Terahertz (THz) spectral properties of human cornea are explored as a function of central corneal thickness (CCT) and corneal water content, and the clinical utility of THz-based corneal water content sensing is discussed. Three candidate corneal tissue water content (CTWC) perturbations, based on corneal physiology, are investigated that affect the axial water distribution and total thickness. The THz frequency reflectivity properties of the three CTWC perturbations were simulated and explored with varying system center frequency and bandwidths (Q-factors). The modeling showed that at effective optical path lengths on the order of a wavelength the cornea presents a lossy etalon bordered by air at the anterior and the aqueous humor at the posterior. The simulated standing wave peak-to-valley ratio is pronounced at lower frequencies and its effect on acquired data can be modulated by adjusting the bandwidth of the sensing system. These observations are supported with experimental spectroscopic data. The results suggest that a priori knowledge of corneal thickness can be utilized for accurate assessments of corneal tissue water content. The physiologic variation of corneal thickness with respect to the wavelengths spanned by the THz band is extremely limited compared to all other structures in the body making CTWC sensing unique amongst all proposed applications of THz medical imaging.

中文翻译：

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角膜组织含水量的太赫兹和毫米波传感：电磁建模和分析

人类角膜的太赫兹 (THz) 光谱特性作为中央角膜厚度 (CCT) 和角膜含水量的函数进行了探索，并讨论了基于太赫兹的角膜含水量传感的临床效用。研究了基于角膜生理学的三个候选角膜组织含水量 (CTWC) 扰动，它们影响轴向水分布和总厚度。三个 CTWC 扰动的太赫兹频率反射率特性通过不同的系统中心频率和带宽（Q 因子）进行了模拟和探索。建模表明，在波长数量级的有效光程长度下，角膜呈现有损标准具，前部为空气，后部为房水。模拟驻波峰谷比在较低频率下很明显，其对采集数据的影响可以通过调整传感系统的带宽来调制。这些观察结果得到了实验光谱数据的支持。结果表明，角膜厚度的先验知识可用于准确评估角膜组织含水量。与身体中的所有其他结构相比，角膜厚度相对于太赫兹波段所跨越的波长的生理变化极其有限，这使得 CTWC 传感在所有提议的太赫兹医学成像应用中独一无二。结果表明，角膜厚度的先验知识可用于准确评估角膜组织含水量。与身体中的所有其他结构相比，角膜厚度相对于太赫兹波段所跨越的波长的生理变化极其有限，这使得 CTWC 传感在所有提议的太赫兹医学成像应用中独一无二。结果表明，角膜厚度的先验知识可用于准确评估角膜组织含水量。与身体中的所有其他结构相比，角膜厚度相对于太赫兹波段所跨越的波长的生理变化极其有限，这使得 CTWC 传感在所有提议的太赫兹医学成像应用中独一无二。