ESTRO 2024 - Abstract Book

S3500

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

ESTRO 2024

[1] Michalski JM, Gay H, Jackson A, Tucker SL, Deasy JO. Radiation Dose–Volume Effects in Radiation-Induced Rectal Injury. International Journal of Radiation Oncology, Biology, Physics. 2010;76:S123-S9.

[2] Olsson CE, Jackson A, Deasy JO, Thor M. A Systematic Post-QUANTEC Review of Tolerance Doses for Late Toxicity After Prostate Cancer Radiation Therapy. International Journal of Radiation Oncology, Biology, Physics. 2018;102:1514-32. [3] Widmark A, Gunnlaugsson A, Beckman L, Thellenberg-Karlsson C, Hoyer M, Lagerlund M, et al. Ultra hypofractionated versus conventionally fractionated radiotherapy for prostate cancer: 5-year outcomes of the HYPO-RT-PC randomised, non-inferiority, phase 3 trial. The Lancet. 2019;394:385-95.

[4] Peacock JA. Two-dimensional goodness-of-fit testing in astronomy. Monthly Notices of the Royal Astronomical Society. 1983;202:615-27.

828

Proffered Paper

Direct aperture optimization-based pathfinding for dynamic-collimator mixed beam radiotherapy

Chengchen Zhu 1 , Gian Guyer 1 , Jenny Bertholet 1 , Silvan Mueller 1 , Hannes A Loebner 1 , Marco F M Stampanoni 2 , Michael K Fix 1 , Peter Manser 1 1 Inselspital, Bern University Hospital, and University of Bern, Division of Medical Radiation Physics and Department of Radiation Oncology, Bern, Switzerland. 2 ETH Zürich and PSI, Institute for Biomedical Engineering, Villigen, Switzerland

Purpose/Objective:

Using non-coplanar beam setups or combining different particle types has the potential to improve dosimetric treatment plan quality compared to state-of-the-art volumetric modulated arc therapy (VMAT). Dynamic collimator mixed beam radiotherapy (colli-DYMBER) is a novel treatment technique that extends VMAT by including two different particle types (photon and electron beams both shaped with photon multi-leaf collimator (MLC)), by using non-coplanar arcs, and by dynamically rotating the collimator during beam-on. Finding favorable beam directions and contributions of each particle type for such a technique becomes challenging because of the numerous degrees of freedom.

The aim of this work is to develop a dosimetrically motivated pathfinding approach based on direct aperture optimization (DAO) to solve the beam angle optimization problem for colli-DYMBER.

Material/Methods:

The proposed pathfinding process, illustrated in Fig. 1, consists of generating a pool of candidate beam directions and finding favorable beam directions to form paths. The user defines the resolution along gantry and table angle axes used for creating the candidate pool, the minimum number of beam directions required before starting the formation of a new path (m start ), the maximum number of paths to be generated in the pathfinding process, and the maximum total gantry angle range allowed. Beam directions with potential risk of collision or entering through the end of CT are excluded from the pool of candidate beam directions. For electrons, the source-to-surface