Evaluation of atherosclerotic plaques with nano-probes for intravascular cardiological imaging diagnosis

• Autor(a) principal: Fonseca, Sara Cristina Pereira
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/92935
• topic: atherosclerosis; inflammation; contrast agents; optical coherence tomography; imaging processing software; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Médica

Cardiovascular diseases represent the leading cause of mortality and disability worldwide. Besides, it is estimated that these numbers will increase significantly in the future. More specifically, atherosclerosis is present in most of the main cardiovascular diseases, making its study urgent and important to develop new diagnostic tools. The most relevant limitation in the current investigation of the evaluation of atherosclerosis is the impossibility to distinguish stable and prone to rupture (unstable) plaques in coronary arteries. Associated with the instability phenomena, in plaques prone to rupture, are increased thickness of tissue layers (already detectable but not provide an unequivocal diagnosis) and inflammatory processes (not yet detectable but only present when the lesion evolves higher risk to rupture). Aiming to detect the precise location of inflammatory processes, two types of contrast agents (nano probes) were synthetized, gold nanoparticles and microbubbles. Also, to replicate the behavior of human arteries, three-dimensional tissue simulating structures (phantoms) were fabricated and optimized. To evaluate the performance of the contrast agents, both in the phantoms and post-mortem human arteries, optical coherence tomography (OCT) images were acquired in a clinical environment, and other techniques were performed (confocal microscopy, scanning electron microscopy, atomic force microscopy) to characterize the samples. Microbubbles revealed to be a better contrast agent than gold nanoparticles having a clearly noticeable enhancement of the OCT signal. After the acquisition of several OCT images on both types of samples (arteries and phantoms) an automatic imaging processing software was developed to detect the presence of the contrast agents and its posterior location. The software uses MATLAB as a programming language and with a user-friendly interface the user can access numerous parameters of the analyzed image and even edit them manually. In the end of the automatic processing, the user has the information of the number of regions of interest as well as their visual location.