THz Sensing of Human Skin: A Review of Skin Modeling Approaches

The non-ionizing and non-invasive nature of THz radiation, combined with its high sensitivity to water, has made THz imaging and spectroscopy highly attractive for in vivo biomedical applications for many years. Among them, the skin is primarily investigated due to the short penetration depth of THz waves caused by the high attenuation by water in biological samples. However, a complete model of skin describing the THz-skin interaction is still needed. This is also fundamental to reveal the optical properties of the skin from the measured THz spectrum. It is crucial that the correct model is used, not just to ensure compatibility between different works, but more importantly to ensure the reliability of the data and conclusions. Therefore, in this review, we summarize the models applied to skin used in the THz regime, and we compare their adaptability, accuracy, and limitations. We show that most of the models attempt to extract the hydration profile inside the skin while there is also the anisotropic model that displays skin structural changes in the stratum corneum.

Automated summary

THz radiation, with its non-ionizing and non-invasive nature, is highly sensitive to water and widely used in biomedical applications. Models describing the interaction between THz and skin are crucial for understanding the optical properties of skin. Various models have been applied to extract hydration profiles and depict structural changes in the skin, showcasing their adaptability, accuracy, and limitations.