1. Articles from Chenyi Liu

    1-6 of 6
    1. Noise-compensated Homotopic Non-local Regularized Reconstruction for Rapid Retinal Optical Coherence Tomography Image Acquisitions

      Noise-compensated Homotopic Non-local Regularized Reconstruction for Rapid Retinal Optical Coherence Tomography Image Acquisitions

      Background Optical coherence tomography (OCT) is a minimally invasive imaging technique, which utilizes the spatial and temporal coherence properties of optical waves backscattered from biological material. Recent advances in tunable lasers and infrared camera technologies have enabled an increase in the OCT imaging speed by a factor of more than 100, which is important for retinal imaging where we wish to study fast physiological processes in the biological tissue. However, the high scanning rate causes proportional decrease of the detector exposure time, resulting in a reduction of the system signal-to-noise ratio (SNR). One approach to improving the image quality of ...

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    2. Automatic tracking of pupillary dynamics from in vivo functional optical coherence tomography images

      Automatic tracking of pupillary dynamics from in vivo functional optical coherence tomography images

      A major challenge currently faced in measuring visually evoked optical changes in different retinal layers using in vivo and non-invasive functional optical coherence tomography (fOCT) is the need for pupillary dilation drugs to enable reliable measurement of the retinal functional responses. However, there are situations where the use of pupillary dilation drugs is not suitable in both clinical and animal ophthalmic research situations. To overcome this challenge, we propose a new approach to tracking visually evoked pupillary dynamics, based on the use of a fast scanning fOCT system and a novel computerised framework, which can then be used to isolate ...

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    3. Energy-guided learning approach to compressive FD-OCT

      Energy-guided learning approach to compressive FD-OCT

      High quality, large size volumetric imaging of biological tissue with optical coherence tomography (OCT) requires large number and high density of scans, which results in large data acquisition volume. This may lead to corruption of the data with motion artifacts related to natural motion of biological tissue, and could potentially cause conflicts with the maximum permissible exposure of biological tissue to optical radiation. Therefore, OCT can benefit greatly from different approaches to sparse or compressive sampling of the data where the signal is recovered from its sub-Nyquist measurements. In this paper, a new energy-guided compressive sensing approach is proposed for ...

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    4. Stimulus-Specific Pupil Dynamics Measured in Birds (Gallus gallus domesticus) In Vivo with Ultrahigh Resolution Optical Coherence Tomography

      Stimulus-Specific Pupil Dynamics Measured in Birds (Gallus gallus domesticus) In Vivo with Ultrahigh Resolution Optical Coherence Tomography
      Purpose. To demonstrate the ability of high speed, ultrahigh-resolution optical coherence tomography (UHR-OCT) to measure and characterize in vivo visual stimulus-specific pupil dynamics in birds. Methods. Ten two-week old White Leghorn ( Gallus gallus domesticus ) chickens were imaged in this study. The chickens were dark-adapted for 1 hour and anesthetized with 2% isoflurane prior to the imaging procedure. Blue, green, and red single flash visual stimuli of 7 ms duration were used to evoke pupillary responses. UHR-OCT cross-sectional images of the pupil were acquired prior, during, and for several seconds after the visual stimuli onset. Images were processed with a novel ...
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    5. Stimulus Specific Pupil Dynamics Measured in Birds (Gallus Gallus Domesticus) in vivo with Ultrahigh Resolution Optical Coherence Tomography

      Stimulus Specific Pupil Dynamics Measured in Birds (Gallus Gallus Domesticus) in vivo with Ultrahigh Resolution Optical Coherence Tomography

      Purpose:To demonstrate the ability of high speed, ultra-high resolution optical coherence tomography (UHR-OCT) to measure and characterize in vivo visual stimulus specific pupil dynamics in birds. Methods:Ten two-week old White Leghorn (Gallus gallus domesticus) chickens were imaged in this study. The chickens were dark adapted for one hour and anesthetized with 2% isoflurane prior to the imaging procedure. Blue, green, and red single flash visual stimuli of 7ms duration were used to evoke pupillary responses. UHR-OCT cross-sectional images of the pupil were acquired prior, during and for several seconds after the visual stimuli onset. