1. Articles from Ji Yi

    1-24 of 46 1 2 »
    1. A Baseline Study of Oxygen Saturation in Parafoveal Vessels Using Visible Light Optical Coherence Tomography

      A Baseline Study of Oxygen Saturation in Parafoveal Vessels Using Visible Light Optical Coherence Tomography

      The retinal macula is at the center of our visual field, and thus pathological damage in the macula significantly impacts an individual's quality of life. The parafoveal vessels form the inner retina provide oxygen perfusion, and the measurement of parafoveal oxygen saturation (sO 2 ) can evaluate macular metabolism and provide pathophysiological insight. In this paper, for the first time, we present a baseline study of microvascular oxygen saturation (sO 2 ) in perifoveal macular region using visible light optical coherence tomography (VIS-OCT) on normal eyes. The arterial and venous sO 2 from all eyes was 92.1 ± 7.1 (vol ...

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    2. Simultaneous visible light optical coherence tomography and near infrared OCT angiography in retinal pathologies: A case study

      Simultaneous visible light optical coherence tomography and near infrared OCT angiography in retinal pathologies: A case study

      A dual-channel optical coherence tomography system with wavelengths in the visible and near-infrared light ranges can provide both structural and functional information for retinal microvasculature simultaneously. We applied this integrated system in an ongoing clinical study of patients with various retinal pathologies. Here, we present case study results of patients with diabetic retinopathy, central retinal vein occlusion, and sickle cell retinopathy compared to a healthy subject. For the first time, this comparison validates the system's ability to detect structural anomalies in both en face and B-scan images with simultaneous retinal optical coherence tomography angiography and measurement of sO 2 ...

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    3. Deep Learning in Biomedical Optics

      Deep Learning in Biomedical Optics

      This article reviews deep learning applications in biomedical optics with a particular emphasis on image formation. The review is organized by imaging domains within biomedical optics and includes microscopy, fluorescence lifetime imaging, in vivo microscopy, widefield endoscopy, optical coherence tomography, photoacoustic imaging, diffuse tomography, and functional optical brain imaging. For each of these domains, we summarize how deep learning has been applied and highlight methods by which deep learning can enable new capabilities for optics in medicine. Challenges and opportunities to improve translation and adoption of deep learning in biomedical optics are also summarized

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    4. Postdoctoral Positions in Optical Imaging at Johns Hopkins

      Postdoctoral Positions in Optical Imaging at Johns Hopkins

      Description : We are seeking candidates for two postdoctoral positions on cutting-edge 3D imaging projects funded by NIH. The first position focuses on visible light optical coherence tomography (vis-OCT) , a new ophthalmic imaging technique that offers ultrahigh depth resolution, capillary-level oximetry, and rich retinal scattering spectroscopy. The second position focuses mesoscopic oblique plane microscopy , and/or oblique scanning laser ophthalmoscopy (oSLO) . The candidates will learn and be responsible for the end-to-end design of device, imaging, and data processing. We expect the candidates to be motivated and productive, and are committed to propel the candidates’ academic career. The position is open starting ...

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    5. Visible light optical coherence tomography angiography (vis-OCTA) facilitates local microvascular oximetry in the human retina

      Visible light optical coherence tomography angiography (vis-OCTA) facilitates local microvascular oximetry in the human retina

      We report herein the first visible light optical coherence tomography angiography (vis-OCTA) for human retinal imaging. Compared to the existing vis-OCT systems, we devised a spectrometer with a narrower bandwidth to increase the spectral power density for OCTA imaging, while retaining the major spectral contrast in the blood. We achieved a 100 kHz A-line rate, the fastest acquisition speed reported so far for human retinal vis-OCT. We rigorously optimized the imaging protocol such that a single acquisition took < 6 seconds with a field of view (FOV) of 3×7.8 mm 2 . The angiography enables accurate localization of microvasculature down ...

