PhD proposal: Image-based Biomechanical Simulation of Mitral Valve Closure
Position type: PhD Student
Research theme: Applied Mathematics, computation and simulation
The MAGRIT project-team research aims at proposing robust solutions to issues faced in augmented reality. We are particularly involved in medical applications, where 3D models are extracted from patient-based images.
We are interested in modeling Heart valves. They ensures the one-way flow of oxygenated blood from the left atrium to the left ventricle. However, many pathologies damage the valve anatomy producing undesired backflow, or regurgitation, decreasing cardiac efficiency and potentially leading to heart failure if left untreated.
Such cases could be treated by surgical repair for the valve. However it is technically difficult and outcomes are highly
dependent upon the experience of the surgeon. One of the main difficulties of valve repair is that valve tissues must be surgically altered during open heart surgery such that the valve opens and closes effectively after the heart is closed and blood flow is restored. In order to do this successfully, the surgeon must essentially predict the displacement and deformation of anatomically and biomechanically complex valve
leaflets and supporting structures.
One way to facilitate the repair is to simulate the mechanical behavior of the pathological valve with patient-specific data.
PhD research work description
The aim of this project is to develop a technology for patient-specific heart valve model for surgical operation planning and scientific understanding.
Such models have been widely studied in the literature. However, these well-known models were based on generic geometries, dependent of many manual interactions and not fully validated [1, 2, 3 and 4].
The objective of this PhD is to build a complete workflow from the construction of the geometry to the validation of such a model.
The PhD work involves two interconnected components: image processing (in order to segment every valve component geometries) and biomechanical modeling (in order to simulate the mechanical behavior of the valve closure). The strategy is to extract features corresponding to the valve anatomy such that the 3D model is mechanically valid.
The segmentation will more specifically consist in extracting thin flat structures and thin cylinders from 3D CT scans using model-based detector like in . The valve topological separations between leaflets and the corresponding coaptation surface will also need to be estimated. The method should be generic enough to be applied on the 10 cases of mitral valves that have already been scanned. A dataset include 3D CT scans of a close and of a open valve.
The biomechanical simulation will include the study of both the boundary conditions and the mechanical parameters. The valve anisotropy is defined by the collagen fiber directions that should also be studied similarly to  but by extracting the directions from the image. Validation criteria will need to be defined in order to check if the simulation is valid and accurate enough. For instance, a metric should indicate if their is no leak when the valve is close and pressurized. The idea is to use the latter information to monitor the segmentation such as the extracted features satisfy this condition.
This project is included in a collaboration environment with the Harvard Biorobotics Lab and the Boston Children’s’hospital.
This position may be assigned into a restricted-access zone as defined in the decree n 2011-1425 related to the protection of the nation’s scientific and technological assets. Authorization of access is delivered by the Center’s Head, after a favorable notification from the Ministry. An unfavorable notification on a position assigned to restricted-access zone would result in cancellation of the recruitment.
Supervisor and Advisor :
image processing and biomechanical simulation
 Kunzelman K, Einstein D, Cochran R. Fluid–structure interaction models of the mitral valve: function in normal and pathological states. Philosophical Transactions of the Royal Society of London B: Biological Sciences 2007; 362(1484):1393–1406, doi:10.1098/rstb.2007.2123.
 Wang Q, Sun W. Finite element modeling of mitral valve dynamic deformation using patient-specific multi- slices computed tomography scans. Annals of Biomedical Engineering 2013; 41(1):142–153, doi:10.1007/ s10439-012-0620-6. URL: http://dx.doi.org/10.1007/s10439-012-0620-6.
 Prot V, Haaverstad R, Skallerud B. Finite element analysis of the mitral apparatus: annulus shape effect and chordal force distribution. Biomechanics and Modeling in Mechanobiology 2009; 8(1):43–55, doi:10.1007/ s10237-007-0116-8. URL : http://dx.doi.org/10.1007/s10237-007-0116-8.
 Hammer P, del Nido P, Howe R. Anisotropic mass-spring method accurately simulates mitral valve closure from image-based models. Functional Imaging and Modeling of the Heart, Lecture Notes in Computer Science, vol.6666, Metaxas D, Axel L (eds.). Springer Berlin Heidelberg, 2011; 233–240, doi:10.1007/978-3-642-21028-0 29.
 Robust blood vessel surface reconstruction for interactive simulations from patient data, Ahmed Yureidini, PhD Thesis, 2014 URL: https://tel.archives-ouvertes.fr/tel-01010973/file/Thesis_Ahmed_Yureidini.pdf, chapter 3
 Sacks, M.S., Smith, D.B.: Effects of accelerated testing on porcine bioprosthetic heart valve fiber architecture. Biomaterials 19(11) (1998) 1027–1036