Very fast soft tissue predictions with mass tensor model for maxillofacial surgery planning systems

Mass Spring Models (MSM) are widely used to simulate the deformation behavior of soft tissues. The usage of these models has however some serious disadvantages. Most important is that the MSM has no real bio-mechanical foundation. The Finite Element Model (FEM) on the other hand has a strong bio-mechanical foundation but the high computational cost and a difficult architecture make it not very useful for fast simulators. In this paper we present the usage of a Mass Tensor Model (MTM) to simulate the soft tissue deformations after bone displacement. This model tries to combine the advantages of FEM and MSM. Moreover by combining this MTM with a new static solution scheme and a dynamic threshold, we were able to reduce the calculation time seriously when compared to MSM or FEM.