All Articles from Yan Li -Optical Coherence Tomography News

Articles from Yan Li

1-24 of 61 1 2 3 »
1. Keratoconus Detection using OCT Corneal and Epithelial Thickness Map Parameters and Patterns
  
  Explore LWW Online Nov 13 2020 Ophthalmology
  
  Purpose: To detect keratoconus using optical coherence tomography (OCT) corneal map parameters and patterns. Setting: Casey Eye Institute, Oregon Health & Science University, Portland, Oregon, USA DESIGN:: Cross-sectional observational study. Methods: A spectral-domain OCT was used to acquire corneal and epithelial thickness maps in normal, manifest keratoconic, subclinical keratoconic, and forme fruste keratoconic (FFK) eyes. A two-step decision tree was designed. An eye will be classified as keratoconus if both decision tree conditions are met: First, at least one of the four quantitative corneal thickness (minimum, minimum-maximum, superonasal-inferotemporal) and epithelial thickness (standard deviation) map parameters exceed cutoff values. Second, presence of ...
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  Mentions: David Huang Oregon Health & Science University Center for Ophthalmic Optics and Lasers
2. A Coincident Thinning Index for Keratoconus Identification Using OCT Pachymetry and Epithelial Thickness Maps
  
  Explore Healio.com Nov 12 2020 Ophthalmology
  
  PURPOSE: To develop a coincident thinning (CTN) index to differentiate between keratoconic and healthy corneas using optical coherence tomography (OCT) measurements of pachymetry and epithelial thickness. METHODS: Pattern deviation maps of pachymetry and epithelial thickness were generated using Fourier-domain OCT images of the cornea. The co-localized thinning of the two maps was quantified using a novel CTN index, which was calculated from Gaussian fits of the regions of maximum relative thinning. The CTN index was validated using k-fold cross-validation, and its classification performance was compared to minimum pachymetry and maximum keratometry. RESULTS: A total of 82 normal eyes and 133 ...
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  Mentions: David Huang Oregon Health & Science University Center for Ophthalmic Optics and Lasers
3. 2D Ultrasonic Array-based Optical Coherence Elastography
  
  Explore IEEE Xplore Oct 24 2020 Ophthalmology
  
  Acoustic radiation force optical coherence elastography (ARF-OCE) has been successfully implemented to characterize the biomechanical properties of soft tissues such as the cornea and the retina with high resolution using single-element ultrasonic transducers for ARF excitation. Most currently proposed OCE techniques, such as air-puff and ARF, have less capability to control the spatiotemporal information of the induced region of deformation, resulting in limited accuracy and low temporal resolution of the shear wave elasticity imaging. In this study, we propose a new method called 2D ultrasonic array-based optical coherence elastography imaging, which combines the advantages of 3D dynamic electronic steering of ...
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  Mentions: University of Southern California UC Irvine Qifa Zhou
4. Advances in Doppler optical coherence tomography and angiography
  
  Explore Wiley Online Library Oct 4 2020
  
  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
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  Mentions: Zhongping Chen UC Irvine Yan Li
5. Ultrahigh-sensitive optical coherence elastography
  
  Explore Nature Publishing Group Apr 13 2020
  
  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 ...
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  Mentions: Zhongping Chen UC Irvine Yan Li
6. Bulk motion subtraction in optical coherence tomography angiography
  
  Explore uspto.gov Mar 17 2020 Ophthalmology , Patents
  
  Described herein is an algorithm to remove decorrelation noise due to bulk motion in optical coherence tomography angiography (OCTA). OCTA B-frames are divided into segments within which the bulk motion velocity could be assumed constant. This velocity is recovered using linear regression of decorrelation versus the logarithm of reflectance in axial lines (A-lines) identified as bulk tissue by percentile analysis. The fitting parameters are used to calculate a reflectance-adjusted threshold for bulk motion decorrelation. Below this threshold, voxels are identified as non-flow tissue, and their flow values are set to zeros. Above this threshold, the voxels are identified as flow ...
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  Mentions: David Huang Oregon Health & Science University Yali Jia
7. Optical Vaginal Biopsy Using Optical Coherence Tomography
  
  Explore LWW Online Feb 10 2020 Gynecology
  
  Objective Optical coherence tomography is a noninvasive technology that visualizes tissue microstructure with high spatial resolution. We designed a novel vaginal system that demonstrates a clear distinction between vaginal tissues planes. In this study, we sought to compare vaginal tomographic images of premenopausal, perimenopausal, and postmenopausal women, demonstrate feasibility of tracking vaginal tissue changes after treatment with fractional-pixel CO 2 laser therapy, and obtain a histologic correlation of these findings. Methods Enrolled subjects underwent imaging and were divided into 3 groups based on menopausal status. Women with genitourinary syndrome of menopause who received fractional-pixel CO 2 laser therapy were assessed ...
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  Mentions: Zhongping Chen UC Irvine Yan Li
8. Early Diagnostic Value of Optical Coherence Tomography in The Clinical Prediction Model for Optic Nerve Injury in Saddle Space Occupying Patients
  
