1
|
Han X, Zhang Y, Shi G, Liu G, Ai S, Wang Y, Zhang Q, He X. Quantitative assessment of corneal elasticity distribution after FS-LASIK using optical coherence elastography. JOURNAL OF BIOPHOTONICS 2024; 17:e202300441. [PMID: 38221644 DOI: 10.1002/jbio.202300441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 12/12/2023] [Accepted: 01/04/2024] [Indexed: 01/16/2024]
Abstract
Quantifying corneal elasticity after femtosecond laser-assisted in situ keratomileusis (FS-LASIK) procedure plays an important role in improving surgical safety and quality, since some latent complications may occur ascribing to changes in postoperative corneal biomechanics. Nevertheless, it is suggested that current research has been severely constrained due to the lack of an accurate quantification method to obtain postoperative corneal elasticity distribution. In this paper, an acoustic radiation force optical coherence elastography system combined with the improved phase velocity algorithm was utilized to realize elasticity distribution images of the in vivo rabbit cornea after FS-LASIK under various intraocular pressure levels. As a result, elasticity variations within and between the regions of interest could be identified precisely. This is the first time that elasticity imaging of in vivo cornea after FS-LASIK surgery was demonstrated, and the results suggested that this technology may hold promise in further exploring corneal biomechanical properties after refractive surgery.
Collapse
Affiliation(s)
- Xiao Han
- School of Instrument Science and Opto-electronics Engineering, Beihang University, Beijing, P. R. China
- Key Laboratory of Opto-Electronic Information Science and Technology of Jiangxi Province and Jiangxi Engineering Laboratory for Optoelectronics Testing Technology, Nanchang Hangkong University, Nanchang, P. R. China
| | - Yubao Zhang
- Key Laboratory of Opto-Electronic Information Science and Technology of Jiangxi Province and Jiangxi Engineering Laboratory for Optoelectronics Testing Technology, Nanchang Hangkong University, Nanchang, P. R. China
| | - Gang Shi
- School of Mathematics and Physics, University of Science and Technology Beijing, Beijing, China
| | - Guo Liu
- Key Laboratory of Opto-Electronic Information Science and Technology of Jiangxi Province and Jiangxi Engineering Laboratory for Optoelectronics Testing Technology, Nanchang Hangkong University, Nanchang, P. R. China
| | - Sizhu Ai
- Key Laboratory of Opto-Electronic Information Science and Technology of Jiangxi Province and Jiangxi Engineering Laboratory for Optoelectronics Testing Technology, Nanchang Hangkong University, Nanchang, P. R. China
| | - Yidi Wang
- School of Instrument Science and Opto-electronics Engineering, Beihang University, Beijing, P. R. China
- Key Laboratory of Opto-Electronic Information Science and Technology of Jiangxi Province and Jiangxi Engineering Laboratory for Optoelectronics Testing Technology, Nanchang Hangkong University, Nanchang, P. R. China
| | - Qin Zhang
- Key Laboratory of Opto-Electronic Information Science and Technology of Jiangxi Province and Jiangxi Engineering Laboratory for Optoelectronics Testing Technology, Nanchang Hangkong University, Nanchang, P. R. China
| | - Xingdao He
- School of Instrument Science and Opto-electronics Engineering, Beihang University, Beijing, P. R. China
- Key Laboratory of Opto-Electronic Information Science and Technology of Jiangxi Province and Jiangxi Engineering Laboratory for Optoelectronics Testing Technology, Nanchang Hangkong University, Nanchang, P. R. China
| |
Collapse
|
2
|
Luo J, Zhang Y, Ai S, Shi G, Han X, Wang Y, Zhao Y, Yang H, Li Y, He X. Two-dimensional elastic distribution imaging of the sclera using acoustic radiation force optical coherence elastography. JOURNAL OF BIOPHOTONICS 2024; 17:e202300368. [PMID: 38010344 DOI: 10.1002/jbio.202300368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Revised: 10/23/2023] [Accepted: 11/15/2023] [Indexed: 11/29/2023]
Abstract
The scleral elasticity is closely related with many ocular diseases, but the relevant research is still insufficient. Here, we utilized optical coherence elastography to carefully study biomechanical properties of the sclera at different positions and under different intraocular pressures. Meanwhile, elastic wave velocity and Young's modulus of each position were obtained using a phase velocity algorithm. Accordingly, the two-dimensional elasticity distribution image was achieved by mapping the Young's modulus values to the corresponding structure based on the relationship between the position and its Young's modulus. Therefore, elastic information in regions-of-interest can be read and compared directly from the scleral structure, indicating that our method may be a very useful tool to evaluate the elasticity of sclera and provide intuitive and reliable proof for diagnosis and research.
Collapse
Affiliation(s)
- Jiahui Luo
- Key Laboratory of Opto-Electronic Information Science and Technology of Jiangxi Province and Jiangxi Engineering Laboratory for Optoelectronics Testing Technology, Nanchang Hangkong University, Nanchang, PR China
| | - Yubao Zhang
- Key Laboratory of Opto-Electronic Information Science and Technology of Jiangxi Province and Jiangxi Engineering Laboratory for Optoelectronics Testing Technology, Nanchang Hangkong University, Nanchang, PR China
| | - Sizhu Ai
- Key Laboratory of Opto-Electronic Information Science and Technology of Jiangxi Province and Jiangxi Engineering Laboratory for Optoelectronics Testing Technology, Nanchang Hangkong University, Nanchang, PR China
| | - Gang Shi
- Key Laboratory of Opto-Electronic Information Science and Technology of Jiangxi Province and Jiangxi Engineering Laboratory for Optoelectronics Testing Technology, Nanchang Hangkong University, Nanchang, PR China
| | - Xiao Han
- Key Laboratory of Opto-Electronic Information Science and Technology of Jiangxi Province and Jiangxi Engineering Laboratory for Optoelectronics Testing Technology, Nanchang Hangkong University, Nanchang, PR China
| | - Yidi Wang
- Key Laboratory of Opto-Electronic Information Science and Technology of Jiangxi Province and Jiangxi Engineering Laboratory for Optoelectronics Testing Technology, Nanchang Hangkong University, Nanchang, PR China
| | - Yanzhi Zhao
- Eye Center, Second Affiliated Hospital of Nanchang University, Nanchang, PR China
| | - Hongwei Yang
- Eye Center, Second Affiliated Hospital of Nanchang University, Nanchang, PR China
| | - Yingjie Li
- Department of Ophthalmology, Nanchang First Hospital, Nanchang, PR China
| | - Xingdao He
- Key Laboratory of Opto-Electronic Information Science and Technology of Jiangxi Province and Jiangxi Engineering Laboratory for Optoelectronics Testing Technology, Nanchang Hangkong University, Nanchang, PR China
| |
Collapse
|
3
|
Wang C, Zhu J, Ma J, Meng X, Ma Z, Fan F. Optical coherence elastography and its applications for the biomechanical characterization of tissues. JOURNAL OF BIOPHOTONICS 2023; 16:e202300292. [PMID: 37774137 DOI: 10.1002/jbio.202300292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 09/19/2023] [Accepted: 09/27/2023] [Indexed: 10/01/2023]
Abstract
The biomechanical characterization of the tissues provides significant evidence for determining the pathological status and assessing the disease treatment. Incorporating elastography with optical coherence tomography (OCT), optical coherence elastography (OCE) can map the spatial elasticity distribution of biological tissue with high resolution. After the excitation with the external or inherent force, the tissue response of the deformation or vibration is detected by OCT imaging. The elastogram is assessed by stress-strain analysis, vibration amplitude measurements, and quantification of elastic wave velocities. OCE has been used for elasticity measurements in ophthalmology, endoscopy, and oncology, improving the precision of diagnosis and treatment of disease. In this article, we review the OCE methods for biomechanical characterization and summarize current OCE applications in biomedicine. The limitations and future development of OCE are also discussed during its translation to the clinic.
Collapse
Affiliation(s)
- Chongyang Wang
- Key Laboratory of the Ministry of Education for Optoelectronic Measurement Technology and Instrument, Beijing Information Science and Technology University, Beijing, China
| | | | - Jiawei Ma
- Key Laboratory of the Ministry of Education for Optoelectronic Measurement Technology and Instrument, Beijing Information Science and Technology University, Beijing, China
| | - Xiaochen Meng
- Key Laboratory of the Ministry of Education for Optoelectronic Measurement Technology and Instrument, Beijing Information Science and Technology University, Beijing, China
| | - Zongqing Ma
- Key Laboratory of the Ministry of Education for Optoelectronic Measurement Technology and Instrument, Beijing Information Science and Technology University, Beijing, China
| | - Fan Fan
- Key Laboratory of the Ministry of Education for Optoelectronic Measurement Technology and Instrument, Beijing Information Science and Technology University, Beijing, China
| |
Collapse
|
4
|
Singh M, Zvietcovich F, Larin KV. Introduction to optical coherence elastography: tutorial. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2022; 39:418-430. [PMID: 35297425 PMCID: PMC10052825 DOI: 10.1364/josaa.444808] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 01/25/2022] [Indexed: 06/03/2023]
Abstract
Optical coherence elastography (OCE) has seen rapid growth since its introduction in 1998. The past few decades have seen tremendous advancements in the development of OCE technology and a wide range of applications, including the first clinical applications. This tutorial introduces the basics of solid mechanics, which form the foundation of all elastography methods. We then describe how OCE measurements of tissue motion can be used to quantify tissue biomechanical parameters. We also detail various types of excitation methods, imaging systems, acquisition schemes, and data processing algorithms and how various parameters associated with each step of OCE imaging can affect the final quantitation of biomechanical properties. Finally, we discuss the future of OCE, its potential, and the next steps required for OCE to become an established medical imaging technology.
Collapse
Affiliation(s)
- Manmohan Singh
- Biomedical Engineering, University of Houston, Houston, Texas 77204, USA
| | - Fernando Zvietcovich
- Biomedical Engineering, University of Houston, Houston, Texas 77204, USA
- Department of Engineering, Pontificia Universidad Catolica del Peru, San Miguel, Lima 15088, Peru
| | - Kirill V. Larin
- Biomedical Engineering, University of Houston, Houston, Texas 77204, USA
- Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030, USA
| |
Collapse
|
5
|
Zvietcovich F, Larin KV. Wave-based optical coherence elastography: The 10-year perspective. PROGRESS IN BIOMEDICAL ENGINEERING (BRISTOL, ENGLAND) 2022; 4:012007. [PMID: 35187403 PMCID: PMC8856668 DOI: 10.1088/2516-1091/ac4512] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
After 10 years of progress and innovation, optical coherence elastography (OCE) based on the propagation of mechanical waves has become one of the major and the most studied OCE branches, producing a fundamental impact in the quantitative and nondestructive biomechanical characterization of tissues. Preceding previous progress made in ultrasound and magnetic resonance elastography; wave-based OCE has pushed to the limit the advance of three major pillars: (1) implementation of novel wave excitation methods in tissues, (2) understanding new types of mechanical waves in complex boundary conditions by proposing advance analytical and numerical models, and (3) the development of novel estimators capable of retrieving quantitative 2D/3D biomechanical information of tissues. This remarkable progress promoted a major advance in answering basic science questions and the improvement of medical disease diagnosis and treatment monitoring in several types of tissues leading, ultimately, to the first attempts of clinical trials and translational research aiming to have wave-based OCE working in clinical environments. This paper summarizes the fundamental up-to-date principles and categories of wave-based OCE, revises the timeline and the state-of-the-art techniques and applications lying in those categories, and concludes with a discussion on the current challenges and future directions, including clinical translation research.
