Pierre-Frédéric Villard

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• Ph.D.
• Professor (Associate) at University of Lorraine

In this study, we describe a model of the human left ventricle (LV) that uses a hybrid immersed boundary–finite element method. The LV model is derived from clinical cardiac magnetic resonance images and completed with the inflow and outflow tracts. The model simulates LV dynamics with fully coupled fluid–structure interaction. Model parameters are...

Tendon-driven robotic catheters are capable of precise execution of minimally invasive cardiac procedures including ablations and imaging. These procedures require accurate mathematical models of not only the catheter and tendons but also their interactions with surrounding tissue and vasculature in order to control the robot path and interaction....

The dynamic behavior of the mitral valve (MV) is highly influenced by the material model used to describe the leaflet motion. Due to the presence of collagen fibers, MV leaflets show an anisotropic behavior. The aim of this study is to investigate the influence of anisotropy on the fluid-structure interaction (FSI) simulation of the MV dynamic clos...

The thoracic diaphragm is the muscle that drives the respiratory cycle of a human being. Using a system of partial differential equations (PDEs) that models linear elasticity we compute displacements and stresses in a two-dimensional cross section of the diaphragm in its contracted state. The boundary data consists of a mix of displacement and trac...

Purpose: Realistic fluid-structure interaction (FSI) simulation of the mitral valve opens the way toward planning for surgical repair. In the literature, blood leakage is identified by measuring the flow rate, but detailed information about closure efficiency is missing. We present in this paper an FSI model that improves the detection of blood le...

PurposeMitral valve computational models are widely studied in the literature. They can be used for preoperative planning or anatomical understanding. Manual extraction of the valve geometry on medical images is tedious and requires special training, while automatic segmentation is still an open problem.Methods We propose here a fully automatic pip...

The thoracic diaphragm is the muscle that drives the respiratory cycle of a human being. Using a system of partial differential equations (PDEs) that models linear elasticity we compute displacements and stresses in a two-dimensional cross section of the diaphragm in its contracted state. The boundary data consists of a mix of displacement and trac...

The diaphragm is the main muscle that regulates the human respiration. When a patient is put under controlled mechanical ventilation, the diaphragm is exposed to forces that damage the muscle function. The long-term aim of this work is to study this process through numerical simulation. Here, we take the first steps in developing a meshless numeric...

We present an Open-source library called gVirtualXRay to simulate realistic X-ray images in realtime. It implements the attenuation law (also called Beer-Lambert) on GPU. It takes into account the polychromatism of the beam spectra as well as the finite size of X-ray tubes. The library is written in C++ using modern OpenGL. It is fully portable and...

Background: Common surgical procedures on the mitral valve of the heart include modifications to the chordae tendineae. Such interventions are used when there is extensive leaflet prolapse caused by chordae rupture or elongation. Understanding the role of individual chordae tendineae before operating could be helpful to predict whether the mitral...

We present a framework that combines evolutionary optimisation, soft tissue modelling and ray tracing on GPU to simultaneously compute the respiratory motion and X-ray imaging in real-time. Our aim is to provide validated building blocks with high fidelity to closely match both the human physiology and the physics of X-rays. A CPU-based set of algo...

We propose a simulation framework to simulate the computed tomography acquisition process. It includes five components: anatomic data, respiration modelling, automatic parametrisation, X-ray simulation, and tomography reconstruction. It is used to generate motion artefacts in reconstructed CT volumes. Our framework can be used to evaluate CT recons...

We propose in this paper a new method for tongue tracking in ultrasound images which is based on a biomechanical model of the tongue. The deformation is guided both by points tracked at the surface of the tongue and by inner points of the tongue. Possible uncertainties on the tracked points are handled by this algorithm. Experiments prove that the...

We present in this paper a preliminary study of rib motion tracking during Interventional Radiology (IR) fluoroscopy guided procedures. It consists in providing a physician with moving rib three-dimensional (3D) models projected in the fluoroscopy plane during a treatment. The strategy is to help to quickly recognize the target and the no-go areas...

Whilst laparoscopic surgical simulators are becoming increasingly realistic they can not, as yet, fully replicate the experience of live surgery. In particular tissue dissection in one task that is particularly challenging to replicate. Limitation of current attempts to simulate tissue dissection include: poor visual rendering; over simplification...

