1. Articles from Hao F. Zhang

    1-24 of 50 1 2 »
    1. Designing visible-light optical coherence tomography towards clinics

      Designing visible-light optical coherence tomography towards clinics

      Background: The capabilities of visible-light optical coherence tomography (vis-OCT) in noninvasive anatomical and functional retinal imaging have been demonstrated by multiple groups in both rodents and healthy human subjects. Translating laboratory prototypes to an integrated clinical-environment-friendly system is required to explore the full potential of vis-OCT in disease management. Methods: We developed and optimized a portable vis-OCT system for human retinal imaging in clinical settings. We acquired raster- and circular-scan images from both healthy and diseased human eyes. Results: The new vis-OCT provided high-quality retinal images of both subjects without any known eye diseases and patients with various retinal diseases ...

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    2. Product Development Engineer Opening at Opticent Health

      Product Development Engineer Opening at Opticent Health

      Opticent, Inc. (Opticent Health – www.opticenthealth.com) , established in 2015, is a fast growing medical device start-up company commercializing visible-light optical coherence tomography (vis-OCT), a novel imaging modality for a variety of applications, including advanced ophthalmic diagnostics. First developed at Northwestern University, Opticent Health’s core technologies have been embraced by leading researchers in clinical and pre-clinical ophthalmic investigations, which has fueled rapid commercial development of vis-OCT products. Opticent Health is located in Evanston IL, part of the greater Chicago metropolitan area. The company’s management team, with guidance from its medical and technical advisory board, is expanding its engineering ...

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    3. Product Development Engineer Opening at Opticent Health

      Product Development Engineer Opening at Opticent Health

      Opticent, Inc. , established in 2015, is a fast growing medical device start-up company commercializing visible-light optical coherence tomography (vis-OCT), a novel imaging modality for a variety of applications, including advanced ophthalmic diagnostics. First developed at Northwestern University, Opticent Health’s core technologies have been embraced by leading researchers in clinical ophthalmic research which has fueled rapid commercial development of vis-OCT products. Opticent Health is located in Evanston IL, part of the greater Chicago metropolitan area. The company’s management team, with guidance from its medical and technical advisory board, is expanding its engineering staff for product development and seeks highly ...

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    4. Product Development Engineering Opening at Opticent Health.

      Product Development Engineering Opening at Opticent Health.

      Opticent, Inc. ( Opticent Health ) is a start-up company commercializing an in-house developed patent portfolio related to visible-light optical coherence tomography (OCT) targeting the ophthalmic market. Opticent Health’s core technologies were initially developed at Northwestern University. Since its founding, Opticent Health has experienced rapid market adoption of its OCT instruments and rapid commercial expansion. Opticent Health is located in Evanston IL, part of the greater Chicago metropolitan area. The company’s management team, with guidance from its prominent advisory board, is expanding its engineering staff and seeks highly qualified personnel for the following position: Product Development Engineer (software focus) Qualifications ...

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    5. 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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    6. Visible-light optical coherence tomography oximetry based on circumpapillary scan and graph-search segmentation

      Visible-light optical coherence tomography oximetry based on circumpapillary scan and graph-search segmentation

      Visible-light optical coherence tomography (vis-OCT) enables retinal oximetry by measuring the oxygen saturation of hemoglobin (sO 2 ) from within individual retinal blood vessels. The sO 2 calculation requires reliable estimation of the true spectrum of backscattered light from the posterior vessel wall. Unfortunately, subject motion and image noise make averaging from multiple A-lines at the same depth position challenging, and lead to inaccurate sO 2 estimation. In this study, we developed an algorithm to reliably extract the backscattered light’s spectrum. We used circumpapillary scanning to sample the vessels repeatedly at the same location. A combination of cross-correlation and graph-search ...

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    7. Visible-light optical coherence tomography: a review

      Visible-light optical coherence tomography: a review

      Visible-light optical coherence tomography (vis-OCT) is an emerging imaging modality, providing new capabilities in both anatomical and functional imaging of biological tissue. It relies on visible light illumination, whereas most commercial and investigational OCTs use near-infrared light. As a result, vis-OCT requires different considerations in engineering design and implementation but brings unique potential benefits to both fundamental research and clinical care of several diseases. Here, we intend to provide a summary of the development of vis-OCT and its demonstrated applications. We also provide perspectives on future technology improvement and applications.

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    8. 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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    9. Two Engineering Openings at Startup Company Opticent Health

      Two Engineering Openings at Startup Company Opticent Health

      Opticent, Inc. (Opticent Health – www.opticenthealth.com) is a start-up company commercializing an in-house developed patent portfolio related to visible-light optical coherence tomography (OCT) targeting the ophthalmic market. Opticent Health’s core technologies were developed at Northwestern University. Since its founding, Opticent Health has experienced rapid market adoption of its OCT instruments and rapid commercial expansion. Opticent Health is located in Evanston IL, part of the greater Chicago metropolitan area. The company’s management team, with guidance from its prominent advisory board, is expanding its engineering staff and seeks highly qualified personnel for the following two positions: 1. Ph.D ...