Collapse
Affiliation(s)
- Fernando Zvietcovich
- University of Houston, Biomedical Engineering, Houston, TX, United States, 77204
| | - Kirill V. Larin
- University of Houston, Biomedical Engineering, Houston, TX, United States, 77204,
| |
Collapse
|
6
|
Wang X, Wu Q, Chen J, Mo J. Development of a handheld compression optical coherence elastography probe with a disposable stress sensor. OPTICS LETTERS 2021; 46:3669-3672. [PMID: 34329252 DOI: 10.1364/ol.429955] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Accepted: 06/26/2021] [Indexed: 05/25/2023]
Abstract
Optical coherence elastography (OCE) is a functional extension of optical coherence tomography (OCT). OCE measures a sample's deformation under force stimuli. Compression is often used to generate the force stimuli in OCE. In this Letter, we report the development of a handheld quantitative compression OCE probe with a novel stress senor, dedicated to measuring the force. The stress sensor consists of a circular glass window and a metal ring which are connected with polyurethane spokes. This sensor is mounted on the tip of the OCT sample arm as an imaging window, so that the force applied to the sample through the window can be measured by detecting the window displacement from the OCT image. The force-displacement function was first developed through simulation on COMSOL Multiphysics and eventually calibrated experimentally. A phase-sensitive OCT technique was employed to measure both the window displacement and the sample deformation. The performance of an OCE probe with this stress sensor was evaluated on a two-layer phantom. The results show that it is extremely capable of measuring the sample Young's modulus. Finally, we successfully measured the elasticity of the human fingertip, indicating a good potential of this OCE probe for in vivo elastogram measurement on human skin.
Collapse
|
7
|
Yang F, Chen Z, Xing D. Single-Cell Photoacoustic Microrheology. IEEE TRANSACTIONS ON MEDICAL IMAGING 2020; 39:1791-1800. [PMID: 31825862 DOI: 10.1109/tmi.2019.2958112] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Rheological properties, such as elasticity and viscosity, are fundamental biomechanical parameters that are related to the function and pathological status of cells and tissues. In this paper, an innovative photoacoustic microrheology (PAMR), which utilized the time and phase characteristics of photoacoustic (PA) response, was proposed to extract elastic modulus and viscosity. The feasibility and accuracy of the method were validated by tissue-mimicking agar-gelatin phantoms with various viscoelasticity values. PAMR realized single cell elasticity and viscosity mappings on the adipocyte and myocyte with micrometer scale. In clinical samples, normal blood cells and iron deficiency anemia cells were successfully distinguished due to their various rheological properties. This method expands the scope of conventional PA imaging and opens new possibilities for developing microrheological technology, prefiguring great clinical potential for interrogating mechanocellular properties.
Collapse
|
8
|
Lan G, Larin KV, Aglyamov S, Twa MD. Characterization of natural frequencies from nanoscale tissue oscillations using dynamic optical coherence elastography. BIOMEDICAL OPTICS EXPRESS 2020; 11:3301-3318. [PMID: 32637256 PMCID: PMC7316029 DOI: 10.1364/boe.391324] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 05/01/2020] [Accepted: 05/12/2020] [Indexed: 05/09/2023]
Abstract
We demonstrate the use of OCT-based elastography for soft-tissue characterization using natural frequency oscillations. Sub-micrometer to sub-nanometer oscillations were induced in tissue phantoms and human cornea in vivo by perpendicular air-pulse stimulation and observed by common-path OCT imaging (sensitivity: 0.24 nm). Natural frequency and damping ratio were acquired in temporal and frequency domains using a single degree of freedom method. The dominant natural frequency was constant for different stimulation pressures (4-32 Pa) and measured distances (0.3-5.3 mm), and decreased as the sample thickness increased. The dominant natural frequencies of 0.75-2% agar phantoms were 127-774 Hz (mean coefficient of variation [CV]: 0.9%), and correlated with the square root of Young's moduli (16.5-117.8 kPa, mean CV: 5.8%). These preliminary studies show repeatable in vivo corneal natural frequency measurements (259 Hz, CV: 1.9%). This novel OCE approach can distinguish tissues and materials with different mechanical properties using the small-amplitude tissue oscillation features, and is suitable for characterizing delicate tissues in vivo such as the eye.
Collapse
Affiliation(s)
- Gongpu Lan
- Foshan University, School of Physics and Optoelectronic Engineering, Foshan, Guangdong, 528000, China
- University of Alabama at Birmingham, School of Optometry, Birmingham, AL 35290, USA
- University of Houston, College of Optometry, Houston, TX 77204, USA
| | - Kirill V. Larin
- University of Houston, Biomedical Engineering, Houston, TX 77204, USA
| | - Salavat Aglyamov
- University of Houston, Mechanical Engineering, Houston, TX 77204, USA
| | - Michael D. Twa
- University of Alabama at Birmingham, School of Optometry, Birmingham, AL 35290, USA
- University of Houston, College of Optometry, Houston, TX 77204, USA
| |
Collapse
|
9
|
Li Y, Moon S, Chen JJ, Zhu Z, Chen Z. Ultrahigh-sensitive optical coherence elastography. LIGHT, SCIENCE & APPLICATIONS 2020; 9:58. [PMID: 32337022 PMCID: PMC7154028 DOI: 10.1038/s41377-020-0297-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 03/16/2020] [Accepted: 03/19/2020] [Indexed: 05/07/2023]
Abstract
The phase stability of an optical coherence elastography (OCE) system is the key determining factor for achieving a precise elasticity measurement, and it can be affected by the signal-to-noise ratio (SNR), timing jitters in the signal acquisition process, and fluctuations in the optical path difference (OPD) between the sample and reference arms. In this study, we developed an OCE system based on swept-source optical coherence tomography (SS-OCT) with a common-path configuration (SS-OCECP). Our system has a phase stability of 4.2 mrad without external stabilization or extensive post-processing, such as averaging. This phase stability allows us to detect a displacement as small as ~300 pm. A common-path interferometer was incorporated by integrating a 3-mm wedged window into the SS-OCT system to provide intrinsic compensation for polarization and dispersion mismatch, as well as to minimize phase fluctuations caused by the OPD variation. The wedged window generates two reference signals that produce two OCT images, allowing for averaging to improve the SNR. Furthermore, the electrical components are optimized to minimize the timing jitters and prevent edge collisions by adjusting the delays between the trigger, k-clock, and signal, utilizing a high-speed waveform digitizer, and incorporating a high-bandwidth balanced photodetector. We validated the SS-OCECP performance in a tissue-mimicking phantom and an in vivo rabbit model, and the results demonstrated a significantly improved phase stability compared to that of the conventional SS-OCE. To the best of our knowledge, we demonstrated the first SS-OCECP system, which possesses high-phase stability and can be utilized to significantly improve the sensitivity of elastography.
Collapse
Affiliation(s)
- Yan Li
- Beckman Laser Institute, University of California, Irvine, Irvine, CA 92612 USA
- Department of Biomedical Engineering, University of California, Irvine, Irvine, CA 92617 USA
| | - Sucbei Moon
- Beckman Laser Institute, University of California, Irvine, Irvine, CA 92612 USA
- Department of Physics, Kookmin University, Seoul, 02707 South Korea
| | - Jason J. Chen
- Beckman Laser Institute, University of California, Irvine, Irvine, CA 92612 USA
- Department of Biomedical Engineering, University of California, Irvine, Irvine, CA 92617 USA
| | - Zhikai Zhu
- Beckman Laser Institute, University of California, Irvine, Irvine, CA 92612 USA
- Department of Biomedical Engineering, University of California, Irvine, Irvine, CA 92617 USA
| | - Zhongping Chen
- Beckman Laser Institute, University of California, Irvine, Irvine, CA 92612 USA
- Department of Biomedical Engineering, University of California, Irvine, Irvine, CA 92617 USA
| |
Collapse
|
10
|
Lan G, Gu B, Larin KV, Twa MD. Clinical Corneal Optical Coherence Elastography Measurement Precision: Effect of Heartbeat and Respiration. Transl Vis Sci Technol 2020; 9:3. [PMID: 32821475 PMCID: PMC7401940 DOI: 10.1167/tvst.9.5.3] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Accepted: 11/30/2019] [Indexed: 01/29/2023] Open
Abstract
Purpose Normal physiological movements (e.g., respiration and heartbeat) induce eye motions during clinical measurements of human corneal biomechanical properties using optical coherence elastography (OCE). We quantified the effects of respiratory and cardiac-induced eye motions on clinical corneal OCE measurement precision and repeatability. Methods Corneal OCE was performed using low-force, micro-air-pulse tissue stimulation and high-resolution phase-sensitive optical coherence tomography (OCT) imaging. Axial surface displacements of the corneal apex were measured (M-mode) at a 70-kHz sampling rate and three different stimulation pressures (20-60 Pa). Simultaneously, the axial corneal position was tracked with structural OCT imaging, while the heartrate and respiration were monitored over a 90 second period. Results Respiratory- and cardiac-induced eye motions have distinctly lower frequency (0.1-1 Hz) and much greater amplitude (up to ± 50 µm movements) than air-pulse-induced corneal tissue deformations (∼250 Hz, <1 µm). The corneal displacements induced during OCE measurements in vivo were -0.41 ± 0.06 µm (n = 22 measurements, coefficient of variation [CV]: 14.6%) and -0.44 ± 0.07 µm (n = 50 measurements, CV: 15.9%), respectively, from two human subjects at 40 Pa stimulation pressure. Observed variation in corneal tissue displacements were not associated with tissue stimulation magnitude, or the amplitude of physiologically induced axial eye motion. Conclusions The microsecond timescale and submicron tissue displacements observed during corneal OCE measurements are separable from normal involuntary physiological movements, such as the oculocardiac pulse and respiratory movements. Translational Relevance This work advances innovations in biomedical imaging and engineering for clinical diagnostic applications for soft-tissue biomechanical testing.
