Human liver multiphysics modeling for 4D dosimetry during hadrontherapy

Organ motion, especially respiratory motion, is a technical challenge to hadrontherapy planning and dosimetry. This motion induces the displacement and the deformation of the organs tissues along the radiation beam path which need to be taken into account when computing dose distribution during the treatment. In this paper we present an original approach of virtual patient modeling for 4D radiation therapy simulations. As opposed to classical image-based models, where the necessary information is distributed over a rigid structured grid of voxels, we represent the human anatomy with a deformable grid of tetrahedra where the mass density is mapped to the vertices of the grid. In this way, we can simulate within the same structure organ motion, mass density variations and dose distribution without having to perform voxel tissue tracking.