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    6. Postdoctoral positions for ophthalmic imaging at Johns Hopkins

      Postdoctoral positions for ophthalmic imaging at Johns Hopkins

      Description: We are seeking outstanding candidates for two postdoctoral positions on cutting‐edge 3D ophthalmic imaging projects funded by NIH. The first position focuses on visible light optical coherence tomography (vis‐OCT) , a new ophthalmic imaging technique that offers ultrahigh depth resolution, capillary level oximetry, and rich retinal scattering spectroscopy. The second position focuses oblique scanning laser ophthalmoscopy (oSLO), a “fluorescent‐version” of OCT that implements light sheet microscopy in the eye and uniquely allowing high speed volumetric retinal imaging. The candidates will learn and be responsible for the end‐to‐end design of device, imaging, and data processing. We ...

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    7. Visible light optical coherence tomography angiography (vis-OCTA)

      Visible light optical coherence tomography angiography (vis-OCTA)

      We report herein the first visible light optical coherence tomography angiography (vis-OCTA) for human retinal imaging. Compared to the existing vis-OCT systems, we devised a spectrometer with a narrower bandwidth to increase the spectral power density for OCTA imaging, while retaining the major spectral contrast in the blood. We achieved a 100 kHz A-line rate, the fastest acquisition speed reported so far for human retinal vis-OCT. We rigorously optimized the imaging protocol such that a single acquisition takes <6 seconds with a field of view (FOV) of 3x7.8 mm2. The angiography enables accurate localization of microvasculature down to the ...

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    8. Special Section Guest Editorial: Advances in Retinal Imaging

      Special Section Guest Editorial: Advances in Retinal Imaging

      The guest editorial provides an introduction to the Special Section on Advanced Retinal Imaging: Instrumentation, Methods, and Applications. The retina is a peripheral part of the central nerve system (CNS) and shares many similarities with the cerebral cortex. They both have layered anatomy, the same types of functional elements and neurotransmitters, and similar vascular organization and blood-tissue barriers. With far fewer neuronal cell types and simpler anatomical structures, the retina is an excellent target for studying neural circuitry and neurovascular coupling. Meanwhile, approximately 80 percent of information from the outside world is processed as visual perception, 1 and retina-related blindness ...

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    9. Deep spectral learning for label-free optical imaging oximetry with uncertainty quantification

      Deep spectral learning for label-free optical imaging oximetry with uncertainty quantification

      Measurement of blood oxygen saturation ( s O 2 ) by optical imaging oximetry provides invaluable insight into local tissue functions and metabolism. Despite different embodiments and modalities, all label-free optical-imaging oximetry techniques utilize the same principle of s O 2 -dependent spectral contrast from haemoglobin. Traditional approaches for quantifying s O 2 often rely on analytical models that are fitted by the spectral measurements. These approaches in practice suffer from uncertainties due to biological variability, tissue geometry, light scattering, systemic spectral bias, and variations in the experimental conditions. Here, we propose a new data-driven approach, termed deep spectral learning (DSL), to ...

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    10. Longitudinal detection of retinal alterations by visible and near-infrared optical coherence tomography in a dexamethasone-induced ocular hypertension mouse model

      Longitudinal detection of retinal alterations by visible and near-infrared optical coherence tomography in a dexamethasone-induced ocular hypertension mouse model

      The retina, as part of the central nervous system, has distinct anatomical and structural properties for its visual function. Light scattering spectroscopy, while widely used for tissue structural characterization and disease diagnosis, has been relatively unexplored in the living retina. Recently, we have developed a fiber-based visible and near-infrared optical coherence tomography system (vnOCT) for in vivo retinal imaging, to uniquely measure a spectroscopic marker (VN ratio) sensitive to nanoscale pathological changes. In the present study, we applied vnOCT in an animal model of glaucoma (dexamethasone-induced ocular hypertension mouse) and tested the capabilities of four optical markers, VN ratio, peripapillary ...