Collapse
Affiliation(s)
- Gongpu Lan
- Department of Photoelectric Technology, Foshan University, Foshan, Guangdong, China.,School of Optometry, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Boyu Gu
- Department of Ophthalmology, Doheny Eye Institute, University of California -Los Angeles, Los Angeles, CA, USA
| | - Kirill V Larin
- Department of Biomedical Engineering, University of Houston, Houston, TX, USA
| | - Michael D Twa
- School of Optometry, University of Alabama at Birmingham, Birmingham, AL, USA.,College of Optometry, University of Houston, Houston, TX, USA
| |
Collapse
|
11
|
Zhao L, Vanderlaan D, Yoon H, Liu J, Li C, Emelianov SY. Ultrafast ultrasound imaging of surface acoustic waves induced by laser excitation compared with acoustic radiation force. OPTICS LETTERS 2020; 45:1810-1813. [PMID: 32236005 PMCID: PMC8957894 DOI: 10.1364/ol.383932] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Accepted: 01/25/2020] [Indexed: 06/11/2023]
Abstract
Two generation mechanisms-optical perturbation and acoustic radiation force (ARF)-were investigated where high frame rate ultrasound imaging was used to track the propagation of induced SAWs. We compared ARF-induced SAWs with laser-induced SAWs generated by laser beam irradiation of the uniformly absorbing tissue-like viscoelastic phantom, where light was preferentially absorbed at the surface. We also compared the frequency content of SAWs generated by ARF versus pulsed laser light, using the same duration of excitation. Differences in the SAW bandwidth were expected because, in general, laser light can be focused into a smaller area. Finally, we compared wave generation and propagation when the wave's origin was below the surface. We also investigated the relationship between shear wave amplitude and optical fluence. The investigation reported here can potentially extend the applications of laser-induced SAW generation and imaging in life sciences and other applications.
Collapse
Affiliation(s)
- Lingyi Zhao
- Walter H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University School of Medicine, Atlanta, Georgia 30332, USA
- Department of Biomedical Engineering, College of Engineering, Peking University, Beijing, 100871, China
| | - Don Vanderlaan
- School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - Heechul Yoon
- School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - Jingfei Liu
- School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - Changhui Li
- Department of Biomedical Engineering, College of Engineering, Peking University, Beijing, 100871, China
| | - Stanislav Y. Emelianov
- Walter H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University School of Medicine, Atlanta, Georgia 30332, USA
- School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
- Corresponding author:
| |
Collapse
|
12
|
Jin Z, Zhou Y, Shen M, Wang Y, Lu F, Zhu D. Assessment of corneal viscoelasticity using elastic wave optical coherence elastography. JOURNAL OF BIOPHOTONICS 2020; 13:e201960074. [PMID: 31626371 DOI: 10.1002/jbio.201960074] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Revised: 09/21/2019] [Accepted: 10/16/2019] [Indexed: 06/10/2023]
Abstract
The corneal viscoelasticity have great clinical significance, such as the early diagnosis of keratoconus. In this work, an analysis method which utilized the elastic wave velocity, frequency and energy attenuation to assess the corneal viscoelasticity is presented. Using phase-resolved optical coherence tomography, the spatial-temporal displacement map is derived. The phase velocity dispersion curve and center frequency are obtained by transforming the displacement map into the wavenumber-frequency domain through the 2D fast Fourier transform (FFT). The shear modulus is calculated through Rayleigh wave equation using the phase velocity in the high frequency. The normalized energy distribution is plotted by transforming the displacement map into the spatial-frequency domain through the 1D FFT. The energy attenuation coefficient is derived by exponential fitting to calculate the viscous modulus. Different concentrations of tissue-mimicking phantoms and porcine corneas are imaged to validate this method, which demonstrates that the method has the capability to assess the corneal viscoelasticity.
Collapse
Affiliation(s)
- Zi Jin
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, China
| | - Yuheng Zhou
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, China
| | - Meixiao Shen
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, China
| | - Yuanyuan Wang
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, China
| | - Fan Lu
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, China
| | - Dexi Zhu
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, China
| |
Collapse
|
13
|
Jin Z, Khazaeinezhad R, Zhu J, Yu J, Qu Y, He Y, Li Y, Gomez Alvarez-Arenas TE, Lu F, Chen Z. In-vivo 3D corneal elasticity using air-coupled ultrasound optical coherence elastography. BIOMEDICAL OPTICS EXPRESS 2019; 10:6272-6285. [PMID: 31853399 PMCID: PMC6913398 DOI: 10.1364/boe.10.006272] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 10/03/2019] [Accepted: 10/10/2019] [Indexed: 05/03/2023]
Abstract
Corneal elasticity can resist elastic deformations under intraocular pressure to maintain normal corneal shape, which has a great influence on corneal refractive function. Elastography can measure tissue elasticity and provide a powerful tool for clinical diagnosis. Air-coupled ultrasound optical coherence elastography (OCE) has been used in the quantification of ex-vivo corneal elasticity. However, in-vivo imaging of the cornea remains a challenge. The 3D air-coupled ultrasound OCE with an axial motion artifacts correction algorithm was developed to distinguish the in-vivo cornea vibration from the axial eye motion in anesthetized rabbits and visualize the elastic wave propagation clearly. The elastic wave group velocity of in-vivo rabbit cornea was measured to be 5.96 ± 0.55 m/s, which agrees with other studies. The results show the potential of 3D air-coupled ultrasound OCE with an axial motion artifacts correction algorithm for quantitative in-vivo assessment of corneal elasticity.
Collapse
Affiliation(s)
- Zi Jin
- Beckman Laser Institute, Department of Biomedical Engineering, University of California, Irvine, Irvine, California 92612, USA
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou 325003, Zhejiang, China
- These authors contributed equally to this work
| | - Reza Khazaeinezhad
- Beckman Laser Institute, Department of Biomedical Engineering, University of California, Irvine, Irvine, California 92612, USA
- These authors contributed equally to this work
| | - Jiang Zhu
- Beckman Laser Institute, Department of Biomedical Engineering, University of California, Irvine, Irvine, California 92612, USA
| | - Junxiao Yu
- Beckman Laser Institute, Department of Biomedical Engineering, University of California, Irvine, Irvine, California 92612, USA
| | - Yueqiao Qu
- Beckman Laser Institute, Department of Biomedical Engineering, University of California, Irvine, Irvine, California 92612, USA
| | - Youmin He
- Beckman Laser Institute, Department of Biomedical Engineering, University of California, Irvine, Irvine, California 92612, USA
| | - Yan Li
- Beckman Laser Institute, Department of Biomedical Engineering, University of California, Irvine, Irvine, California 92612, USA
| | - Tomas E Gomez Alvarez-Arenas
- Institute of Physical and Information Technologies, Spanish National Research Council (CSIC), 28006 Madrid, Spain
| | - Fan Lu
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou 325003, Zhejiang, China
| | - Zhongping Chen
- Beckman Laser Institute, Department of Biomedical Engineering, University of California, Irvine, Irvine, California 92612, USA
| |
Collapse
|
14
|
Li Y, Chen J, Chen Z. Advances in Doppler optical coherence tomography and angiography. TRANSLATIONAL BIOPHOTONICS 2019; 1:e201900005. [PMID: 33005888 PMCID: PMC7523705 DOI: 10.1002/tbio.201900005] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Accepted: 11/14/2019] [Indexed: 12/22/2022] Open
Abstract
Since the first demonstration of Doppler optical coherence tomography (OCT) in 1997, several functional extensions of Doppler OCT have been developed, including velocimetry, angiogram, and optical coherence elastography. These functional techniques have been widely used in research and clinical applications, particularly in ophthalmology. Here, we review the principles, representative methods, and applications of different Doppler OCT techniques, followed by discussion on the innovations, limitations, and future directions of each of these techniques.
Collapse
Affiliation(s)
- Yan Li
- Beckman Laser Institute, University of California, Irvine, California
- Department of Biomedical Engineering, University of California, Irvine, California
| | - Jason Chen
- Beckman Laser Institute, University of California, Irvine, California
- Department of Biomedical Engineering, University of California, Irvine, California
| | - Zhongping Chen
- Beckman Laser Institute, University of California, Irvine, California
- Department of Biomedical Engineering, University of California, Irvine, California
| |
Collapse
|
15
|
Li Y, Zhu J, Chen JJ, Yu J, Jin Z, Miao Y, Browne AW, Zhou Q, Chen Z. Simultaneously imaging and quantifying in vivo mechanical properties of crystalline lens and cornea using optical coherence elastography with acoustic radiation force excitation. APL PHOTONICS 2019; 4:106104. [PMID: 32309636 PMCID: PMC7164808 DOI: 10.1063/1.5118258] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The crystalline lens and cornea comprise the eye's optical system for focusing light in human vision. The changes in biomechanical properties of the lens and cornea are closely associated with common diseases, including presbyopia and cataract. Currently, most in vivo elasticity studies of the anterior eye focus on the measurement of the cornea, while lens measurement remains challenging. To better understand the anterior segment of the eye, we developed an optical coherence elastography system utilizing acoustic radiation force excitation to simultaneously assess the elasticities of the crystalline lens and the cornea in vivo. A swept light source was integrated into the system to provide an enhanced imaging range that covers both the lens and the cornea. Additionally, the oblique imaging approach combined with orthogonal excitation also improved the image quality. The system was tested through first ex vivo and then in vivo experiments using a rabbit model. The elasticities of corneal and lens tissue in an excised normal whole-globe and a cold cataract model were measured to reveal that cataractous lenses have a higher Young's modulus. Simultaneous in vivo elasticity measurements of the lens and cornea were performed in a rabbit model to demonstrate the correlations between elasticity and intraocular pressure and between elasticity and age. To the best of our knowledge, we demonstrated the first in vivo elasticity of imaging of both the lens and cornea using acoustic radiation force-optical coherence elastography, thereby providing a potential powerful clinical tool to advance ophthalmic research in disorders affecting the lens and the cornea.
