Modeling and Real-Time Simulation of a Vascularized Liver Tissue

International audienceIn Europe only, about 100,000 deaths per year are related to cirrhosis or liver cancer. While surgery remains the option that offers the foremost success rate against such pathologies, several limitations still hinder its widespread development. Among the limiting factors is the lack of accurate planning systems, which has been a motivation for several recent works, aiming at better resection planning and training systems, relying on pre-operative imaging, anatomical and biomechanical modelling. While the vascular network in the liver plays a key role in defining the operative strategy, its influence at a biomechanical level has not been taken into account. In the paper we propose a real-time model of vascularized organs such as the liver. The model takes into account separate constitutive laws for the parenchyma and vessels, and defines a coupling mechanism between these two entities. In the evaluation section, we present results of in vitro porcine liver experiments that indicate a significant influence of vascular structures on the mechanical behaviour of tissue. We confirm the val- ues obtained in the experiments by computer simulation using standard FEM. Finally, we show that the conventional modelling approach can be efficiently approximated with the proposed composite model capable of real-time calculations

Interactive Soft Object Simulation with Quadratic Finite Elements

We present a new method to simulate deformable volumetric objects interactively using finite elements. With quadratic basis functions and a non-linear strain tensor, we are able to model realistic local compression as well as large global deformation. The construction of the di#erential equations is described in detail including the Jacobian matrix required to solve the non-linear system. The results show that the bending of solids is reflected more realistically than with the linear refinement previously used in computer graphics. At the same time higher frame rates are achieved as the number of elements can be drastically reduced. Finally, an application to virtual tissue simulation is presented with the objective to improve surgical training

LASTIC: a Light Aspiration device for in vivo Soft TIssue Characterization

International audienceThis paper introduces a new Light Aspiration device for in vivo Soft TIssue Characterization (LASTIC). This device is designed to be used during surgery, and can undergo sterilization. It provides real-time estimation of the elastic parameters. LASTIC is a 3cm x 3cm metallic cylinder divided in two compartments. The lower compartment is a cylindrical chamber made airtight by a glass window in which a negative pressure can be applied. Put in contact with soft tissues, it can aspire the tissues inside the chamber through a circular aperture in its bottom side. The upper compartment is clinched onto the lower part. A miniature digital camera is fixed inside the upper chamber, focusing on the aspired soft tissue. LASTIC is operated by applying a range of negative pressures in the lower compartment while measuring the resulting aspired tissue deformations with the digital camera. These measurements are used to estimate the tissue elasticity parameters by inverting a Finite Element model of the suction experiment. In order to use LASTIC during surgical interventions, a library-based optimization process is used to provide an interactive time inversion