Mètodes polarimètrics per a la millora de la qualitat d'imatge en aplicacions biològiques
- Autores: Albert van Eeckhout Alsinet
- Directores de la Tesis: Juan Ignacio Pedro Campos Coloma (dir. tes.), Ángel Lizana Tutusaus (codir. tes.)
- Lectura: En la Universitat Autònoma de Barcelona ( España ) en 2021
- Idioma: catalán
- Tribunal Calificador de la Tesis: Susana Marcos Celestino (presid.), Elisabet Pérez Cabré (secret.), Colin Sheppard (voc.)
- Programa de doctorado: Programa de Doctorado en Física por la Universidad Autónoma de Barcelona
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
Since the invention of the microscope in the 17th century, the use of imaging technologies has been fundamental in the study of biological tissues. Over the centuries, new imaging technologies have been developed and implemented to enhance the visualization of tissues and ease the understanding of their structure from the measurement of some of their physical properties. In that context, polarimetry is an interesting non-contact and non-invasive optical technique that has been used for image enhancement in a wide range of fields such as astronomy, remote sensing, and characterization of materials. Moreover, polarimetry can be combined with other optical techniques to further improve the visualization of samples.
Polarimetry comprises a group of optical methods that are based on measuring the polarization of light and how it varies when interacting with samples. In this thesis, some polarimetric methods recently proposed in the literature (as well as new ones) are studied, experimentally implemented, and applied for the first time in the analysis of biological tissues to improve the visualization of animal and plant tissues.
In the field of biomedicine, the potential of polarimetry is demonstrated in a wide variety of studies. These studies are usually based on two groups of polarimetric techniques: Polarization Gating techniques and Mueller matrix-based techniques. In this thesis, we investigate the relationship between these two groups of polarimetric techniques and we propose a new generalized polarimetric method that allows the analysis of different Polarization Gating configurations from a single Mueller matrix measurement.
Concerning to the biomedical studies based on the Mueller matrix, different polarimetric properties (diattenuation, retardance, and depolarization) are analyzed from a group of observables to obtaining physical information related to the structure of biological tissues and also to enhance their visualization. In these studies, retardance is completely studied through the Lu-Chipman decomposition and the calculation of the linear retardance, the circular retardance, and the orientation of the fast axis, among others. By contrast, the analysis of depolarization content is restricted to the calculation of observables that quantify the overall depolarization of samples and do not allow the study of more specific information, as can be possible anisotropies in that depolarization process. For that reason, in this thesis, different observables that further describe the depolarization properties of the sample are studied to, afterwards, be applied for visualization enhancement of the measured animal tissues. In that sense, the parameters called Indices of Polarimetric Purity are applied to inspect animal tissues. These depolarizing observables are used to improve tissue visualization, revealing certain structures hidden in standard depolarization channels, and also to classify, with improved efficiency, different animal tissues.
Finally, we also study the use of polarimetry for the analysis of plant tissues. Unlike animal tissues, polarimetry is much less used in the plant analysis framework, being Mueller-based techniques scarcely used. For this reason, this thesis studies the potential of Mueller polarimetry for plant tissue analysis and compares the obtained results with those obtained with some commonly used polarimetric and non-polarimetric techniques. As a result, Mueller polarimetry is an optimal polarimetric method for obtaining non-invasive images of plant tissues that, in addition, can be used as a complementary tool to other non-polarimetric optical techniques.
