Selection of optimal hyperosmotic agent for tissue immersion optical clearing in the terahertz range

In terahertz (THz) spectroscopy water content correlates with the tissue pathological changes. At the same time, water reduces the depth of THz-wave penetration in tissues. In order to unmask cells’ and tissues’ biophysical properties and to increase the tissues probing depth, immersion optical clearing (IOC) was recently introduced in the THz range. For studying common IOC agent’s optical properties in the frequency range of 0.1–2.5 THz, pulsed spectroscopy was used. Diffusion coefficients of IOC agents in ex vivo rat brain tissue were studied 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.