ESTRO 2023 - Abstract Book

S161

Saturday 13 May

ESTRO 2023

Results 60 patients were prospectively enrolled. SBRT planning optimized to spare lung functional regions led to a significant reduction (p<0.0001) of the MLD and V5 to V20 Gy in all functional volumes. Median relative difference of the MLD in the FV50%, FV70% and FV90% was -7.98% (-43.00 to 1.17%), -7.07% (-34.26 to 1.23%) and -5.66% (-22.26 to 4.38%), respectively. Median relative differences for VxGy ranged from -12.5% to -9.2% in the FV50%, -11.3% to -7.2% in the FV70%, -8.0% to - 5.3% in the FV90%.

Conclusion This study shows the feasibility of significantly decreasing the doses delivered to the lung functional volumes using 68Ga perfusion PET/CT without compromising target volume coverage and doses to other organs at risk. MO-0227 Validation of 4DMRI-based virtual 4DCT and application in gated particle therapy of lung cancer S. Annunziata 1 , M. Rabe 2 , A. Vai 3 , S. Molinelli 4 , A. Nakas 1 , G. Meschini 1 , A. Pella 5 , V. Vitolo 6 , A. Barcellini 6 , S. Imparato 6 , M. Ciocca 4 , E. Orlandi 6 , G. Landry 2 , F. Kamp 2,7 , C. Kurz 2 , G. Baroni 1 , M. Riboldi 8 , C. Paganelli 1 1 Politecnico di Milano, Department of Electronics, Information and Bioengineering, Milano, Italy; 2 LMU Munich, Department of Radiation Oncology, University Hospital, Munich, Germany; 3 Centro Nazionale di Adroterapia Oncologica, Medical Physics Unit , Pavia, Italy; 4 Centro Nazionale di Adroterapia Oncologica, Medical Physics Unit, Pavia, Italy; 5 Centro Nazionale di Adroterapia Oncologica, Bioengineering Unit, Pavia, Italy; 6 Centro Nazionale di Adroterapia Oncologica, Clinical Unit, Pavia, Italy; 7 University Hospital Cologne, Department of Radiooncology and Cyberknife Center, Faculty of Medicine, Cologne, Germany; 8 LMU Munich, Department of Medical Physics, Faculty of Physics, Munich, Germany Purpose or Objective To validate a method for virtual four-dimensional computed tomography (4DCT) generation from four-dimensional magnetic resonance imaging (4DMRI) in a porcine lung phantom, and to evaluate its use in respiratory gated particle therapy using patient data. Materials and Methods Deformable image registration was used to: (a) register each respiratory phase of the 4DMRI to the end-exhale MRI phase; (b) register a static 3DCT at end-exhale (used as reference) to the end-exhale MRI volume; (c) generate the virtual 4DCT by warping the registered CT according to the obtained deformation fields (see figure 1). A carbon ion and a proton treatment plan were optimized on the end-exhale reference CT and the corresponding RBE-weighted dose distributions were recalculated over the virtual and ground truth (GT) 4DCTs. The method was validated on a physical phantom and