1
|
Virk AS, Harris ZB, Arbab MH. Design and characterization of a hyperbolic-elliptical lens pair in a rapid beam steering system for single-pixel terahertz spectral imaging of the cornea. OPTICS EXPRESS 2023; 31:39568-39582. [PMID: 38041275 DOI: 10.1364/oe.496894] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Accepted: 10/10/2023] [Indexed: 12/03/2023]
Abstract
Terahertz (THz) time-domain spectroscopy has been investigated for assessment of the hydration levels in the cornea, intraocular pressure, and changes in corneal topography. Previous efforts at THz imaging of the cornea have employed off-axis parabolic mirrors to achieve normal incidence along the spherical surface. However, this comes at the cost of an asymmetric field-of-view (FOV) and a long scan time because it requires raster-scanning of the collimated beam across the large mirror diameter. This paper proposes a solution by designing a pair of aspheric lenses that can provide a larger symmetric spherical FOV (9.6 mm) and reduce the scan time by two orders of magnitude using a novel beam-steering approach. A hyperbolic-elliptical lens was designed and optimized to achieve normal incidence and phase-front matching between the focused THz beam and the target curvature. The lenses were machined from a slab of high-density polyethylene and characterized in comparison to ray-tracing simulations by imaging several targets of similar sizes to the cornea. Our experimental results showed excellent agreement in the increased symmetric FOV and confirmed the reduction in scan time to about 3-4 seconds. In the future, this lens design process can be extended for imaging the sclera of the eye and other curved biological surfaces, such as the nose and fingers.
Collapse
|
2
|
Chen A, Harris ZB, Virk A, Abazari A, Varadaraj K, Honkanen R, Arbab MH. Assessing Corneal Endothelial Damage Using Terahertz Time-Domain Spectroscopy and Support Vector Machines. SENSORS (BASEL, SWITZERLAND) 2022; 22:9071. [PMID: 36501773 PMCID: PMC9735956 DOI: 10.3390/s22239071] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 11/16/2022] [Accepted: 11/19/2022] [Indexed: 06/17/2023]
Abstract
The endothelial layer of the cornea plays a critical role in regulating its hydration by actively controlling fluid intake in the tissue via transporting the excess fluid out to the aqueous humor. A damaged corneal endothelial layer leads to perturbations in tissue hydration and edema, which can impact corneal transparency and visual acuity. We utilized a non-contact terahertz (THz) scanner designed for imaging spherical targets to discriminate between ex vivo corneal samples with intact and damaged endothelial layers. To create varying grades of corneal edema, the intraocular pressures of the whole porcine eye globe samples (n = 19) were increased to either 25, 35 or 45 mmHg for 4 h before returning to normal pressure levels at 15 mmHg for the remaining 4 h. Changes in tissue hydration were assessed by differences in spectral slopes between 0.4 and 0.8 THz. Our results indicate that the THz response of the corneal samples can vary according to the differences in the endothelial cell density, as determined by SEM imaging. We show that this spectroscopic difference is statistically significant and can be used to assess the intactness of the endothelial layer. These results demonstrate that THz can noninvasively assess the corneal endothelium and provide valuable complimentary information for the study and diagnosis of corneal diseases that perturb the tissue hydration.
