ESTRO 2021 Abstract Book

S219

ESTRO 2021

Conclusion The proposed novel beam angle optimization approach was able to automatically generate plans with clinically feasible numbers of beams (~25) with a plan quality highly similar to that of the 91-beam ideal reference plans. For any beam angle selection approach, ideal reference plans can be used to validate generated plans. OC-0310 Planning dose constraint corrections due to changes in treatment and measurement accuracy J. Stroom 1 , A. Taborda 1 , S. Vieira 1 , C. Greco 1 , B. Nijsten 2 1 Champalimaud Centre for the Unknown, Radiation Oncology, Lisbon, Portugal; 2 MAASTRO Clinic, Medical Physics, Maastricht, The Netherlands Purpose or Objective Currently used RT planning dose constraints for OARs are often based on data from decades ago, when treatment uncertainties were significantly larger than nowadays. We investigated on how present treatment uncertainties will change these constraints, and how they can be affected by QA measurement uncertainties. Materials and Methods Planned DVHs represent an approximation of the real dose delivered to OARs due to dosimetrical and geometrical treatment errors, also in dose-effect studies used for dose constraint (D crit (V crit )