  Intraoperative observation of tissue internal structure is often difficult.
Hence, real-time soft tissue deformation is essential for the localization of
tumor and other internal structures. We propose a method to simulate the
internal structural deformations in a soft tissue with surface profile
variations. The deformation simulation utilizes virtual physical particles that
receive interaction forces from the surface and other particles and adjust
their positions accordingly. The proposed method involves two stages. In the
initialization stage, the three-dimensional internal structure of the surface
mesh is uniformly sampled using the particle expansion and attracting-repelling
force models whilst simultaneously building the internal particle connections.
In the simulation stage, under surface profile variations, we simulate the
internal structural deformation based on a deformation force model that uses
the internal particle connections. The main advantage of this method is that it
greatly reduces the computational burden as it only involves simplified
calculations and also does not require generating three-dimensional meshes.
Preliminary experimental results show that the proposed method can handle up to
10,000 particles in 0.3s.
