Patient-specific biomechanical model of human lung using four-dimensional CT

Introduction: Radiotherapy aims to deliver a lethal beam of radiation onto lung tumor while minimizing exposure to surrounding healthy tissues. In order to achieve this objective, the radiation must be targeted, requiring the spatio-temporal location the tumor. In this work, we describe a method to integrate FEA/CFD ((Finite Element Analysis/Computational Fluid Dynamic)) technique with four dimensional CT (4D-CT) imaging to effectively predict the transient displacement of the lung and by so doing, track the tumor motion during radiation therapy. Emphasis is placed on utilizing realistic elasticity of the lung to investigate its impact on the resulting lung deformation. Numerical modeling of lung dynamics during respiration is a challenging work due to the complexity of geometry, structural heterogeneity and anisotropy, and boundary constraints. The presence of tumor usually significantly increases the local elastic modulus due to stiffness. Thus, a commonly used uniform Young's modulus (YM) setup in the simulation may not accurately predict the tumor displacement during respiration process. In this work, we propose a patientspecific and spatially distributed YM model derived from 4D-CT to consider different elastic properties of different parts of lung.