Development of a prototype Time Domain Spectroscopy system for in vivo terahertz thermal imaging.

Caraffini, Diego (2020). Development of a prototype Time Domain Spectroscopy system for in vivo terahertz thermal imaging. Mémoire. Québec, Maîtrise en sciences de l’énergie et des matériaux, Université du Québec, Institut national de la recherche scientifique, 154 p.

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Résumé

Terahertz radiation (THZ or Terahertz) is that part of the electromagnetic spectrum lying between the electrical domain of microwaves and the optical domain of infrared radiation (0.1 THz to 10 THz), which is now blooming with a myriad of new applications after decades where it was only considered as some sort of technological ‘gap’, mainly because of a lack of standardized generation and detection systems. The most common applications of THZ are in the industrial domain as a non-contact means to perform material identification, measure thickness of plastic objects and coatings, as well as carry out spectroscopic analysis of packaged substances. It is also used for cultural heritage diagnostics, security inspections (body scan) and many other uses. The intrinsic safety of THZ, due to its characteristic low photon energy that cannot cause ionization, makes it suitable for probing living tissues, and a highly attractive candidate for sensing and monitoring systems in the biological and biomedical fields. We are particularly interested in the use of THZ as a complementary instrument in the therapy of skin cancer, which is becoming an increasingly common occurrence in developed countries and imposes a significant burden on society. After being reflected by the skin, THZ carries information about the refractive index of the water contained in epidermal tissue that can be used to infer the temperature and hydration of the skin. This could prove to be invaluable as a monitoring tool during sessions of Photothermal Therapy (PTT) and enable us to assess its outcome afterwards. This thesis is part of a larger research project that aims first to demonstrate the feasibility and utility of a THZ-based monitoring system for PTT and then to refine the analysis algorithms and measurement procedures to allow this idea to exit the physics research laboratory and become a tool commonly used in the healthcare system. This work focuses on the development of a fast and reliable data acquisition system that will constitute the basis of the project. The setup will have to be powerful and flexible enough to accommodate the necessities of a research environment, but present an interface that is simple to use and understand for operators that have no specific training in spectroscopy and nonlinear optics. The first chapter briefly reviews the medical and social issues that physics is called upon to address and summarizes why this new approach to thermal monitoring is an interesting alternative to other well-established techniques. The second chapter illustrates the state of the art in the field of THZ generation and detection, in order to allow us to i) evaluate the viability of the various options for use in a clinical context and ii) choose the most appropriate ones. The third chapter describes in detail the setup itself, from the point of view of both the hardware components and the software used to drive them, thereby providing adequate justification for the choice of components and software architecture. This chapter also contains the description of the measurement procedures employed for each operating mode of the setup. The fourth chapter describes a set of measurements performed with the aim i) of characterizing the instrument used, ii) determining how its operating mode affects the collected data and iii) establishing the limits within which the settings of the various sub-systems should lie to ensure optimal performance. One of the tests involves the simulation of a PTT session on a porcine skin model to show that the setup is actually capable of performing its function, in conditions as close as possible to its intended use. The fifth chapter contains the conclusion and several suggestions for future development of the system.

Type de document:	Thèse Mémoire
Directeur de mémoire/thèse:	Morandotti, Roberto
Co-directeurs de mémoire/thèse:	Razzari, Luca
Mots-clés libres:	énergie; matériaux
Centre:	Centre Énergie Matériaux Télécommunications
Date de dépôt:	14 oct. 2020 19:24
Dernière modification:	14 oct. 2020 19:24
URI:	https://espace.inrs.ca/id/eprint/10398

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