ESTRO 2021 Abstract Book

S729

ESTRO 2021

Conclusion The suggested approach can be used as a tool for benchmarking different MP software packages intended for clinical use. The evaluated software provides a reliable tool to calculate MPCT and estimate the motion of ROIs. PD-0891 Cardio-respiratory ITV for cardiac radioablation in case of ventricular tachycardia J. Bellec 1 , L. Rigal 2 , N. Jaksic 3 , P. Caille 1 , M. Lederlin 4 , C. Lafond 1 , R. Martins 5,6 , R. De Crevoisier 3,6 , A. Simon 7 1 Centre Eugene Marquis, Department of Medical Physics, Rennes, France; 2 Université de Rennes 1, LTSI- INSERM U1099, Rennes, France; 3 Centre Eugene Marquis, Department of Radiation Oncology, Rennes, France; 4 CHU Rennes, Department of Radiology, Rennes, France; 5 CHU Rennes, Department of Cardiology, Rennes, France; 6 Université de Rennes 1, LTSI-INSERM U1099, Rennes, France; 7 Universite de Rennes 1, LTSI - INSERM U1099, Rennes, France Purpose or Objective Cardiac radioablation is a new appealing, however complex, SBRT technique for patients with refractory ventricular tachycardias (VT). A single ablative radiation dose of 25 Gy is delivered to the predefined arrhythmogenic region. The definition of the PTV is a critical and complex step, integrating a combination of cardiac and respiratory motions. The main objective of this study was to evaluate the geometric impact of both cardiac-induced and respiratory-induced motions on the definition of the target volume. Materials and Methods The first four patients enrolled in our institution for VT radioablation were included. For each patient, the definition of the target and the assessment of cardio-respiratory motions were performed using a cardiac 4D CT (contrast-enhanced ECG-gated CT) and a respiration correlated 4D CT, each one reconstructed in 10 3D images datasets. The clinical target volume (CTV) was delineated on the images corresponding to the two extreme cardiac phases (end of diastole and of systole) of the cardiac 4D CT. A cardiac internal target volume (ITV) was generated as the union of these two delineations. To include the impact of respiratory motions, an average cardiac CT was reconstructed and rigidly registered to the two extreme respiratory phases (end of inspiration and of expiration) of the respiratory 4D CT. The cardiac ITV was propagated on these two phases and the resulting delineations were merged to generate a cardio-respiratory ITV, combining both cardiac and respiratory motions. Results Results are reported in the table 1 below.