Catálogo de publicaciones - libros

It has been assumed that myocardial structure is uniform amongst individuals of a species, and between higher mammalian species. However, recent studies show that myolaminar structure, a critical component in myocardial function, varies markedly between dogs. Diffusion tensor magnetic resonance imaging (DT-MRI) data from 12 canine hearts is visualised and described qualitatively and quantitatively. Large confluent zones of primarily positive or negative sheet angles intersect at approximately 90°. The location of these stacks and their zones of intersection differ between dog hearts, but their overall morphology is consistent. As such there is no single model of adult canine heart structure; rather cardiac form belongs to a constrained distribution between extremes of structure. This variation must be considered in the construction of averaged anatomical atlases of myocardial architecture, where a range of maps may be required. These could be produced from DT-MRI datasets grouped by myolaminar structure.

In this paper, a statistical atlas of DT-MRIs based on a population of nine ex vivo normal canine hearts is compared with a human cardiac DT-MRI and with a synthetic model of the fibre orientation. The aim of this paper is to perform a statistical inter-species comparison of the cardiac fibre architecture and to assess the quality of a synthetic description of the fibre orientation. We present the framework to build a statistical atlas of cardiac DT-MRIs providing a mean and a covariance matrix of diffusion tensors at each voxel of an average geometry. The comparison of human and synthetic data with this atlas involves the non-rigid registration into the average atlas geometry where voxel to voxel comparison can be performed. For each eigenvector of the diffusion tensors, we compute the angular difference with the average atlas and its Mahalanobis distance to the canine population. The results show a better consistence of the fibre orientation than the laminar sheet orientation between the human and the canine heart, while the homogeneous synthetic model appears to be too simple compared to the complexity of real cardiac geometry and fibre architecture.

Quantitative measurements of the coronary artery tree substructures from Cardiac Multislice-CT data sets is an important goal to improve the diagnosis and treatment of coronary artery disease. This paper presents an algorithm based on morphological grayscale reconstruction through 2D slice images devoted to the extraction of the 3D coronary artery tree. The proposed procedure is conceived as a first step prior to the segmentation and inspection of interesting substructures in the coronaries. The correct extraction of the left coronary arteries has been validated in 9 CT-datasets with satisfactory results, particularly concerning speed and robustness.

We present an original Radial Basis Functions-based multiphase level set approach for the segmentation of cardiac structures in echocardiography. The method relies on two main contributions. We first describe a distribution allowing for the modeling of the radiofrequency signal for both blood and myocardial regions. We then formulate the problem of segmenting several cardiac regions in echocardiography using a Maximum Likelihood framework based on the proposed distribution. We minimize the resulting functional using a RBF-based multiphase level set model. Results obtained on both simulation and data acquired in vivo demonstrate the ability of our method to segment myocardial regions in echocardiography imaging.

This article proposes a hyperelastic 3D deformable template for the segmentation of soft structures. It relies on a template, which is a topological, geometrical and material model of the structure to segment. The template is modeled as an elastic body which is deformed by forces derived from the image. The proposed model is based on the nonlinear three-dimensional elasticity problem with a boundary condition of pure traction. In addition, the applied forces depend on the displacements. For computations, a convergent algorithm is proposed to minimize the global energy of template deformation. A discrete algorithm using the finite element method is presented and illustrated on MR images of mice.

A novel approach to segment cardiac magnetic resonance (CMR) images is presented in order to overcome some challenges such as problems with papillary muscles and the non homogeneities of the cavity due to blood flow. It consists in filtering short axis CMR images, using connected operators (area-open and area-close filters) to homogenize the cavity, prior to the segmentation which is performed using GVF-Snake algorithm in two steps. Validation was performed on thirty-nine slices by comparing resulting segmentation to the manual contours traced by an expert. This comparison showed good results with an overall average similarity area of 90.7% and an average distance between the two contours of 0.6 pixel.

This paper presents a first set of experiments to integrate a realistic electro-mechanical model of a beating heart into simulated real-time three-dimensional (RT3D) ultrasound data. A novel ultrasound simulation framework is presented, extended from the model of Meunier [12]. True three-dimensional transducer modeling was performed, using RT3D acquisition design. Myocardium and blood scattering parameters were defined in three dimensions. Ultrasound data sets were generated for a normal case and a pathological case, simulating left bundle branch block. Accuracy of an optical flow tracking method was evaluated on the simulated data to measure displacements on the myocardial surfaces and inside the myocardium over a cardiac cycle. The proposed simulation framework has important motivations in a cardiac modeling context as part of this project is focused on the design of effective parameter estimation methods, based on cardiac imaging.

We propose a new automated and fast procedure to segment the left ventricular myocardium in 4D (3D+t) cine-MRI sequences based on discrete mathematical morphology. Thanks to the comparison with manual segmentation performed by two cardiologists, we demonstrate the accuracy of the proposed method. The precision of the ejection fraction and myocardium mass measured from segmentations is also assessed. Furthermore, we show that the proposed 4D procedure maintains the temporal coherency between successive 3D segmentations.