Determination of optimal control parameters for the tracking Radixact Synchrony system: dosimetric validation for different patient-specific respiratory patterns

Intrafractional organ motion in the thoracic region, mainly caused by respiration, can significantly affect the accuracy of dose delivery in radiation therapy. Several strategies have been developed to manage this motion, ranging from simple clinical approaches, such as target-volume expansion, abdominal compression, and breath-hold techniques, to more advanced methods such as respiratory gating and real-time tumor tracking. The Radixact® helical tomotherapy system installed at the Veneto Oncology Institute (IOV) was recently upgraded with the Synchrony® motion management system, with the aim of optimizing treatments for moving thoracic targets. Synchrony builds predictive models of target motion by combining target positions obtained from frequent kV images acquired during treatment with the signal provided by an external respiratory surrogate. Based on this model, the system dynamically modifies the positions of the jaws and the leaves of the multileaf collimator (MLC), adapting the radiation field in real time to follow target motion. The aim of this thesis is to evaluate the performance of the Synchrony tracking system for thoracic lesions treated with helical tomotherapy, namely its ability to compensate for tumor motion and preserve the accuracy of the prescribed dose. In particular, this work investigates the most effective control parameters for the tracking system and validates the system by assessing dosimetric accuracy for different respiratory motion profiles.