145 research outputs found
Thérapies ultrasonores cardiaques guidées par élastographie et échographie ultrarapides
Atrial fibrillation (AF) affects 2-3% of the European and North-American population, whereas ventricular tachyarrhythmia (VT) is related to an important risk of sudden death. AF and VT originate from dysfunctional electrical activity in cardiac tissues. Minimally-invasive approaches such as Radio-Frequency Catheter Ablation (RFCA) have revolutionized the treatment of these diseases; however the success rate of RFCA is currently limited by the lack of monitoring techniques to precisely control the extent of thermally ablated tissue.The aim of this thesis is to propose novel ultrasound-based approaches for minimally invasive cardiac ablation under guidance of ultrasound imaging. For this, first, we validated the accuracy and clinical viability of Shear-Wave Elastography (SWE) as a real-time quantitative imaging modality for thermal ablation monitoring in vivo. Second we implemented SWE on an intracardiac transducer and validated the feasibility of evaluating thermal ablation in vitro and in vivo on beating hearts of a large animal model. Third, a dual-mode intracardiac transducer was developed to perform both ultrasound therapy and imaging with the same elements, on the same device. SWE-controlled High-Intensity-Focused-Ultrasound thermal lesions were successfully performed in vivo in the atria and the ventricles of a large animal model. At last, SWE was implemented on a transesophageal ultrasound imaging and therapy device and the feasibility of transesophageal approach was demonstrated in vitro and in vivo. These novel approaches may lead to new clinical devices for a safer and controlled treatment of a wide variety of cardiac arrhythmias and diseases.La fibrillation atriale affecte 2-3% des europĂ©ens et nord-amĂ©ricains, les tachycardies ventriculaires sont liĂ©es Ă un risque important de mort subite. Les approches minimalement invasives comme lâAblation par CathĂ©ter RadiofrĂ©quence (RFCA) ont rĂ©volutionnĂ© le traitement de ces maladies, mais le taux de rĂ©ussite de la RFCA est limitĂ© par le manque de techniques dâimagerie pour contrĂŽler cette ablation thermique.Le but de cette thĂšse est de proposer de nouvelles approches ultrasonores pour des traitements cardiaques minimalement invasifs guidĂ©s par Ă©chographie.Pour cela nous avons dâabord validĂ© la prĂ©cision et la viabilitĂ© clinique de lâĂlastographie par Ondes de Cisaillement (SWE) en tant que modalitĂ© dâimagerie quantitative et temps rĂ©el pour lâablation thermique in vivo. Ensuite nous avons implĂ©mentĂ© la SWE sur un transducteur intracardiaque et validĂ© la faisabilitĂ© dâĂ©valuer lâablation thermique in vitro et in vivo sur cĆur battant de gros animal. Puis nous avons dĂ©veloppĂ© un transducteur intracardiaque dual-mode pour effectuer lâablation et lâimagerie ultrasonores avec les mĂȘmes Ă©lĂ©ments, sur le mĂȘme dispositif. Les lĂ©sions thermiques induites par Ultrasons FocalisĂ©s de Haute IntensitĂ© (HIFU) et contrĂŽlĂ©es par la SWE ont Ă©tĂ© rĂ©alisĂ©es avec succĂšs in vivo dans les oreillettes et les ventricules chez le gros animal. Finalement la SWE a Ă©tĂ© implĂ©mentĂ©e sur un dispositif dâimagerie et thĂ©rapie ultrasonores transĆsophagien et la faisabilitĂ© de cette approche a Ă©tĂ© dĂ©montrĂ©e in vitro et in vivo. Ces approches originales pourraient conduire Ă de nouveaux dispositifs cliniques pour des traitements plus sĂ»rs et contrĂŽlĂ©s dâun large Ă©ventail dâarythmies et maladies cardiaques
CT Scanning
Since its introduction in 1972, X-ray computed tomography (CT) has evolved into an essential diagnostic imaging tool for a continually increasing variety of clinical applications. The goal of this book was not simply to summarize currently available CT imaging techniques but also to provide clinical perspectives, advances in hybrid technologies, new applications other than medicine and an outlook on future developments. Major experts in this growing field contributed to this book, which is geared to radiologists, orthopedic surgeons, engineers, and clinical and basic researchers. We believe that CT scanning is an effective and essential tools in treatment planning, basic understanding of physiology, and and tackling the ever-increasing challenge of diagnosis in our society
Characterization, prevalence, and risk factors of spontaneous and experimental atherosclerosis and vascular imaging in psittaciformes
Atherosclerosis is a degenerative and inflammatory vascular disease characterized by the accumulation of inflammatory cells, lipids, calcium, and formation of large fibrofatty lesions within the intima of arteries resulting in the disorganization of the arterial wall and stenosis of the lumen. Despite the importance of atherosclerosis in psittacine cardiology, there are few pathologic, clinical, and experimental investigations in psittaciformes. In order to expand the knowledge on psittacine atherosclerosis and provide fundamental observational information for future research, a series of studies was conducted on psittaciformes: 1) psittacine atherosclerotic lesions were characterized and categorized based on histopathology, histochemistry, transmission (TEM), and scanning electron microscopy (SEM) of 63 arterial samples, 2) the prevalence of clinically significant atherosclerotic lesions and the influence of several epidemiological variables were investigated in a multi-center case-control study on 7683 psittaciformes, 3) a diet-induced experimental model of atherosclerosis was developed and characterized in Quaker parrots (Myiopsitta monachus), and 4) a computed-tomography angiographic (CTA) protocol was developed and standardized to image the arterial lumen in Hispaniolan Amazon parrots (Amazona ventralis). Seven lesion types could be described in psittaciformes, which were similar to the human classification system. Digital image analysis, TEM, and SEM helped to further describe the lesions and refine the classification system. Atherosclerosis prevalence significantly increased with age, female sex, and the genera Psittacus, Amazona, and Nymphicus. Mild associations with reproductive, hepatic diseases, and myocardial fibrosis were also evidenced. Experimental induction of atherosclerosis with dietary 1% cholesterol lead to significant lesions within 2 months in Quaker parrots. An increase in arterial and plasma cholesterol and LDL was also documented. Reference limits for arterial luminal diameter of Hispaniolan Amazon parrots were determined by CTA and measurements revealed high intraobserver and interobserver agreement. In conclusion, psittacine atherosclerotic lesions displayed distinctive features that allowed the development of an effective classification system. The prevalence of advanced lesions (type IV-VI) was associated with several risk factors: age, female sex, and three psittacine genera. The Quaker parrot was found to be a suitable experimental model for psittacine atherosclerosis and dyslipidemia. Finally CTA was determined to be safe, reliable, and of potential diagnostic value in parrots for diagnosing stenotic atherosclerotic lesions
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