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    10. 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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    11. 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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    12. 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. Example methods and systems of the disclosure may be used in assessing metabolism of a tissue, where ...

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    13. 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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    14. 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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    15. 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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    16. Imaging hemodynamic response after ischemic stroke in mouse cortex using visible-light optical coherence tomography

      Imaging hemodynamic response after ischemic stroke in mouse cortex using visible-light optical coherence tomography

      Visible-light optical coherence tomography (Vis-OCT) is an emerging technology that can image hemodynamic response in microvasculature. Vis-OCT can retrieve blood oxygen saturation (sO 2 ) mapping using intrinsic optical absorption contrast while providing high-resolution anatomical vascular structures at the same time. To improve the accuracy of Vis-OCT oximetry on vessels embedded in highly scattering medium, i.e., brain cortex, we developed and formulated a novel dual-depth sampling and normalization strategy that allowed us to minimize the detrimental effect of ubiquitous tissue scattering. We applied our newly developed approach to monitor the hemodynamic response in mouse cortex after focal photothrombosis. We observed ...

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    17. Postdoctoral Fellows Openings at Northwestern University

      Postdoctoral Fellows Openings at Northwestern University

      Functional Optical Imaging lab (FOIL) in the Department of Biomedical Engineering at Northwestern University develops optical imaging and sensing technologies for biomedical applications, including ophthalmology, vision science, neuroscience, HIV, and cancers. We are looking for two new postdoctoral fellows to join our extremely friendly, vibrant, productive, and collaborative group to develop novel optical microscopy technologies for ophthalmology and single-molecule imaging. We especially encourage applicants with extensive instrumentation and signal processing experiences in optical coherence tomography, ultra-fast optics, and super-resolution optical imaging. Experiences with small animal imaging, human retinal imaging, or cell culture and staining are also desired. The successful candidate ...

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    18. 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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    19. Dual-band optical coherence tomography using a single supercontinuum laser source

      Dual-band optical coherence tomography using a single supercontinuum laser source

      We developed a simultaneous visible-light (Vis) and near-infrared (NIR) dual-band optical coherence tomography (OCT) system using a single supercontinuum laser source. The goal was to benchmark our newly developed Vis-OCT against the well-developed NIR-OCT. The Vis-OCT subsystem operated at 91 nm full-width-at-half-maximum (FWHM) bandwidth centered at 566 nm; the NIR-OCT subsystem operated at 93 nm FWHM bandwidth centered at 841 nm. The axial resolutions were 1.8 and 4.4    μ m 4.4  μm in air for the Vis- and NIR-OCT subsystems, respectively. We compared the respective performances, including anatomical imaging, angiography, absolute retinal blood flow measurements, and spectroscopic analysis ...

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    20. Single all-fiber-based nanosecond-pulsed supercontinuum source for multispectral photoacoustic microscopy and optical coherence tomography

      Single all-fiber-based nanosecond-pulsed supercontinuum source for multispectral photoacoustic microscopy and optical coherence tomography

      We report the usefulness of a single all-fiber-based supercontinuum (SC) source for combined photoacoustic microscopy (PAM) and optical coherence tomography (OCT). The SC light is generated by a tapered photonic crystal fiber pumped by a nanosecond pulsed master oscillator power amplifier at 1064 nm. The spectrum is split into a shorter wavelength band (500–800 nm) for single/multi-spectral PAM and a longer wavelength band (800–900 nm) band for OCT. In vivo mouse ear imaging was achieved with an integrated dual-modality system. We further demonstrated its potential for spectroscopic photoacoustic imaging by doing multispectral measurements on retinal pigment epithelium ...

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    21. 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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    22. 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.

      Read Full Article
    23. 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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    24. Human retinal imaging using visible-light optical coherence tomography guided by scanning laser ophthalmoscopy

      Human retinal imaging using visible-light optical coherence tomography guided by scanning laser ophthalmoscopy

      We achieved human retinal imaging using visible-light optical coherence tomography (vis-OCT) guided by an integrated scanning laser ophthalmoscopy (SLO). We adapted a spectral domain OCT configuration and used a supercontinuum laser as the illumating source. The center wavelength was 564 nm and the bandwidth was 115 nm, which provided a 0.97 µm axial resolution measured in air. We characterized the sensitivity to be 86 dB with 226 µW incidence power on the pupil. We also integrated an SLO that shared the same optical path of the vis-OCT sample arm for alignment purposes. We demonstrated the retinal imaging from both ...

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    1-24 of 50 1 2 »
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  2. Topics in the News

    1. (48 articles) Hao F. Zhang
    2. (46 articles) Northwestern University
    3. (19 articles) Ji Yi
    4. (16 articles) Shuliang Jiao
    5. (10 articles) University of Southern California
    6. (7 articles) Vadim Backman
    7. (6 articles) University of Wisconsin
    8. (6 articles) Carmen A. Puliafito
    9. (6 articles) Opticent Health
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