Obtenção das propriedades ópticas e dinâmicas do tecido biológico com técnicas de espectroscopia óptica de difusão

Author(s)

Giovani Grisotti Martins

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Física Gleb Wataghin
• Defense date: 2024-06-06

Examining board members

Rickson Coelho Mesquita; André Monteiro Paschoal; Felippe Alexandre Silva Barbosa; Luciano Bachmann; Diogo Coutinho Soriano

• Advisor: Rickson Coelho Mesquita; Gabriela Castellano

Abstract

Early disease detection can increase the chances of successful treatment and improve the efficiency of healthcare resource use. One method to achieve early detection is through the identification of biomarkers, which are quantifiable physiological parameters that indicate the potential presence of a specific disease. Biomarkers can enhance healthcare delivery by providing valuable insights that improve diagnosis, prognosis, and therapeutic monitoring. This work focuses on Diffuse Optical (DO) techniques, which offer a potential solution for identifying biomarkers for vascular diseases. DO techniques estimate hemodynamic-related parameters such as blood volume, flow, and oxygen saturation, which can help detect physiological differences between patients and healthy individuals. Despite their potential, DO techniques have limitations due to oversimplified assumptions about tissue structure, such as homogeneity and flatness. In this context, this research aims to refine these methodologies by investigating the impact of tissue heterogeneity and curvature on DO estimations. The thesis proposes enhanced models that better represent the macroscopic structural complexities of tissues, such as heterogeneity and non-planar geometries, which could significantly improve the accuracy of physiological parameter estimations. The thesis encompasses a comprehensive approach to validate the methodologies that consider tissue heterogeneity and curvature when analyzing DO data. Furthermore, the research explores the combined effects of tissue curvature and heterogeneity on real DO data. It also addresses the biases introduced by darker skin tones on blood oxygen saturation estimations using optical methods, offering a preliminary correction strategy to mitigate this bias. The conclusion reached is that the refined methodologies enhance the accuracy of physiological parameter estimations, which could potentially improve early diagnosis and patient care. The investigation also concluded that a crucial aspect of accurate model predictions is integrating prior knowledge about the individual anatomy. By proposing and validating methodologies that can improve parameter accuracy by incorporating tissue macroscopic complexity, the research suggests that diffuse optical techniques could potentially meet the precision required for clinical applications in the future, moving a step closer to practical healthcare implementation (AU)

• FAPESP's process: 19/25281-9 - Obtaining optical and dynamic properties of biological tissues with diffuse optical spectroscopy
• Grantee: Giovani Grisotti Martins
• Support Opportunities: Scholarships in Brazil - Doctorate