ESTRO 2023 - Abstract Book

S673

Monday 15 May 2023

ESTRO 2023

main challenge of the PS method was that it favors the planning shape while the DVFN had difficulties to predict large deformations.

Conclusion The methods presented in this work were developed for data from fractionated MRgRT, where prior knowledge from the planning phase can be used at the time of irradiation. DVFN appears to predict limited deformations and is therefore less suitable for organs undergoing substantial volume changes. Conversely, PS networks on average improve segmentation compared to the BM. PS is particularly beneficial for patients with unusual anatomies and helps to adjust the top and the bottom ends of the rectum. However, it could propagate errors in initial contouring and over-favour the planning shape. Therefore, PS and BM should be used as complementary methods. MO-0802 Automatic target delineation in on-line adaptive H&N IMPT with plan library approach. Are we ready? M. Gi ż y ń ska 1 , M. Oud 1,2 , S. Breedveld 2 , B. Heijmen 2 , M. Hoogeman 1,2 1 HollandPTC, Department of Medical Physics & Informatics, Delft, The Netherlands; 2 Erasmus MC Cancer Institute, University Medical Center Rotterdam, Department of Radiotherapy, Rotterdam, The Netherlands Purpose or Objective On-line adaptive proton therapy is not clinically available. In part this is related to challenges in fast on-line plan (re- )optimization and QA. Recently, we have proposed an on-line adaptive approach for IMPT, based on patient-specific pre- treatment established plan libraries [Oud et al. 2022]. In this approach, for each patient, a set of plans with different setup robustness (SR) settings is generated prior to the treatment. Every fraction, the plan best fitting with the current anatomy, Work funded by the Wilhelm Sander-Stiftung