ABSTRACT
The potential of terahertz (THz) technology is beyond doubt, with water being a key endogenous marker of pathological processes in tissue in the THz medical diagnosis. The content and state (free or bound) of tissue water can reflect biochemical changes in normal tissues, as well as the presence and severity of pathological changes. At the same time, water acts as a “two-faced Janus”: it strongly absorbs THz radiation, masking many morphological and biochemical determinants and limiting the depth of THz-wave penetration in tissues. This chapter discusses approaches to tissue unmasking in the THz range – namely, optical clearing methods. Different tools for tissue dehydration that maintain its morphological and biochemical properties are considered. Most attention is paid to the potentially promising method of optical clearing using hyperosmotic agents. This approach has already taken its first steps in several fields of medicine, in particular, in oncology and metabolic disorders. The degree of prevalence and severity of the pathological process with the identification of principal molecular features and their dynamic monitoring are possible forms of translation into practice. The key parameters for choosing the optimal agent for optical clearing in the THz range are its optical properties and diffusion coefficient. Nevertheless, the amount of data in the literature on the parameters under consideration is relatively small, which prompts further research in this demanding area of THz biophotonics.
