S2261
Physics - Intra-fraction motion management and real-time adaptive radiotherapy
ESTRO 2026
1 Department of Radiation Oncology, University Medical Center Mannheim, University of Heidelberg, Mannheim, Germany. 2 Department of Medical Physics, Istituto di Ricovero e Cura a Carattere Scienti fi co (IRCCS) Fondazione Policlinico San Matteo, Pavia, Italy. 3 EBAMed SA, External Beam Ablation Medical Devices, Geneva, Switzerland. 4 Department of Radiation Oncology, Istituto di Ricovero e Cura a Carattere Scienti fi co (IRCCS) Fondazione Policlinico San Matteo, Pavia, Italy. 5 Radiation Oncology Unit, Clinical Department, CNAO National Center for Oncological Hadrontherapy, Pavia, Italy. 6 Medical Physics Unit, Clinical Department, CNAO National Center for Oncological Hadrontherapy, Pavia, Italy. 7 Arrhythmias and Electrophysiology Unit, Division of Cardiology- Fondazione, Istituto di Ricovero e Cura a Carattere Scienti fi co (IRCCS) Fondazione Policlinico San Matteo, Pavia, Italy. 8 Radiology Unit-Diagnostic Imaging I, Department of Diagnostic Medicine, Istituto di Ricovero e Cura a Carattere Scienti fi co (IRCCS) Fondazione Policlinico San Matteo, Pavia, Italy. 9 DKFZ- Hector Cancer Institute, University Medical Center Mannheim, University of Heidelberg, Mannheim, Germany. 10 Department of Radiation Oncology, University Medical Center Schleswig-Holstein, Kiel, Germany Purpose/Objective: Cardiorespiratory ultrasound (US) tracking ensures precise dose delivery for Stereotactic Arrhythmia Radioablation (STAR) of ventricular tachycardia (VT). Sparing of the US-probe from the primary beam can present technical challenges due to its placement near the left ventricle. This bi-centric retrospective treatment planning study aimed to evaluate the feasibility of STAR planning in the presence of an US- probe of an experimental cardiorespiratory tracking system. Material/Methods: Treatment plans on cardiac CT data from eleven patients were compared. Organs-of-interest (OOI) and US-probe were contoured and planning target volumes (PTVs) were accepted as used for STAR. Prescribed PTV dose was 25Gy according to RAVENTA protocol [1]. For each patient, three photon volumetric modulated arc therapy (VMAT) treatment plans were created: A reference plan without US-probe and two plans with US-probe sparing from primary beam (apical and parasternal US-probe position, Figure 1). Descriptive analysis was performed for PTV and OOI dose volume histogram (DVH) parameters, focusing on potential major deviations according to RAVENTA (Table 1).
stability and reproducibility. TTT significantly decreased by more than 10% (p < 0.05). BHT increased by 19%. Although not all parameters reached statistical significance, this may reflect the limited cohort size rather than a lack of effect.
Conclusion: Analysis of over 150 treatment sessions suggested that DIBH performance improves during radiotherapy, evidencing a learning or adaptation effect. These findings support the hypothesis that structured respiratory training prior to simulation could optimize DIBH quality from the first session—an especially relevant consideration for hypofractionated regimens, where less adaptation time is available during treatment. To our knowledge, this is the first study quantifying intra-treatment DIBH performance evolution using day to day RPM breathing curves during treatment. Keywords: DIBH, Trainning, Breast Echocardiographic real-time cardiorespiratory tracking for photon-based stereotactic arrhythmia radioablation: feasibility and dosimetric analysis Hans Oppitz 1 , Lena Kästner 1 , Laura Mantovani 2 , Amelie Luisa Matusche 1 , Kerstin Siebenlist 1 , Nour Alfakhori 1 , Mathieu Kruska 1 , Adriano Garonna 3 , Elisabetta Bonzano 4 , Viviana Vitolo 5 , Alfredo Mirandola 6 , Roberto Rordorf 7 , Adele Valentini 8 , Nicoletta Basla 8 , Frank Anton Giordano 1,9 , Oliver Blanck 10 , Jens Fleckenstein 1 , Judit Boda-Heggemann 1 Poster Discussion 3951
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