Real-time visio-haptic interaction with static soft tissue models having geometric and material nonlinearity

Abstract

Simulation of real-time interactions with soft tissue models is necessary for the development of computer-based medical training systems. To provide realistic visual and haptic feedback to a user by integrating measured material properties into the models, finite element (FE) modeling techniques are typically preferred. However, running a static nonlinear FE model in real-time is a highly challenging task since the resulting stiffness matrix (K) is not constant and varies with the depth of indentation into tissue. We propose a new approach allowing visio-haptic interaction with a FE model of a human liver having both non-linear geometric and material properties. The material properties used in the model are extracted from the experimental data of pig liver to make the simulations more realistic. Our computational approach consists of two main steps: a pre-computation of the configuration space of all possible deformation states of the model, followed by the interpolation of the precomputed data for the calculation of the reaction forces displayed to the user through a haptic device during the real-time interactions. No a priori assumptions or modeling simplifications about the mathematical complexity of the underlying soft tissue model, size and irregularity of the FE mesh are necessary. We show that deformation and force response of the liver in simulations are heavily influenced by the material model, boundary conditions, path of the loading and the type of function used for the interpolation of the pre-computed data.

Development of In Vivo Constitutive Models for Liver: Application to Surgical Simulation

“…Recently, real-time finite element methods have been adapted for the simulation of nonlinear constitutive models with the inclusion of haptic feedback [20][18]. Picinbono et al .…”

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“…Peterlik et al [13] used the Phantom as an active and haptic user interface for real-time physically-based deformation. To provide interactive reactions to acting forces, the system applies interpolations of precomputed data.…”

Haptic rendering of hyperelastic models with friction

“…The response forces can be computed at each step of the haptic loop, through a simple update of inverse stiffness matrix. In [17], [28] and [23], precomputations based methods are proposed; stable haptic rendering is efficiently achieved calculating response forces from precomputed data, e.g. by interpolations performed directly in the haptic loop.…”