ESTRO 2024 - Abstract Book

S4310

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

ESTRO 2024

Results:

Target coverage resulting from dose accumulated on the initial or last CT of each patient was not significantly different. Patients with minimal anatomical changes had differences not exceeding 0.5 Gy RBE for D98% and V95%, whilst patients with more pronounced anatomical changes showed maximum differences in the same metrics of 1 Gy RBE for the high-risk CTV (Table 1). For these patients with significant anatomical changes, the low dose CTV between the planning CT and the last CT showed a reduction of 33 mL, while both parotids had a mean shrinkage of 4 ml. Significant differences were however observed in OAR sparing, particularly for the Maximum Dose (Dmax) delivered to the brainstem and the chiasm, with differences up to 2.2 Gy RBE and 12 Gy RBE for the brainstem and chiasm respectively, in patients with substantial anatomical changes. When using the Demons DIR for dose deformation, similar but even more pronounced dosimetric differences were observed, with differences of up to 2 GyRBE for the target coverage and 6.5/14.3 Gy RBE for brainstem/chiasm Dmax respectively (Table 1). This highlights the importance