1. Articles from Yan Li

    1-24 of 78 1 2 3 4 »
    1. Detection of Corneal Ectasia Using OCT Maps of Pachymetry and Posterior Surface Mean Curvature

      Detection of Corneal Ectasia Using OCT Maps of Pachymetry and Posterior Surface Mean Curvature

      Purpose: To quantify the abnormal corneal thinning and posterior surface steepening that is observed in keratoconus with an Ectasia Index. Methods: Optical coherence tomography (OCT) was used to image the corneas of normal individuals and patients with varying stages of keratoconus (manifest, subclinical, and forme fruste). Maps of corneal pachymetry and posterior surface mean curvature were generated, and an Ectasia Index was calculated by multiplying Gaussian fits obtained from the two types of maps. Repeated five-fold cross-validation was used to evaluate the ability of the Ectasia Index to differentiate between normal and keratoconic eyes. The classification performance of the Ectasia ...

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    2. Effects of smoking on the retina of patients with dry age-related macular degeneration by optical coherence tomography angiography

      Effects of smoking on the retina of patients with dry age-related macular degeneration by optical coherence tomography angiography

      Background The macula of the retina is analysed using optical coherence tomography angiography (OCTA) to provide clinical basis and explain the mechanism of smoking as a risk factor in dry age-related macular degeneration (AMD). Methods This cross-sectional study included 49 normal control nonsmokers, 12 normal control smokers, 38 dry AMD nonsmokers and 35 dry AMD smokers. The foveal avascular zone (FAZ), foveal density (FD) in a 300 μm region around FAZ, vessel densities of the superficial (SCP) and deep (DCP) capillary plexuses and central fovea retinal thickness (FRT) were compared using OCTA. The bivariate correlation analysis was used to evaluate ...

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    3. OCT Evaluation of Vaginal Epithelial Thickness during CO2 Laser Treatment: A Pilot Study

      OCT Evaluation of Vaginal Epithelial Thickness during CO2 Laser Treatment: A Pilot Study

      Genitourinary syndrome of menopause (GSM) negatively affects more than half of postmenopausal women. Energy-based therapy has been explored as a minimally invasive treatment for GSM; however, its mechanism of action and efficacy is controversial. Here, we report on a pilot imaging study conducted on a small group of menopause patients undergoing laser treatment. Intravaginal optical coherence tomography (OCT) endoscope was used to quantitatively monitor the changes in the vaginal epithelial thickness (VET) during fractional-pixel CO 2 laser treatment. 11 patients with natural menopause and 1 surgically induced menopause patient were recruited in this clinical study. Following the laser treatment, the ...

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      Mentions: UC Irvine
    4. Visualization of ex vivo rabbit olfactory mucosa and foramina with three-dimensional optical coherence tomography

      Visualization of ex vivo rabbit olfactory mucosa and foramina with three-dimensional optical coherence tomography

      There is increasing interest in developing a minimally invasive imaging modality to safely evaluate dynamic microscopic changes of the olfactory mucosa and cribriform foramina. Herein, we utilized three-dimensional (3D) optical coherence tomography (OCT) to characterize the ex vivo stratified substructure of olfactory mucosa in rabbits and create 3D reconstructed images of olfactory foramina. Olfactory mucosa and cribriform plates from four New Zealand White rabbits were dissected and imaged using two swept-source OCT systems: (1) 1.3-µm (μm) center wavelength, 100-nm bandwidth, 200-kHz sweep rate, and (2) 1.7-μm center wavelength, 120-nm bandwidth, 90-kHz sweep rate. Volumetric OCT images ...

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      Mentions: UC Irvine
    5. A Randomized Comparison of the Healing Response Between the Firehawk Stent and the Xience Stent in Patients With ST-Segment Elevation Myocardial Infarction at 6 Months of Follow-Up (TARGET STEMI OCT China Trial): An Optical Coherence Tomography Study

      A Randomized Comparison of the Healing Response Between the Firehawk Stent and the Xience Stent in Patients With ST-Segment Elevation Myocardial Infarction at 6 Months of Follow-Up (TARGET STEMI OCT China Trial): An Optical Coherence Tomography Study

      Background: The healing response of the Firehawk stent in patients with ST-segment elevation myocardial infarction (STEMI) remains unclear. Aim: We compared the vascular healing of a biodegradable polymer sirolimus-eluting stent (Firehawk) vs. a durable polymer everolimus-eluting stent (Xience) at 6 months after percutaneous coronary intervention (PCI) in patients with STEMI. Methods: In this prospective, multicenter, randomized, non-inferiority study, patients within 12 h of STEMI onset were randomized in a ratio of 1:1 to receive Firehawk or Xience stents. Optical coherence tomography (OCT) follow-up was performed 6 months after the index procedure and assessed frame by frame. The primary endpoint ...

