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Doctoral Thesis
DOI
10.11606/T.5.2018.tde-13062018-110733
Document
Author
Full name
Cristiano Guedes Bezerra
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2018
Supervisor
Committee
Lemos Neto, Pedro Alves (President)
Gowdak, Luís Henrique Wolff
Falcão, Breno de Alencar Araripe
Silva, Expedito Eustáquio Ribeiro da
Title in Portuguese
Processamento de imagens médicas e parâmetros hemodinâmicos: validação clínica de modelos cardiovasculares assistidos por computação científica
Keywords in Portuguese
Atherosclerosis
Coronary artery disease
Coronary vessels/diagnostic imaging
Fractional flow reserve myocardial
Image processing computer-assisted
Imaging three-dimensional
Intravascular ltrasonography
Abstract in Portuguese
Introdução: A doença arterial coronária (DAC) é avaliada através dos aspectos anatômicos da placa aterosclerótica ou a partir da repercussão funcional da estenose, por métodos diagnósticos diversos. O ultrassom intravascular (IVUS) fornece uma avaliação anatômica precisa do lúmen e da parede do vaso, tendo sido validado como uma ferramenta útil para guiar a intervenção coronária percutânea (ICP). No entanto, do ponto de vista diagnóstico, o IVUS representa mal o estado funcional (isto é, informação relacionada ao comprometimento de fluxo) do vaso interrogado. A reserva de fluxo fracionada (FFR) é método importante para identificação de isquemia, discriminando as estenoses coronárias que podem se beneficiar de ICP. Objetivamos desenvolver e avaliar o desempenho diagnóstico de um novo algoritmo computacional para estimar a FFR à partir das imagens do IVUS tridimensional (IVUSFR), comparando-o com o método padrão ouro para estimação de fluxo coronário invasivo (FFRPW). Métodos: Pacientes com DAC estável conhecida ou suspeita encaminhados para cateterismo cardíaco eletivo foram submetidos a avaliação complementar com medida de fluxo coronário pelo FFRPW e com imagem intravascular pelo IVUS, no mesmo procedimento, a fim de avaliar lesões intermediárias. As imagens do IVUS foram processadas para gerar uma malha computacional tridimensional que condensa as características geométricas do vaso. O IVUSFR foi obtido utilizando dinâmica de fluido computacional, configurando-se as condições de contorno a partir de características específicas do paciente e do território coronário irrigado. As medidas de FFRPW foram dicotomizadas no limiar de 0,80 para definir lesões hemodinamicamente significativas e avaliar o desempenho diagnóstico do IVUSFR. Resultados: Um total de 34 artérias coronárias de 24 pacientes foi analisado. A área luminal mínima média avaliada pelo IVUS de 4,14 ± 1,74 mm2, e carga de placa média de 66±10% caracterizam o grau intermediário das lesões. O IVUSFR correlacionou significativamente (r = 0,79; p < 0,001) e mostrou boa concordância com a FFRPW, apresentando diferença média de -0,008 ± 0,067 (p = 0,47). O IVUSFR apresentou acurácia, sensibilidade, especificidade, valor preditivo positivo e valor preditivo negativo de 91%, 89%, 92%, 80% e 96%, respectivamente, para detectar estenoses hemodinamicamente significativas. Conclusão: O processamento computacional do IVUSFR é um novo método que permite a avaliação funcional da estenose coronária intermediária de forma acurada, enriquecendo as informações anatômicas do IVUS
Title in English
Processing of medical imaging and hemodynamic parameters: clinical
Keywords in English
Atherosclerosis
Coronary artery disease
Coronary vessels/diagnostic imaging
Fractional flow reserve myocardial
Image processing computer-assisted
Imaging three-dimensional
Ultrasonography intravascular
Abstract in English
Introduction: Coronary artery disease (CAD) is assessed through the anatomical aspects of the atherosclerotic plaque or through the functional impairment of the stenosis, by different diagnostic methods. Intravascular ultrasound (IVUS) provides accurate anatomic assessment of lumen and vessel wall and has been validated as a useful tool to guide percutaneous coronary intervention (PCI). However, from the diagnostic point of view, IVUS poorly represents the functional status (i.e. flow-related information) of the imaged vessel. Fractional flow reserve (FFR) is an important tool to identify ischemia, discriminating coronary stenosis that may benefit from PCI. We aimed to develop and evaluate the diagnostic performance of a novel computational algorithm based on three-dimensional IVUS imaging in estimating fractional flow reserve (IVUSFR), compared to gold-standard invasive measurements (FFRPW). Methods: Patients with known or suspected stable coronary disease scheduled for elective cardiac catheterization underwent FFRPW measurement and IVUS imaging in the same procedure to evaluate intermediate lesions. A processing methodology was applied on IVUS to generate a computational mesh condensing the geometric characteristics of the vessel. Through computational fluid dynamics, IVUSFR was obtained from patient-level morphological definition of arterial districts and from territory-specific boundary conditions. FFRPW measurements were dichotomized at the 0.80 thresholds to define hemodynamically significant lesions and evaluate diagnostic performance of IVUSFR. Results: A total of 24 patients with 34 vessels were analyzed. The mean minimum luminal area assessed by IVUS was 4.14 ± 1.74 mm2, and mean plaque burden was 66 ± 10%, characterizing intermediate lesions. IVUSFR significantly correlated (r = 0.79; p < 0.001) and showed good agreement with FFRPW, with a mean difference of -0.008 ± 0.067 (p = 0.47). IVUSFR presented an overall accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of 91%, 89%, 92%, 80%, and 96% respectively to detect significant stenosis. Conclusion: The computational processing of IVUSFR is a new method that allows the evaluation of the functional significance of coronary stenosis in an accurate way, enriching the anatomical information of IVUS
 
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Publishing Date
2018-06-13
 
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