My research works concerns the multiphysics modeling and simulation of respiratory organ motion of the respiratory system for radiation therapy and for lung cancer treatment particularly. We have proposed an approach which takes into account the physiology of respiratory motion and the density variations of the tissues, including the appropriate mechanical behavior and the real boundary conditions of the organs. The proposed approach not only enables to take into account the respiratory motion variabilities, but also ensures high precision and able to monitoring the internal motion with respiratory surrogate signal(s) during the radiation treatment. The other particularity of our research concerns the implementation of " multi-physical  and continuous approach", which all the physical quantities calculated (deformation of the organs, their densities, deposit dose and nuclear activities (PET imaging)) are assigned to the vertices of the tetrahedrons, which represent the organ geometry obtained from scanner images. Furthermore, the multidisciplinary nature of this work has led my team and I to collaborate with teams from different disciplines. These activities are mainly conducted within national and international collaborative research projects