Collapse
Affiliation(s)
- Andrew Chen
- Department of Biomedical Engineering, Stony Brook University, 100 Nicolls Rd, Stony Brook, NY 11794, USA
| | - Zachery B. Harris
- Department of Biomedical Engineering, Stony Brook University, 100 Nicolls Rd, Stony Brook, NY 11794, USA
| | - Arjun Virk
- Department of Biomedical Engineering, Stony Brook University, 100 Nicolls Rd, Stony Brook, NY 11794, USA
| | - Azin Abazari
- Department of Ophthalmology, Renaissance School of Medicine, 101 Nicolls Rd, Stony Brook, NY 11794, USA
| | - Kulandaiappan Varadaraj
- Department of Physiology and Biophysics, Renaissance School of Medicine, 101 Nicolls Rd, Stony Brook, NY 11794, USA
| | - Robert Honkanen
- Department of Ophthalmology, Renaissance School of Medicine, 101 Nicolls Rd, Stony Brook, NY 11794, USA
| | - Mohammad Hassan Arbab
- Department of Biomedical Engineering, Stony Brook University, 100 Nicolls Rd, Stony Brook, NY 11794, USA
| |
Collapse
|
3
|
Sasaki K, Porter E, Rashed EA, Farrugia L, Schmid G. Measurement and image-based estimation of dielectric properties of biological tissues —past, present, and future—. Phys Med Biol 2022; 67. [DOI: 10.1088/1361-6560/ac7b64] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2022] [Accepted: 06/22/2022] [Indexed: 12/23/2022]
Abstract
Abstract
The dielectric properties of biological tissues are fundamental pararmeters that are essential for electromagnetic modeling of the human body. The primary database of dielectric properties compiled in 1996 on the basis of dielectric measurements at frequencies from 10 Hz to 20 GHz has attracted considerable attention in the research field of human protection from non-ionizing radiation. This review summarizes findings on the dielectric properties of biological tissues at frequencies up to 1 THz since the database was developed. Although the 1996 database covered general (normal) tissues, this review also covers malignant tissues that are of interest in the research field of medical applications. An intercomparison of dielectric properties based on reported data is presented for several tissue types. Dielectric properties derived from image-based estimation techniques developed as a result of recent advances in dielectric measurement are also included. Finally, research essential for future advances in human body modeling is discussed.
Collapse
|
4
|
Zarrinkhat F, Baggio M, Lamberg J, Tamminen A, Nefedova I, Ala-Laurinaho J, Khaled EEM, Rius JM, Romeu J, Taylor Z. Calibration Alignment Sensitivity in Corneal Terahertz Imaging. SENSORS 2022; 22:s22093237. [PMID: 35590925 PMCID: PMC9105978 DOI: 10.3390/s22093237] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 04/12/2022] [Accepted: 04/20/2022] [Indexed: 11/16/2022]
Abstract
Improving the longitudinal modes coupling in layered spherical structure contributes significantly to corneal terahertz sensing, which plays a crucial role in the early diagnosis of cornea dystrophies. Using a steel sphere to calibrate reflection from the cornea sample assists in enhancing the resolution of longitudinal modes. The requirement and challenges toward applying the calibration sphere are introduced and addressed. Six corneas with different properties are spotted to study the effect of perturbations in the calibration sphere in a frequency range from 100 GHz to 600 GHz. A particle-swarm optimization algorithm is employed to quantify corneal characteristics considering cases of accurately calibrated and perturbed calibrated scenarios. For the first case, the study is carried out with signal-to-noise values of 40 dB, 50 dB and 60 dB at waveguide bands WR-5.1, WR-3.4, and WR-2.2. As expected, better estimation is achieved in high-SNR cases. Furthermore, the lower waveguide band is revealed as the most proper band for the assessment of corneal features. For perturbed cases, the analysis is continued for the noise level of 60 dB in the three waveguide bands. Consequently, the error in the estimation of corneal properties rises significantly (around 30%).
Collapse
Affiliation(s)
- Faezeh Zarrinkhat
- CommSensLab, Technical University of Catalonia/UPC, 08034 Barcelona, Spain; (J.M.R.); (J.R.)
- Department of Electronics and Nanoengineering, Millilab, Aalto University, 02150 Espoo, Finland; (M.B.); (J.L.); (A.T.); (I.N.); (J.A.-L.); (Z.T.)
- Correspondence:
| | - Mariangela Baggio
- Department of Electronics and Nanoengineering, Millilab, Aalto University, 02150 Espoo, Finland; (M.B.); (J.L.); (A.T.); (I.N.); (J.A.-L.); (Z.T.)
| | - Joel Lamberg
- Department of Electronics and Nanoengineering, Millilab, Aalto University, 02150 Espoo, Finland; (M.B.); (J.L.); (A.T.); (I.N.); (J.A.-L.); (Z.T.)
| | - Aleksi Tamminen
- Department of Electronics and Nanoengineering, Millilab, Aalto University, 02150 Espoo, Finland; (M.B.); (J.L.); (A.T.); (I.N.); (J.A.-L.); (Z.T.)