Training in Interventional Radiology currently uses the apprenticeship model, where clinical and technical skills of invasive procedures are learnt during practice in patients. This apprenticeship training method is increasingly limited by regulatory restrictions on working hours, concerns over patient risk through trainees' inexperience and the va...

This paper is an overview of a method recently published in a biomedical journal (IEEE Transactions on Biomedical Engineering, http://tbme.embs.org). The method is based on an optimisation technique called "evolutionary strategy" and it has been designed to estimate the parameters of a complex 15-D respiration model. This model is adaptable to acco...

We present and analyze the behavior of an evolutionary algorithm designed to estimate the parameters of a complex organ behavior model. The model is adaptable to account for patient's specificities. The aim is to finely tune the model to be accurately adapted to various real patient datasets. It can then be embedded, for example, in high fidelity s...

We propose a method to automatically tune a patient-based virtual environment training simulator for abdominal needle insertion. The key attributes to be customized in our framework are the elasticity of soft-tissues and the respiratory model parameters. The estimation is based on two 3D Computed Tomography (CT) scans of the same patient at two dif...

The use of simulation to train skills has grown exponentially in the last few decades, especially in medicine, where simulator models can provide a platform where trainees can practice procedures without risk or harm to patients. Potential advantages of computer based simulator models over other forms of medical simulators include: (i) anatomical

ISBN-13: 978-613-1-56604-2 ISBN-10:6131566046

Objectives: The aim of this article was to identify and prospectively investigate simulated ultrasound-guided targeted liver biopsy performance metrics as differentiators between levels of expertise in interventional radiology. Methods: Task analysis produced detailed procedural step documentation allowing identification of critical procedure st...

Inguinal hernia repair procedures are often one of the first surgical procedures faced by junior surgeons. The biggest challenge in this procedure for novice trainees is understanding the 3D spatial relations of the complex anatomy of the inguinal region, which is crucial for the effective and careful handling of the present anatomical structures i...

Purpose: We previously proposed to compute the X-ray attenuation from polygons directly on the GPU, using OpenGL, to significantly increase performance without loss of accuracy. The method has been deployed into a training simulator for percutaneous transhepatic cholangiography. The simulations were however restricted to monochromatic X-rays using...

Purpose: We previously proposed to compute the X-ray attenuation from polygons directly on the GPU, using OpenGL, to significantly increase performance without loss of accuracy. The method has been deployed into a training simulator for percutaneous transhepatic cholangiography. The simulations were however restricted to monochromatic X-rays using...

Tumour motion is an essential source of error for treatment planning in radiation therapy. This motion is mostly due to patient respiration. To account for tumour motion, we propose a solution that is based on the biomechanical modelling of the respiratory system. To compute deformations and displacements, we use continuous mechanics laws solved wi...

An overview to medical simulation has been provided. In the context of procedural interventional radiology training, we start with the definition and history of simulation, address its increasing importance in medicine reflect on its theoretical basis and current evidence and finally review its advantages/ limitations and prospects for the future.

Purpose We present here a simulator for interventional radiology focusing on percutaneous transhepatic cholangiography (PTC). This procedure consists of inserting a needle into the biliary tree using fluoroscopy for guidance. Methods The requirements of the simulator have been driven by a task analysis. The three main components have been identifie...

Modelling of diaphragm behaviour is of relevance to a number of clini cal procedures such as lung cancer radiotherapy and liver access interventions. The heterogeneity in tissue composition of the diaphragm, as well as the various physiological phenomena influencing its behaviour, requires a complex model in order to accurately capture its motion....

AIM: To determine face and content validity of a physics based virtual reality interventional radiology simulator, Imagine-S (Imaging guided interventional needle puncture simulation).

The success of radiotherapy treatment could be compromised by motion. Lung tumours are particularly concerned by this problem because their positions are subject to breathing motion. To reduce the uncertainty on the position of pulmonary tumours during breathing cycle, we propose to develop a complete thoracic biomechanical model. This model will b...

We present an integrated system for training visceral needle puncture procedures. Our aim is to provide a cost effective and validated training tool that uses actual patient data to enable interventional radiology trainees to learn how to carry out image-guided needle puncture. The input data required is a computed tomography scan of the patient th...

We present an integrated system for training visceral needle puncture procedures. Our aim is to provide a cost effective and validated training tool that uses actual patient data to enable interventional radiology trainees to learn how to carry out image-guided needle puncture. The input data required is a computed tomography scan of the patient th...

