The impact of hydration changes in fresh bio-tissue on THz spectroscopic measurements

Abstract

We present a study of how residual hydration in fresh rat tissue samples can vastly alter their extracted terahertz (THz) optical properties and influence their health assessment. Fresh (as opposed to preserved) tissue most closely mimics in vivo conditions, but high water content creates many challenges for tissue handling and THz measurement. Our THz measurements of fresh tissue over time highlight the effect of tissue hydration on tissue texture and dimension, the latter directly influencing the accuracy of calculated optical properties. We then introduce lyophilization (freeze drying) as a viable solution for overcoming hydration and freshness problems. Lyophilization removes large amounts of water while retaining sample freshness. In addition, lyophilized tissue samples are easy to handle and their textures and dimensions do not vary over time, allowing for consistent and stable THz measurements. A comparison of lyophilized and fresh tissue shows for the first time that freeze drying may be one way of overcoming tissue hydration issues while preserving tissue cellular structure. Finally, we compare THz measurements from fresh tissue against necrotic tissue to verify freshness over time. Indeed, THz measurements from fresh and necrotic tissues show marked differences.

Modeling terahertz heating effects on water

“…Since the use of terahertz techniques within medical applications and other related areas is becoming commonplace [2,[23][24][25][26] it is still interesting to carry out the calculations to give an idea of how THz radiation might heat the human body in the worst-case.…”

Using a portable terahertz spectrometer to measure the optical properties ofin vivohuman skin

“…[1][2][3] Several medical and biological applications are also under development to improve detection and diagnosis of skin cancers, burns, and other pathologies. [4][5][6][7][8][9][10][11][12] Despite the elevated interest to develop THz-based applications, few basic science research investigations have been conducted to better understand the fundamental mechanisms governing THz-tissue interactions. In fact, only a few studies have been conducted to characterize the optical properties of in vivo human tissues at THz frequencies.…”

Freeze-thaw hysteresis effects in terahertz imaging of biomedical tissues

“…Such methods require an isotonic medium to balance the osmotic pressure. Alternatively, removing the water content in the ex vivo tissue by lyophilization [11] or formalin fixing [12] may avoid issues caused by tissue hydration. Lyophilized or fixed samples are more rigid than fresh samples and are more robust.…”