  Explore ScienceDirect Jan 14 2020 Ophthalmology
  
  In this study, 50 patients with anterior ischemic optic neuropathy due to saddle block were selected as the experimental group, and 50 healthy subjects were used as the control group to conduct a study. The best corrected visual acuity examination, optical coherence tomography and visual evoked potential examination were performed on the two groups. The results of the study showed that the majority of patients were middle-aged and older people over the age of 50, but the youngest patients were only 37 years old. After various examinations, it was found that patients with optic nerve injury had a significant reduction ...
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  Mentions: Yan Li
9. In vivo evaluation of posterior eye elasticity using shaker-based optical coherence elastography
  
  Explore SAGE Journals Jan 12 2020 Ophthalmology
  
  Age-related macular degeneration (AMD) is a progressive retinal disease and becomes the leading cause of blindness. It is well established that early detection is the key to preservation of functional vision. However, it is very difficult to diagnose AMD in very early stages, before structural changes are evident. Consequently, investigating the biomechanical properties of the retina maybe essential for understanding its physiological function. In this study, we present a shear wave-based quantitative method for estimating the elasticity of the posterior eye using shaker-based optical coherence elastography. This technique has been developed and validated on both a homogeneous phantom and a ...
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  Mentions: Zhongping Chen University of Southern California UC Irvine
10. Application of Corneal Optical Coherence Tomography Angiography for Assessment of Vessel Depth in Corneal Neovascularization
  
  Explore LWW Online Dec 28 2019 Ophthalmology
  
  Purpose: To map and measure the depths of corneal neovascularization (NV) using 3-dimensional optical coherence tomography angiography (OCTA) at 2 different wavelengths. Methods: Corneal NV of varying severity, distribution, and underlying etiology was examined. Average NV depth and vessel density were measured using 840-nm spectral-domain OCTA and 1050-nm swept-source OCTA. The OCTA results were compared with clinical slit-lamp estimation of NV depth. Results: Twelve eyes with corneal NV from 12 patients were imaged with OCTA. Clinically “superficial,” “midstromal,” and “deep” cases had an average vessel depth of 23%, 39%, and 66% on 1050-nm OCTA, respectively. Average vessel depth on OCTA ...
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  Mentions: Massachusetts Institute of Technology James G. Fujimoto David Huang
11. Cerebral edema detection in vivo after middle cerebral artery occlusion using swept-source optical coherence tomography
  
  Explore SPIE Digital Library Nov 12 2019 Neurology
  
  Cerebral edema is a severe complication of ischemic cerebrovascular disease, which can lead to microcirculation compression resulting in additional ischemic damage. Real-time and continuous in vivo imaging techniques for edema detection are of great significance to basic research on cerebral edema. We attempted to monitor the cerebral edema status in rats with middle cerebral artery occlusion (MCAO) over time, using a wide field-of-view swept-source optical coherence tomography (SS-OCT) system. Optical attenuation coefficients (OACs) were calculated by an optimized depth-resolved estimation method, and en face OAC maps covering the whole cortex were obtained. Then, the tissue affected by edema was segmented ...
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  Mentions: University of Michigan Yan Li
12. Simultaneous detection of cerebral blood perfusion and cerebral edema using swept‐source optical coherence tomography
  
  Explore Wiley Online Library Nov 12 2019 Neurology
  
  The progression of ischemic cerebral edema (CE) is closely related to the level of cerebral blood perfusion (CBP) and affects each other. Simultaneous detection of CBP and CE is helpful in understanding the mechanisms of ischemic cerebral edema development. In this article, a wide field of view (FOV) SS‐OCT system was used to detect CE status and CBP levels simultaneously in middle cerebral artery occlusion (MCAO) rats. Images reflecting these two physiological states can be reconstructed with only one C‐scan. We quantify these two physiological states into 4 parameters, which contain two vascular parameters (vascular displacement distance and ...
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13. Multimodal endoscopy for colorectal cancer detection by optical coherence tomography and near-infrared fluorescence imaging
  
