Remote photoacoustic sensing using speckle-analysis for biomedical imaging

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This thesis investigates contact-free speckle-analysis for photoacoustic detection. A simulation model is developed to theoretically confirm the detectability of photoacoustic surface deformations through speckle-analysis. The feasibility of contact-free detection is demonstrated via experiments on phantoms and ex-vivo tissue using a high-speed camera system. Multiple speckles are analyzed, showcasing the technique's endoscopic applicability with an imaging fiber bundle. To accelerate speckle acquisition, the high-speed camera is replaced with a lower-resolution diode-based sensor. This faster system experimentally demonstrates the feasibility of contact-free photoacoustic detection and its automation through single speckle-analysis. The two analysis techniques are compared based on sensitivity, measuring range, linearity, and measuring depth. Investigations on ex-vivo tissue reveal that speckle wavelength is a crucial factor for the quality of speckle patterns and analysis. Finally, the potential for photoacoustic imaging in speckle-analysis is explored through a reconstruction approach tested in simulations and an initial experiment.