| | - Irina Nefedova
- Department of Electronics and Nanoengineering, Millilab, Aalto University, 02150 Espoo, Finland; (M.B.); (J.L.); (A.T.); (I.N.); (J.A.-L.); (Z.T.)
| | - Juha Ala-Laurinaho
- Department of Electronics and Nanoengineering, Millilab, Aalto University, 02150 Espoo, Finland; (M.B.); (J.L.); (A.T.); (I.N.); (J.A.-L.); (Z.T.)
| | - Elsayed E. M. Khaled
- Department of Electrical Engineering, Assiut University, Assiut 71515, Egypt;
- High Institute of Engineering and Technology, Sohag 82524, Egypt
| | - Juan M. Rius
- CommSensLab, Technical University of Catalonia/UPC, 08034 Barcelona, Spain; (J.M.R.); (J.R.)
| | - Jordi Romeu
- CommSensLab, Technical University of Catalonia/UPC, 08034 Barcelona, Spain; (J.M.R.); (J.R.)
| | - Zachary Taylor
- Department of Electronics and Nanoengineering, Millilab, Aalto University, 02150 Espoo, Finland; (M.B.); (J.L.); (A.T.); (I.N.); (J.A.-L.); (Z.T.)
| |
Collapse
|
5
|
Osman OB, Harris ZB, Khani ME, Zhou JW, Chen A, Singer AJ, Hassan Arbab M. Deep neural network classification of in vivo burn injuries with different etiologies using terahertz time-domain spectral imaging. BIOMEDICAL OPTICS EXPRESS 2022; 13:1855-1868. [PMID: 35519269 PMCID: PMC9045889 DOI: 10.1364/boe.452257] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Revised: 01/28/2022] [Accepted: 01/28/2022] [Indexed: 05/22/2023]
Abstract
Thermal injuries can occur due to direct exposure to hot objects or liquids, flames, electricity, solar energy and several other sources. If the resulting injury is a deep partial thickness burn, the accuracy of a physician's clinical assessment is as low as 50-76% in determining the healing outcome. In this study, we show that the Terahertz Portable Handheld Spectral Reflection (THz-PHASR) Scanner combined with a deep neural network classification algorithm can accurately differentiate between partial-, deep partial-, and full-thickness burns 1-hour post injury, regardless of the etiology, scanner geometry, or THz spectroscopy sampling method (ROC-AUC = 91%, 88%, and 86%, respectively). The neural network diagnostic method simplifies the classification process by directly using the pre-processed THz spectra and removing the need for any hyperspectral feature extraction. Our results show that deep learning methods based on THz time-domain spectroscopy (THz-TDS) measurements can be used to guide clinical treatment plans based on objective and accurate classification of burn injuries.
Collapse
Affiliation(s)
- Omar B. Osman
- State University of New York at Stony Brook, THz Biophotonics Laboratory, Department of Biomedical Engineering, 101 Nicolls Rd., Stony Brook, NY 11794, USA
| | - Zachery B. Harris
- State University of New York at Stony Brook, THz Biophotonics Laboratory, Department of Biomedical Engineering, 101 Nicolls Rd., Stony Brook, NY 11794, USA
| | - Mahmoud E. Khani
- State University of New York at Stony Brook, THz Biophotonics Laboratory, Department of Biomedical Engineering, 101 Nicolls Rd., Stony Brook, NY 11794, USA
| | - Juin W. Zhou
- State University of New York at Stony Brook, THz Biophotonics Laboratory, Department of Biomedical Engineering, 101 Nicolls Rd., Stony Brook, NY 11794, USA
| | - Andrew Chen
- State University of New York at Stony Brook, THz Biophotonics Laboratory, Department of Biomedical Engineering, 101 Nicolls Rd., Stony Brook, NY 11794, USA
| | - Adam J. Singer
- Renaissance School of Medicine at Stony Brook University, Department of Emergency Medicine, 101 Nicolls Rd., Stony Brook, NY 11794, USA
| | - M. Hassan Arbab
- State University of New York at Stony Brook, THz Biophotonics Laboratory, Department of Biomedical Engineering, 101 Nicolls Rd., Stony Brook, NY 11794, USA
| |
Collapse
|
6
|
Hu Y, Baggio M, Dabironezare S, Tamminen A, Toy B, Ala-Laurinaho J, Brown E, Llombart N, Deng SX, Wallace V, Taylor ZD. 650 GHz imaging as alignment verification for millimeter wave corneal reflectometry. IEEE TRANSACTIONS ON TERAHERTZ SCIENCE AND TECHNOLOGY 2022; 12:151-164. [PMID: 36185397 PMCID: PMC9518788 DOI: 10.1109/tthz.2021.3140199] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
