ESTRO 2025 - Abstract Book

S3346

Physics - Intra-fraction motion management and real-time adaptive radiotherapy

ESTRO 2025

Fig 1b Seven patients were analyzed for a total of 123 CBCTs. Target coverage and OAR dose did not show significant variation between the original and the re-calculated plans: differences between planned and delivered dose were within 3% for both PTV and V17Gy ipsilateral lung. The discrepancies between mean heart dose in the original plan and all recalculated plans were always lower than 0.6 Gy and differences in V17Gy were always within 2cc. Patients plans re-calculated on the SynCTs fulfilled all PTV and OAR constraints; Figure 1 reports mean heart dose (1a) and heart V17Gy (1b) of the SynCT plans and accepted clinical goals. Conclusion: Calculated dose-volume parameters retrieved from dose distributions re-calculated on the SynCTs fulfilled patient adapted treatment planning goals in all patients. Residual errors during DIBH radiotherapy when combining SGRT and IGRT have a negligible dosimetric impact on target coverage and OAR doses.

Keywords: SGRT, IGRT, Breast cancer

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Digital Poster Quantitative Interplay Effect Evaluation of Two different Proton Therapy machine Delivery Systems for Lung Cancer SBRT Peilin Liu 1 , Xiaoda Cong 1 , Lewei Zhao 2 , Gang Liu 3 , Xuanfeng Ding 1 1 Radiation Oncology, Corewellhealth William Beaumont Hospital, Royal Oak, USA. 2 Radiation Oncology, Stanford University, Palo Alto, USA. 3 Radiation Oncology, Tongji Medical College, Wuhan, China Purpose/Objective: To quantitatively evaluate the interplay effect between two distinct proton therapy machine delivery systems: IBA ProteusONE (synchrocyclotron-based, pulsed beam extraction) and IBA ProteusPlus (cyclotron-based, continuous beam extraction). The objective is to determine differences in plan quality for lung cancer stereotactic body radiotherapy (SBRT). Material/Methods: An interplay evaluation tool was developed to combine 4D CT data with two validated delivery sequence models, IBA ProteusONE and IBA ProteusPlus. The simulation used a 5-second patient breathing cycle. Five lung cancer SBRT cases planned with intensity-modulated proton therapy (IMPT) were retrospectively selected. Dosimetric metrics of the target—D99%, D1%, homogeneity index (HI), and conformity index (CI)—were utilized to quantify the interplay