THz and mm-wave sensing of corneal tissue water content: Electromagnetic modeling and analysis

Zachary D. Taylor, James Garritano, Shijun Sung, Neha Bajwa, David B. Bennett, Bryan Nowroozi, Priyamvada Tewari, James Sayre, Jean Pierre Hubschman, Sophie Deng, Elliott R. Brown, Warren S. Grundfest

Research output: Contribution to journalArticlepeer-review

78 Scopus citations

Abstract

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.

Original languageEnglish
Article number7044605
Pages (from-to)170-183
Number of pages14
JournalIEEE Transactions on Terahertz Science and Technology
Volume5
Issue number2
DOIs
StatePublished - 1 Mar 2015
Externally publishedYes

Keywords

  • Biological and medical imaging
  • clinical instruments
  • hydration interactions
  • medical diagnostics

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