ESTRO 2023 - Abstract Book

S1542 ESTRO 2023 Δ R ₁₀ , similarly defined, is always less than 0.1 mm for the deconvolution and the evolutionary algorithms, and less than 1.5 mm for the ML-EM. It was also shown that the methods are sensitive to detect range shifts of the order of 1 mm. Conclusion The final aim of this work is the comparison of the evaluated dose reconstruction approaches as part of their applicability to real-time adaptive particle therapy. Dose reconstruction accuracy, computation time and integration into clinical workflow will be considered based on in silico studies using both homogeneous and heterogeneous phantoms and patient data and on measurements in a 3D printed head phantom. This work is performed as part of the RAPTOR project, funded by the EU’s Horizon 2020 MSCA, Grant Agreement No. 955956. Digital Posters

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PO-1815 CBCT dose distribution calculation with GATE Monte Carlo simulations for lymphoma patients

M. Riveira-Martin 1 , I. Sánchez-Díaz 1 , R. Dorado Dorado 2 , F.J. Salvador Gomez 2 , B. Andrade Álvarez 2 , M. Salgado Fernández 2 , V. Muñoz Garzón 3 , V. Ochagavía Galilea 3 , I. Nieto Regueira 3 , M. Myronakis 4 , A. López Medina 2 1 Galicia Sur Health Research Institute, Medical Physics, Vigo, Spain; 2 Hospital do Meixoeiro, Galaria, SERGAS, Medical Physics and RP, Vigo, Spain; 3 Hospital do Meixoeiro, Galaria, SERGAS, Radiation Oncology, Vigo, Spain; 4 University of Crete, School of Medicine, Medical Physics, Heraklion, Crete, Greece Purpose or Objective The council directive 2013/59/EURATOM requires ensuring that “new medical radiodiagnostic equipment producing ionising radiation has a device, or an equivalent means, informing the practitioner of relevant parameters for assessing the patient dose”. In contrast, commercial CBCT equipment provides poor information on the dose received by the patient. Although CBCT involves low patient doses compared to the prescribed dose of radiotherapy (RT), patients may undergo several images during treatment, which may lead to an increase in the absorbed dose and thus in the risk of developing radio induced cancer. Our aim is to calculate the organ-at-risk (OAR) dose distribution due to CBCT scans throughout the RT procedure in lymphoma patients. In addition, the H2020-funded SINFONIA project aims to predict the radiation risk associated with medical imaging, especially in young patients with lymphomas, whose survival is expected to be very high. Materials and Methods Simulated CBCT dose maps were calculated with Monte Carlo (MC) methods using Geant4 GATE software with an Elekta’s Synergy model [1] on planning CT chest scans (Fig. 1A) from 5 lymphoma adult patients. The CBCT simulations (Fig. 1C) were performed with 1e9 particles. To calibrate the dose, the CTDIw was calculated on the simulation of a CTDI phantom (4.84e-8 mGy) and normalized to the CTDIw measured on the same phantom (21.1 mGy). The OARs were contoured in Aria (Varian Medical Systems, v 15.1). An open-source software (3D Slicer, v 5.0.3) was used to calculate the mean absorbed dose (MD) in each OAR. The dose absorbed by each organ due to the overall treatment was obtained from the TPS (Eclipse, v 15.6).