Contact surface and material nonlinearity modeling of human lungs.

A finite element model has been developed to investigate the effect of contact surfaces and hyperelastic material properties on the mechanical behavior of human lungs of one lung cancer patient. The three-dimensional model consists of four parts, namely the left lung, right lung, tumor in the left lung and chest wall. The interaction between the lungs and chest wall was modeled using frictionless surface-based contact. Hyperelastic material properties of the lungs are used in the model. The effect of the two parameters is investigated by tracking the tumor movement, and by comparing the analytical results to the patient bifurcation points: 45 points in each lung and 18 points around the tumor. The accuracy of the model is improved by including the contact surface and hyperelastic material properties. The average error and the standard deviation (SD) in modeling the displacement in the SI direction are reduced from 0.68 (SD = 0.34) cm in the elastic model to 0.09 (0.21) cm in the contact-hyperelastic model. Similarly, the average error (SD) of tumor location decreases from 0.71 (0.21) cm in the elastic material without contact to -0.03 (0.24) cm in the hyperelastic material with contact model.