A system concept for online alignment verification of millimeter-wave, corneal reflectometry is presented. The system utilizes beam scanning to generate magnitude-only reflectivity maps of the cornea at 650 GHz and compares these images to a precomputed/measured template map to confirm/reject sufficient alignment. A system utilizing 5 off-axis parabolic mirrors, a thin film beam splitter, and 2-axis galvanometric mirror was designed, simulated, and evaluated with geometric and physical optics. Simulation results informed the construction of a demonstrator system which was tested with a reference reflector. Similarity metrics computed with the aligned template and 26 misaligned positions, distributed on a 0.5 mm x 0.5 mm x 0.5 mm mesh, demonstrated sufficient misalignment detection sensitivity in 23 out of 26 positions. The results show that positional accuracy on the order of 0.5 mm is possible using 0.462 mm wavelength radiation due to the perturbation of coupling efficiency via beam distortion and beam walk-off.
Collapse
Affiliation(s)
- Yong Hu
- Department of Bioengineering, University of California, Los Angeles, CA 90095 USA
| | - Mariangela Baggio
- Department of Electronics and Nanoengineering, Aalto University, Espoo, FI-02150, Finland
| | - Shahab Dabironezare
- Center for Wireless Systems and Technology, Delft University of Technology, 2628 CD Delft, The Netherlands
| | - Aleksi Tamminen
- Department of Electronics and Nanoengineering, Aalto University, Espoo, FI-02150, Finland
| | - Brandon Toy
- Electrical and Computer Engineering Department, University of California, Los Angeles, CA 90095 USA
| | - Juha Ala-Laurinaho
- Department of Electronics and Nanoengineering, Aalto University, Espoo, FI-02150, Finland
| | - Elliott Brown
- College of Engineering and Computer Science, Wright State University, Dayton, OH, 45435, USA
| | - Nuria Llombart
- Center for Wireless Systems and Technology, Delft University of Technology, 2628 CD Delft, The Netherlands
| | - Sophie X Deng
- Cornea Division, University of California, Los Angeles, 90095-1436, USA
| | - Vincent Wallace
- Department of Engineering and Mathematical Sciences, University of Western Australia, Crawley, WA, 6009, Australia
| | - Zachary D Taylor
- Department of Electronics and Nanoengineering, Aalto University, Espoo, FI-02150, Finland
| |
Collapse
|
7
|
Terahertz radiation in ophthalmology (review). ACTA BIOMEDICA SCIENTIFICA 2021. [DOI: 10.29413/abs.2021-6.6-1.20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Terahertz (THz) radiation is one of the new, intensively studied interdisciplinary fi elds of scientifi c knowledge, including medicine, in the fi rst decades of the 21st century. At the beginning of this article (review), in a brief form, the basic statements on THz radiation, the main parameters and properties are presented; the modern THz biophtonics technologies used in biology and medicine are considered – THz refl ectometry, THz spectroscopy methods. Then a number of directions and examples of possible use of THz technologies in biology and medicine, including pharmaceuticals, are given. The main part of the review presents the progress of experimental research and the prospects for the clinical application of medical technologies of THz spectroscopy, THz imaging, in ophthalmology in the study of the morphological and functional state of the ocular surface structures, diagnosis, medical testing, and treatment of ophthalmopathology of the ocular surface. The article concludes with a review of experimental studies on the safety of using THz waves for medical diagnostics and treatment of ophthalmopathology. In the fi nal part, the main problems and prospects of introducing medical THz technologies into the clinical practice of an ophthalmologist are considered.
