ESTRO 2022 - Abstract Book

S544

Abstract book

ESTRO 2022

Conclusion SRS and Hyperarc are challenging to validate with measurement due to the multiple lesion targets. A new method has been developed for verification of SRS/Hyperarc that is efficient to perform and enables rigorous 3D assessment of the delivered dose distribution. It has been shown to accurately reproduce measured dose in phantom and the the 3D dose distributions in the VSP show a high level of agreement to TPS dose distributions.

OC-0619 Flat panel proton radiography with a patient specific imaging field for accurate WEPL assessment

C. Seller Oria 1 , J. Free 1 , G. Guterres Marmitt 1 , B. Knäusl 2 , S. Brandenburg 1 , A.C. Knopf 1,3 , A. Meijers 1 , J.A. Langendijk 1 , S. Both 1 1 University Medical Center Groningen, University of Groningen, Radiation Oncology, Groningen, The Netherlands; 2 Medical University of Vienna, Radiation Oncology, Vienna, Austria; 3 Center for Integrated Oncology Cologne, University Hospital of Cologne, Internal Medicine, Cologne, Germany Purpose or Objective Water-equivalent path length (WEPL) measurements using flat panel proton radiography (FP-PR) has the potential to enable the detection of proton range uncertainties, the basis of high-precision proton therapy irradiations. Accurate WEPL measurements can be obtained using a FP-PR imaging field with several energy layers, which impose a high imaging dose. In this study we propose a FP-PR method for accurate WEPL determination based on a patient specific imaging field with a reduced number of energies (n) to minimize imaging dose. Materials and Methods Patient specific FP-PRs of 27x27 cm2 were first simulated across a head and neck phantom (CIRS 731-HN) from a gantry angle of 270° as illustrated in figure 1. An energy selection algorithm estimated spot-wise the lowest energy required to cross the anatomy using a water equivalent thickness (WET) map of the phantom and a FP calibration dataset (figure 1(a)). At each spot coordinate (i,j), subsequent energies in steps of 3 MeV were restricted to certain quantities (n=26, 24, 22, …, 2)(figure 1(a, right)), resulting in a patient specific FP-PR imaging field (figure 1(b)). WEPL maps were reconstructed using the FP calibration (figure 1(c)).