University Cancer Center, GuangZhou, China Purpose/Objective: Relative biological effectiveness (RBE) is the most important biological parameter in heavy ion therapy. In the microdosimetric kinetic model (MKM) proposed by Kase, the quadric term β was considered as a radiation quality independent parameter. In 2018, Chen developed a modified microdosimetric kinetic model (MMKM) based on the