A real-time stable volumetric Mass-Spring Model based on a multi-scale mesh representation

Representation of soft tissues in virtual reality environments has been focused by researchers with applications including training medical students and surgeons, treatment planning, monitoring and telesurgery. A major challenge of current modeling schemes such as Boundary Element, Finite Element, and Mass-Spring Models is to deal with volume preserving. Another challenge is the complexity of a model which results in a more realistic visualization; however, it increases computational cost. In this paper, we propose a Mass-Spring model to represent liver volume. It contains a series of multi-scale surface meshes with interconnections between the models and therefore it is considered as a volumetric mesh model. To preserve the volume of the gland, an external force is transmitted from the surface to internal meshes. By designing a specific data structure to hold coordinates of mesh points, we are able to render mesh movement in nearly real-time using conventional CPU architectures. Localization of the external force is adjusted by the penetration depth parameter. Qualitative evaluation of the results revealed the promising performance of the proposed model. The stability of our Mass-Spring model under large deformation is another novelty of our method too.