A biomechanical model is proposed to predict deflated lung tumor motion caused by diaphragm respiratory motion. This
model can be very useful for targeting the tumor in tumor ablative procedures such as lung brachytherapy. To minimize
motion within the target lung, these procedures are performed while the lung is deflated. However, significant amount of
tissue deformation still occurs during respiration due to the diaphragm contact forces. In the absence of effective realtime
image guidance, biomechanical models can be used to estimate tumor motion as a function of diaphragm's position.
To develop this model, Finite Element Method (FEM) was employed. To demonstrate the concept, we conducted an
animal study of an ex-vivo porcine deflated lung with a tumor phantom. The lung was deformed by compressing a
diaphragm mimicking cylinder against it. Before compression, 3D-CT image of this lung was acquired, which was
segmented and turned into FE mesh. The lung tissue was modeled as hyperelastic material with a contact loading to
calculate the lung deformation and tumor motion during respiration. To validate the results from FE model, the motion
of a small area on the surface close to the tumor was tracked while the lung was being loaded by the cylinder. Good
agreement was demonstrated between the experiment results and simulation results. Furthermore, the impact of tissue
hyperelastic parameters uncertainties in the FE model was investigated. For this purpose, we performed in-silico
simulations with different hyperelastic parameters. This study demonstrated that the FEM was accurate and robust for
tumor motion prediction.