ESTRO 2023 - Abstract Book

S509

Sunday 14 May 2023

ESTRO 2023

Conclusion The use of dedicated SIP concepts in combination with multiparametric prescription requirements and objectives in the context of multi-center benchmark studies with group consensus and training can lead to high treatment plan quality. Harmonization of SIB treatment planning appears possible in the context of international multi-center clinical trials. [1] T. B. Brunner et al., Simultaneous integrated protection : A new concept for high-precision radiation therapy. Strahlenther Onkol. 2016 Dec;192(12):886-894. doi: 10.1007/s00066-016-1057-x. Epub 2016 Oct 18. PMID: 27757502; PMCID: PMC5122615. [2] C. Moustakis et al., Planning Benchmark Study for Stereotactic Body Radiation Therapy of Liver Metastases: Results of the DEGRO/DGMP Working Group on Stereotactic Radiation Therapy and Radiosurgery. Int J Radiat Oncol Biol Phys. 2022 May 1;113(1):214-227. doi: 10.1016/j.ijrobp.2022.01.008. Epub 2022 Jan 22. PMID: 35074434. OC-0621 Dosimetric beam-angle optimization for non-coplanar dynamic-collimator trajectory radiotherapy J. Bertholet 1 , C. Zhu 1 , S. Mueller 1 , G. Guyer 1 , P. Mackeprang 1 , H.A. Loebner 1 , W. Volken 1 , M.M.F. Stampanoni 2 , D.M. Aebersold 1 , M.K. Fix 1 , P. Manser 1 1 Inselspital, Bern University Hospital and University of Bern, Division of Medical Radiation Physics and Department of Radiation Oncology, Bern, Switzerland; 2 Institute for Biomedical Engineering, ETH Zürich and PSI, Villigen, Switzerland Purpose or Objective Dynamic-collimator trajectory radiotherapy (colli-DTRT) delivers intensity modulated radiotherapy using multiple non- coplanar partial arcs with dynamic collimator rotation. We solve the beam angle optimization problem for colli-DTRT by determining the table-angle and gantry-angle ranges of the partial arcs through iterative 4pi fluence map optimizations (FMOs) and beam direction elimination. Materials and Methods The treatment planning process is shown in figure 1. First, available beam directions are sampled on a gantry-table map and the collimator angle is aligned to the patient superior-inferior axis. In-house Monte Carlo (MC) dose calculation is performed for all beamlets. Second, FMO is carried out on the set of beams to map the relative contribution of each beam direction to the mean PTV dose. The map is thresholded to eliminate the least contributing beams. Third, candidate arcs are formed by remaining adjacent beams with the same table-angle. These are trimmed by iterative FMO and elimination of the least contributing beams at the arcs’ edges. Short candidates are rejected. Step 3 is repeated until the total gantry- angle range reaches a user-defined value. Fourth, the final set of candidates are considered as dynamic arcs for hybrid direct aperture optimization (HDAO) to obtain a deliverable colli-DTRT plan. Final MC dose calculation is performed.