1. Articles from Yan Li

    1-24 of 49 1 2 »
    1. Multimodal endoscopy for colorectal cancer detection by optical coherence tomography and near-infrared fluorescence imaging

      Multimodal endoscopy for colorectal cancer detection by optical coherence tomography and near-infrared fluorescence imaging

      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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    2. 1.7 micron optical coherence tomography for vaginal tissue characterization in vivo

      1.7 micron optical coherence tomography for vaginal tissue characterization in vivo

      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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    3. Deep imaging in highly scattering media by combining reflection matrix measurement with Bessel-like beam based optical coherence tomography

      Deep imaging in highly scattering media by combining reflection matrix measurement with Bessel-like beam based optical coherence tomography

      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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    4. Multimodality endoscopic optical coherence tomography and fluorescence imaging technology for visualization of layered architecture and subsurface microvasculature

      Multimodality endoscopic optical coherence tomography and fluorescence imaging technology for visualization of layered architecture and subsurface microvasculature

      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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    5. Optical coherence tomography angiography of a pigmented Fuchs' adenoma (age-related hyperplasia of the nonpigmented ciliary body epithelium) masquerading as a ciliary body melanoma

      Optical coherence tomography angiography of a pigmented Fuchs' adenoma (age-related hyperplasia of the nonpigmented ciliary body epithelium) masquerading as a ciliary body melanoma

      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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    6. Imaging of Iris Lesions With High-Speed Optical Coherence Tomography

      Imaging of Iris Lesions With High-Speed Optical Coherence Tomography

      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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    7. Intravascular Optical Coherence Tomography for Characterization of Atherosclerosis with a 1.7 Micron Swept-Source Laser

      Intravascular Optical Coherence Tomography for Characterization of Atherosclerosis with a 1.7 Micron Swept-Source Laser

      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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    8. Methods and systems to measure corneal epithelial thickness and power, stromal thickness, subepithelial corneal power and topography for disease diagnosis

      Methods and systems to measure corneal epithelial thickness and power, stromal thickness, subepithelial corneal power and topography for disease diagnosis

      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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    9. Extended axial imaging range, widefield swept source optical coherence tomography angiography

      Extended axial imaging range, widefield swept source optical coherence tomography angiography

      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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    10. Distinguishing between contact lens warpage and ectasia: Usefulness of optical coherence tomography epithelial thickness mapping

      Distinguishing between contact lens warpage and ectasia: Usefulness of optical coherence tomography epithelial thickness mapping

      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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    11. Fully integrated optical coherence tomography, ultrasound, and indocyanine green-based fluorescence tri-modality system for intravascular imaging

      Fully integrated optical coherence tomography, ultrasound, and indocyanine green-based fluorescence tri-modality system for intravascular imaging

      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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    12. Optical Coherence Tomography Angiography Characteristics of Iris Melanocytic Tumors

      Optical Coherence Tomography Angiography Characteristics of Iris Melanocytic Tumors

      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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    13. Subclinical keratoconus detection by pattern analysis of corneal and epithelial thickness maps with optical coherence tomography

      Subclinical keratoconus detection by pattern analysis of corneal and epithelial thickness maps with optical coherence tomography

      Purpose To screen for subclinical keratoconus by analyzing corneal, epithelial, and stromal thickness map patterns with Fourier-domain optical coherence tomography (OCT). Setting Four centers in the United States. Design Cross-sectional observational study. Methods Eyes of normal subjects, subclinical keratoconus eyes, and the topographically normal eye of a unilateral keratoconus patient were studied. Corneas were scanned using a 26 000 Hz Fourier-domain OCT system (RTVue). Normal subjects were divided into training and evaluation groups. Corneal, epithelial, and stromal thickness maps and derived diagnostic indices, including pattern standard deviation (PSD) variables and pachymetric map–based keratoconus risk scores, were calculated from the ...

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    14. Imaging the anterior eye with dynamic-focus swept-source optical coherence tomography.

      Imaging the anterior eye with dynamic-focus swept-source optical coherence tomography.

