S2949
RTT- RTT operational practice and workflow innovations
ESTRO 2026
isocenters in both pediatric and adult patients. References: Sandt M, Marcet S, Guesnel N, Claude L, Martel I, Biston MC. Implementation of Linac-based VMAT total body irradiation technique on Elekta platform using surface-guided radiation therapy. Phys Med. 2025 Mar;131:104940. doi: 10.1016/j.ejmp.2025.104940. Epub 2025 Feb 20. PMID: 39983594. Keywords: TBI-VMAT, SGRT, Intra-fraction Motion Deformable registration-based identification of breathing patterns to quantify the clinical Impact of DIBH in right breast cancer radiotherapy Daniele Carlotti 1 , Claudia Tacconi 1 , Cintia De Almeida Ribeiro 1 , Gabriele D'Ercole 1 , Claudio Dionisi 1 , Michele Fiore 1,2 , Carlo Greco 1,2 , Teresa Insero 1 , Edy Ippolito 1,2 , Aurelia Iurato 1 , Corrado Macauda 1 , Valerio Marè 1 , Paola Martucci 1 , Guenda Meffe 1 , Salvatore Minuti 1 , Angelo Montagnoli 1 , Marta Moraschi 1 , Gian Marco Petrianni 1 , Lucrezia Toppi 1 , Lisa Vicenzi 1 , Sara Ramella 1,2 1 Radiation Oncology, Fondazione Policlinico Universitario Campus Bio-Medico, Rome, Italy. 2 Medicine and Surger, Università Campus Bio-Medico di Roma, Rome, Italy Poster Discussion 4517 Purpose/Objective: This study aims to investigate the use of deformable image registration (DIR) for the determination and characterization of patient-specific breathing patterns, with the objective of quantifying and assessing the clinical benefits of Deep Inspiration Breath Hold (DIBH) in right-sided breast cancer radiotherapy. In order to prepare patients for therapy, it is essential to implement an effective training program designed to teach correct and reproducible breathing techniques. Proper pre-therapy training ensures consistent breath- hold performance, thereby improving the accuracy and reliability of image registration and dose delivery. Material/Methods: A total of 51 patients, with a mean age of 58 years, was included in a monocentric study conducted across two departments. Patient enrollment took place from September 2024 to September 2025. Deformable image registration (DIR) was performed using the ANACONDA algorithm between planning CT scans acquired under free-breathing (FB) and deep inspiration breath hold (DIBH) conditions to map and analyze respiratory-induced anatomical variations. Each DIR result was independently reviewed and validated by an experienced radiation oncologist to
to ensure accurate positioning, with particular attention to the hands and feet (Figure 1).Setup verification initially (3 patients) included two extended CBCT acquisitions: chin-to-pelvis (head-first supine, HFS) and pelvis-to-knees (feet-first supine, FFS). Setup displacements were recorded, but not applied if within a 0.5cm threshols and if within the skin flash, prioritizing the thoracic region during registration. All treatments were delivered with Beam Hold activated to verify intra-fraction stability. kV images were acquired before each isocenter was treated.
Results: Extended CBCT registrations showed discrepancies below the established threshold, allowing image- guided radiotherapy (IGRT) to be reduced to a single thoracic CBCT and a second CBCT at the pelvis junction (transition from HFS to FFS) while maintaining accurate multi-isocenter treatment delivery. This resulted in fewer imaging acquisitions per fraction compared with standard TBI-VMAT workflows.Registration shifts for all patients are shown in Figure 2. In both the thoracic and pelvic regions, displacements were within the predefined tolerance thresholds across all patients. No intra-fraction movement was detected with the SGRT system which was consistent with the kV images.
Conclusion: In TBI-VMAT treatments, the SGRT workflow enables a decrease in CBCT acquisitions while maintaining precise and reproducible patient positioning, including challenging areas such as the hands and feet. It also provides intra-fraction motion monitoring. This ensures accurate dose delivery across multiple
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