Collapse
Affiliation(s)
- Yan Li
- Beckman Laser Institute, University of California, Irvine, Irvine, California 92612, USA
- Department of Biomedical Engineering, University of California, Irvine, Irvine, California 92617, USA
| | - Jiang Zhu
- Beckman Laser Institute, University of California, Irvine, Irvine, California 92612, USA
| | - Jason J. Chen
- Beckman Laser Institute, University of California, Irvine, Irvine, California 92612, USA
- Department of Biomedical Engineering, University of California, Irvine, Irvine, California 92617, USA
| | - Junxiao Yu
- Beckman Laser Institute, University of California, Irvine, Irvine, California 92612, USA
- Department of Biomedical Engineering, University of California, Irvine, Irvine, California 92617, USA
| | - Zi Jin
- Beckman Laser Institute, University of California, Irvine, Irvine, California 92612, USA
| | - Yusi Miao
- Beckman Laser Institute, University of California, Irvine, Irvine, California 92612, USA
- Department of Biomedical Engineering, University of California, Irvine, Irvine, California 92617, USA
| | - Andrew W. Browne
- Department of Biomedical Engineering, University of California, Irvine, Irvine, California 92617, USA
- Department of Ophthalmology, School of Medicine, University of California, Irvine, Irvine, California 92617, USA
- Gavin Herbert Eye Institute, University of California, Irvine, Irvine, California 92697, USA
| | - Qifa Zhou
- Department of Ophthalmology and Biomedical Engineering, University of Southern California, Los Angeles, California 90089, USA
- Roski Eye Institute, University of Southern California, Los Angeles, California 90007, USA
| | - Zhongping Chen
- Beckman Laser Institute, University of California, Irvine, Irvine, California 92612, USA
- Department of Biomedical Engineering, University of California, Irvine, Irvine, California 92617, USA
| |
Collapse
|
16
|
Du Z, Li R, Qian X, Lu G, Li Y, He Y, Qu Y, Jiang L, Chen Z, Humayun MS, Chen Z, Zhou Q. Quantitative confocal optical coherence elastography for evaluating biomechanics of optic nerve head using Lamb wave model. NEUROPHOTONICS 2019; 6:041112. [PMID: 31763352 PMCID: PMC6857697 DOI: 10.1117/1.nph.6.4.041112] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Accepted: 10/30/2019] [Indexed: 05/26/2023]
Abstract
The mechanosensitivity of the optic nerve head (ONH) plays a pivotal role in the pathogenesis of glaucoma. Characterizing elasticity of the ONH over changing physiological pressure may provide a better understanding of how changes in intraocular pressure (IOP) lead to changes in the mechanical environment of the ONH. Optical coherence elastography (OCE) is an emerging technique that can detect tissue biomechanics noninvasively with both high temporal and spatial resolution compared with conventional ultrasonic elastography. We describe a confocal OCE system in measuring ONH elasticity in vitro, utilizing a pressure inflation setup in which IOP is controlled precisely. We further utilize the Lamb wave model to fit the phase dispersion curve during data postprocessing. We present a reconstruction of Young's modulus of the ONH by combining our OCE system with a Lamb wave model for the first time. This approach enables the quantification of Young's modulus of the ONH, which can be fit using a piecewise polynomial to the corresponding IOP.
Collapse
Affiliation(s)
- Zhaodong Du
- The Affiliated Hospital of Qingdao University, Department of Ophthalmology, Qingdao, China
- University of Southern California, Roski Eye Institute, Los Angeles, California, United States
| | - Runze Li
- University of Southern California, Roski Eye Institute, Los Angeles, California, United States
- University of Southern California, Department of Biomedical Engineering, Los Angeles, California, United States
| | - Xuejun Qian
- University of Southern California, Roski Eye Institute, Los Angeles, California, United States
- University of Southern California, Department of Biomedical Engineering, Los Angeles, California, United States
| | - Gengxi Lu
- University of Southern California, Roski Eye Institute, Los Angeles, California, United States
- University of Southern California, Department of Biomedical Engineering, Los Angeles, California, United States
| | - Yan Li
- University of California Irvine, Beckman Laser Institute, Irvine, California, United States
- University of California Irvine, Department of Biomedical Engineering, Irvine, California, United States
| | - Youmin He
- University of California Irvine, Beckman Laser Institute, Irvine, California, United States
- University of California Irvine, Department of Biomedical Engineering, Irvine, California, United States
| | - Yueqiao Qu
- University of California Irvine, Beckman Laser Institute, Irvine, California, United States
- University of California Irvine, Department of Biomedical Engineering, Irvine, California, United States
| | - Laiming Jiang
- University of Southern California, Roski Eye Institute, Los Angeles, California, United States
| | - Zeyu Chen
- University of Southern California, Department of Biomedical Engineering, Los Angeles, California, United States
| | - Mark S. Humayun
- University of Southern California, Roski Eye Institute, Los Angeles, California, United States
| | - Zhongping Chen
- University of California Irvine, Beckman Laser Institute, Irvine, California, United States
- University of California Irvine, Department of Biomedical Engineering, Irvine, California, United States
| | - Qifa Zhou
- University of Southern California, Roski Eye Institute, Los Angeles, California, United States
- University of Southern California, Department of Biomedical Engineering, Los Angeles, California, United States
| |
Collapse
|
17
|
Kirby MA, Zhou K, Pitre JJ, Gao L, Li D, Pelivanov I, Song S, Li C, Huang Z, Shen T, Wang R, O’Donnell M. Spatial resolution in dynamic optical coherence elastography. JOURNAL OF BIOMEDICAL OPTICS 2019; 24:1-16. [PMID: 31535538 PMCID: PMC6749618 DOI: 10.1117/1.jbo.24.9.096006] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2019] [Accepted: 08/26/2019] [Indexed: 05/03/2023]
Abstract
Dynamic optical coherence elastography (OCE) tracks elastic wave propagation speed within tissue, enabling quantitative three-dimensional imaging of the elastic modulus. We show that propagating mechanical waves are mode converted at interfaces, creating a finite region on the order of an acoustic wavelength where there is not a simple one-to-one correspondence between wave speed and elastic modulus. Depending on the details of a boundary’s geometry and elasticity contrast, highly complex propagating fields produced near the boundary can substantially affect both the spatial resolution and contrast of the elasticity image. We demonstrate boundary effects on Rayleigh waves incident on a vertical boundary between media of different shear moduli. Lateral resolution is defined by the width of the transition zone between two media and is the limit at which a physical inclusion can be detected with full contrast. We experimentally demonstrate results using a spectral-domain OCT system on tissue-mimicking phantoms, which are replicated using numerical simulations. It is shown that the spatial resolution in dynamic OCE is determined by the temporal and spatial characteristics (i.e., bandwidth and spatial pulse width) of the propagating mechanical wave. Thus, mechanical resolution in dynamic OCE inherently differs from the optical resolution of the OCT imaging system.
Collapse
Affiliation(s)
- Mitchell A. Kirby
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| | - Kanheng Zhou
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
- University of Dundee, School of Science and Engineering, Dundee, United Kingdom
| | - John J. Pitre
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| | - Liang Gao
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| | - David Li
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
- University of Washington, Department of Chemical Engineering, Seattle, Washington, United States
| | - Ivan Pelivanov
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
- Address all correspondence to Ivan Pelivanov, E-mail:
| | - Shaozhen Song
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| | - Chunhui Li
- University of Dundee, School of Science and Engineering, Dundee, United Kingdom
| | - Zhihong Huang
- University of Dundee, School of Science and Engineering, Dundee, United Kingdom
| | - Tueng Shen
- University of Washington, Department of Ophthalmology, Seattle, Washington, United States
| | - Ruikang Wang
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
- University of Washington, Department of Ophthalmology, Seattle, Washington, United States
| | - Matthew O’Donnell
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| |
Collapse
|
18
|
Liou HC, Sabba F, Packman AI, Wells G, Balogun O. Nondestructive characterization of soft materials and biofilms by measurement of guided elastic wave propagation using optical coherence elastography. SOFT MATTER 2019; 15:575-586. [PMID: 30601536 DOI: 10.1039/c8sm01902a] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Biofilms are soft multicomponent biological materials composed of microbial communities attached to surfaces. Despite the crucial relevance of biofilms to diverse industrial, medical, and environmental applications, the mechanical properties of biofilms are understudied. Moreover, most of the available techniques for the characterization of biofilm mechanical properties are destructive. Here, we detail a model-based approach developed to characterize the viscoelastic properties of soft materials and bacterial biofilms based on experimental data obtained using the nondestructive dynamic optical coherence elastography (OCE) technique. The model predicted the frequency- and geometry-dependent propagation velocities of elastic waves in a soft viscoelastic plate supported by a rigid substratum. Our numerical calculations suggest that the dispersion curves of guided waves recorded in thin soft plates by the dynamic OCE technique are dominated by guided waves, whose phase velocities depend on the viscoelastic properties and plate thickness. The numerical model was validated against experimental measurements in agarose phantom samples with different thicknesses and concentrations. The model was then used to interpret guided wave dispersion curves obtained by the OCE technique in bacterial biofilms developed in a rotating annular reactor, which allowed the quantitative characterization of biofilm shear modulus and viscosity. This study is the first to employ measurements of elastic wave propagation to characterize biofilms, and it provides a novel framework combining a theoretical model and an experimental approach for studying the relationship between the biofilm internal physical structure and mechanical properties.
Collapse
Affiliation(s)
- Hong-Cin Liou
- Mechanical Engineering Department, Northwestern University, Evanston, IL 60208, USA
| | - Fabrizio Sabba
- Civil and Environmental Engineering Department, Northwestern University, Evanston, IL 60208, USA.
| | - Aaron I Packman
- Civil and Environmental Engineering Department, Northwestern University, Evanston, IL 60208, USA.
| | - George Wells
- Civil and Environmental Engineering Department, Northwestern University, Evanston, IL 60208, USA.
| | - Oluwaseyi Balogun
- Mechanical Engineering Department, Northwestern University, Evanston, IL 60208, USA and Civil and Environmental Engineering Department, Northwestern University, Evanston, IL 60208, USA.
| |
Collapse
|
19
|
Xu X, Zhu J, Yu J, Chen Z. Viscosity monitoring during hemodiluted blood coagulation using optical coherence elastography. IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS : A PUBLICATION OF THE IEEE LASERS AND ELECTRO-OPTICS SOCIETY 2019; 25:7200406. [PMID: 31857783 PMCID: PMC6922089 DOI: 10.1109/jstqe.2018.2833455] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Rapid and accurate clot diagnostic systems are needed for the assessment of hemodiluted blood coagulation. We develop a real-time optical coherence elastography (OCE) system, which measures the attenuation coefficient of a compressional wave induced by a piezoelectric transducer (PZT) in a drop of blood using optical coherence tomography (OCT), for the determination of viscous properties during the dynamic whole blood coagulation process. Changes in the viscous properties increase the attenuation coefficient of the sample. Consequently, dynamic blood coagulation status can be monitored by relating changes of the attenuation coefficient to clinically relevant coagulation metrics, including the initial coagulation time and the clot formation rate. This system was used to characterize the influence of activator kaolin and the influence of hemodilution with either NaCl 0.9% or hydroxyethyl starch (HES) 6% on blood coagulation. The results show that PZT-OCE is sensitive to coagulation abnormalities and is able to characterize blood coagulation status based on viscosity-related attenuation coefficient measurements. PZT-OCE can be used for point-of-care testing for diagnosis of coagulation disorders and monitoring of therapies.
