1. Articles from Wenzhong Liu

    1-17 of 17
    1. Monitoring Acute Stroke in Mouse Model Using Laser Speckle Imaging-Guided Visible-Light Optical Coherence Tomography

      Monitoring Acute Stroke in Mouse Model Using Laser Speckle Imaging-Guided Visible-Light Optical Coherence Tomography

      Objective: Monitoring hemodynamic and vascular changes in the acute stages of mouse stroke models is invaluable in studying ischemic stroke pathophysiology. However, there lacks a tool to simultaneously and dynamically investigate these changes. Methods: We integrated laser speckle imaging (LSI) and visible-light optical coherence tomography (Vis-OCT) to reveal dynamic vascular responses in acute stages in the distal middle cerebral artery occlusion (dMCAO) model in rodents. LSI provides full-field, real-time imaging to guide Vis-OCT imaging and monitor the dynamic cerebral blood flow (CBF). Vis-OCT offers depth-resolved angiography and oxygen saturation (sO 2 ) measurements. Results: Our results showed detailed CBF and vasculature ...

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    2. Spectroscopic Doppler analysis for visible-light optical coherence tomography

      Spectroscopic Doppler analysis for visible-light optical coherence tomography

      Retinal oxygen metabolic rate can be effectively measured by visible-light optical coherence tomography (vis-OCT), which simultaneously quantifies oxygen saturation and blood flow rate in retinal vessels through spectroscopic analysis and Doppler measurement, respectively. Doppler OCT relates phase variation between sequential A-lines to the axial flow velocity of the scattering medium. The detectable phase shift is between − π −π and π π due to its periodicity, which limits the maximum measurable unambiguous velocity without phase unwrapping. Using shorter wavelengths, vis-OCT is more vulnerable to phase ambiguity since flow induced phase variation is linearly related to the center wavenumber of the probing light. We eliminated the ...

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    3. Methodology for Image-driven High-resolution Additive Manufacturing Using Discretized Data Set

      Methodology for Image-driven High-resolution Additive Manufacturing Using Discretized Data Set

      Additive manufacturing of patient-specific biomedical devices from 3D medical scans involves several steps of conversion which can introduce error into the final part. This is particularly critical to the fabrication of minute anatomical features, such as microvasculature. We show a direct conversion of the raw optical coherence tomography (OCT) volumetric data into photomasks in bitmap format, which streamlines the typical process steps used in 3D printing medical scans. OCT scans of rodent retinal microvasculature and projection microstereolithography are used to fabricate a solid vascular replica and a solid volume with hollow embedded microvessels.

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    4. Optical coherence tomography angiography of retinal vascular occlusions produced by imaging-guided laser photocoagulation

      Optical coherence tomography angiography of retinal vascular occlusions produced by imaging-guided laser photocoagulation

      Retinal vascular occlusive diseases represent a major form of vision loss worldwide. Rodent models of these diseases have traditionally relied upon a slit-lamp biomicroscope to help visualize the fundus and subsequently aid delivery of high-power laser shots to a target vessel. Here we describe a multimodal imaging system that can produce, image, and monitor retinal vascular occlusions in rodents. The system combines a spectral-domain optical coherence tomography system for cross-sectional structural imaging and three-dimensional angiography, and a fluorescence scanning laser ophthalmoscope for Rose Bengal monitoring and high-power laser delivery to a target vessel. This multimodal system facilitates the precise production ...

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    5. Colposcopic imaging using visible-light optical coherence tomography

      Colposcopic imaging using visible-light optical coherence tomography

      High-resolution colposcopic optical coherence tomography (OCT) provides key anatomical measures, such as thickness and minor traumatic injury of vaginal epithelium, of the female reproductive tract noninvasively. This information can be helpful in both fundamental investigations in animal models and disease screenings in humans. We present a fiber-based visible-light OCT and two probe designs for colposcopic application. One probe conducts circular scanning using a DC motor, and the other probe is capable of three-dimensional imaging over a 4.6 × 4.6 - mm 2 4.6×4.6-mm2 area using a pair of galvo scanners. Using this colposcopic vis-OCT with both probes ...

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    6. Retinal oximetry in humans using visible-light optical coherence tomography [Invited]

      Retinal oximetry in humans using visible-light optical coherence tomography [Invited]

      We measured hemoglobin oxygen saturation (sO 2 ) in the retinal circulation in healthy humans using visible-light optical coherence tomography (vis-OCT). The measurements showed clear oxygenation differences between central retinal arteries and veins close to the optic nerve head. Spatial variations at different vascular branching levels were also revealed. In addition, we presented theoretical and experimental results to establish that noises in OCT intensity followed Rice distribution. We used this knowledge to retrieve unbiased estimation of true OCT intensity to improve the accuracy of vis-OCT oximetry, which had inherently lower signal-to-nose ratio from human eyes due to safety and comfort limitations ...

