ESTRO 2023 - Abstract Book

S1580

Digital Posters

ESTRO 2023

Conclusion An X-irradiator based on a standard imaging X-ray tube with FLASH dose-rates capabilities for preclinical research is feasible. A prototype has already been built by SEDECAL (Sociedad Española de Electromedicina y Calidad, S.A) (see figure 1), one of the largest manufacturers of X-ray portable imaging systems worldwide.

Figure 1. Prototype of the X-ray irradiator

[1] Mazal, A., et al. Brit. J. Radiol., 2020, 93, (1107), pp. 20190807 [2] Ghita, M., et al. Cancers, 2019, 11, (2), pp. 170 [3] Cecchi, D.D et al. Med. Phys. 2021, 48, (11), pp. 7399-7409 [4] Rezaee, et al. Phys. Med. Biol., 2021, 66, (9), pp. 095006

PO-1844 Optimization of metal collimators for proton minibeam radiation therapy (pMBRT)

F. Reaz 1 , M. Krzysztof Sitarz 2 , E. Traneus 3 , N. Bassler 4

1 Aarhus University , Department of Clinical Medicine, Aarhus, Denmark; 2 Aarhus University Hospital, DCPT, Aarhus, Denmark; 3 RaySearch Laboratories AB, -, Stockholm, Sweden; 4 Aarhus University, Department of Clinical Medicine, Aarhus, Denmark Purpose or Objective Spatially fractionated radiotherapy (SFRT) has obtained recent attention due to its clinical potential to increase the therapeutic ratio, i.e. to achieve tumour control at reduced toxicity. An inhomogeneous dose distribution of pMBRT in healthy tissue is hypothed to reduce radiation-induced damage, while it is possible to retain a homogeneous dose distribution in the PTV. However, a workflow to produce the optimal beam profile for pMBRT is yet to be established for spread-out Bragg peaks (SOBPs). A multi-slit collimator (MSC) is the most pragmatic solution to produce peak and valley dose distributions with sharp contrast. Its thickness, center-to-center (ctc) distance, choice of material, throughput, and collimator-to-phantom distance (CPD) can strongly impact the dose profile. A clear understanding of their impacts with precise optimization is a prerequisite for the clinical applications of pMBRT. Materials and Methods We have investigated the collimator's properties using the Geant4 Monte Carlo (MC) particle transport simulation tool. Using a realistic model of our active beam scanning system at the Danish Centre for Particle Therapy (DCPT), we aim to minimize the valley-to-peak dose ratio (VPDR) in the healthy tissue, obtain the lowest valley doses and minimize neutron contamination. A treatment plan (prepared in Eclipse) with a uniform field of 10 cm x 2.5 cm and a 3 cm wide SOBP (84 107 MeV), was implemented in the simulation (fig. 1). We developed a feedback algorithm to reoptimize the weight of each energy layer to ensure a uniform SOBP in the PTV when the MSC is inserted.