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A Novel Anisotropic Elasticity-Palpography IVUS Imaging Tool and Characterization of the Viscoelasto-Plastic Properties of Angioplasty Balloon : Towards a Better Assessment and Treatment of Coronary Artery Diseases

Abstract : Cardiac catheterization has evolved from being initially received with great skepticism to becoming a standard for the diagnosis and treatment of cardiovascular disease. A myriad of derived techniques like balloon angioplasty, intravascular imaging, as well as valve and stent implantation are now routine procedures for interventional cardiologists. Despite these and other great advances in cardiovascular medicine, cardiovascular disease (CVD) still represents the main cause of mortality, accounting for as much as one out of three deaths worldwide. Due to the complexity of CVD, it has become the field of study of researchers among various disciplines in hopes to reduce the burden of the disease. One of such disciplines is mechanics, that applies its principles and approaches to create innovative tools to diagnose, prevent and treat CVD.The present thesis belongs to the field of cardiovascular biomechanics and aims to develop tools that can be of assistance to physicians in the diagnosis and treatment of coronary artery disease. This dissertation is divided into two parts:Part I: Imaging the atherosclerotic plaque in clinics, is related to the identification and assessment of coronary atherosclerotic plaque with the presentation of a novel palpography algorithm based on continuum mechanics theory.First, it was investigated whether gray-scale IVUS images are enough for obtaining an accurate elasticity map to assess plaque composition and evolution. Indeed, it was concluded that radiofrequency (RF) data provides more detailed data than b-mode IVUS images. Then a novel anisotropic elasticity-palpography algorithm is described. It computes an apparent elasticity of the plaque from radiofrequency signals obtained through IVUS images. The derivation of an anisotropic index (AI) that can be related to the mechanical properties of the arterial wall, along with a first validation using simulated IVUS images based on real patient geometries of atherosclerotic and healthy plaques is presented. Using this new palpography algorithm, a study was that aimed to validate this technique in vitro was performed. Polyvinyl-alcohol (PVA) cryogel vascular phantoms were fabricated, two of them with increased anisotropy. The phantoms were imaged with IVUS and their mechanical properties were obtained using different characterization techniques. Then, the anisotropy indices modeld with the experimental results and the ones computed with the algorithm were compared.Part II: Balloon angioplasty is focused on the treatment of coronary plaque and analyzes the mechanical properties of the balloons used for coronary angioplasty.First, the visco-elasto-plastic mechanical characterization of a specific balloon catheter model, the Maverick2 from Boston Scientific, is presented. Geometrical measurements using different microscopy techniques, balloon inflation tests, tensile tests and high-speed images are used to describe the mechanical behavior of the balloon components. The previous results are used in to define a model that can accurately predict the viscoelasto-plastic behavior of the angioplasty balloon film. These results could be used as the basis for a model to predict the inflation behavior of the angioplasty balloon during consecutive inflations in clinics.
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Submitted on : Thursday, December 19, 2019 - 12:04:06 PM
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Armida Gomez Lara. A Novel Anisotropic Elasticity-Palpography IVUS Imaging Tool and Characterization of the Viscoelasto-Plastic Properties of Angioplasty Balloon : Towards a Better Assessment and Treatment of Coronary Artery Diseases. Human health and pathology. Université Grenoble Alpes, 2019. English. ⟨NNT : 2019GREAS012⟩. ⟨tel-02419090⟩

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