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    11. Postdoctoral Positions Immediately Open at Boston University School of Medicine, Boston Medical Center

      Postdoctoral Positions Immediately Open at Boston University School of Medicine, Boston Medical Center

      Postdoctoral positions immediately open at Boston University School of Medicine, Boston Medical Center. About the position : We are looking for highly motivated individuals to join the lab, to develop novel optical imaging techniques for ophthalmic and endoscopic applications. Candidates with experiences on ophthalmic imaging, endoscopy, optical coherence tomography, fiber sensing and imaging system will be highly competitive. The position will require PhD degree on scientific discipline, for example, electrical engineering, computer science, biomedical engineering etc. The position also requires good communication skill, willingness for collaboration, and is expected to independently publish scientific papers. Please contact the PI, Dr. Ji Yi ...

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    12. Detection of Malignancy in Ocular Surface Lesions by Inverse Spectroscopic Optical Coherence Tomography and Two-Photon Autofluorescence

      Detection of Malignancy in Ocular Surface Lesions by Inverse Spectroscopic Optical Coherence Tomography and Two-Photon Autofluorescence

      Purpose : Advanced imaging is increasingly important in the diagnosis of ocular surface malignancy. Inverse spectroscopic optical coherence tomography (ISOCT) and two-photon autofluorescence microscopy (2P-AF) are emerging techniques capable of quantifying ultrastructural and metabolic changes, respectively. We aimed to detect malignancy in ocular surface lesions using ISOCT and 2P-AF. Methods : Portions of excised specimens from patients undergoing conjunctival biopsy at Boston Medical Center were imaged by ISOCT and/or 2P-AF, and submitted for histologic diagnosis. Lesions were categorized as malignant, premalignant (with dysplasia) or benign. ISOCT and 2P-AF findings were compared between categories. Results : Fourteen specimens from 13 patients were collected ...

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    13. Quantitative quality-control metrics for in vivo oximetry in small vessels by visible light optical coherence tomography angiography

      Quantitative quality-control metrics for in vivo oximetry in small vessels by visible light optical coherence tomography angiography

      Biological functions rely on local microvasculature to deliver oxygen and nutrients and carry away metabolic waste. Alterations to local oxygenation levels are manifested in diseases including cancer, diabetes mellitus, etc. The ability to quantify oxygen saturation (sO 2 ) within microvasculature in vivo to assess local tissue oxygenation and metabolic function is highly sought after. Visible light optical coherence tomography (vis-OCT) angiography has shown promise in reaching this goal. However, achieving reliable measurements in small vessels can be challenging due to the reduced contrast and requires data averaging to improve the spectral data quality. Therefore, a method for quality-control of the ...

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    14. Single capillary oximetry and tissue ultrastructural sensing by dual-band dual-scan inverse spectroscopic optical coherence tomography

      Single capillary oximetry and tissue ultrastructural sensing by dual-band dual-scan inverse spectroscopic optical coherence tomography

      Measuring capillary oxygenation and the surrounding ultrastructure can allow one to monitor a microvascular niche and better understand crucial biological mechanisms. However, capillary oximetry and pericapillary ultrastructure are challenging to measure in vivo. Here, we demonstrate a novel optical imaging system, Dual-band Dual-scan Inverse Spectroscopic Optical Coherence Tomography (D2- ISOCT), that, for the first time, can simultaneously obtain the following metrics in vivo using endogenous contrast: (1) capillary-level oxygen saturation and arteriolar-level blood flow rates, oxygen delivery rates, and oxygen metabolic rates; (2) spatial characteristics of tissue structures at length scales down to 30 nm; and (3) morphological images up ...

