S2237
Physics - Intra-fraction motion management and real-time adaptive radiotherapy
ESTRO 2026
immobilization to maintain consistent positioning. However, long treatment sessions can be physically demanding, and the immobilization and positioning platform of the device may contribute to patient discomfort, potentially limiting endurance. This research explores the design of a breast immobilization platform that balances movement stability and patient comfort for prone hyperthermia treatments. Material/Methods: To quantify comfort and immobilization, a design evaluation was conducted (METC approved, N-WMO, MEC-2024-0767). Ten healthy female participants were evaluated in prone position using a clinically established breast MRI platform (8-channel breast coil®, GE Healthcare, USA) and asked to assess discomfort (0-10: 0=no discomfort, 10=extreme discomfort) and pressure points by completing a questionnaire after laying on the platform for a duration of 90 minutes. Immobilization was monitored with Electromagnetic Tracking (EMT) sensors (Figure 1) placed on the back and nipple of the volunteer’s evaluated breast, which was submerged in water during each assessment. The reported outcomes provided baseline data which were used as input for the development of the new hyperthermia immobilization platform (Figure 1B). This platform included a soft foam mattress and extra cushioning to improve pressure distribution along the body, and a silicone layer to stabilize the breast position. The same healthy volunteers returned approximately two months after initial assessment to test the new platform using the same approach.
to 4.22 mm(95%) vs. 3.09 mm(98%). Further margin expansion to 4 mm provide minimal gain, this rose to 5.19 mm(95%) vs. 4.48 mm(98%). These correlations highlight that lower VOICE thresholds accommodate larger displacements for given margins, though envelope margins are constrained by duty cycle and motion amplitude to preserve dosimetry.
Conclusion: This study revealed the correlations among target size, displacement, envelope margin, and VOICE threshold for CMM-based treatments on the Unity system. The results provide foundational insights for selecting envelope margins and VOICE thresholds, supporting balanced decisions between normal tissue sparing and treatment efficiency. References: 1. Unity Comprehensive Motion Management – Physics training, E061632 / 03, Elekta Keywords: VOICE , envelope margin, target displacement Digital Poster 2775 Design and Evaluation of a Comfortable Breast Immobilization Platform for MR-Guided Hyperthermia for Breast Cancer Patients Linnea Verbeek 1,2 , Alexandra D de Boer 1 , Jenny Dankelman 2 , Nick van de Berg 1,2 , Sergio Curto 1 1 Department of Radiotherapy, Erasmus MC Cancer Institue, Rotterdam, Netherlands. 2 Department of BioMechanical Engineering, Delft University of Technology, Delft, Netherlands Purpose/Objective: Accurate treatment delivery during hyperthermia therapy of the intact breast requires effective
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