  Explore OSA | OSA Publishing Apr 20 2019 Gastroenterology
  
  While colonoscopy is the gold standard for diagnosis and classification of colorectal cancer (CRC), its sensitivity and specificity are operator-dependent and are especially poor for small and flat lesions. Contemporary imaging modalities, such as optical coherence tomography (OCT) and near-infrared (NIR) fluorescence, have been investigated to visualize microvasculature and morphological changes for detecting early stage CRC in the gastrointestinal (GI) tract. In our study, we developed a multimodal endoscopic system with simultaneous co-registered OCT and NIR fluorescence imaging. By introducing a contrast agent into the vascular network, NIR fluorescence is able to highlight the cancer-suspected area based on significant change ...
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  Mentions: Zhongping Chen UC Irvine Yan Li
14. 1.7 micron optical coherence tomography for vaginal tissue characterization in vivo
  
  Explore Wiley Online Library Jul 30 2018 Gynecology
  
  Objectives Optical coherence tomography (OCT) can noninvasively visualize in vivo tissue microstructure with high spatial resolution that approaches the histologic level. Currently, OCT studies in gynecology are few and limited to a conventional 1.3 μm center wavelength swept light source which provides high spatial resolution but limited penetration depth. Here, we present a novel endoscopic OCT system with improved penetration depth and high resolution. Methods A novel endoscopic OCT system was developed based on a 1.7 µm swept source laser, which is capable of deeper tissue penetration due to its longer wavelength. To evaluate the performance of system ...
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  Mentions: Zhongping Chen UC Irvine Yan Li
15. Deep imaging in highly scattering media by combining reflection matrix measurement with Bessel-like beam based optical coherence tomography
  
  Explore aip.scitation.org Jul 7 2018
  
  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 ...
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  Mentions: Zhongping Chen UC Irvine Yan Li
16. Multimodality endoscopic optical coherence tomography and fluorescence imaging technology for visualization of layered architecture and subsurface microvasculature
  
  Explore OSA | OSA Publishing May 2 2018 Gastroenterology , Probes
  
  Endoscopic imaging technologies, such as endoscopic optical coherence tomography (OCT) and near-infrared fluorescence, have been used to investigate vascular and morphological changes as hallmarks of early cancer in the gastrointestinal tract. Here we developed a high-speed multimodality endoscopic OCT and fluorescence imaging system. Using this system, the architectural morphology and vasculature of the rectum wall were obtained simultaneously from a Sprague Dawley rat in vivo . This multimodality imaging strategy in a single imaging system permits the use of a single imaging probe, thereby improving prognosis by early detection and reducing costs.
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  Mentions: Zhongping Chen UC Irvine Yan Li
17. Optical coherence tomography angiography of a pigmented Fuchs' adenoma (age-related hyperplasia of the nonpigmented ciliary body epithelium) masquerading as a ciliary body melanoma
  
  Explore ScienceDirect Jan 13 2018 Ophthalmology
  
  Purpose To report a case of age-related hypertrophy of the nonpigmented ciliary epithelium (ARH-NPCE) clinically resembling a ciliary body melanoma and report the optical coherence tomography angiography (OCTA) findings associated with this lesion. Observations A 51-year-old male was referred for evaluation of a deeply pigmented ciliary body mass with extension through the iris root. Iridocyclectomy was performed due to concern for ciliary body melanoma. Histopathologic analysis was instead consistent with ARH-NPCE, also known as Fuchs' adenoma. Prior to surgery, OCTA images revealed abnormal vasculature in the area of the lesion. Vessels in the peripheral iris approaching the lesion appeared more ...
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  Mentions: David Huang Oregon Health & Science University Center for Ophthalmic Optics and Lasers
18. Imaging of Iris Lesions With High-Speed Optical Coherence Tomography
  
  Explore m4.healio.com Dec 3 2017 Ophthalmology
  
  n BACKGROUND AND OBJECTIVES:To image and measure iris tumors with optical coherence tomography (OCT). n PATIENTS AND METHODS:High-speed(2,000– 4,000 axial-scan/sec and 4–16 frames/sec) 1.3-micron wavelength anterior segment OCT prototypes were used to image 6 eyes of 6 patients with a variety of iris lesions, including focal iris nevus, diffuse iris nevus, amelanotic iris nevus, iris melanocytosis, and iris melanoma. OCT images were compared with slit-lamp photography and ultrasound biomicroscopy. n RESULTS: OCT at 1.3-micron wavelength could penetrate the full thickness of the iris lesions and allow three-dimensional measurement of lesion ...
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  Mentions: Joseph A. Izatt Andrew M. Rollins David Huang
19. Intravascular Optical Coherence Tomography for Characterization of Atherosclerosis with a 1.7 Micron Swept-Source Laser
  
