Biomechanical model-based 4DCT simulation

We present a biomechanical model-based four-dimensional computed tomography (4DCT) simulation method for examining the patient lung deformation induced by respiratory motion, given only one CT scan as an input. First, we model the lung stress–strain behaviour using a sophisticated hyperelastic model, and solve the lung deformation problem through finite element (FE) analysis. We introduce robust algorithms to segment out the diaphragm control points and spine regions to carefully define the boundary conditions and loads, and to improve the FE convergence through our mesh optimisation algorithm. Next, we treat the remaining CT volume as discretised mass points connected by springs and dampers, and simulate the motion of liver, bones and other organs using finite difference analysis. This novel heterogeneous design can leverage the advantages of both continuum mechanics and mass–spring–damper system in the way that the lung deformation is computed in very high accuracy while the deformation of the rest CT volume can be achieved under practical computation constraints. Experimental results through comparing with the manually labelled landmark points in real patient 4DCT data demonstrate that our 4DCT simulator is very accurate.