Optimal agents for immersion optical clearing of tissues at terahertz frequencies
Water plays the role of a key marker in terahertz (THz) spectroscopy. Moreover, the content of free water may correlate with the presence of pathological changes in the tissues, as well as the severity of these changes. Nevertheless, water shields a significant part of the properties of cells and tissues that are potentially useful for medical purposes, reducing the THz wave penetration depth to hundreds (or even tens) microns. Therefore, to unmask the properties of cells and tissues that are not related to free water, and to increase the penetration depth of THz radiation, immersion optical clearing (IOC) in the THz range was studied. For research of the optical properties of common IOC agents, particularly, their absorption coefficients pulsed spectroscopy in the frequency range of 0.1-2.5 THz was applied. Their diffusion coefficients in ex vivo rat brain tissue were measured using the collimated transmission spectroscopy in the visible range. Two-dimensional nomogram was used to objectively compare IOC agents, based on their THz-wave absorption coefficients and diffusion rates.
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Prokhorov General Physics Institute of the Russian Academy of Sciences
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