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    6. Measuring Corneal Astigmatism Using Optical Coherence Tomography in Keratoconus

      Measuring Corneal Astigmatism Using Optical Coherence Tomography in Keratoconus

      Purpose: To measure net corneal astigmatism using optical coherence tomography (OCT, Avanti, Optovue) in individuals with keratoconus and compare its repeatability and accuracy with those obtained using Scheimpflug imaging (Pentacam HR, Oculus). Setting: Casey Eye Institute, Portland, Oregon, USA. Design: Prospective cross-sectional observational study. Methods: Net corneal astigmatism was calculated in keratoconic and normal eyes with OCT and Scheimpflug imaging using four settings - pupil or vertex centration settings with a 3 or 4 mm circular analytical zone. Corneal elevation maps were obtained from OCT images and fitted with Zernike polynomials to obtain net corneal astigmatism. Manifest refraction astigmatism was used ...

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    7. Intravascular polarization-sensitive optical coherence tomography based on polarization mode delay

      Intravascular polarization-sensitive optical coherence tomography based on polarization mode delay

      Intravascular polarization-sensitive optical coherence tomography (IV-PSOCT) provides depth-resolved tissue birefringence which can be used to evaluate the mechanical stability of a plaque. In our previous study, we reported a new strategy to construct polarization-sensitive optical coherence tomography in a microscope platform. Here, we demonstrated that this technology can be implemented in an endoscope platform, which has many clinical applications. A conventional intravascular OCT system can be modified for IV-PSOCT by introducing a 12-m polarization-maintaining fiber-based imaging probe. Its two polarization modes separately produce OCT images of polarization detection channels spatially distinguished by an image separation of 2.7 mm. We ...

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      Mentions: UC Irvine
    8. Enhance the delivery of light energy ultra-deep into turbid medium by controlling multiple scattering photons to travel in open channels

      Enhance the delivery of light energy ultra-deep into turbid medium by controlling multiple scattering photons to travel in open channels

      Multiple light scattering is considered as the major limitation for deep imaging and focusing in turbid media. In this paper, we present an innovative method to overcome this limitation and enhance the delivery of light energy ultra-deep into turbid media with significant improvement in focusing. Our method is based on a wide-field reflection matrix optical coherence tomography (RM-OCT). The time-reversal decomposition of the RM is calibrated with the Tikhonov regularization parameter in order to get more accurate reversal results deep inside the scattering sample. We propose a concept named model energy matrix, which provides a direct mapping of light energy ...

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      Mentions: UC Irvine
    9. Research progress of optical coherence tomography and angiography in the diagnosis of Alzheimer's disease

      Research progress of optical coherence tomography and angiography in the diagnosis of Alzheimer's disease

      Alzheimer's disease(AD)is a progressive and irreversible neurological disease characterized by changes in neurons and blood vessels of the brain. Its etiology is unknown, and there is no feasible non-invasive technique for early diagnosis. Because the retina and the central nervous system have similar embryonic origins and physiological characteristics, an ophthalmic examination may provide a simple and non-invasive diagnostic method. Optical coherence tomography(OCT)can accurately measure the thickness of various tissue layers of the retina to assess degenerative changes of the retina. Optical coherence tomography angiography(OCTA)can provide high-resolution three-dimensional imaging, which can more directly detect ...

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    10. Novel predictors of stent under-expansion regarding calcified coronary lesions assessed by optical coherence tomography

      Novel predictors of stent under-expansion regarding calcified coronary lesions assessed by optical coherence tomography

      A previous calcium scoring system using circumferential angle, thickness, and length of coronary calcium by OCT could assist in predicting stent under-expansion. However, this scoring system only reflects the calcification distribution within a single cross-section and fails to consider the lumen's original size. The current study aims to investigate whether novel parameters to quantify calcium lesions, including calcium burden, area, and volume assessed by optical coherence tomography (OCT), could predict stent under-expansion related to calcium lesions. Consecutive patients admitted between March 10th to October 19th 2021 with calcified coronary lesions undergoing percutaneous coronary intervention (PCI) with OCT guidance were ...