Collapse
Affiliation(s)
- Xiangqun Xu
- College of Life Sciences, Zhejiang Sci-Tech University, Hangzhou, Zhejiang 310018, China, and the Beckman Laser Institute, University of California, Irvine, Irvine, California 92612, USA
| | - Jiang Zhu
- Beckman Laser Institute, University of California, Irvine, Irvine, California 92612, USA
| | - Junxiao Yu
- Department of Biomedical Engineering, and the Beckman Laser Institute, University of California, Irvine, Irvine, California 92612, USA
| | - Zhongping Chen
- Department of Biomedical Engineering, and the Beckman Laser Institute, University of California, Irvine, Irvine, California 92612, USA
| |
Collapse
|
20
|
He Y, Qu Y, Zhu J, Zhang Y, Saidi A, Ma T, Zhou Q, Chen Z. Confocal Shear Wave Acoustic Radiation Force Optical Coherence Elastography for Imaging and Quantification of the In Vivo Posterior Eye. IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS : A PUBLICATION OF THE IEEE LASERS AND ELECTRO-OPTICS SOCIETY 2019; 25:10.1109/jstqe.2018.2834435. [PMID: 32042240 PMCID: PMC7008613 DOI: 10.1109/jstqe.2018.2834435] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Retinal diseases, such as age-related macular degeneration (AMD), are the leading cause of blindness in the elderly population. Since no known cures are currently present, it is crucial to diagnose the condition in its early stages so that disease progression is monitored. Recent advances show that the mechanical elasticity of the posterior eye changes with the onset of AMD. In this work, we present a quantitative method of mapping the mechanical elasticity of the posterior eye using confocal shear wave acoustic radiation force optical coherence elastography (SW-ARF-OCE). This technique has been developed and validated with both an ex-vivo porcine tissue model and a customized in-vivo rabbit model, which both showed the quantified elasticity variations between different layers. This study verifies the feasibility of using this technology for the quantification and diagnosis of retinal diseases from the in-vivo posterior eye.
Collapse
Affiliation(s)
- Youmin He
- Department of Biomedical Engineering and the Beckman Laser Institute, University of California, Irvine, CA 92697 USA
| | - Yueqiao Qu
- Department of Biomedical Engineering and the Beckman Laser Institute, University of California, Irvine, CA 92697 USA
| | - Jiang Zhu
- Department of Biomedical Engineering and the Beckman Laser Institute, University of California, Irvine, CA 92697 USA
| | - Yi Zhang
- Roski Eye Institute, Department of Ophthalmology and Biomedical Engineering, University of Southern California, Los Angeles, CA 90089 USA
| | - Arya Saidi
- Marshall B. Ketchum University. Southern California College of Optometry, 2575 Yorba Linda Blvd, Fullerton, CA 92831 USA
| | - Teng Ma
- Roski Eye Institute, Department of Ophthalmology and Biomedical Engineering, University of Southern California, Los Angeles, CA 90089 USA
| | - Qifa Zhou
- Roski Eye Institute, Department of Ophthalmology and Biomedical Engineering, University of Southern California, Los Angeles, CA 90089 USA
| | - Zhongping Chen
- Department of Biomedical Engineering and the Beckman Laser Institute, University of California, Irvine, CA 92697 USA
| |
Collapse
|
21
|
Zhu J, He X, Chen Z. Acoustic radiation force optical coherence elastography for elasticity assessment of soft tissues. APPLIED SPECTROSCOPY REVIEWS 2019; 54:457-481. [PMID: 31749516 PMCID: PMC6867804 DOI: 10.1080/05704928.2018.1467436] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Biomechanical properties of soft tissues are important indicators of tissue functions which can be used for clinical diagnosis and disease monitoring. Elastography, incorporating the principles of elasticity measurements into imaging modalities, provides quantitative assessment of elastic properties of biological tissues. Benefiting from high-resolution, noninvasive and three-dimensional optical coherence tomography (OCT), optical coherence elastography (OCE) is an emerging optical imaging modality to characterize and map biomechanical properties of soft tissues. Recently, acoustic radiation force (ARF) OCE has been developed for elasticity measurements of ocular tissues, detection of vascular lesions and monitoring of blood coagulation based on remote and noninvasive ARF excitation to both internal and superficial tissues. Here, we describe the advantages of the ARF-OCE technique, the measurement methods in ARF-OCE, the applications in biomedical detection, current challenges and advances. ARF-OCE technology has the potential to become a powerful tool for in vivo elasticity assessment of biological samples in a non-contact, non-invasive and high-resolution nature.
Collapse
Affiliation(s)
- Jiang Zhu
- Beckman Laser Institute, University of California, Irvine, Irvine, California 92612, USA
| | - Xingdao He
- Key Laboratory of Nondestructive Test (Ministry of Education), Nanchang Hangkong University, Nanchang 330063, China
| | - Zhongping Chen
- Beckman Laser Institute, University of California, Irvine, Irvine, California 92612, USA
- Key Laboratory of Nondestructive Test (Ministry of Education), Nanchang Hangkong University, Nanchang 330063, China
- Department of Biomedical Engineering, University of California, Irvine, Irvine, California 92697, USA
| |
Collapse
|
22
|
Wu C, Aglyamov SR, Han Z, Singh M, Liu CH, Larin KV. Assessing the biomechanical properties of the porcine crystalline lens as a function of intraocular pressure with optical coherence elastography. BIOMEDICAL OPTICS EXPRESS 2018; 9:6455-6466. [PMID: 31065442 PMCID: PMC6491010 DOI: 10.1364/boe.9.006455] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Revised: 11/11/2018] [Accepted: 11/14/2018] [Indexed: 05/04/2023]
Abstract
In this study, we investigated the relationship between the biomechanical properties of the crystalline lens and intraocular pressure (IOP) using a confocal acoustic radiation force (ARF) and phase-sensitive optical coherence elastography (OCE) system. ARF induced a small displacement at the apex of porcine lenses in situ at various artificially controlled IOPs. Maximum displacement, relaxation rate, and Young's modulus were utilized to assess the stiffness of the crystalline lens. The results showed that the stiffness of the crystalline increased as IOP increased, but the lens stiffening was not as significant as the stiffening of other ocular tissues such as the cornea and the sclera. A mechanical hysteresis in the lens was also observed while cycling IOP, indicating that the viscoelastic response of the lens is crucial to fully understanding its biomechanical properties.
Collapse
Affiliation(s)
- Chen Wu
- Department of Biomedical Engineering, University of Houston, Houston, TX 77204, USA
| | - Salavat R Aglyamov
- Department of Mechanical Engineering, University of Houston, Houston, TX 77204, USA
- Department of Biomedical Engineering, University of Texas, Austin, TX 78712, USA
| | - Zhaolong Han
- Department of Biomedical Engineering, University of Houston, Houston, TX 77204, USA
- School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Manmohan Singh
- Department of Biomedical Engineering, University of Houston, Houston, TX 77204, USA
| | - Chih-Hao Liu
- Department of Biomedical Engineering, University of Houston, Houston, TX 77204, USA
| | - Kirill V Larin
- Department of Biomedical Engineering, University of Houston, Houston, TX 77204, USA
- Interdisciplinary Laboratory of Biophotonics, Tomsk State University, Tomsk, Russia
- Molecular Physiology and Biophysics, Baylor College of Medicine, TX 77584, USA
| |
Collapse
|
23
|
Moon S, Chen Z. Phase-stability optimization of swept-source optical coherence tomography. BIOMEDICAL OPTICS EXPRESS 2018; 9:5280-5295. [PMID: 30460128 PMCID: PMC6238911 DOI: 10.1364/boe.9.005280] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 09/21/2018] [Accepted: 09/25/2018] [Indexed: 05/18/2023]
Abstract
Phase-resolved imaging of swept-source optical coherence tomography (SS-OCT) is subject to phase measurement instabilities involved with the sweep variation of a frequency-swept source. In general, optically generated timing references are utilized to track the variations imposed on OCT signals. But they might not be accurately synchronized due to relative time delays. In this research, we investigated the impact of the signal delays on the timing instabilities and the consequent deviations of the measured phases. We considered two types of timing signals utilized in a popular digitizer operation mode: a sweep trigger from a fiber Bragg grating (FBG) that initiates a series of signal sampling actions clocked by an auxiliary Mach-Zehnder interferometer (MZI) signal. We found that significant instabilities were brought by the relative delays through incoherent timing corrections and timing collisions between the timing references. The best-to-worst ratio of the measured phase errors was higher than 200 while only the signal delays varied. Noise-limited phase stability was achieved with a wide dynamic range of OCT signals above 50 dB in optimized delays. This demonstrated that delay optimization is very effective in phase stabilization of SS-OCT.
Collapse
Affiliation(s)
- Sucbei Moon
- Beckman Laser Institute, University of California, Irvine, Irvine, CA 92617, USA
- Department of Physics, Kookmin University, Seoul 02707, South Korea
| | - Zhongping Chen
- Beckman Laser Institute, University of California, Irvine, Irvine, CA 92617, USA
- Department of Biomedical Engineering, University of California, Irvine, Irvine, CA 92697, USA
| |
Collapse
|
24
|
Qu Y, He Y, Zhang Y, Ma T, Zhu J, Miao Y, Dai C, Humayun M, Zhou Q, Chen Z. Quantified elasticity mapping of retinal layers using synchronized acoustic radiation force optical coherence elastography. BIOMEDICAL OPTICS EXPRESS 2018; 9:4054-4063. [PMID: 30615733 PMCID: PMC6157789 DOI: 10.1364/boe.9.004054] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Revised: 06/25/2018] [Accepted: 07/04/2018] [Indexed: 05/20/2023]
Abstract
Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly (over the age of 60 years) in western countries. In the early stages of the disease, structural changes may be subtle and cannot be detected. Recently it has been postulated that the mechanical properties of the retina may change with the onset of AMD. In this manuscript, we present a novel, non-invasive means that utilizes synchronized acoustic radiation force optical coherence elastography (ARF-OCE) to measure and estimate the elasticity of cadaver porcine retina. Both regions near the optic nerve and in the peripheral retina were studied. An acoustic force is exerted on the tissue for excitation and the resulting tissue vibrations, often in the nanometer scale, are detected with high-resolution optical methods. Segmentation has been performed to isolate individual layers and the Young's modulus has been estimated for each. The results have been successfully compared and mapped to corresponding histological results using H&E staining. Finally, 64 elastograms of the retina were analyzed, as well as the elastic properties, with stiffness ranging from 1.3 to 25.9 kPa in the ganglion to the photoreceptor sides respectively. ARF-OCE allows for the elasticity mapping of anatomical retinal layers. This imaging approach needs further evaluation but has the potential to allow physicians to gain a better understanding of the elasticity of retinal layers in retinal diseases such as AMD.
