THz and mm-Wave Sensing of Corneal Tissue Water Content: In Vivo Sensing and Imaging Results

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

doi:10.1109/TTHZ.2015.2392628

THz and mm-Wave Sensing of Corneal Tissue Water Content: In Vivo Sensing and Imaging Results

IEEE Trans Terahertz Sci Technol. 2015 Mar;5(2):184-196. doi: 10.1109/TTHZ.2015.2392628.

Authors

Affiliations

¹ Department of Bioengineering, University of California (UCLA), Los Angeles, CA 90095 USA, and also with the Center for Advanced Surgical and Interventional Technology (CASIT), University of California (UCLA), Los Angeles, CA 90095 USA.
² Department of Electrical Engineering, University of California (UCLA), Los Angeles, CA 90095 USA.
³ Department of Electrical Engineering, University of California (UCLA), Los Angeles, CA 90095 USA. He is now with Fitbit, San Francisco, CA 94105 USA.
⁴ Department of Bioengineering, University of California (UCLA), Los Angeles, CA 90095 USA, and also with the Center for Advanced Surgical and Interventional Technology (CASIT), University of California (UCLA), Los Angeles, CA 90095 USA. He is now with Mimeo Labs Inc, Santa Monica, CA 90404 USA.
⁵ Department of Bioengineering, University of California (UCLA), Los Angeles, CA 90095 USA, and also with the Center for Advanced Surgical and Interventional Technology (CASIT), University of California (UCLA), Los Angeles, CA 90095 USA. She is now with Elsevier Life Science solutions, San Francisco, CA 94105 USA.
⁶ Department of Biostatistics, University of California (UCLA), Los Angeles, CA 90095 USA.
⁷ Department of Ophthalmology, University of California (UCLA), Los Angeles, CA 90095 USA.
⁸ Department. of Electrical Engineering, Wright State University, Dayton, OH 45435 USA.

Abstract

A pulsed terahertz (THz) imaging system and millimeter-wave reflectometer were used to acquire images and point measurements, respectively, of five rabbit cornea in vivo. These imaging results are the first ever produced of in vivo cornea. A modified version of a standard protocol using a gentle stream of air and a Mylar window was employed to slightly dehydrate healthy cornea. The sensor data and companion central corneal thickness (CCT) measurements were acquired every 10-15 min over the course of two hours using ultrasound pachymmetry.. Statistically significant positive correlations were established between CCT measurements and millimeter wave reflectivity. Local shifts in reflectivity contrast were observed in the THz imagery; however, the THz reflectivity did not display a significant correlation with thickness in the region probed by the 100 GHz and CCT measurements. This is explained in part by a thickness sensitivity at least 10× higher in the mm-wave than the THz systems. Stratified media and effective media modeling suggest that the protocol perturbed the thickness and not the corneal tissue water content (CTWC). To further explore possible etalon effects, an additional rabbit was euthanized and millimeter wave measurements were obtained during death induced edema. These observations represent the first time that the uncoupled sensing of CTWC and CCT have been achieved in vivo.

Keywords: Biological and medical imaging; clinical instruments; medical diagnostics; tissue water content interactions.

Abstract

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