      A custom-built dynamic-focus swept-source optical coherence tomography (SS-OCT) system with a central wavelength of 1310 nm was used to image the anterior eye from the cornea to the lens. An electrically tunable lens was utilized to dynamically control the positions of focusing planes over the imaging range of 10 mm. The B-scan images were acquired consecutively at the same position but with different focus settings. The B-scan images were then registered and averaged after filtering the out-of-focus regions using a Gaussian window. By fusing images obtained at different depth focus locations, high-resolution and high signal-strength images were obtained over the ...

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    15. Change of Retinal Nerve Layer Thickness in Non-Arteritic Anterior Ischemic Optic Neuropathy Revealed by Fourier Domain Optical Coherence Tomography

      Change of Retinal Nerve Layer Thickness in Non-Arteritic Anterior Ischemic Optic Neuropathy Revealed by Fourier Domain Optical Coherence Tomography

      Purpose : To examine the changes of non-arteritic anterior ischemic optic neuropathy (NAION) by serial morphometry using Fourier domain optical coherence tomography (FD-OCT). Materials and methods : Retrospective study in patients with newly diagnosed NAION ( n =33, all unilateral) and controls ( n =75 unilateral NAION patients with full contralateral eye vision) who underwent FD-OCT of the optic disk, optic nerve head (ONH), and macula within 1 week of onset and again 1, 3, 6, and 12 months later. The patients showed no improvement in vision during follow-up. Results : Within 1 week of onset, all NAION eyes exhibited severe ONH fiber crowding and ...

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      Mentions: Yan Li
    16. Corneal Epithelial Remodeling after LASIK Measured by Fourier-Domain Optical Coherence Tomography

      Corneal Epithelial Remodeling after LASIK Measured by Fourier-Domain Optical Coherence Tomography

      Purpose . To quantify corneal epithelial thickness changes after myopic LASIK by OCT. Methods. Epithelial thickness before and after myopic LASIK were measured by a Fourier-domain OCT system. Average central (within 1 mm diameter) and paracentral epithelial thickness (5~6 mm diameter) before and after LASIK were compared. Correlation between central epithelial thickness change and laser spherical equivalent setting was evaluated. An epithelial smoothing constant was estimated based on a mathematical model published previously. Results. Nineteen eyes from 11 subjects were included in the study. Eyes had myopic LASIK ranging from −1.69 D to −6.75 D spherical equivalent. The ...

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    17. Aqueous Cell Differentiation in Anterior Uveitis Using Fourier-domain Optical Coherence Tomography

      Aqueous Cell Differentiation in Anterior Uveitis Using Fourier-domain Optical Coherence Tomography

      Purpose: The differential diagnosis of a patient presenting with anterior uveitis is broad and can present a diagnostic challenge. In this study, we evaluate the characteristic findings of inflammatory cells on optical coherence tomography (OCT) both in vitro and in vivo. Methods: Blood from two healthy volunteers was prepared using standardized methods for cell sorting with a flow cytometer (FASCAria; BD Biosciences). Neutrophils, lymphocytes, monocytes, and red blood cells were placed in suspension and scanned with a 26 kHz Fourier-domain OCT system (RTVue; Optovue, Inc.) with 5 µm axial resolution. Custom software algorithms were used to identify cells based on ...

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    18. Dual-channel spectral-domain optical-coherence tomography system based on 3 × 3 fiber coupler for extended imaging range

      Dual-channel spectral-domain optical-coherence tomography system based on 3 × 3 fiber coupler for extended imaging range

      We have demonstrated a dual-channel multiplexing spectral-domain optical-coherence tomography (SD-OCT) system based on a 3 × 3 fiber coupler for extended imaging range of whole human eye depth, with a single light source and spectrometer. OCT images of anterior segments of a human eye were sequentially performed and constructed to demonstrate an extended depth range as large as 15 mm in air. A good quality OCT image of the whole anterior segment of an eye was present. Furthermore, whole eye segmental imaging was performed and ocular distances were calculated to show the validation of the system for whole eye morphological measurement.

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    19. Predicting Transepithelial Phototherapeutic Keratectomy Outcomes Using Fourier Domain Optical Coherence Tomography

      Predicting Transepithelial Phototherapeutic Keratectomy Outcomes Using Fourier Domain Optical Coherence Tomography

      PURPOSE:: The aim of this study was to use Fourier domain optical coherence tomography to predict transepithelial phototherapeutic keratectomy outcomes. METHODS:: This is a prospective case series. Subjects with anterior stromal corneal opacities underwent an excimer laser phototherapeutic keratectomy (PTK) combined with a photorefractive keratectomy using the VISX S4 excimer laser (AMO, Inc, Santa Ana, CA). Preoperative and postoperative Fourier domain optical coherence tomography images were used to develop a simulation algorithm to predict treatment outcomes. Main outcome measures included preoperative and postoperative uncorrected distance visual acuities and corrected distance visual acuity. RESULTS:: Nine eyes of 8 patients were treated ...