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    11. Differentiating Between Contact Lens Warpage and Keratoconus Using OCT Maps of Corneal Mean Curvature and Epithelial Thickness

      Differentiating Between Contact Lens Warpage and Keratoconus Using OCT Maps of Corneal Mean Curvature and Epithelial Thickness

      Purpose: To formulate an Epithelial Modulation index to differentiate between eyes with contact lens warpage and keratoconus. Methods: Normal eyes and eyes with either contact lens warpage or keratoconus were scanned by a Fourier-domain optical coherence tomography (OCT) system. Maps of epithelial thickness and anterior surface mean curvature were generated and converted to deviation maps by subtracting the average maps from a healthy population. The Epithelial Modulation index was defined as the covariance between the two types of deviation maps. A logistic regression model was used to classify eyes as non-keratoconus (normal or warp-age) or keratoconus (manifest, subclinical, or forme ...

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    12. High speed, long range, deep penetration swept source OCT for structural and angiographic imaging of the anterior eye

      High speed, long range, deep penetration swept source OCT for structural and angiographic imaging of the anterior eye

      This study reports the development of prototype swept-source optical coherence tomography (SS-OCT) technology for imaging the anterior eye. Advances in vertical-cavity surface-emitting laser (VCSEL) light sources, signal processing, optics and mechanical designs, enable a unique combination of high speed, long range, and deep penetration that addresses the challenges of anterior eye imaging. We demonstrate SS-OCT with a 325 kHz A-scan rate, 12.2 µm axial resolution (in air), and 15.5 mm depth range (in air) at 1310 nm wavelength. The ultrahigh 325 kHz A-scan rate not only facilitates biometry measurements by minimizing acquisition time and thus reducing motion, but ...

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    13. Prospective evaluation of optical coherence tomography for disease detection in the Casey mobile eye clinic

      Prospective evaluation of optical coherence tomography for disease detection in the Casey mobile eye clinic

      This study was designed to evaluate iVue Spectral-domain optical coherence tomography (SD-OCT) effectiveness in screening for eye disease compared to clinical examination. Subjects were recruited from the Casey Eye Community Outreach Program Mobile Clinic during its routinely scheduled outreach clinics to indigent, underserved populations throughout Oregon. Macular optical coherence tomography interpretation and automated optical coherence tomography analysis were compared to the clinical examination, with specific attention to findings indicative of retinal abnormalities, risks for glaucoma, and narrow angles. As a result, a total of 114 subjects were included in this study. In diabetics, optical coherence tomography and clinical exam were ...

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    14. High-Speed, Long-Range Swept-Source Optical Coherence Tomography for the Anterior Segment of the Eye

      High-Speed, Long-Range Swept-Source Optical Coherence Tomography for the Anterior Segment of the Eye

      Purpose : The anterior segment (AS) of the eye is of interest in multiple diseases and procedures, including glaucoma, ocular surface inflammation, and refractive / cataract surgeries. Visualizing the anterior eye using optical coherence tomography (OCT) has unique challenges, and AS OCT technology is less developed than retinal imaging. We developed next generation swept-source OCT (SS-OCT) technology to enable high-speed and long-range AS structural and angiographic imaging in clinical settings. Methods : We designed a SS-OCT prototype instrument using wavelength-tunable, vertical-cavity surface-emitting laser (VCSEL) with linearized frequency sweep. The OCT wavelength centers at 1310 nm with a 105 nm bandwidth. The A-scan rate ...

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    15. Accuracy of OCT-derived net corneal astigmatism measurement

      Accuracy of OCT-derived net corneal astigmatism measurement

      Purpose: To assess the repeatability and accuracy of corneal astigmatism measurement with a spectral-domain optical coherence tomography (OCT) system (Avanti, Optovue) and compare them with Scheimpflug imaging (Pentacam HR, Oculus) and swept-source optical biometry (IOLMaster 700, Carl Zeiss Mediatec AG). Setting: Casey Eye Institute, Oregon Health & Science University, Portland, Oregon, USA. Design: Prospective cross-sectional observational study. Methods: Sixty pseudophakic eyes with monofocal non-toric intraocular lens that previously had refractive surgery were analyzed. To assess accuracy, simulated keratometric (SimK) and net corneal astigmatism, obtained from each device were compared with subjective manifest refraction astigmatism. Repeatability for corneal astigmatism was assessed for ...

