Effect of Gravity on Human Lung Deformation

The effect of gravity is considered on biomechanical modeling of human lung deformation for radiotherapy application. The lung is assumed to behave as a poro-elastic medium with spatially dependent property. Finite element simulation is performed on a three-dimensional (3D) lung geometry reconstructed from four-dimensional computed tomography (4DCT) scan dataset of real human patient. The spatially-dependent Young’s modulus (YM) values are estimated using inverse analysis from a linear elastic deformation model. First, the gravity-generated deformation in the lung is calculated. Next, inlet pressure loading is applied at the hilium from an initial stress-free resting volume. Then, the lung model is preloaded by its weight, followed by prescription of the inlet pressure. In each case the maximum and minimum deformation of selected landmarks are monitored with and without gravity. The results show that gravity indeed significantly affects the magnitude and distribution of lung deformation. The maximum displacement increases by 54% in the direction of gravity when it is considered in the model.