Finite Element Simulation of Moving Targets in Radio Therapy

Among other options, radiotherapy plays an increasing role for the treatment of lung cancer. This has raised the need for strategies to compensate for respiratory motion of the target. Sophisticated techniques such as tracking of the tumour position have become feasible. However, calculations for adequate dose delivery to moving targets with maximum preservation of healthy tissue require understanding the principle of soft tissue deformation In this paper, we introduce a new approach using non-linear finite element method to simulate lung tissue displacement during respiration. The geometric non-linearity and the material non-linearity were applied. The respiration movement was regarded as steady gradual process with equal velocity, and was simulated statically. Boundary condition was set on lung’s surface, and the deformation of whole volume could be calculated. Simulation of diaphragm breathing was compared with 4DCT of ventilated porcine lung inside a chest phantom. The average difference of internal point movement was 3 mm vertically. Our vision is to integrate the concept of FEM simulation of respiratory motion into motion adapted radiotherapy planning.