High Powered GASMAS Lung Diagnostics - Towards Larger Geometries

Sammanfattning

The optical technique, Gas in scattering media absorption spectroscopy (GASMAS) shows promise in application to address current challenges in lung monitoring during intensive care, improving respiratory care by allowing for continuous, non-invasive monitoring. While the technique is already developed in neonatal infant care, the patient profile can be expanded by using higher powered laser systems, by increasing the geometries probed. GASMAS is an optical technique that utilizes the scattering properties of gas-filled porous materials. In lung diagnostics, the lung tissue is probed, assessing the oxygen concentration present in the lungs. Since the light quickly attenuates by the tissue, a stronger light source is required to acquire a signal through larger patients. To investigate the potential of expanding the geometries, this thesis assesses signal detectability when bulk absorbing material is added to the porous medium. Using a pork encased extruded polystyrene foam model and ex vivo porcine lungs, investigating SNR reduction and the oxygen absorption signal when pork-padding is added. For high powered illumination, skin heating resulting in tissue damage to the patient was identified as a central risk. To assess this potential obstacle, the heating for different volunteers was assessed using two different illumination methods, free beam and probe illumination, different powers of the laser, along with skin tone and illumination area. The results showed promise in future clinical applications demonstrating a strong SNR through thick pieces of pork padding both for the extruded polystyrene foam model and for the ex vivo porcine lungs. In heating, the area, illumination method, skin tone and illumination power all showed impacts on the resulting heating, exhibiting predictable patterns that can be used to assess heating risks in future clinical applications. Both studies indicated a potential for future clinical applications, as well as a need for future research before the method can be implemented.