ESTRO 2024 - Abstract Book

S3655

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

ESTRO 2024

[1] Mittauer KE, Hill PM, Geurts MW, De Costa AM, Kimple RJ, Bassetti MF, Bayouth JE. STAT-ART: The Promise and Practice of a Rapid Palliative Single Session of MR-Guided Online Adaptive Radiotherapy (ART). Front Oncol. 2019;9:1013. [2] Nelissen KJ, Versteijne E, Senan S, Hoffmans D, Slotman BJ, Verbakel WFAR. Evaluation of a workflow for cone beam CT-guided online adaptive palliative radiotherapy planned using diagnostic CT scans. Journal of Applied Clinical Medical Physics. 2023;24:e13841. [3] Schiff JP, Zhao T, Huang Y, Sun B, Hugo GD, Spraker MB, Abraham CD. Simulation-Free Radiation Therapy: An Emerging Form of Treatment Planning to Expedite Plan Generation for Patients Receiving Palliative Radiation Therapy. Advances in Radiation Oncology. 2023;8:101091. [4] Wong S, Roderick S, Kejda A, Atyeo J, Grimberg K, Porter B, et al. Diagnostic Computed Tomography Enabled Planning for Palliative Radiation Therapy: Removing the Need for a Planning Computed Tomography Scan. Practical Radiation Oncology. 2021;11:e146-e53.

[5] Coric I, Shreshtha K, Roque T, Paragios N, Gani C, Zips D, et al. Dosimetric Evaluation of Dose Calculation Uncertainties for MR-Only Approaches in Prostate MR-Guided Radiotherapy. Frontiers in Physics. 2022;10.

2362

Poster Discussion

Dynamic collimator rotation optimization framework for O-ring treatment systems

Michael K Fix, Werner Volken, Daniel Frei, Gian Guyer, Daniel Schmidhalter, Peter Manser

Division of Medical Radiation Physics and Department of Radiation Oncology, Inselspital, Bern University Hospital, and University of Bern, Bern, Switzerland

Purpose/Objective:

Currently, intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) are using fixed collimator angles per field or arc. While dynamic collimator rotation as a degree of freedom for dynamic collimator radiotherapy was investigated for C-arm linear accelerator, this was not investigated for O-ring ETHOS or Halcyon treatment systems. Thus, the aim of this work is the development of an optimization framework for VMAT and IMRT treatment plans with dynamic collimator rotation for O-ring ETHOS or Halcyon treatment systems.

Material/Methods:

The optimization framework consists of a hybrid direct aperture optimization (hDAO) algorithm, which combines a column generation algorithm with simulated annealing and is based on Monte Carlo (MC) generated beamlet dose distributions used to determine the aperture shape along with the MU-weight. An MC model of the beam defining system for an ETHOS treatment system was implemented and commissioned in order to calculate the beamlet dose distributions considering the double-stack multi-leaf collimator (MLC). For IMRT the input for the hDAO included a set of 12 gantry angles {-150°, -120°, -90°, …, 0°, 30°, …, 180°} and for each gantry angle beamlet dose calculations were performed for a set of discrete collimator angles separated by 4°. The number of apertures was limited to a total of 50, which is based on previous experiences. For VMAT, the change of the collimator