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    7. Visible-Light Optical Coherence Tomography Angiography for Monitoring Laser-Induced Choroidal Neovascularization in Mice

      Visible-Light Optical Coherence Tomography Angiography for Monitoring Laser-Induced Choroidal Neovascularization in Mice

      Purpose : This study sought to determine the earliest time-point at which evidence of choroidal neovascularization (CNV) could be detected with visible-light optical coherence tomography angiography (vis-OCTA) in a mouse model of laser-induced CNV. Methods : Visible light-OCTA was used to study laser-induced CNV at different time-points after laser injury to monitor CNV development and measure CNV lesion size. Measurements obtained from vis-OCTA angiograms were compared with histopathologic measurements from isolectin-stained choroidal flatmounts. Results : Choroidal neovascularization area measurements between the vis-OCTA system and isolectin-stained choroidal flatmounts were significantly different in area for days 2 to 4 postlaser injury, and were not significantly ...

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    8. Simultaneous optical coherence tomography angiography and fluorescein angiography in rodents with normal retina and laser-induced choroidal neovascularization

      Simultaneous optical coherence tomography angiography and fluorescein angiography in rodents with normal retina and laser-induced choroidal neovascularization

      Fluorescein angiography (FA) is the current clinical imaging standard for vascular related retinal diseases such as macular degeneration and diabetic retinopathy. However, FA is considered invasive and can provide only two-dimensional imaging. In comparison, optical coherence tomography angiography (OCTA) is noninvasive and can generate three-dimensional imaging; investigations of OCTA already demonstrated great promise in retinal vascular imaging. Yet, to further develop and apply OCTA, strengths and weaknesses between OCTA and FA need to be thoroughly compared. To avoid complications in image registration, an ideal comparison requires co-registered and simultaneous imaging by both FA and OCTA. In this Letter, we developed ...

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    9. Devices, Methods, And Systems Of Functional Optical Coherence Tomography

      Devices, Methods, And Systems Of Functional Optical Coherence Tomography

      The present disclosure provides systems and methods for the determining a rate of change of one or more analyte concentrations in a target using non invasive non contact imaging techniques such as OCT. Generally, OCT data is acquired and optical information is extracted from OCT scans to quantitatively determine both a flow rate of fluid in the target and a concentration of one or more analytes. Both calculations can provide a means to determine a change in rate of an analyte over time.

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    10. Visible light optical coherence tomography measures retinal oxygen metabolic response to systemic oxygenation

      Visible light optical coherence tomography measures retinal oxygen metabolic response to systemic oxygenation

      The lack of capability to quantify oxygen metabolism noninvasively impedes both fundamental investigation and clinical diagnosis of a wide spectrum of diseases including all the major blinding diseases such as age-related macular degeneration, diabetic retinopathy, and glaucoma. Using visible light optical coherence tomography (vis-OCT), we demonstrated accurate and robust measurement of retinal oxygen metabolic rate (rMRO 2 ) noninvasively in rat eyes. We continuously monitored the regulatory response of oxygen consumption to a progressive hypoxic challenge. We found that both oxygen delivery, and rMRO 2 increased from the highly regulated retinal circulation (RC) under hypoxia, by 0.28 ± 0.08 µL ...

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    11. Measuring retinal blood flow in rats using Doppler optical coherence tomography without knowing eyeball axial length

      Measuring retinal blood flow in rats using Doppler optical coherence tomography without knowing eyeball axial length

      Purpose: Doppler optical coherence tomography (OCT) is widely used for measuring retinal blood flow. Existing Doppler OCT methods require the eyeball axial length, in which empirical values are usually used. However, variations in the axial length can create a bias unaccounted for in the retinal blood flow measurement. The authors plan to develop a Doppler OCT method that can measure the total retinal blood flow rate without requiring the eyeball axial length. Methods: The authors measured the retinal blood flow rate using a dual-ring scanning protocol. The small and large scanning rings entered the eye at different incident angles (small ...

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    12. Monte Carlo Investigation of Optical Coherence Tomography Retinal Oximetry

      Monte Carlo Investigation of Optical Coherence Tomography Retinal Oximetry

      Optical coherence tomography (OCT) oximetry explores the possibility to measure retinal hemoglobin oxygen saturation level (sO2). We investigated the accuracy of OCT retinal oximetry using Monte Carlo simulation in a commonlyused four-layer retinal model. After we determined the appropriate number of simulated photon packets, we studied the effects of blood vessel diameter, signal sampling position, physiological sO2 level, and the blood packing factor on the accuracy of sO2 estimation in OCT retinal oximetry . The simulation results showed that a packing factor between 0.2 and 0.4 yields a reasonably accurate estimation of sO2 within a 5% error tolerance, which ...

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    13. Measuring absolute microvascular blood flow in cortex using visible-light optical coherence tomography

      Measuring absolute microvascular blood flow in cortex using visible-light optical coherence tomography

      Understanding regulating mechanisms of cerebral blood flow (CBF) is important for clinical diagnosis and biomedical researches. We demonstrate here that phase sensitive Doppler optical coherence tomography is able to measure absolute CBF in mouse visual cortex in vivo when working in the visible-light spectral range. Both temporal and spatial profile of regional CBF variations can be resolved. We further assessed the accuracy of our method by in vitro experiments, which showed great consistency between the measured values and controlled ones. Finally, we enhanced the contrast of blood vessels to generate an angiogram showing great details of mouse cortical microvasculature.