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    15. Multimodal Volumetric Retinal Imaging by Oblique Scanning Laser Ophthalmoscopy (oSLO) and Optical Coherence Tomography (OCT)

      Multimodal Volumetric Retinal Imaging by Oblique Scanning Laser Ophthalmoscopy (oSLO) and Optical Coherence Tomography (OCT)

      While fluorescence imaging is widely used in ophthalmology, a large field of view (FOV) three-dimensional (3D) fluorescence retinal image is still a big challenge with the state-of-the-art retinal imaging modalities because they would require z-stacking to compile a volumetric dataset. Newer optical coherence tomography (OCT) and OCT angiography (OCTA) systems overcome these restrictions to provide three-dimensional (3D) anatomical and vascular images, but the dye-free nature of OCT cannot visualize leakage indicative of vascular dysfunction. This protocol describes a novel oblique scanning laser ophthalmoscopy (oSLO) technique that provides 3D volumetric fluorescence retinal imaging. The setup of the imaging system generates the ...

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    16. Fiber-based visible and near infrared optical coherence tomography (vnOCT) enables quantitative elastic light scattering spectroscopy in human retina

      Fiber-based visible and near infrared optical coherence tomography (vnOCT) enables quantitative elastic light scattering spectroscopy in human retina

      Elastic light scattering spectroscopy (ELSS) has been proven a powerful method in measuring tissue structures with exquisite nanoscale sensitivity. However, ELSS contrast in the living human retina has been relatively underexplored, primarily due to the lack of imaging tools with a large spectral bandwidth. Here, we report a simple all fiber-based setup to implement dual-channel visible and near infrared (NIR) optical coherence tomography (vnOCT) for human retinal imaging, bridging over a 300nm spectral gap. Remarkably, the fiber components in our vnOCT system support single-mode propagation for both visible and NIR light, both of which maintain excellent interference efficiencies with fringe ...

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    17. Measurement of Flow‐Mediated Dilation of Mouse Femoral Artery in vivo by Optical Coherence Tomography

      Measurement of Flow‐Mediated Dilation of Mouse Femoral Artery in vivo by Optical Coherence Tomography

      Flow‐mediated vasodilation (FMD) is used for assessment of vascular endothelial function in humans as a predictor of cardiovascular events. It has been challenging to carry it on preclinical murine models due to the diminutive size of the femoral artery. Here, we present a new approach to accurately measure the blood velocity and femoral artery diameters of mice by acquiring Doppler optical coherence tomography (DOCT) and optical coherence tomography angiography (OCTA) continuously within one single experimental scanning protocol. Using the high precision three‐dimensional imaging and new velocity algorithm, the measurement precision of diameter, blood flow, velocity, and wall shear ...

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    18. Postdoctoral positions open at Boston University School of Medicine, Boston Medical Center

      Postdoctoral positions open at Boston University School of Medicine, Boston Medical Center

      Postdoctoral positions open at Boston University School of Medicine, Boston Medical Center. Our lab develops and implements optical imaging method in biomedical applications. We work closely with clinicians to translate the latest imaging technologies into clinical settings. The current focus of the lab is ophthalmic imaging for retinal diseases, and endoscopic imaging for GI and intravascular diseases. We are collaborative, interdisciplinary and also highly productive with several new imaging methods developed in recent two years. The lab is located in the vibrant Boston area, providing an excellent living environment out of work. We are looking for strong postdoc candidates with ...

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    19. In vivo broadband visible light optical coherence tomography probe enables inverse spectroscopic analysis

      In vivo broadband visible light optical coherence tomography probe enables inverse spectroscopic analysis

      We report the design and characterization of a 6 mm outer diameter pull-back circumferential scanning visible optical coherence tomography probe. The probe’s large visible bandwidth (500–695 nm) allowed for inverse spectroscopic analysis and an axial resolution of ∼ 1.1    μm ∼1.1  μm in tissue. We verify spectral imaging capabilities by measuring microsphere backscattering spectra and demonstrate in vivo spatial nanoscale characterization of tissue.

