ESTRO 2025 - Abstract Book

S3258

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

ESTRO 2025

21 patient alignment CBCTs of 9 retrospective patients with target shifts were selected to assess the performance of SA. To evaluate whether GTVprim is in the correct position in synthetic CTs, registration vector lengths were used to quantify residual GTVprim misalignments between each synthetic CT and its corresponding patient alignment CBCT. Results: Figure 1 illustrates the advantage of using synthetic CTs with corrected target positions, as opposed to using the original planning CT in IGRT with GTVprim misalignments. Residual GTVprim misalignment vectors between planning CT and CBCT were 5.3mm on average (max=12.6mm, min=2mm, SD=2.6mm). Vectors between synthetic CTs and CBCTs were 0.6mm on average (SD=0.3mm), demonstrating the ability of SA to correct for residual GTVprim misalignments (figure 2).