An interdisciplinary team led by Professor Zachary Taylor’s team in the Departments of Bioengineering, Electrical Engineering, and Surgery has won the 2016 THz Science and Technology Best Paper Award for their work on Corneal Tissue Water Content sensing using THz imaging. The award is given annually to the best paper published in the IEEE Transactions on Terahertz Science and Technology in the previous calendar year. The award cites two papers; a first in the history of IEEE Transactions on Terahertz Science and Technology. The papers are (1) “THz and mm-Wave Sensing of Corneal Tissue Water Content: Electromagnetic Modeling and Analysis” and (2) “THz and mm-Wave Sensing of Corneal Tissue Water Content: In Vivo Sensing and Imaging Results”.
The assembled team is composed of students and faculty from the UCLA Departments of Bioengineering, Electrical Engineering, Ophthalmology, and Biostatistics and funded by a grant from the National Eye Institute. The grant supports the development of diagnostic imaging systems, based on THz and millimeter wave frequency transceivers, capable of detecting and quantifying small changes in corneal tissue water content that are correlated with a range of ophthalmologic diseases and pathologies. Current clinical practice utilizes thickness measurements of cornea center to indirectly characterize corneal water content. This method is highly inaccurate and lacks the sensitivity for sufficient early detection of disease and graft rejection.
In the two cited papers, the team developed new theory to describe the THz frequency electromagnetic properties of cornea based on an ensemble of disease states. Then a millimeter wave reflectometer and THz imaging system were constructed and tested on rabbit models in the animal operating room. The results confirmed that THz sensing can detect tiny changes in corneal tissue water content that are too small for clinical gold standard thickness measurement. Further, the systems were able to differentiate between thickness changes induced by water and those induced by pressure (no change in water content). This differentiation is not possible with current clinical technique and is a major barrier to early disease detection.
This work represents the first ever in vivo images of cornea ever acquired at THz frequencies and the first time ever that the limited specificity standard corneal water content diagnostics has been quantified.
The most exciting discovery of this work is the lossy etalon like properties of the cornea. The extremely limited variance in shape and thickness of the cornea as referenced to a THz wavelength enables one to treat in vivo cornea as a lossy thin film sandwiched between air and a lossy back short (water). The result is a tissue construct that displays distinct, clinically relevant spectral signatures due not to the bulk tissue properties but to the morphology of the tissue. This allows the application of thin film metrology techniques to the measurement of corneal water and in the future, will enable resolution of corneal tissue water content gradients that can be used as an early predictor of disease.