ESTRO 2025 - Abstract Book

S2890

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2025

Conclusion: Although some form of automation is already used in over 80% of cases, there remains potential for further improvement. Differences in automation usage across planners are particularly noteworthy, despite the limited group size. Additional training will be provided to improve familiarity and acceptance of available options. In addition, the in-house scripts will be further optimized to increase user-friendliness based on the collected data.

Keywords: automation, treatment planning, optimization

3692

Digital Poster Plan-of-the-Day strategies in Locally Advanced Cervical Cancer: Dosimetric comparisation of contrasting approaches from EMBRACE II recruiting centers Silje S Os 1,2 , Trine Martens 1 , Annelen D Schmidt 3 , Mathilde H Lystad 3 , Eva Schaake 4 , Martjin Ketelaars 4 , Kjersti Bruheim 1 , Taran P Hellebust 3 1 Department of Oncology, Oslo University Hospital, Oslo, Norway. 2 Faculty of clinical medicine, University of Oslo, Oslo, Norway. 3 Deparment of Medical Physics, Oslo University Hospital, Oslo, Norway. 4 Department of Radiation therapy, The Netherlands Cancer Institute, Amsterdam, Netherlands Purpose/Objective: Plan-of-the-day (PotD) radiotherapy for locally advanced cervical cancer is implemented in many centers worldwide. The treatment plans are based on image acquisitions with full and empty bladder. However, the number of plans, and thereby the complexity of the treatment, varies considerably from center to center. In the EMBRACE II database such information is not included. In order to prepare for an analysis of possible gain of PotD radiotherapy, we have simulated the dosimetrical impact of various approaches using data from patients with different degree of internal movement. Material/Methods: By contacting EMBRACE II centers that have included PotD patients, two contrasting planning approaches were identified: (1) a simple method using two plans plus a backup and (2) a complex method with one plan per 1 cm movement of the uterine fundus. Using image data from two patients, fundus movements of 3 cm (Patient A) and 8 cm (Patient B) were analyzed. For the complex method, three and seven plans were created for Patients A and B, respectively. Daily ConeBeam CTs (CBCT) was assessed to determine the optimal plan for each fraction, and summed dose distributions were calculated on a full-bladder CT-scan (CT full ). Bladder, rectum and target volume (CTVp_LR) were delineated on each CBCT (N=25 per patient), enabling fraction-specific dose calculations. Deformable image registration (DIR) was performed using the Hybrid intensity and structure based algorithm in