Application of terahertz pulsed spectroscopy for analysis of ex vivo biological tissue freezing

Terahertz (THz) technologies demonstrate significant potential for medical and biological applications. Despite a low penetration depth of THz waves into biological tissues due to the absorption by interstitial water, tissue freezing can be used for overcoming this limitation up to a certain limit. Moreover, application of low temperatures leads to changes of tissue dielectric properties, which yields additional perspectives of THz spectroscopy for study of different states and conditions of tissues, in particular, for observation of their freezing during cryoablation. In this work, the contrast of refractive index featured by unfrozen and frozen adipose and liver ex vivo tissue samples is demonstrated experimentally, along with the ability to detect the freezing depth using THz pulsed spectroscopy.