We present an integrated system for training ultrasound guided needle puncture. Our aim is to provide a cost effective and validated training tool that uses actual patient data to enable interventional radiology trainees to learn how to carry out image-guided needle puncture. The input data required is a computed tomography scan of the patient that...

During a standard procedure of liver biopsy, the motion due to respiration may be difficult to handle. The patient is often requested to hold his breath or to breathe shallowly. Ideally, this physiological behaviour should be taken into account in a virtual reality biopsy simulator. This paper presents a framework that accurately simulates respirat...

We present a method to merge two distinct CT scans acquired from different patients such that the second scan can supplement the first when it is missing necessary supporting anatomy. The aim is to provide vascular intervention simulations with full body anatomy. Often, patient CT scans are confined to a localised region so that the patient is not...

Throughout the practice of procedural medicine, there is an unrelenting shift to management by less invasive techniques such as interventional radiology (IR). This subspecialty within radiology uses imaging to guide needles, wires and catheters using tiny access incisions. Like other minimally invasive techniques, risk, pain and recovery times are...

In this paper we propose a new framework for deformation modelling based on a combined mass spring and tensional integrity method. The synergy between balanced tension and compression components offered by the tensegrity model helps the deforming organ retain its shape more consistently. We chose the diaphragm as our test object given its heterogen...

PURPOSE-MATERIALS: To use patient imaging as the basis for developing virtual environments (VE). BACKGROUND Interventional radiology basic skills are still taught in an apprenticeship in patients, though these could be learnt in high fidelity simulations using VE. Ideally, imaging data sets for simulation of image-guided procedures would alter dyna...

Certificate of Merit Award

Motion estimation is an important issue in radiation therapy of moving organs. In particular, motion estimates from 4-D imaging can be used to compute the distribution of an absorbed dose during the therapeutic irradiation. We propose a strategy and criteria incorporating spatiotemporal information to evaluate the accuracy of model-based methods ca...

To monitor a lung mechanical model and then predict tumour motion we proposed a approach based on the pleura physiology. By comparing the predictions to landmarks set by medical experts, we observed better results with regards to the one obtained with approaches found in the literature. Beside, we focus on the rib cage kinematics, which play a sign...

The aim of this thesis is to improve lung cancer treatment by radiotherapy or hadrontherapy. We focus on simulating lung's patient motions and deformations.We define initial and boundary conditions thanks to medical collaborations to obtain a biomechanical model following the continuous mechanics laws and patient's customised. The mechanical comput...

Radiation therapy of cancer necessitates accurate tumour targeting. Unfortunately, during the treatment the tumour and the related organs can undergo large displacement and deformation. Physicians need an estimation of these movements, for an adapted therapy. In this paper, we propose a methodology to provide physicians with reconstructed 4D (3D+ti...

Cancer treatments by ionising beam need accurate tumour targeting, which is dicult for lung cancer, due to breathing motions. We propose here to pro-vide physicians with 3D + time CT scan of lung from a physically based simulation of respiratory organs motion.

We present here an approach to convert the geometrical information produced by a physical simulation of soft-organ motion into a 3D+time CT scan. The paper describes how we calculate matter density at mesh points and how we produce dynamic 3D CT scan using the convolution parameters of medical scanners. The aim of this work is to provide physicians...

Motivated by medical needs, we propose to simulate lung deformation and motion during respiration to track tumours. This paper presents a model of lung behaviour based on a continuous media mechanics model and solved with a finite element method. The result is a simulation of a normal breathing, matching with patient customised data. Moreover, we c...

Numerical modelling of lung behaviour during the respiration cycle is a difficult challenge due to its complex geometry and surrounding environment constraints. This paper presents an approach to simulate a patient's lung motion during inhaling and exhaling based on a continuous media mechanics model and solved with a finite element method. One of...

Motivated by radiotherapy and hadrontherapy improvement, we consider in a first step the potential of a simple elastic mechanical modelling to simulate lung deformations and motions during respiration, towards tumour tracking. Two approaches are presented: one is the finite-element based method and the other is the mass-spring system. For these app...

9th workchop HCPBM. Lyon (Fr). p 31

9th workchop HCPBM. Lyon (Fr). p 31.

Curative treatment of lung cancer is difficult because of organ motions. A treatment improvement consists in tracking the tumour displacement and deformation during patient breathing in order to optimise the ballistics of the particles. The aim of this work is to simulate the motions and deformations of the lung using personalised parameters for ea...