Department of Electronic Engineering, The Chinese University of Hong Kong, Shatin, Hong Kong 999077, China.
Department of Physics, University of Warwick, Coventry CV4 7AL, UK.
Sensors (Basel). 2021 May 23;21(11):3624. doi: 10.3390/s21113624.
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.
太赫兹辐射的非电离和非侵入特性，加上其对水的高灵敏度，多年来使其在体内生物医学应用中的太赫兹成像和光谱学变得非常有吸引力。其中，由于太赫兹波在生物样本中被水高度衰减而导致的短穿透深度，皮肤是主要研究对象。然而，仍然需要一个完整的皮肤模型来描述太赫兹与皮肤的相互作用。这对于从测量的太赫兹光谱中揭示皮肤的光学性质也是至关重要的。使用正确的模型至关重要，不仅是为了确保不同工作之间的兼容性，更重要的是为了确保数据和结论的可靠性。因此，在这篇综述中，我们总结了太赫兹波段应用于皮肤的模型，并比较了它们的适应性、准确性和局限性。我们表明，大多数模型试图提取皮肤内部的水合状态，而还有各向异性模型显示了角质层中的皮肤结构变化。