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    20. Oblique scanning laser microscopy for simultaneously volumetric structural and molecular imaging using only one raster scan

      Oblique scanning laser microscopy for simultaneously volumetric structural and molecular imaging using only one raster scan

      Multi-modal three dimensional (3D) optical imaging combining both structural sensitivity and molecular specificity is highly desirable in biomedical research. In this paper, we present a method termed oblique scanning laser microscopy (OSLM) to combine optical coherence tomography (OCT), for simultaneously volumetric structural and molecular imaging with cellular resolution in all three dimensions. Conventional 3D laser scanning fluorescence microscopy requires repeated optical sectioning to create z-stacks in depth. Here, the use of an obliquely scanning laser eliminates the z-stacking process, then allows highly efficient 3D OCT and fluorescence imaging by using only one raster scan. The current setup provides ~3.6 ...

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    21. Biological tissue analysis by inverse spectroscopic optical coherence tomography

      Biological tissue analysis by inverse spectroscopic optical coherence tomography

      A method and system to measure and image the full optical scattering properties by inverse spectroscopic optical coherence tomography (ISOCT) is disclosed. Tissue is modeled as a medium with continuous refractive index (RI) fluctuation and such a fluctuation is described by the RI correlation functions. By measuring optical quantities of tissue (including the scattering power of the OCT spectrum, the reflection albedo .alpha. defined as the ratio of scattering coefficient .mu..sub.s, and the backscattering coefficient .mu..sub.b), the RI correlation function can be inversely deduced and the full set of optical scattering properties can be obtained.

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    22. Feature Of The Week 10/16/2016: Real-time Functional Analysis of Inertial Microfluidic Devices via Spectral Domain Optical Coherence Tomography

      Feature Of The Week 10/16/2016: Real-time Functional Analysis of Inertial Microfluidic Devices via Spectral Domain Optical Coherence Tomography

      Inertial microfluidic devices have recently attracted considerable interest due to their unique capability of high-throughput filtration, separation, and sorting of particles and live cells in a continuous flow manner. However, the underlying mechanism is not fully understood yet, which is due to limited options for real-time three-dimensional (3D) tracking and analysis of particles and live cells in microfluidic channels. Although micro-particle image velocimetry using optical confocal microscopy can be used to resolve the position of microparticles in 3D, it often requires exogenous labels to provide fluorescence contrast which is not always favorable for live cell analysis. To better understand the ...

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    23. Real-time Functional Analysis of Inertial Microfluidic Devices via Spectral Domain Optical Coherence Tomography

      Real-time Functional Analysis of Inertial Microfluidic Devices via Spectral Domain Optical Coherence Tomography

      We report the application of spectral-domain optical coherence tomography (SD-OCT) technology that enables real-time functional analysis of sorting microparticles and cells in an inertial microfluidic device. We demonstrated high-speed, high-resolution acquisition of cross-sectional images at a frame rate of 350 Hz, with a lateral resolution of 3 μm and an axial resolution of 1 μm within the microfluidic channel filled with water. We analyzed the temporal sequence of cross-sectional SD-OCT images to determine the position and diameter of microspheres in a spiral microfluidic channel under various flow rates. We used microspheres with known diameters to validate the sub-micrometer precision of ...

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    24. Detection of extracellular matrix modification in cancer models with inverse spectroscopic optical coherence tomography

      Detection of extracellular matrix modification in cancer models with inverse spectroscopic optical coherence tomography

      In cancer biology, there has been a recent effort to understand tumor formation in the context of the tissue microenvironment. In particular, recent progress has explored the mechanisms behind how changes in the cell-extracellular matrix ensemble influence progression of the disease. The extensive use of in vitro tissue culture models in simulant matrix has proven effective at studying such interactions, but modalities for non-invasively quantifying aspects of these systems are scant. We present the novel application of an imaging technique, Inverse Spectroscopic Optical Coherence Tomography, for the non-destructive measurement of in vitro biological samples during matrix remodeling. Our findings indicate ...

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    1-24 of 46 1 2 »
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