Collapse
Affiliation(s)
- Yueqiao Qu
- Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Road East, Irvine, CA 92612, USA
- First two authors contributed equally to this work
| | - Youmin He
- Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Road East, Irvine, CA 92612, USA
- First two authors contributed equally to this work
| | - Yi Zhang
- USC Roski Eye Institute & Institute for Biomedical Therapeutics, University of Southern California, Los Angeles, CA 90033, USA
| | - Teng Ma
- NIH Ultrasonic Transducer Resource Center, Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA
| | - Jiang Zhu
- Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Road East, Irvine, CA 92612, USA
| | - Yusi Miao
- Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Road East, Irvine, CA 92612, USA
| | - Cuixia Dai
- Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Road East, Irvine, CA 92612, USA
| | - Mark Humayun
- USC Roski Eye Institute & Institute for Biomedical Therapeutics, University of Southern California, Los Angeles, CA 90033, USA
| | - Qifa Zhou
- USC Roski Eye Institute & Institute for Biomedical Therapeutics, University of Southern California, Los Angeles, CA 90033, USA
- NIH Ultrasonic Transducer Resource Center, Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA
| | - Zhongping Chen
- Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Road East, Irvine, CA 92612, USA
| |
Collapse
|
25
|
Qu Y, He Y, Saidi A, Xin Y, Zhou Y, Zhu J, Ma T, Silverman RH, Minckler DS, Zhou Q, Chen Z. In Vivo Elasticity Mapping of Posterior Ocular Layers Using Acoustic Radiation Force Optical Coherence Elastography. Invest Ophthalmol Vis Sci 2018; 59:455-461. [PMID: 29368002 PMCID: PMC5783626 DOI: 10.1167/iovs.17-22971] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose We used acoustic radiation force optical coherence elastography (ARF-OCE) to map out the elasticity of retinal layers in healthy and diseased in vivo rabbit models for the first time. Methods A healthy rabbit eye was proptosed and imaged using ARF-OCE, by measuring the tissue deformation after an acoustic force is applied. A diseased retinal inflammation model was used to observe the contrast before and after disease formation. Retinal histologic analysis was performed to identify layers of the retina corresponding with the optical images. Results The general trend of the retinal layer elasticity is increasing stiffness from the ganglion side to the photoreceptor side, with the stiffest layer being the sclera. In a healthy rabbit model, the mechanical properties varied from 3 to 16 kPa for the five layers that were identified via optical imaging and histology (3.09 ± 0.46, 3.82 ± 0.88, 4.53 ± 0.74, 6.59 ± 2.27, 16.11 ± 5.13 kPa). In the diseased model, we have induced optical damage in a live rabbit and observed a change in the stiffness trend in its retina. Conclusions High sensitivity elasticity maps can be obtained using the ARF-OCE system to differentiate different retinal layers. Subtle changes in the mechanical properties during the onset of diseases, such as retinal degeneration, can be measured and aid in early clinical diagnosis. This study validates our imaging system for the characterization of retinal elasticity for the detection of retinal diseases in vivo.
Collapse
Affiliation(s)
- Yueqiao Qu
- Beckman Laser Institute, University of California, Irvine, Irvine, California, United States
| | - Youmin He
- Beckman Laser Institute, University of California, Irvine, Irvine, California, United States
| | - Arya Saidi
- Beckman Laser Institute, University of California, Irvine, Irvine, California, United States.,Marshall B. Ketchum University. Southern California College of Optometry, Fullerton, California, United States
| | - Yihang Xin
- Beckman Laser Institute, University of California, Irvine, Irvine, California, United States
| | - Yongxiao Zhou
- Beckman Laser Institute, University of California, Irvine, Irvine, California, United States
| | - Jiang Zhu
- Beckman Laser Institute, University of California, Irvine, Irvine, California, United States
| | - Teng Ma
- Roski Eye Institute, Department of Ophthalmology and Biomedical Engineering, University of Southern California, Los Angeles, California, United States
| | - Ronald H Silverman
- Department of Ophthalmology, Columbia University Medical Center, New York, New York, United States
| | - Don S Minckler
- Gavin Herbert Eye Institute, University of California, Irvine, Irvine, California, United States
| | - Qifa Zhou
- Roski Eye Institute, Department of Ophthalmology and Biomedical Engineering, University of Southern California, Los Angeles, California, United States
| | - Zhongping Chen
- Beckman Laser Institute, University of California, Irvine, Irvine, California, United States
| |
Collapse
|
26
|
Yang Q, Miao Y, Huo T, Li Y, Heidari E, Zhu J, Chen Z. Deep imaging in highly scattering media by combining reflection matrix measurement with Bessel-like beam based optical coherence tomography. APPLIED PHYSICS LETTERS 2018; 113:011106. [PMID: 30034015 PMCID: PMC6029932 DOI: 10.1063/1.5036661] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 06/11/2018] [Indexed: 05/25/2023]
Abstract
Multiple scattering in biomedical tissue limits the imaging depth within a range of 1-2 mm for conventional optical imaging techniques. To extend the imaging depth into the scattering medium, a computational method based on the reflection matrix measurement has been developed to retrieve the singly back-scattered signal light from the dominant detrimental multiple-scattered background. After applying singular value decomposition on the measured matrix in the post-process, the target image underneath the turbid media is clearly recovered. To increase the depth of focus of the incident light by elongating the focal spot along the optical axis, a digital grating pattern is specially designed and displayed on a phase-only spatial light modulator to generate the Bessel-like beam for lateral point scanning. According to the results, the depth of focus is increased up to 2.4 mm which is much longer than the value of ∼50 μm obtained by using the conventional focused Gaussian beam, leading to a deeper penetration depth due to the self-healing feature of the Bessel-like beam. In addition, generation of the Bessel-like beam simplifies the axial scanning process by getting rid of the need to mechanically translate the focal zone along the optical axis of an objective with a high numerical aperture. By combining this method with an optical coherence tomography system with a low coherence light source, a depth-resolved optical image is obtained underneath a highly turbid medium.
Collapse
Affiliation(s)
- Qiang Yang
- Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Road East, Irvine, California 92612, USA
| | | | - Tiancheng Huo
- Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Road East, Irvine, California 92612, USA
| | | | | | - Jiang Zhu
- Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Road East, Irvine, California 92612, USA
| | | |
Collapse
|
27
|
Zhu J, Yu J, Qu Y, He Y, Li Y, Yang Q, Huo T, He X, Chen Z. Coaxial excitation longitudinal shear wave measurement for quantitative elasticity assessment using phase-resolved optical coherence elastography. OPTICS LETTERS 2018; 43:2388-2391. [PMID: 29762599 DOI: 10.1364/ol.43.002388] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Optical coherence elastography (OCE) is an emerging imaging modality for the assessment of mechanical properties in soft tissues. Transverse shear wave measurements using OCE can quantify the elastic moduli perpendicular to the force direction, however, missing the elastic information along the force direction. In this study, we developed coaxial excitation longitudinal shear wave measurements for quantification of elastic moduli along the force direction using M-scans. Incorporating Rayleigh wave measurements using non-coaxial lateral scans into longitudinal shear wave measurements, directionally dependent elastic properties can be quantified along the force direction and perpendicular to the force direction. Therefore, the reported system has the capability to image elasticity of anisotropic biological tissues.
Collapse
|
28
|
Kirby MA, Pelivanov I, Song S, Ambrozinski Ł, Yoon SJ, Gao L, Li D, Shen TT, Wang RK, O’Donnell M. Optical coherence elastography in ophthalmology. JOURNAL OF BIOMEDICAL OPTICS 2017; 22:1-28. [PMID: 29275544 PMCID: PMC5745712 DOI: 10.1117/1.jbo.22.12.121720] [Citation(s) in RCA: 116] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 12/14/2017] [Indexed: 05/03/2023]
Abstract
Optical coherence elastography (OCE) can provide clinically valuable information based on local measurements of tissue stiffness. Improved light sources and scanning methods in optical coherence tomography (OCT) have led to rapid growth in systems for high-resolution, quantitative elastography using imaged displacements and strains within soft tissue to infer local mechanical properties. We describe in some detail the physical processes underlying tissue mechanical response based on static and dynamic displacement methods. Namely, the assumptions commonly used to interpret displacement and strain measurements in terms of tissue elasticity for static OCE and propagating wave modes in dynamic OCE are discussed with the ultimate focus on OCT system design for ophthalmic applications. Practical OCT motion-tracking methods used to map tissue elasticity are also presented to fully describe technical developments in OCE, particularly noting those focused on the anterior segment of the eye. Clinical issues and future directions are discussed in the hope that OCE techniques will rapidly move forward to translational studies and clinical applications.
Collapse
Affiliation(s)
- Mitchell A. Kirby
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| | - Ivan Pelivanov
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| | - Shaozhen Song
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| | - Łukasz Ambrozinski
- Akademia Górniczo-Hutnicza University of Science and Technology, Krakow, Poland
| | - Soon Joon Yoon
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| | - Liang Gao
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| | - David Li
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
- University of Washington, Department of Chemical Engineering, Seattle, Washington, United States
| | - Tueng T. Shen
- University of Washington, Department of Ophthalmology, Seattle, Washington, United States
| | - Ruikang K. Wang
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
- University of Washington, Department of Ophthalmology, Seattle, Washington, United States
| | - Matthew O’Donnell
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
- Address all correspondence to: Matthew O’Donnell, E-mail:
| |
Collapse
|
29
|
Li Y, Jing J, Heidari E, Zhu J, Qu Y, Chen Z. Intravascular Optical Coherence Tomography for Characterization of Atherosclerosis with a 1.7 Micron Swept-Source Laser. Sci Rep 2017; 7:14525. [PMID: 29109462 PMCID: PMC5674044 DOI: 10.1038/s41598-017-15326-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Accepted: 10/25/2017] [Indexed: 11/17/2022] Open
Abstract
The main cause of acute coronary events, such as thrombosis, is the rupture of atherosclerotic plaques. Typical intravascular optical coherence tomography (IVOCT) imaging systems that utilize a 1.3 μm swept source laser are often used for identifying fibrous cap thickness of plaques, yet cannot provide adequate depth penetration to resolve the size of the lipid pool. Here, we present a novel IVOCT system with a 1.7 μm center wavelength swept light source that can readily penetrate deeper into the tissue because of the longer wavelength and allows for better identification of plaques due to the lipid absorption spectrum at 1.7 μm. Using this system, we have imaged a human coronary artery to evaluate the performance of the novel OCT system and verified the results by hematoxylin and eosin (H&E) histology. The significantly improved imaging depth and better identification sensitivity suggest that the 1.7 μm OCT system holds great potential that can be further translated for in-vivo applications of atherosclerosis characterization.