Collapse
|
8
|
Ke L, Zhang N, Wu QYS, Gorelik S, Abdelaziem A, Liu Z, Teo EPW, Mehta JS, Liu YC. In vivo sensing of rabbit cornea by terahertz technology. JOURNAL OF BIOPHOTONICS 2021; 14:e202100130. [PMID: 34105892 DOI: 10.1002/jbio.202100130] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2021] [Revised: 06/03/2021] [Accepted: 06/04/2021] [Indexed: 06/12/2023]
Abstract
A Novel scalable approach using Terahertz (THz) waves together with the electromagnetic field simulation was applied to investigate four rabbits of eight rabbit corneas in vivo. One eye of each rabbits' corneas was edema induced; the other eye of the corneas served as the control. The simulation revealed the propagation of THz waves at a certain distance along the sub-surface of the cornea. THz spectra have been collected close to the corneal surface by deviating the direct reflection of the THz beam for the edema cornea, the reflected wave intensity for edema corneas is generally larger compared with the control cornea. Upon edema becomes severe at the end of the observation, the reflected wave intensities obtained by detector corresponding to the corneal deep stroma layer approach to the same value for all observed corneas. Good correlation is observed between central corneal thickness measurements and THz wave reflection signal intensities. Our results demonstrated that THz spectroscopy technique could obtain the information from different corneal sublayers.
Collapse
Affiliation(s)
- Lin Ke
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*Star), Singapore
| | - Nan Zhang
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*Star), Singapore
| | - Qing Yang Steve Wu
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*Star), Singapore
| | - Sergey Gorelik
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*Star), Singapore
- Singapore Institute of Food and Biotechnology Innovation (SIFBI), Agency for Science, Technology and Research (A*STAR), Singapore
| | - Ali Abdelaziem
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*Star), Singapore
- School of Material Science and Engineering (MSE), Nanyang Technological University (NTU), Singapore
- National Institute of Laser Enhanced Sciences (NILES), Cairo University, Giza, Egypt
| | - Zheng Liu
- School of Material Science and Engineering (MSE), Nanyang Technological University (NTU), Singapore
| | | | - Jodhbir S Mehta
- Singapore Eye Research Institute (SERI), Singapore
- Singapore National Eye Centre (SNEC), Singapore
- Ophthalmology and Visual Science Academic Clinical Research Program, Duke-NUS Medical School, Singapore
| | - Yu-Chi Liu
- Singapore Eye Research Institute (SERI), Singapore
- Singapore National Eye Centre (SNEC), Singapore
- Ophthalmology and Visual Science Academic Clinical Research Program, Duke-NUS Medical School, Singapore
| |
Collapse
|
9
|
Chen A, Virk A, Harris Z, Abazari A, Honkanen R, Arbab MH. Non-contact terahertz spectroscopic measurement of the intraocular pressure through corneal hydration mapping. BIOMEDICAL OPTICS EXPRESS 2021; 12:3438-3449. [PMID: 34221670 PMCID: PMC8221940 DOI: 10.1364/boe.423741] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 05/03/2021] [Accepted: 05/04/2021] [Indexed: 05/03/2023]
Abstract
Elevated intraocular pressure (IOP) results in endothelial layer damage that can induce corneal hydration perturbations. We investigated the potential of terahertz spectroscopy in measuring the IOP levels through mapping corneal water content. We controlled the IOP levels in ex vivo rabbit and porcine eye samples while monitoring the change in corneal hydration using a terahertz time-domain spectroscopy (THz-TDS) scanner. Our results showed a statistically significant increase in the THz reflectivity between 0.4 and 0.6 THz corresponding to the increase in the IOP. Endothelial layer damage was confirmed using scanning electron microscopy (SEM) of the corneal biopsy samples. Our empirical results indicate that the THz-TDS can be used to track IOP levels through the changes in corneal hydration.
