ESTRO 2025 - Abstract Book

S4143

RTT - Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO 2025

The analysis revealed that 95% of deviations were within institutional thresholds of 5 mm and 5°. The calculated translational deviations for gynaecological patients were 2.53 mm (lateral), 2.74 mm (longitudinal), and 2.70 mm (vertical), with rotational deviations of 1.52° (yaw), 1.03° (roll), and 1.45° (pitch). For prostate patients, calculated deviations were 2.53 mm (lateral), 3.03 mm (longitudinal), and 2.70 mm (vertical), with rotational values of 0.91° (yaw), 1.14° (roll), and 1.47° (pitch). Tighter thresholds, encompassing 95% of deviations, limited beam interruptions while avoiding excessive interruptions during treatment. The approach kept treatment workflow efficient and improved treatment accuracy. Conclusion: Optimizing SGRT tolerance thresholds for pelvic cancer patients achieves a better balance between precision and efficiency. This strategy effectively reduces intra-fraction motion while maintaining clinically acceptable interruptions. The data-driven approach enhances radiotherapy delivery and supports its integration into clinical practice. SGRT users should be encouraged to optimize their tolerance thresholds to minimize excessive intrafraction motion.

Keywords: SGRT,Tolerance Optimization,Intrafraction Motion

4270

Digital Poster Accidental Discovery of a Unique High-Density Bolus Property Enabling Single-Step Bolus Alignment and Patient Positioning in SGRT Fernando Picon-Garcia 1 , Javier Sanchez-Esperon 1 , Nerea Lopez-Martin 1 , Ana Isabel Sanchez-Fernandez 2 , Santiago Velazquez-Miranda 1 1 Medical Physics, HOSPITAL UNIVERSITARIO VIRGEN ROCIO, SEVILLE, Spain. 2 Radiation Oncology, HOSPITAL UNIVERSITARIO VIRGEN ROCIO, SEVILLE, Spain Purpose/Objective: Surface-guided radiation therapy (SGRT) relies on accurate surface tracking for patient positioning. Traditional water-equivalent boluses often complicate workflows due to optical interference. During routine testing, we identified a unique property of a high-density bolus (HDB), which enables clearly defined postural lines (PVL), facilitating simultaneous patient positioning and bolus alignment in a single step (figure 1). This communication aims to describe the methods and results of our testing process for this novel property.