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    20. NON-INVASIVE 3D Imaging And Measuring Of Anterior Chamber Angle Of The Eye

      NON-INVASIVE 3D Imaging And Measuring Of Anterior Chamber Angle Of The Eye

      Embodiments of OCT measurement and analysis techniques described herein enable precise 3D anterior chamber angle measurement from major, pertinent landmarks in the eye. Such techniques result in a more reliable, quantifiable angle measurement technique that is both non-invasive and non- contact in nature, thereby improving clinical practicality, while improving patient comfort and care.

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    21. Keratoconus diagnosis with optical coherence tomography–based pachymetric scoring system

      Keratoconus diagnosis with optical coherence tomography–based pachymetric scoring system

      Purpose To develop an optical coherence tomography (OCT) pachymetry map–based keratoconus risk scoring system. Settings Doheny Eye Institute, University of Southern California, Los Angeles, California, and Brass Eye Center, New York, New York, USA; Department of Ophthalmology, Affiliated Eye Hospital of Wenzhou Medical College, Wenzhou, China. Design Cross-sectional study. Methods Fourier-domain OCT was used to acquire corneal pachymetry maps in normal and keratoconus subjects. Pachymetric variables were minimum, minimum−median, superior–inferior (S–I), superonasal–inferotemporal (SN–IT), and the vertical location of the thinnest cornea (Ymin). A logistic regression formula and a scoring system were developed based on ...

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    22. Anterior Chamber Cell Grading by Optical Coherence Tomography

      Anterior Chamber Cell Grading by Optical Coherence Tomography

      Purpose: To quantify cells in the ocular anterior chamber by optical coherence tomography (OCT). Methods: A time-domain anterior segment OCT system was used to image latex microsphere suspensions in vitro and the anterior chamber of uveitis and normal subjects in vivo. The OCT scan pattern, consisting of 2- and 4-mm diameter concentric circular scans, was divided into central, superior, and inferior regions. A computer algorithm was developed to automatically identify particles in OCT images. A uveitis specialist used slit-lamp biomicroscopy to grade the anterior chamber cells on a scale of 0 to 4+. Results: Latex microspheres and anterior chamber cells ...

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    23. Study on application of optical clearing technique in skin diseases

      Study on application of optical clearing technique in skin diseases

      So far, the study of the optical clearing is almost always about healthy tissue. However, the ultimate goal is to detect diseases for clinical application. Optical clearing on diseased skins is explored. The effect is evaluated by applying a combined liquid paraffin and glycerol mixed solution on several kinds of diseased skins in vitro . Scanning experiments from optical coherence tomography show that it has different effects among fibroma, pigmented nevus, and seborrheic keratosis. Based on the results, we conclude that different skin diseases have different compositions and structures, and their optical parameters and biological characteristics should be different, which implies ...

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    24. Corneal Epithelial Thickness Mapping by Fourier-Domain Optical Coherence Tomography in Normal and Keratoconic Eyes

      Corneal Epithelial Thickness Mapping by Fourier-Domain Optical Coherence Tomography in Normal and Keratoconic Eyes

      Objective To map the corneal epithelial thickness with Fourier-domain optical coherence tomography (OCT) and to develop epithelial thickness–based variables for keratoconus detection. Design Cross-sectional observational study. Participants One hundred forty-five eyes from 76 normal subjects and 35 keratoconic eyes from 22 patients. Methods A 26 000-Hz Fourier-domain OCT system with 5-μm axial resolution was used. The cornea was imaged with a Pachymetry+Cpwr scan pattern (6-mm scan diameter, 8 radials, 1024 axial-scans each, repeated 5 times) centered on the pupil. Three scans were obtained at a single visit in a prospective study. A computer algorithm was developed to ...

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    1-24 of 49 1 2 »
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    1. (48 articles) Yan Li
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