Collapse
Affiliation(s)
- Andrew Chen
- Department of Biomedical Engineering, Stony Brook University, 100 Nicolls Rd, Stony Brook, NY 11794, USA
| | - Arjun Virk
- Department of Biomedical Engineering, Stony Brook University, 100 Nicolls Rd, Stony Brook, NY 11794, USA
| | - Zachery Harris
- Department of Biomedical Engineering, Stony Brook University, 100 Nicolls Rd, Stony Brook, NY 11794, USA
| | - Azin Abazari
- Department of Ophthalmology, Renaissance School of Medicine, 101 Nicolls Rd, Stony Brook, NY 11794, USA
| | - Robert Honkanen
- Department of Ophthalmology, Renaissance School of Medicine, 101 Nicolls Rd, Stony Brook, NY 11794, USA
| | - M. Hassan Arbab
- Department of Biomedical Engineering, Stony Brook University, 100 Nicolls Rd, Stony Brook, NY 11794, USA
| |
Collapse
|
10
|
Ke L, Wu QYS, Zhang N, Yang Z, Teo EPW, Mehta JS, Liu YC. Terahertz spectroscopy analysis of human corneal sublayers. JOURNAL OF BIOMEDICAL OPTICS 2021; 26:JBO-210014SSRR. [PMID: 33899380 PMCID: PMC8071781 DOI: 10.1117/1.jbo.26.4.043011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Accepted: 03/29/2021] [Indexed: 06/12/2023]
Abstract
SIGNIFICANCE Corneal diseases is a major cause of reversible blindness in the world. Monitoring the progression of human corneal edema or corneal scarring to prevent the disease entering into the end stage is crucial. AIM We present a method for sensing human corneal composition at different depths, namely focused on the epithelium and stromal layer, using high-sensitivity terahertz (THz) broadband spectroscopy. APPROACH From the proposed methodology, the THz temporal and absorption spectra of human corneas at different edema stages have been studied. THz wave signals were collected from the direct reflection and four other collection points along the THz wave propagation direction as reviewed from the simulation THz electrical field. RESULT Our results show that the epithelium layer acts as a good barrier to maintain hydration level of the stroma, and the quality of the epithelium can be used to predict the level of corneal swelling in corneal edema. At the detection points near to the incident point, the THz frequency spectra demonstrated interference oscillation behavior. At the final edema observing time, results showed that the epithelium lose its barrier properties. The intactness of the epithelium can be used to predict the edema severity in the final stage. When the detection points are further away from the incident point, the THz spectra are believed to contain information from stromal layer. Stromal absorption spectra demonstrated correlation with optical coherence tomography thickness results. CONCLUSION The hydration concentration from stromal layer was further quantitatively calculated. At the end of the experiment, all the corneal hydration levels reach to the same value which shows that the edema hydration has reached maximum saturation. The information of individual sublayers of the cornea is obtained by characterizing noninvasively with the use of THz spectroscopy. To our knowledge, this is the first report of using THz for noninvasive characterization of sublayers of the cornea.
Collapse
Affiliation(s)
- Lin Ke
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research, Singapore
| | - Qing Yang Steve Wu
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research, Singapore
| | - Nan Zhang
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research, Singapore
| | - Zaifeng Yang
- Institute of High Performance Computing, Agency for Science, Technology and Research, Singapore
| | | | - Jodhbir S. Mehta
- Singapore Eye Research Institute, Singapore
- Singapore National Eye Centre, Singapore
- Duke-NUS Medical School, Ophthalmology and Visual Science Academic Clinical Research Program, Singapore
| | - Yu-Chi Liu
- Singapore Eye Research Institute, Singapore
- Singapore National Eye Centre, Singapore
- Duke-NUS Medical School, Ophthalmology and Visual Science Academic Clinical Research Program, Singapore
| |
Collapse
|
11
|
Mizuno M, Kitahara H, Sasaki K, Tani M, Kojima M, Suzuki Y, Tasaki T, Tatematsu Y, Fukunari M, Wake K. Dielectric property measurements of corneal tissues for computational dosimetry of the eye in terahertz band in vivo and in vitro. BIOMEDICAL OPTICS EXPRESS 2021; 12:1295-1307. [PMID: 33796354 PMCID: PMC7984789 DOI: 10.1364/boe.412769] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 01/16/2021] [Accepted: 01/27/2021] [Indexed: 05/08/2023]
Abstract
The dielectric constant of the normal corneal tissue of a rabbit eye was obtained in vitro in the range from approximately 0.1 to 1 THz, and the drying process on the eye surface exposed to high-power terahertz waves was investigated by in vivo reflectance measurement using terahertz time-domain spectroscopy. When the rabbit eye was exposed to terahertz waves at 162 GHz for 6 min with an irradiation power of 360 or 480 mW/cm2, the reflectance temporally increased and then decreased with a temperature increase. Based on multiple-reflection calculation using the dielectric constant and anterior segment optical coherence tomography images, those changes in reflectance were attributed to drying of the tear and epithelium of the cornea, respectively. Furthermore, the drying progressed over a temperature increase of around 5°C under our exposure conditions. These findings suggest that the possibility of eye damage increases with the progress of drying and that the setting of the eye surface conditions can be a cause of disagreement between computational and experimental data of absorbed energy under high-level irradiation because reflectance is related to terahertz wave penetration in the eye tissue. The time-domain spectroscopic measurements were useful for the acquisition of the dielectric constant as well as for the real-time monitoring of the eye conditions during exposure measurement.