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    14. A combined method to quantify the retinal metabolic rate of oxygen using photoacoustic ophthalmoscopy and optical coherence tomography

      A combined method to quantify the retinal metabolic rate of oxygen using photoacoustic ophthalmoscopy and optical coherence tomography

      Quantitatively determining physiological parameters at a microscopic level in the retina furthers the understanding of the molecular pathways of blinding diseases, such as diabetic retinopathy and glaucoma. An essential parameter, which has yet to be quantified noninvasively, is the retinal oxygen metabolic rate (rMRO 2 ). Quantifying rMRO 2 is challenging because two parameters, the blood flow rate and hemoglobin oxygen saturation (sO 2 ), must be measured together. We combined photoacoustic ophthalmoscopy (PAOM) with spectral domain-optical coherence tomography (SD-OCT) to tackle this challenge, in which PAOM measured the sO 2 and SD-OCT mapped the blood flow rate. We tested the integrated ...

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    15. Visible-light optical coherence tomography for retinal oximetry

      Visible-light optical coherence tomography for retinal oximetry

      We applied a visible-light spectroscopic optical coherence tomography (vis-OCT) for in vivo retinal oximetry. To extract hemoglobin oxygen saturation (sO2) in individual retinal vessels, we established a comprehensive analytical model to describe optical absorption, optical scattering, and blood cell packing factor in the whole blood and fit the acquired vis-OCT signals from the bottom of each imaged vessel. We found that averaged sO2 values in arterial and venous bloods were 95% and 72%, respectively.

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    16. Combining light and sound for retinal imaging

      Combining light and sound for retinal imaging

      Photoacoustic ophthalmoscopy provides exceptional contrast when visualizing the retina, assisting in the early diagnosis of some eye diseases. The diagnosis, treatment, and prognosis of eye diseases have greatly benefited from innovation in modern ophthalmic imaging technologies. Photoacoustic ophthalmoscopy (PAOM) is a 3D imaging method that allows non-invasive visualization of the back of the eye through angiography (where an x-ray-based technique is used to create an image). But unlike an angiogram, the image is made using no exogenous contrast agents. 1–3 PAOM instead uses the endogenous light-absorption contrast from hemoglobin and melanin to generate images of the retina's vascular ...

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    17. Automatic retinal vessel segmentation based on active contours method in Doppler spectral-domain optical coherence tomography

      Automatic retinal vessel segmentation based on active contours method in Doppler spectral-domain optical coherence tomography

      We achieved fast and automatic retinal vessel segmentation by employing the active contours method in Doppler spectral-domain optical coherence tomography (SD-OCT). In a typical OCT B-scan image, we first extracted the phase variations between adjacent A-lines and removed bulk motion. Then we set the initial contour as the boundary of the whole image and iterated until all of the segmented vessel contours became stabilized. Using a typical office computer, the whole segmentation took no more than 50 s, making real-time retinal vessel segmentation possible. We tested the active contours method segmentation in both controlled phantom and in vivo rodent eye ...

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    1-17 of 17
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  2. Topics in the News

    1. (17 articles) Northwestern University
    2. (16 articles) Hao F. Zhang
    3. (10 articles) Ji Yi
    4. (4 articles) Vadim Backman
    5. (3 articles) Shuliang Jiao
    6. (2 articles) University of Wisconsin
    7. (2 articles) Cheng Sun
    8. (1 articles) Harbin Medical University
    9. (1 articles) University of Miami
    10. (1 articles) Opticent Health
    11. (1 articles) Jikei University School of Medicine
    12. (1 articles) Macquarie University
    13. (1 articles) Medical University of Vienna
    14. (1 articles) University of Florence
    15. (1 articles) National Institutes of Health
    16. (1 articles) Beth Israel Deaconess Medical Center
    17. (1 articles) Giacomo Savini
    18. (1 articles) Bernhard Baumann
    19. (1 articles) Antonia Lichtenegger
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    Automatic retinal vessel segmentation based on active contours method in Doppler spectral-domain optical coherence tomography Combining light and sound for retinal imaging Visible-light optical coherence tomography for retinal oximetry A combined method to quantify the retinal metabolic rate of oxygen using photoacoustic ophthalmoscopy and optical coherence tomography Measuring absolute microvascular blood flow in cortex using visible-light optical coherence tomography Monte Carlo Investigation of Optical Coherence Tomography Retinal Oximetry Devices, Methods, And Systems Of Functional Optical Coherence Tomography Colposcopic imaging using visible-light optical coherence tomography Optical coherence tomography angiography of retinal vascular occlusions produced by imaging-guided laser photocoagulation Spectroscopic Doppler analysis for visible-light optical coherence tomography Heterogeneity of Neointimal Healing Following Biodegradable-polymer Drug-Eluting Coronary Stent Implantation Swept-source and multimodal OCT technologies offer clinical advantages