ESTRO 2024 - Abstract Book

S4309

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

ESTRO 2024

Material/Methods:

For five Head and Neck (H&N) patients for which daily cone beam CTs (CBCT) are available, an online daily adaptive proton therapy workflow has been simulated. All patients were planned using a Simultaneous Integrated Boost (SIB) approach, delivering 54 Gy RBE to the low-risk and 72 Gy RBE to the high-risk CTV. All plans were range robustly optimized (+/-3%) to a 2 mm isotropic expansion of the CTV. Daily synthetic CTs (synCTs) were generated by deforming the reference CT to match the anatomy of each daily cone beam CT (CBCT) and all targets and OARs were propagated to the daily synCT using a BSpline approach. For all patients, the online daily adapted treatment (DAPT) scenario developed at our institute was simulated, whereby a plan is completely reoptimized on each daily synCT. For dose accumulation, daily optimized doses were accumulated (using B Spline based DIR) on two different reference CTs: the initial planning CT and the last available CT for each patient. Differences in the accumulated doses were evaluated by analyzing target coverage (D98% and V95%) and OAR doses (e.g., Brainstem, Optical structures, Cochleas, Eyes, Parotids, Spinal Cord, and Thyroid). The same exercise was repeated using the Demons algorithm for dose deformation to minimize potential biases. In Fig.1, a schematic representation of the simulated workflows is presented.