Collapse
Affiliation(s)
- Maya Mizuno
- National Institute of Information and Communications Technology, Koganei, Tokyo 184-8795, Japan
| | - Hideaki Kitahara
- Research Center for Development of Far-Infrared Region, University of Fukui, Fukui 910-8507, Japan
| | - Kensuke Sasaki
- National Institute of Information and Communications Technology, Koganei, Tokyo 184-8795, Japan
| | - Masahiko Tani
- Research Center for Development of Far-Infrared Region, University of Fukui, Fukui 910-8507, Japan
| | - Masami Kojima
- Medical Research Institute, Kanazawa Medical University, Kahoku, Ishikawa 920-0293, Japan
| | - Yukihisa Suzuki
- Graduate School of Systems Design, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan
| | - Takafumi Tasaki
- Medical Research Institute, Kanazawa Medical University, Kahoku, Ishikawa 920-0293, Japan
- Department of Medical Zoology, Kanazawa Medical University, Kahoku, Ishikawa 920-0293, Japan
| | - Yoshinori Tatematsu
- Research Center for Development of Far-Infrared Region, University of Fukui, Fukui 910-8507, Japan
| | - Masafumi Fukunari
- Research Center for Development of Far-Infrared Region, University of Fukui, Fukui 910-8507, Japan
| | - Kanako Wake
- National Institute of Information and Communications Technology, Koganei, Tokyo 184-8795, Japan
| |
Collapse
|
12
|
Virk AS, Harris ZB, Arbab MH. Development of a terahertz time-domain scanner for topographic imaging of spherical targets. OPTICS LETTERS 2021; 46:1065-1068. [PMID: 33649658 PMCID: PMC10760507 DOI: 10.1364/ol.419140] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 02/04/2021] [Indexed: 05/08/2023]
Abstract
Topographical abnormality in corneal tissue is a common diagnostic marker for many eye diseases and injuries. Using an asynchronous optical sampling terahertz time-domain spectroscopy setup, we developed a non-contact and normal-incidence imaging system to measure topographic changes along the surface of spherical samples. We obtained orthogonal 1D scans of calibration spheres to evaluate the minimum axial resolution of our system. We determined the axial and spatial resolution of the scanner using 3D-printed spherical cross and Boehler star targets. Furthermore, we characterized the asymmetrical performance of the scanner due to the use of an off-axis parabolic mirror. Finally, we developed an edge-detection filter to aid with improving the topographic scans. We showed that when imaging samples were comparable in size to the human cornea, the axial and spherical spatial resolutions were limited to about 15 µm (∼λ/67) and 1 mm, respectively.
Collapse
Affiliation(s)
- Arjun S. Virk
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, New York 11794, USA
| | - Zachery B. Harris
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, New York 11794, USA
| | - M. Hassan Arbab
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, New York 11794, USA
| |
Collapse
|
13
|
Yao J, Ma J, Zhao J, Qi P, Li M, Lin L, Sun L, Wang X, Liu W, Wang Y. Corneal hydration assessment indicator based on terahertz time domain spectroscopy. BIOMEDICAL OPTICS EXPRESS 2020; 11:2073-2084. [PMID: 32341867 PMCID: PMC7173912 DOI: 10.1364/boe.387826] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 03/10/2020] [Accepted: 03/12/2020] [Indexed: 06/11/2023]
Abstract
Terahertz technology has shown broad prospects for measuring corneal water content, which is an important parameter of ocular health. Based on terahertz time-domain spectroscopy, a new indicator named characteristic ratio (CR) of the sum of low (0.2-0.7 THz) and high (0.7-1.0 THz) frequency spectral intensities, for characterizing corneal hydration is introduced in this work. CR is calculated from the real-time reflection spectra after error elimination of ex vivo human corneal stroma samples which is collected during dehydration under natural conditions (temperature: 22.4 ± 0.3°C; humidity: 20.0 ± 3%). The corresponding relationships between CR and corneal water content are reported. Comparing the linear fitting results with the published similar study, the coefficients of variation of the fitting slope and intercept are 39.4% and 27.6% lower, respectively. This indicates that this approach has the potential to achieve corneal water content in-vivo detection in the future.