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    16. 1.7-micron Optical Coherence Tomography Angiography for Characterization of Skin Lesions – A Feasibility Study

      1.7-micron Optical Coherence Tomography Angiography for Characterization of Skin Lesions – A Feasibility Study

      Optical coherence tomography (OCT) is a non-invasive diagnostic method that offers real-time visualization of the layered architecture of the skin in vivo. The 1.7-micron OCT system has been applied in cardiology, gynecology and dermatology, demonstrating an improved penetration depth in contrast to conventional 1.3-micron OCT. To further extend the capability, we developed a 1.7-micron OCT/OCT angiography (OCTA) system that allows for a visualization of both morphology and microvasculature in the deeper layers of the skin. Using this imaging system, we imaged human skin with different benign lesions and described the corresponding features of both structure and ...

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      Mentions: UC Irvine
    17. Quantitative research on the interaction between cerebral edema and peripheral cerebral blood perfusion using swept-source optical coherence tomography

      Quantitative research on the interaction between cerebral edema and peripheral cerebral blood perfusion using swept-source optical coherence tomography

      Background: Ischemic cerebral edema (CE) is a major leading cause of death in patients with ischemic stroke. The CE progression is closely related to the local cerebral blood perfusion (LCBP) level surrounding the edema area. Quantitative studying the interaction between the CE and peripheral LCBP may provide new inspiration for control and even treatment of CE. Methods: Photothrombosis ischemia mouse model was established and observed for 9 hours using swept-source optical coherence tomography (SS-OCT). OCT-based angiography and OCT-based attenuation imaging techniques were used to reconstruct the angiograms reflecting the cerebral blood perfusion (CBP) level and optical attenuation coefficient (OAC) maps ...

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    18. Keratoconus Detection using OCT Corneal and Epithelial Thickness Map Parameters and Patterns

      Keratoconus Detection using OCT Corneal and Epithelial Thickness Map Parameters and Patterns

      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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    19. A Coincident Thinning Index for Keratoconus Identification Using OCT Pachymetry and Epithelial Thickness Maps

      A Coincident Thinning Index for Keratoconus Identification Using OCT Pachymetry and Epithelial Thickness Maps

      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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    20. 2D Ultrasonic Array-based Optical Coherence Elastography

      2D Ultrasonic Array-based Optical Coherence Elastography

      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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    21. Advances in Doppler optical coherence tomography and angiography

      Advances in Doppler optical coherence tomography and angiography

      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: UC Irvine
    22. Ultrahigh-sensitive optical coherence elastography

      Ultrahigh-sensitive optical coherence elastography

      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: UC Irvine
    23. Bulk motion subtraction in optical coherence tomography angiography

      Bulk motion subtraction in optical coherence tomography angiography

      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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    24. Optical Vaginal Biopsy Using Optical Coherence Tomography

      Optical Vaginal Biopsy Using Optical Coherence Tomography

      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: UC Irvine
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    Image Processing and Clinical Applications of Anterior Segment Optical Coherence Tomography (Thesis) Corneal power measurement with Fourier-domain optical coherence tomography Repeatability of laser in situ keratomileusis flap thickness measurement by Fourier-domain optical coherence tomography Normal and keratoconic corneal epithelial thickness mapping using Fourier-domain optical coherence tomography Intraocular lens power calculation after myopic and hyperopic laser vision correction using optical coherence tomography Study of Anterior Chamber Aqueous Tube Shunt by Fourier-Domain Optical Coherence Tomography Corneal Epithelial Thickness Mapping by Fourier-Domain Optical Coherence Tomography in Normal and Keratoconic Eyes The truth about invisible posterior vitreous structures The Influence of Eyelid Position and Environmental Conditions on the Corneal Changes in Early Postmortem Interval: A Prospective, Multicentric OCT Study The Use of Optical Coherence Tomography for Gross Examination and Sampling of Fixed Breast Specimens: A Pilot Study The Role of Widefield and Ultra Widefield Optical Coherence Tomography in the Diagnosis and Management of Vitreoretinal Diseases Acute Idiopathic Blind Spot Enlargement Syndrome-New Perspectives in the OCT Era