ESTRO 2025 - Abstract Book

S3342

Physics - Intra-fraction motion management and real-time adaptive radiotherapy

ESTRO 2025

cases and peripheral in 6 cases. Prior to treatment initiation, simulation sessions were conducted to evaluate the compatibility of target position, density, and motion characteristics with Synchrony-based treatment requirements. Patients with poor overall performance (n=6) were positioned with their arms at their sides, while those with good performance status (n=7) used a wingboard to elevate their arms above their heads. Treatment planning was performed with the Accuray Precision TPS, utilizing the VoloUltra optimization algorithm. Field sizes were set at 2.5 cm, and the TPS automatically determined the modulation factor. The pitch factor was adjusted to meet the maximum gantry period required for the Synchrony technique. Target coverage, gradient index, and dose to organs at risk were evaluated in accordance with UK SABR 2022 guidelines for SBRT planning. Plan verification was performed using a PTW 1500 detector with a Cheese phantom for patient-specific quality assurance, including a 3D gamma analysis (2 mm/3%). Respiratory motion during irradiation was simulated using the CIRS dynamic motion platform (Model 008PL). Routine follow-ups were conducted every three months, with assessments based on PET/CT imaging. The median follow-up duration was 6 months (range: 3–9 months).

Results:

Table 1 provides an overview of the median, minimum, and maximum values for key parameters, including prescribed doses, Synchrony simulation duration, the number of radiographs acquired during simulation, planning parameters, as well as the number of radiographs captured during treatment and the treatment duration. Routine follow-up assessments revealed a local control rate of 100% with no toxicity. Conclusion: Our short-term clinical experience indicates that the Synchrony "lung with respiratory" motion tracking system is a precise and effective technique for lung SBRT in appropriately selected patients.

Keywords: Radixact Synchrony, Motion management, Lung SBRT