ESTRO 2021 Abstract Book

S214

ESTRO 2021

back to simulate noise effects due to radioactive decay, and the delivered dose was measured using the ArcCHECK phantom. For the purpose of Gamma analysis, these targets are static. Gamma analysis (3%/3mm criteria) was used to compare ArcCHECK measurements with the TPS calculated dose.

Results BgRT delivery for the spherical target with FDG-avid, C-shape OAR achieved a gamma pass rate of 95.2%, while the cylindrical target enclosing the C-shape (partially PET-avid target) with a nearby pet-avid, spherical structure achieved a pass rate of 98.9%.

Conclusion The results provide physical validation that BgRT plans robustly deliver dose to multiple FDG-avid targets and that the BTZ successfully segregates targets from nearby non-target structures with FDG-avidity.

Proffered papers: Proffered papers 19: Plan optimisation and algorithms

OC-0307 Results of the ESTRO plan quality assessment 2020 online survey L.P. Kaplan 1,2 , L. Placidi 3 , A. Bäck 4,5 , M. Hussein 6 , R. Canters 7 , V. Hernandez 8 , M. Fusella 9 , T. Piotrowski 10,11 , A. Vaniqui 7 , C.R. Hansen 12,13 , L. Widesott 14 1 Aarhus University Hospital, Department of Oncology, Aarhus, Denmark; 2 Aarhus University, Department of Clinical Medicine, Aarhus, Denmark; 3 Fondazione Policlinico A. Gemelli IRCCS, UOC Radioterapia Oncologica, Dipartimento di Diagnostica per Immagini, Radioterapia Oncologica ed Ematologia, Rome, Italy; 4 Sahlgrenska University Hospital, Department of Therapeutic Radiation Physics, Gothenburg, Sweden; 5 University of Gothenburg, Department of Radiation Physics, Sahlgrenska Academy, Gothenburg, Sweden; 6 National Physical Laboratory, Metrology for Medical Physics Centre, Teddington, United Kingdom; 7 Maastricht University Medical Centre+, Department of Radiation Oncology (Maastro), GROW School for Oncology, Maastricht, The Netherlands; 8 Hospital Sant Joan de Reus, Department of Medical Physics, Reus, Spain; 9 Veneto Institute of Oncology - IOV IRCCS, Department of Medical Physics, Padua, Italy; 10 Poznan University of Medical Sciences, Department of Electroradiology, Poznan, Poland; 11 Greater Poland Cancer Centre, Department of Medical Physics, Poznan, Poland; 12 Odense University Hospital, Laboratory of Radiation Physics, Department of Oncology, Odense, Denmark; 13 University of Southern Denmark, Department of Clinical Research, Odense, Denmark; 14 Proton Therapy Center, APSS, -, Trento, Italy Purpose or Objective Innovations in treatment planning are making plan quality assessment ever more important and challenging, while guidance and consensus on tools and metrics to use are lacking. The ESTRO working group on plan quality assessment was founded following the 3 rd ESTRO Physics workshop in 2019. The first aim of this group was to map the current use of methods to control and assess plan quality in ESTRO member centres. Materials and Methods An online survey was sent out to ESTRO members in March 2020. It contained 75 questions focusing on plan complexity and plan robustness. Complexity was defined as modulation of machine parameters leading to increased demand on accuracy of dose calculation and treatment delivery, and robustness as the dose distribution’s sensitivity towards errors from patient setup, range calculation uncertainties, or anatomical changes. Complexity questions aimed to see for which types of treatments (if any) centres consider complexity to be an issue, and how it is controlled and evaluated during plan optimization and evaluation. Robustness questions focused on the use of safety margins, robust optimization (RO), and robust evaluation (RE). Centres were also asked which methods and metrics they used to evaluate a plan’s dosimetric quality. Survey questions were written by two separate groups and reviewed by the entire working group to ensure