Over three years of dedicated work, this thesis embarked on a comprehensive exploration of TD-NIRS technique. The journey commenced with a theoretical introduction and an in-depth look at the device hardware. Facing challenges of lack of portability, fragility, and high costs linked to traditional TD-NIRS devices, the NIRSBox system was developed. The NIRSBox system, a compact TD-NIRS device, addressed these challenges, enabling in-vivo oximetry measurements on freely moving subjects. The significance of the NIRSBox system was further underscored in the third chapter, where meticulous characterization unfolded using the Medphot protocol. Parameters crucial for system evaluation, such as linearity, precision, accuracy, and reproducibility, were scrutinized. Notably, a specific parameter, the time shift (t-shift), emerged as a pivotal, influencing accuracy and precision in optical parameter assessments. Building upon this foundation, the thesis explored the practical applications of TD-NIRS spectroscopy in-vivo. Diverse tissues, from highly perfused muscles in horses to over oxygen stimulated muscles tissues on dogs, were investigated. The veterinary context provided a unique lens, allowing for a cross-sectional feasibility study across different animal species. Clinical applications extended to assessing oxygen concentration in peripheral tissues on dogs undergoing hyperbaric chamber treatment. The study provided valuable insights into physiological responses to treatment. The final chapter unveiled research conducted during an internship in Zurich, addressing a fundamental limitation of TD-NIRS related to limited SNR across high interfiber distance measurements. The “deep” TD-NIRS device developed showed promising results, mitigating the SNR-depth limitation in both transmittance and reflectance scenarios. A substantial depth of investigation was achieved, reaching 15.4 cm in transmittance geometry with a low absorption coefficient of 0.04 cm⁻¹. Although reductions in penetration distance occurred in scenarios with a higher absorption coefficient, the groundwork laid by these results holds promise for future advancements. In conclusion, my work has passed through theoretical foundations, device development, meticulous characterization, and in-vivo applications. The contributions significantly propel the field of optical spectroscopy for biomedical applications, offering innovative possibilities for non-invasive tissue assessment in the future.
In questi tre anni di dottorato ho affrontando sfide legate alla mancanza di portabilità, fragilità e costi elevati associati ai dispositivi TD-NIRS tradizionali, e grazie a questo lavoro è nata la NIRSBox. Il sistema NIRSBox, un dispositivo TD-NIRS compatto, che superando queste sfide, ha consentito misurazioni di ossimetria in-vivo su soggetti in movimento libero. La significatività dei risultati ottenuti dal sistema NIRSBox è stata ulteriormente sottolineata nel terzo capitolo, dove una meticolosa caratterizzazione è stata svolta utilizzando il protocollo Medphot. Sono stati valutati parametri cruciali per l’affidabilità del sistema, come: linearità, precisione, accuratezza e riproducibilità. In particolare, un parametro specifico, ossia lo spostamento temporale(t-shift) della Instrument Response Function (IRF) a causa dalla propagazione libera in aria in fase di acquisizione, è emerso come cruciale; influenzando l'accuratezza e la precisione nelle valutazioni dei parametri ottici. Su questa base, in questo lavoro vengono mostrate le misure in-vivo che sono state rese possibili tramite utilizzo di questo dispositivo. Sono stati esaminati diversi tessuti, dalle muscolature altamente perfuse dei cavalli ai tessuti muscolari sovra-stimolati dall'ossigeno nei cani. Il contesto veterinario ha fornito una prospettiva unica, consentendo uno studio trasversale di fattibilità tra diverse specie animali. Le applicazioni cliniche si sono estese alla valutazione della concentrazione di ossigeno nei tessuti periferici nei cani sottoposti a trattamento in camera iperbarica. Lo studio ha fornito preziose informazioni sulle risposte fisiologiche al trattamento. Il capitolo finale approfondisce la ricerca condotta durante il mio stage a Zurigo, affrontando una primaria limitazione della TD-NIRS legata al limitato numero di fotoni che raggiungo i tessuti profondi. Il dispositivo ha mostrato risultati promettenti, mitigando la limitazione sul SNR in profondità sia in geometria di trasmissione che di riflessione. In trasmissione sono stati raccolti un numero di fotoni sufficiente per ricavare le proprietà ottiche fino a 15.4 cm, considerando però bassi coefficiente di assorbimento nominali (0,04 cm⁻¹). Sebbene si siano verificate riduzioni nella distanza di penetrazione su tessuti con un coefficiente di assorbimento più elevato, il lavoro svolto è promette in vista di avanzamenti futuri. In conclusione, il mio lavoro ha attraversato studi del modello, sviluppo e caratterizzazione del dispositivo e applicazioni in-vivo. Pertanto, i contributi forniti da questo lavoro potrebbero offrire in futuro possibilità innovative per la valutazione non invasiva dei tessuti.
A comprehensive approach to devolopment, characterization, and in-vivo application of the time domain near infrared technique
FRABASILE, LORENZO
2023/2024
Abstract
Over three years of dedicated work, this thesis embarked on a comprehensive exploration of TD-NIRS technique. The journey commenced with a theoretical introduction and an in-depth look at the device hardware. Facing challenges of lack of portability, fragility, and high costs linked to traditional TD-NIRS devices, the NIRSBox system was developed. The NIRSBox system, a compact TD-NIRS device, addressed these challenges, enabling in-vivo oximetry measurements on freely moving subjects. The significance of the NIRSBox system was further underscored in the third chapter, where meticulous characterization unfolded using the Medphot protocol. Parameters crucial for system evaluation, such as linearity, precision, accuracy, and reproducibility, were scrutinized. Notably, a specific parameter, the time shift (t-shift), emerged as a pivotal, influencing accuracy and precision in optical parameter assessments. Building upon this foundation, the thesis explored the practical applications of TD-NIRS spectroscopy in-vivo. Diverse tissues, from highly perfused muscles in horses to over oxygen stimulated muscles tissues on dogs, were investigated. The veterinary context provided a unique lens, allowing for a cross-sectional feasibility study across different animal species. Clinical applications extended to assessing oxygen concentration in peripheral tissues on dogs undergoing hyperbaric chamber treatment. The study provided valuable insights into physiological responses to treatment. The final chapter unveiled research conducted during an internship in Zurich, addressing a fundamental limitation of TD-NIRS related to limited SNR across high interfiber distance measurements. The “deep” TD-NIRS device developed showed promising results, mitigating the SNR-depth limitation in both transmittance and reflectance scenarios. A substantial depth of investigation was achieved, reaching 15.4 cm in transmittance geometry with a low absorption coefficient of 0.04 cm⁻¹. Although reductions in penetration distance occurred in scenarios with a higher absorption coefficient, the groundwork laid by these results holds promise for future advancements. In conclusion, my work has passed through theoretical foundations, device development, meticulous characterization, and in-vivo applications. The contributions significantly propel the field of optical spectroscopy for biomedical applications, offering innovative possibilities for non-invasive tissue assessment in the future.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/217650