  Explore Nature Publishing Group Nov 15 2017 Cardiology
  
  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 ...
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  Mentions: Zhongping Chen UC Irvine Yan Li
20. Methods and systems to measure corneal epithelial thickness and power, stromal thickness, subepithelial corneal power and topography for disease diagnosis
  
  Explore uspto.gov May 23 2017 Ophthalmology , Patents
  
  This invention discloses methods and systems for measuring corneal epithelial thickness and power, stromal thickness, subepitheila corneal power and topography. The systems and methods disclosed herein are non-invasive, non-contact and automated imaging methods which preferably makes use of Fourier-domain optical tomography. Also disclosed herein are scanning patterns and image analysis methods for utilizing and analyzing Fourier-domain optical coherence tomography images to obtain information about conical epithelial and stromal properties as well as parameters useful for evaluating the properties. The methods and systems described herein are useful as eye disease diagnostic tools and eye surgery planning tools.
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  Mentions: David Huang University of Southern California Ou Tan
21. Extended axial imaging range, widefield swept source optical coherence tomography angiography
  
  Explore Wiley Online Library May 11 2017
  
  We developed a high-speed, swept source OCT system for widefield OCT angiography (OCTA) imaging. The system has an extended axial imaging range of 6.6 mm. An electrical lens is used for fast, automatic focusing. The recently developed split-spectrum amplitude and phase-gradient angiography allow high-resolution OCTA imaging with only two B-scan repetitions. An improved post-processing algorithm effectively removed trigger jitter artifacts and reduced noise in the flow signal. We demonstrated high contrast 3 mm×3 mm OCTA image with 400×400 pixels acquired in 3 seconds and high-definition 8 mm×6 mm and 12 mm×6 mm OCTA images with ...
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  Mentions: David Huang Oregon Health & Science University UC Irvine
22. Distinguishing between contact lens warpage and ectasia: Usefulness of optical coherence tomography epithelial thickness mapping
  
  Explore Journal of Cataract & Refractive Surgery Mar 24 2017 Ophthalmology
  
  Purpose To distinguish between corneal ectasia and contact lens–related warpage by characteristic patterns on corneal topography and optical coherence tomography (OCT) epithelial thickness maps. Setting Casey Eye Institute, Portland, Oregon, USA. Design Prospective and retrospective case series. Methods Axial and mean power maps were obtained on corneal topography systems. Epithelial thickness maps were generated using RTVue OCT. A sector divider was applied to all maps. The locations of the minimum epithelial thickness, maximum epithelial thickness, maximum axial power, and maximum mean power were determined based on sector averages. Agreement was defined as the extremums occurring in the same or ...
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  Mentions: David Huang Oregon Health & Science University Center for Ophthalmic Optics and Lasers
23. Fully integrated optical coherence tomography, ultrasound, and indocyanine green-based fluorescence tri-modality system for intravascular imaging
  
  Explore OSA | OSA Publishing Jan 28 2017 Cardiology
  
  We present a tri-modality imaging system and fully integrated tri-modality probe for intravascular imaging. The tri-modality imaging system is able to simultaneously acquire optical coherence tomography (OCT), ultrasound (US), and fluorescence imaging. Moreover, for fluorescence imaging, we used the FDA-approved indocyanine green (ICG) dye as the contrast agent to target lipid-loaded macrophages. We conducted imaging from a male New Zealand white rabbit to evaluate the performance of the tri-modality system. In addition, tri-modality images of rabbit aortas were correlated with hematoxylin and eosin (H&E) histology to check the measurement accuracy. The fully integrated miniature tri-modality probe, together with the ...
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  Mentions: Zhongping Chen UC Irvine Yan Li
24. Optical Coherence Tomography Angiography Characteristics of Iris Melanocytic Tumors
  
  Explore Elsevier Health Nov 14 2016 Oncology , Ophthalmology
  
  Purpose To evaluate tumor vasculature with optical coherence tomography angiography (OCTA) in malignant iris melanomas and benign iris lesions. Design Cross-sectional observational clinical study. Participants Patients with iris lesions and healthy volunteers. Methods Eyes were imaged using OCTA systems operating at 1050- and 840-nm wavelengths. Three-dimensional OCTA scans were acquired. Iris melanoma patients treated with radiation therapy were imaged again after I-125 plaque brachytherapy at 6 and 18 months. Main Outcome Measures OCT and OCTA images, qualitative evaluation of iris and tumor vasculature, and quantitative vessel density. Results One eye each of 8 normal volunteers and 9 patients with iris ...
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  Mentions: Massachusetts Institute of Technology James G. Fujimoto David Huang
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