ESTRO 2025 - Abstract Book

S3543

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

ESTRO 2025

References: 1. Rørvik, E., Fjæra, L. F., Dahle, T. J., Dale, J. E., Engeseth, G. M., Stokkevåg, C. H., Thörnqvist, S., & Ytre-Hauge, K. S. (2018). Exploration and application of phenomenological RBE models for proton therapy. Physics in medicine and biology, 63(18), 185013. https://doi.org/10.1088/1361-6560/aad9db 2. Lyngholm, E., Stokkevåg, C. H., Lühr, A., Tian, L., Meric, I., Tjelta, J., Henjum, H., Handeland, A. H., & Ytre-Hauge, K. S. (2024). An updated variable RBE model for proton therapy. Physics in medicine and biology, 69(12), 10.1088/1361 6560/ad3796. https://doi.org/10.1088/1361-6560/ad3796

3748

Mini-Oral A large-animal pilot study of cardio-respiratory-gated radiation ablation for ventricular tachycardia targets using proton therapy Kyung-Wook Jee 1 , Felicitas J Bijari 2,1 , Yanis Chemli 2 , Yen-Lin Chen 1 , Helen Deng 3 , Nicolas Depauw 1 , Maeva Dhaynaut 2 , Adriano Garonna 4 , Jagdip Kang 5 , Hyeongseok Kim 1 , Marina Macdonald-Soccorso 3 , Sung-Hyun Moon 3 , Marc D Normandin 2 , Rebecca Woodcock 5 , K. Moshe Yaghoubian 5 , Robert Levine 5 , H. Immo Lehmann 6,5 , Georges El Fakhri 2 1 Radiation Oncology, Massachusetts General Hospital, Boston, USA. 2 Radiology & Biomedical Imaging, Yale University, New Haven, USA. 3 Radiology, Massachusetts General Hospital, Boston, USA. 4 Physics, EBAMed SA, Geneva, Switzerland. 5 Cardiology, Massachusetts General Hospital, Boston, USA. 6 Internal Medicine, University of Utah, Salt Lake City, USA Purpose/Objective: Radiation-based ablation with photon or particle beams has emerged as an alternative to catheter-based ablation for treating cardiac arrhythmia (specifically, ventricular tachycardia) [1]. While proton radiotherapy benefits from its Bragg peaks, the conformal delivery of an ablative dose to a cardiac target is challenging due to its complex motion and proximity to radiation-sensitive organs at risk (OARs). To facilitate a successful clinical translation, a large animal pilot study was designed and performed, which serves as an opportunity to evaluate a novel ultrasound based image-guidance system, cardio-respiratory gated pencil beam scanning delivery, and proton range/response verification technologies, thereby validating the efficacy of radiation ablation. Material/Methods: Regulated by the internal IACUC, six healthy swine underwent either respiratory (single) or cardio-respiratory (dual) gated cardiac ablation with a prescribed dose of 35GyRBE. The subjects were followed up to 14 weeks when a terminal study, including necropsy, was performed. Breath-held, cardiac-gated 4-D CTs w/o contrast were used to model transmural left-ventricular targets. A new scanning control logic was developed to hold and resume irradiating mid-stream in a beam spot with minimal latency (< 550 µs at Max. current), accommodating the fast cardiac-gated delivery. A novel cardiac-ultrasound IGRT system (CardioKit) provided in-room cardiac position in real time (50 fps) and all single or dual gating signals. To characterize the time course of imaging biomarkers, each subject received three or four multimodal (echocardiography, contrast-enhanced CT, dynamic PET) imaging sessions. Uniquely in this study, the functional assessments of the irradiated myocardium were performed by imaging the time-averaged tissue membrane potential (ΔΨ) using a lipophilic cationic PET tracer ( 18 F-TPP + ) [2]. The study evaluated an early change of ΔΨ since the anti-arrhythmic effects of human trials occurred early. Echocardiography and bloodwork were performed for all treated animals throughout the study courses. Potential toxicities to surrounding tissues were examined during necropsy, and irradiated and control tissues were sampled for histopathology analysis. Results: Radiation-ablation of cardiac targets promises a noninvasive, outpatient-based, and potentially more effective treatment for patients with ventricular arrhythmias with a low complication rate. All subjects finished the study