ESTRO 2023 - Abstract Book

S1758

Digital Posters

ESTRO 2023

Conclusion Dynamic arc proton therapy is a feasible technique from a treatment planning perspective, with the potential advantage of improvement in OAR sparing and delivery efficiency for complex cases that could require multiple IMPT beams. Using avoidance ROIs can help to pArc algorithm to achieve plans as robust as IMPT. Analysis of more cases are needed to confirm these findings. The inclusion of LET optimization could help to further exploit potential radiobiological advantages of this delivery technique (2).

Refs: 1. doi.org 2. doi.org

PO-1987 Exvivo proton range uncertainty verification of dose calculation on CTand CBCT based synthetic ct

J.M. PEREZ MORENO 1 , I. Lorenzo Villanueva 1 , R. Nilsson 2 , S. Andersson 2 , J.A. Vera Sánchez 1 , J. Castro Novais 1 , F. Cerrón Campoo 1 , E. Canals de las Casas 1 , M. Janson 2 , E. Engwall 2 , A. Mazal 1 1 Quirónsalud Protontherapy Center, Radiation Oncology, Pozuelo de Alarcón (Madrid), Spain; 2 RaySearch Laboratories, Research and Development, Stockholm, Sweden Purpose or Objective To estimate dose calculation range uncertainty in CT images and synthetic CT from CBCT of an in-house exvivo phantom. Materials and Methods Using pork and cow exvivo tissues an in house phantom has been built. A single beam PBS plan has been optimized in Raystation 11B in with the aim to achieve a uniform dose distribution with a constant physical range in water behind the ex-vivo phantom (Fig 1). The resulting PBS plan was recalculated on a synthetic CT based on a CBCT acquired in a Proteus One proton system. The synthetic CT was generated using the “Virtual CT” (VCT) algorithm of RayStation 12B, that includes a method for deforming the planning CT to the CBCT geometry combined with corrections for large differences in air/lung regions between the planning CT and the CBCT Using a 2D array of parallel plane ion chambers MatriXX One in a DigiPhant PT water phantom with a housing for the detector, a series of planes at different depths were measured. A 3D dose distribution is reconstructed by stacking the planes measured. Depth dose profiles were extracted from the MatriXX stacked measurement and from the TPS 3D dose distribution respectively, matching coordinates of every MatriXX detector in regions with doses over 80% of maximum dose at center of SOBP. For every depth dose line R90, R80 and R50 were extracted.