Collapse
Affiliation(s)
- Yan Li
- Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Road, Irvine, CA, 92617, USA.,Department of Biomedical Engineering, University of California Irvine, Irvine, CA, 92697-2700, USA
| | - Joseph Jing
- Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Road, Irvine, CA, 92617, USA.,Department of Biomedical Engineering, University of California Irvine, Irvine, CA, 92697-2700, USA
| | - Emon Heidari
- Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Road, Irvine, CA, 92617, USA.,Department of Biomedical Engineering, University of California Irvine, Irvine, CA, 92697-2700, USA
| | - Jiang Zhu
- Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Road, Irvine, CA, 92617, USA
| | - Yueqiao Qu
- Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Road, Irvine, CA, 92617, USA.,Department of Biomedical Engineering, University of California Irvine, Irvine, CA, 92697-2700, USA
| | - Zhongping Chen
- Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Road, Irvine, CA, 92617, USA. .,Department of Biomedical Engineering, University of California Irvine, Irvine, CA, 92697-2700, USA.
| |
Collapse
|
30
|
Lan G, Singh M, Larin KV, Twa MD. Common-path phase-sensitive optical coherence tomography provides enhanced phase stability and detection sensitivity for dynamic elastography. BIOMEDICAL OPTICS EXPRESS 2017; 8:5253-5266. [PMID: 29188118 PMCID: PMC5695968 DOI: 10.1364/boe.8.005253] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 10/16/2017] [Accepted: 10/23/2017] [Indexed: 05/08/2023]
Abstract
Phase-sensitive optical coherence elastography (PhS-OCE) is an emerging optical technique to quantify soft-tissue biomechanical properties. We implemented a common-path OCT design to enhance displacement sensitivity and optical phase stability for dynamic elastography imaging. The background phase stability was greater in common-path PhS-OCE (0.24 ± 0.07nm) than conventional PhS-OCE (1.60 ± 0.11μm). The coefficient of variation for surface displacement measurements using conventional PhS-OCE averaged 11% versus 2% for common-path PhS-OCE. Young's modulus estimates showed good precision (95% CIs) for tissue phantoms: 24.96 ± 2.18kPa (1% agar), 49.69 ± 4.87kPa (1.5% agar), and 116.08 ± 12.14kPa (2% agar), respectively. Common-path PhS-OCE effectively reduced the amplitude of background dynamic optical phase instability to a sub-nanometer level, which provided a larger dynamic detection range and higher detection sensitivity for surface displacement measurements than conventional PhS-OCE.
Collapse
Affiliation(s)
- Gongpu Lan
- School of Optometry, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Manmohan Singh
- Biomedical Engineering, University of Houston, Houston, TX, USA
| | - Kirill V. Larin
- Biomedical Engineering, University of Houston, Houston, TX, USA
- Interdisciplinary Laboratory of Biophotonics, Tomsk State University, Tomsk, Russia
| | - Michael D. Twa
- School of Optometry, University of Alabama at Birmingham, Birmingham, AL, USA
| |
Collapse
|
31
|
Zhu J, Zhang B, Qi L, Wang L, Yang Q, Zhu Z, Huo T, Chen Z. Quantitative angle-insensitive flow measurement using relative standard deviation OCT. APPLIED PHYSICS LETTERS 2017; 111:181101. [PMID: 29151604 PMCID: PMC5663647 DOI: 10.1063/1.5009200] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Accepted: 10/13/2017] [Indexed: 05/09/2023]
Abstract
Incorporating different data processing methods, optical coherence tomography (OCT) has the ability for high-resolution angiography and quantitative flow velocity measurements. However, OCT angiography cannot provide quantitative information of flow velocities, and the velocity measurement based on Doppler OCT requires the determination of Doppler angles, which is a challenge in a complex vascular network. In this study, we report on a relative standard deviation OCT (RSD-OCT) method which provides both vascular network mapping and quantitative information for flow velocities within a wide range of Doppler angles. The RSD values are angle-insensitive within a wide range of angles, and a nearly linear relationship was found between the RSD values and the flow velocities. The RSD-OCT measurement in a rat cortex shows that it can quantify the blood flow velocities as well as map the vascular network in vivo.
Collapse
Affiliation(s)
- Jiang Zhu
- Beckman Laser Institute, University of California, Irvine, Irvine, California 92612, USA
| | | | - Li Qi
- Beckman Laser Institute, University of California, Irvine, Irvine, California 92612, USA
| | | | - Qiang Yang
- Beckman Laser Institute, University of California, Irvine, Irvine, California 92612, USA
| | | | - Tiancheng Huo
- Beckman Laser Institute, University of California, Irvine, Irvine, California 92612, USA
| | | |
Collapse
|
32
|
Qu Y, Ma T, He Y, Yu M, Zhu J, Miao Y, Dai C, Patel P, Shung KK, Zhou Q, Chen Z. Miniature probe for mapping mechanical properties of vascular lesions using acoustic radiation force optical coherence elastography. Sci Rep 2017; 7:4731. [PMID: 28680156 PMCID: PMC5498569 DOI: 10.1038/s41598-017-05077-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Accepted: 05/24/2017] [Indexed: 12/15/2022] Open
Abstract
Cardiovascular diseases are the leading cause of fatalities in the United States. Atherosclerotic plaques are one of the primary complications that can lead to strokes and heart attacks if left untreated. It is essential to diagnose the disease early and distinguish vulnerable plaques from harmless ones. Many methods focus on the structural or molecular properties of plaques. Mechanical properties have been shown to change drastically when abnormalities develop in arterial tissue. We report the development of an acoustic radiation force optical coherence elastography (ARF-OCE) system that uses an integrated miniature ultrasound and optical coherence tomography (OCT) probe to map the relative elasticity of vascular tissues. We demonstrate the capability of the miniature probe to map the biomechanical properties in phantom and human cadaver carotid arteries.
Collapse
Affiliation(s)
- Yueqiao Qu
- Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Rd., Irvine, CA, 92617, USA.,Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, 92697-2700, USA
| | - Teng Ma
- NIH Ultrasonic Transducer Resource Center, University of Southern California, Los Angeles, CA, 90089, USA
| | - Youmin He
- Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Rd., Irvine, CA, 92617, USA.,Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, 92697-2700, USA
| | - Mingyue Yu
- NIH Ultrasonic Transducer Resource Center, University of Southern California, Los Angeles, CA, 90089, USA
| | - Jiang Zhu
- Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Rd., Irvine, CA, 92617, USA
| | - Yusi Miao
- Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Rd., Irvine, CA, 92617, USA.,Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, 92697-2700, USA
| | - Cuixia Dai
- Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Rd., Irvine, CA, 92617, USA.,Shanghai Institute of Technology, 100 Haiquan Road, Fengxian, Shanghai, China
| | - Pranav Patel
- Division of Cardiology, Irvine Medical Center, University of California, Orange, CA, 92868, USA
| | - K Kirk Shung
- NIH Ultrasonic Transducer Resource Center, University of Southern California, Los Angeles, CA, 90089, USA
| | - Qifa Zhou
- NIH Ultrasonic Transducer Resource Center, University of Southern California, Los Angeles, CA, 90089, USA.
| | - Zhongping Chen
- Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Rd., Irvine, CA, 92617, USA. .,Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, 92697-2700, USA.
| |
Collapse
|
33
|
Zhu J, Miao Y, Qi L, Qu Y, He Y, Yang Q, Chen Z. Longitudinal shear wave imaging for elasticity mapping using optical coherence elastography. APPLIED PHYSICS LETTERS 2017; 110:201101. [PMID: 28611483 PMCID: PMC5432373 DOI: 10.1063/1.4983292] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Accepted: 03/28/2017] [Indexed: 05/18/2023]
Abstract
Shear wave measurements for the determination of tissue elastic properties have been used in clinical diagnosis and soft tissue assessment. A shear wave propagates as a transverse wave where vibration is perpendicular to the wave propagation direction. Previous transverse shear wave measurements could detect the shear modulus in the lateral region of the force; however, they could not provide the elastic information in the axial region of the force. In this study, we report the imaging and quantification of longitudinal shear wave propagation using optical coherence tomography to measure the elastic properties along the force direction. The experimental validation and finite element simulations show that the longitudinal shear wave propagates along the vibration direction as a plane wave in the near field of a planar source. The wave velocity measurement can quantify the shear moduli in a homogeneous phantom and a side-by-side phantom. Combining the transverse shear wave and longitudinal shear wave measurements, this system has great potential to detect the directionally dependent elastic properties in tissues without a change in the force direction.
Collapse
Affiliation(s)
- Jiang Zhu
- Beckman Laser Institute, University of California, Irvine, Irvine, California 92612, USA
| | | | - Li Qi
- Beckman Laser Institute, University of California, Irvine, Irvine, California 92612, USA
| | | | | | - Qiang Yang
- Beckman Laser Institute, University of California, Irvine, Irvine, California 92612, USA
| | | |
Collapse
|
34
|
Multi-functional Ultrasonic Micro-elastography Imaging System. Sci Rep 2017; 7:1230. [PMID: 28450709 PMCID: PMC5430777 DOI: 10.1038/s41598-017-01210-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 03/28/2017] [Indexed: 12/13/2022] Open
Abstract
In clinical decision making, in addition to anatomical information, biomechanical properties of soft tissues may provide additional clues for disease diagnosis. Given the fact that most of diseases are originated from micron sized structures, an elastography imaging system of fine resolution (~100 µm) and deep penetration depth capable of providing both qualitative and quantitative measurements of biomechanical properties is desired. Here, we report a newly developed multi-functional ultrasonic micro-elastography imaging system in which acoustic radiation force impulse imaging (ARFI) and shear wave elasticity imaging (SWEI) are implemented. To accomplish this, the 4.5 MHz/40 MHz transducer were used as the excitation/detection source, respectively. The imaging system was tested with tissue-mimicking phantoms and an ex vivo chicken liver through 2D/3D imaging. The measured lateral/axial elastography resolution and field of view are 223.7 ± 20.1/109.8 ± 6.9 µm and 1.5 mm for ARFI, 543.6 ± 39.3/117.6 ± 8.7 µm and 2 mm for SWEI, respectively. These results demonstrate that the promising capability of this high resolution elastography imaging system for characterizing tissue biomechanical properties at microscale level and its translational potential into clinical practice.