Collapse
Affiliation(s)
- Jiali Yao
- Institute of Modern Optics, Nankai University, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Tianjin 300350, China
| | - Jiaonan Ma
- Tianjin Eye Hospital, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Eye Institute, Tianjin 300020, China
- Clinical College of Ophthalmology, Tianjin Medical University, Tianjin 300070, China
| | - Jiehui Zhao
- Institute of Modern Optics, Nankai University, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Tianjin 300350, China
| | - Pengfei Qi
- School of Physics, State Key Laboratory for Mesoscopic Physics, Academy for Advanced Interdisciplinary Studies, Collaborative Innovation Center of Quantum Matter, Nano-optoelectronics Frontier Center of Ministry of Education, Peking University, Beijing 100871, China
| | - Mengdi Li
- Tianjin Eye Hospital, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Eye Institute, Tianjin 300020, China
- Clinical College of Ophthalmology, Tianjin Medical University, Tianjin 300070, China
| | - Lie Lin
- Institute of Modern Optics, Nankai University, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Tianjin 300350, China
| | - Lu Sun
- Institute of Modern Optics, Nankai University, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Tianjin 300350, China
- Key Laboratory for Chemistry and Molecular Engineering of Medicinal Resources, Guangxi Normal University, Guangxi, China
| | - Xiaolei Wang
- Institute of Modern Optics, Nankai University, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Tianjin 300350, China
| | - Weiwei Liu
- Institute of Modern Optics, Nankai University, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Tianjin 300350, China
| | - Yan Wang
- Tianjin Eye Hospital, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Eye Institute, Tianjin 300020, China
- Clinical College of Ophthalmology, Tianjin Medical University, Tianjin 300070, China
| |
Collapse
|
14
|
Chen A, Osman OB, Harris ZB, Abazri A, Honkanen R, Arbab MH. Investigation of water diffusion dynamics in corneal phantoms using terahertz time-domain spectroscopy. BIOMEDICAL OPTICS EXPRESS 2020; 11:1284-1297. [PMID: 32206409 PMCID: PMC7075598 DOI: 10.1364/boe.382826] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 01/10/2020] [Accepted: 01/11/2020] [Indexed: 05/08/2023]
Abstract
Perturbation of normal corneal water content is a common manifestation of many eye diseases. Terahertz (THz) imaging has the potential to serve as a clinical tool for screening and diagnosing such corneal diseases. In this study, we first investigate the diffusive properties of a corneal phantom using simultaneous THz time-domain spectroscopy (THz-TDS) and gravimetric measurements. We will then utilize a variable-thickness diffusion model combined with a stratified composite-media model to simulate changes in thickness, hydration profile, and the THz-TDS signal as a function of time. The simulated THz-TDS signals show very good agreement with the reflection measurements. Results show that the THz-TDS technique can be used to understand water diffusion dynamics in corneal phantoms as a step towards future in vivo quantitative hydration sensing.
Collapse
Affiliation(s)
- Andrew Chen
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY 11794, USA
- Co-first authors with equal contribution
| | - Omar B. Osman
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY 11794, USA
- Co-first authors with equal contribution
| | - Zachery B. Harris
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY 11794, USA
| | - Azin Abazri
- Department of Ophthalmology, Stony Brook University, Stony Brook, NY 11794, USA
| | - Robert Honkanen
- Department of Ophthalmology, Stony Brook University, Stony Brook, NY 11794, USA
| | - M. Hassan Arbab
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY 11794, USA
| |
Collapse
|