The core research topics of the MIMESIS project team essentially aim at improving the realism and fidelity of interactive simulations of medical procedures. This increase in realism will permit to address new clinical applications, in particular per-operative guidance that currently rely on imaging techniques but could greatly benefit from our expertise in real-time numerical simulation. To reach these objectives we have identified several challenges that lie at the intersection of several scientific domains. They include real-time biophysical models, novel numerical strategies, dynamic topological representations and image driven simulation.
The SOFA framework (http://www.sofa-framework.org) is used to integrate our various contributions into a series of prototypes, facilitating validation and technology transfer.
This PhD thesis focuses on dynamic topological representations and aims at developing models and methods to handle the simulation of cuts, tears and fractures in the context of surgical simulation.
Most simulations in the field of biomechanics, physiological modelling, or even computer graphics, are performed using finite element approaches. Such simulations require a discretization of the domain of interest, and this discretization is traditionally made of tetrahedral or hexahedral elements . The topology defined by these elements is also considered constant .
The first objective of this PhD thesis is to jointly develop advanced topological operations and new finite element approaches that can leverage the use of dynamic topologies . This will cover various topics, such as mesh transformations – to support the simulation of cuts, tears and fractures – but also dynamic refinements to increase the precision of the simulation in areas of interest.
Recent approaches tend towards the coupling of distinct models in order to improve the realism and the accuracy of the simulation process . For instance a tetrahedral model of the liver can be coupled with a model of the vascular network it contains and with a visual model of its boundary – usually a surface. An efficient coupling of the underlying meshes and topologies is a crucial issue to support dynamic topologies.
The second objective of this work is to develop topological operations that operate on a set of coupled topologies. The cuts, tears and fractures that are performed in one of the model should soundly and robustly propagate to the others. In the previous liver example, a tear in the tetrahedral model should cause cuts or fractures in some blood vessels and a separation in the visual model.
The developed operations will be implemented in the SOFA framework (www.sofa-framework.org) and applied in the context of real-time augmented reality of minimally invasive hepatic surgery. Model of vessels and tumours computed from pre-operative CT scans will be coupled with a biomechanical model of the liver for surgery guidance.
Required qualification: Master (in computer science or applied mathematics)
This PhD proposal is open to any applicant with (or finishing) a Master Degree in Computer Science or Applied Mathematics with a strong motivation.
A reasonable experience on C/C++ programming and working on Linux/Unix environment is required. Showing skills in computer graphics, real time simulation or finite elements methods is an asset.
Duration: 3 years
Starting date: between Oct. 1st 2015 and Jan. 1st 2016
Salary: 1 958 euros gross monthly (about 1 584 euros net) during the first and the second years. 2 059 euros the last year (about 1 665 euros net). Medical insurance is included.
 H. Courtecuisse, J. Allard, P. Kerfriden, S. Bordas, S. Cotin, C. Duriez. Real-time simulation of contact and cutting of heterogeneous soft-tissues. Medical Image Analysis, Elsevier, 2014.
 Nazim Haouchine, Jérémie Dequidt, Igor Peterlik, Erwan Kerrien, Marie-Odile Berger, Stéphane Cotin. Image-guided Simulation of Heterogeneous Tissue Deformation For Augmented Reality during Hepatic Surgery. ISMAR – IEEE International Symposium on Mixed and Augmented Reality, Oct 2013.
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 Thomas Pitiot, David Cazier, Thomas Jund, Arash Habibi, Pierre Kraemer, « Deformable polygonal agents in crowd simulation », Computer Animation and Virtual Worlds, 2014.
 L. Untereiner, D. Cazier, D. Bechmann, « n-Dimensional Multiresolution Representation of Subdivision Meshes with Arbitrary Topology », Graphical Models, Volume 75, No 5, 2013.