Collapse
|
35
|
Larin KV, Sampson DD. Optical coherence elastography - OCT at work in tissue biomechanics [Invited]. BIOMEDICAL OPTICS EXPRESS 2017; 8:1172-1202. [PMID: 28271011 PMCID: PMC5330567 DOI: 10.1364/boe.8.001172] [Citation(s) in RCA: 217] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Revised: 01/18/2017] [Accepted: 01/19/2017] [Indexed: 05/18/2023]
Abstract
Optical coherence elastography (OCE), as the use of OCT to perform elastography has come to be known, began in 1998, around ten years after the rest of the field of elastography - the use of imaging to deduce mechanical properties of tissues. After a slow start, the maturation of OCT technology in the early to mid 2000s has underpinned a recent acceleration in the field. With more than 20 papers published in 2015, and more than 25 in 2016, OCE is growing fast, but still small compared to the companion fields of cell mechanics research methods, and medical elastography. In this review, we describe the early developments in OCE, and the factors that led to the current acceleration. Much of our attention is on the key recent advances, with a strong emphasis on future prospects, which are exceptionally bright.
Collapse
Affiliation(s)
- Kirill V Larin
- Department of Biomedical Engineering, University of Houston, 3605 Cullen Blvd., Houston, Texas 77204-5060, USA; Department of Molecular Physiology and Biophysics, Baylor College of Medicine, 1 Baylor Plaza, Houston, Texas 77030, USA;
| | - David D Sampson
- Optical + Biomedical Engineering Laboratory, School of Electrical, Electronic & Computer Engineering, The University of Western Australia, 35 Stirling Highway, Perth, WA 6009, Australia; Centre for Microscopy, Characterisation & Analysis, The University of Western Australia, 35 Stirling Highway, Perth, WA 6009, Australia;
| |
Collapse
|
36
|
3D mapping of elastic modulus using shear wave optical micro-elastography. Sci Rep 2016; 6:35499. [PMID: 27762276 PMCID: PMC5071855 DOI: 10.1038/srep35499] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Accepted: 09/30/2016] [Indexed: 12/31/2022] Open
Abstract
Elastography provides a powerful tool for histopathological identification and clinical diagnosis based on information from tissue stiffness. Benefiting from high resolution, three-dimensional (3D), and noninvasive optical coherence tomography (OCT), optical micro-elastography has the ability to determine elastic properties with a resolution of ~10 μm in a 3D specimen. The shear wave velocity measurement can be used to quantify the elastic modulus. However, in current methods, shear waves are measured near the surface with an interference of surface waves. In this study, we developed acoustic radiation force (ARF) orthogonal excitation optical coherence elastography (ARFOE-OCE) to visualize shear waves in 3D. This method uses acoustic force perpendicular to the OCT beam to excite shear waves in internal specimens and uses Doppler variance method to visualize shear wave propagation in 3D. The measured propagation of shear waves agrees well with the simulation results obtained from finite element analysis (FEA). Orthogonal acoustic excitation allows this method to measure the shear modulus in a deeper specimen which extends the elasticity measurement range beyond the OCT imaging depth. The results show that the ARFOE-OCE system has the ability to noninvasively determine the 3D elastic map.
Collapse
|
37
|
Qu Y, Ma T, He Y, Zhu J, Dai C, Yu M, Huang S, Lu F, Shung KK, Zhou Q, Chen Z. Acoustic Radiation Force Optical Coherence Elastography of Corneal Tissue. IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS : A PUBLICATION OF THE IEEE LASERS AND ELECTRO-OPTICS SOCIETY 2016; 22:6803507. [PMID: 27293369 PMCID: PMC4896493 DOI: 10.1109/jstqe.2016.2524618] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
We report on a real-time acoustic radiation force optical coherence elastography (ARF-OCE) system to map the relative elasticity of corneal tissue. A modulated ARF is used as excitation to vibrate the cornea while OCE serves as detection of tissue response. To show feasibility of detecting mechanical contrast using this method, we performed tissue-equivalent agarose phantom studies with inclusions of a different stiffness. We obtained 3-D elastograms of a healthy cornea and a highly cross-linked cornea. Finally we induced a stiffness change on a small portion of a cornea and observed the differences in displacement.
Collapse
Affiliation(s)
- Yueqiao Qu
- Department of Biomedical Engineering, the Edwards Life Sciences Center for Advanced Cardiovascular Technology, and Beckman Laser Institute, University of California, Irvine, Irvine, CA 92697 USA
| | - Teng Ma
- NIH Ultrasonic Transducer Resource Center and the Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, USA
| | - Youmin He
- Beckman Laser Institute, University of California, Irvine, Irvine, CA 92612 USA
| | - Jiang Zhu
- Beckman Laser Institute, University of California, Irvine, Irvine, CA 92612 USA
| | - Cuixia Dai
- Beckman Laser Institute, University of California, Irvine, Irvine, CA 92612 USA, and the Shanghai Institute of Technology, 100 Haiquan Road, Fengxian, Shanghai, China
| | - Mingyue Yu
- NIH Ultrasonic Transducer Resource Center and the Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, USA
| | - Shenghai Huang
- Beckman Laser Institute, University of California, Irvine, Irvine 92612 USA and the School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, 325027 China
| | - Fan Lu
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, 325027 China
| | - K. Kirk Shung
- NIH Ultrasonic Transducer Resource Center and the Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, USA
| | - Qifa Zhou
- NIH Ultrasonic Transducer Resource Center and the Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, USA
| | - Zhongping Chen
- Department of Biomedical Engineering, the Edwards Life Sciences Center for Advanced Cardiovascular Technology, and Beckman Laser Institute, University of California, Irvine, Irvine, CA 92697 USA
| |
Collapse
|
38
|
Dynamic and quantitative assessment of blood coagulation using optical coherence elastography. Sci Rep 2016; 6:24294. [PMID: 27090437 PMCID: PMC4836302 DOI: 10.1038/srep24294] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Accepted: 03/24/2016] [Indexed: 01/29/2023] Open
Abstract
Reliable clot diagnostic systems are needed for directing treatment in a broad spectrum of cardiovascular diseases and coagulopathy. Here, we report on non-contact measurement of elastic modulus for dynamic and quantitative assessment of whole blood coagulation using acoustic radiation force orthogonal excitation optical coherence elastography (ARFOE-OCE). In this system, acoustic radiation force (ARF) is produced by a remote ultrasonic transducer, and a shear wave induced by ARF excitation is detected by the optical coherence tomography (OCT) system. During porcine whole blood coagulation, changes in the elastic property of the clots increase the shear modulus of the sample, altering the propagating velocity of the shear wave. Consequently, dynamic blood coagulation status can be measured quantitatively by relating the velocity of the shear wave with clinically relevant coagulation metrics, including reaction time, clot formation kinetics and maximum shear modulus. The results show that the ARFOE-OCE is sensitive to the clot formation kinetics and can differentiate the elastic properties of the recalcified porcine whole blood, blood added with kaolin as an activator, and blood spiked with fibrinogen.
Collapse
|
39
|
Li J, Chen Z. Integrated intravascular ultrasound and optical coherence tomography technology: a promising tool to identify vulnerable plaques [INVITED PAPER]. JOURNAL OF BIOMEDICAL PHOTONICS & ENGINEERING 2016; 1. [PMID: 28966987 DOI: 10.18287/jbpe-2015-1-4-209] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Heart attack is mainly caused by the rupture of a vulnerable plaque. IVUS-OCT is a novel medical imaging modality that provides opportunities for accurate assessment of vulnerable plaques in vivo in patients. IVUS provides deep penetration to image the whole necrotic core while OCT enables accurate measurement of the fibrous cap of a plaque owing to its high resolution. In this paper, the authors describe the fundamentals, the technical designs and the applications of IVUS-OCT technology. Results from cadaver specimens are summarized, which indicated the complementary nature of OCT and IVUS for assessment of vulnerable plaques, plaque composition, and stent-tissue interactions. Furthermore, previously reported in vivo animal experiments are reviewed to assess the clinical adaptability of IVUS-OCT. Future directions for this technology are also discussed in this review.
Collapse
Affiliation(s)
- Jiawen Li
- Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Road East, Irvine, CA 92612, USA
| | - Zhongping Chen
- Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Road East, Irvine, CA 92612, USA
| |
Collapse
|
40
|
Nandy S, Salehi HS, Wang T, Wang X, Sanders M, Kueck A, Brewer M, Zhu Q. Correlating optical coherence elastography based strain measurements with collagen content of the human ovarian tissue. BIOMEDICAL OPTICS EXPRESS 2015; 6:3806-11. [PMID: 26504631 PMCID: PMC4605040 DOI: 10.1364/boe.6.003806] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Revised: 08/27/2015] [Accepted: 08/30/2015] [Indexed: 05/06/2023]
Abstract
In this manuscript, the initial feasibility of a catheter based phase stabilized swept source optical coherence tomography (OCT) system was studied for characterization of the strain inside different human ovarian tissue groups. The ovarian tissue samples were periodically compressed with 500 Hz square wave signal along the axial direction between the surface of an unfocused transducer and a glass cover slide. The displacement and corresponding strain were calculated during loading from different locations for each tissue sample. A total of 27 ex vivo ovaries from 16 patients were investigated. Statistically significant difference (p < 0.001) was observed between the average displacement and strain of the normal and malignant tissue groups. A sensitivity of 93.2% and a specificity of 83% were achieved using 25 microstrain (με) as the threshold. The collagen content of the tissues was quantified from the Sirius Red stained histological sections. The average collagen area fraction (CAF) obtained from the tissue groups were found to have a strong negative correlation (R = -0.75, p < 0.0001) with the amount of strain inside the tissue. This indicates much softer and degenerated tissue structure for the malignant ovaries as compared to the dense, collagen rich structure of the normal ovarian tissue. The initial results indicate that the swept source OCT system can be useful for estimating the elasticity of the human ovarian tissue.
Collapse
Affiliation(s)
- Sreyankar Nandy
- University of Connecticut, Department of Biomedical Engineering, Storrs, CT 06269, USA
| | - Hassan S. Salehi
- University of Connecticut, Department of Electrical and Computer Engineering, Storrs, CT 06269, USA
| | - Tianheng Wang
- University of Connecticut, Department of Electrical and Computer Engineering, Storrs, CT 06269, USA
| | - Xiaohong Wang
- University of Connecticut Health Center, Division of Pathology, Farmington, CT 06030, USA
| | - Melinda Sanders
- University of Connecticut Health Center, Division of Pathology, Farmington, CT 06030, USA
| | - Angela Kueck
- University of Connecticut Health Center, Division of Gynecologic Oncology, Farmington, CT 06030, USA
| | - Molly Brewer
- University of Connecticut Health Center, Division of Gynecologic Oncology, Farmington, CT 06030, USA
| | - Quing Zhu
- University of Connecticut, Department of Biomedical Engineering, Storrs, CT 06269, USA
- University of Connecticut, Department of Electrical and Computer Engineering, Storrs, CT 06269, USA
| |
Collapse
|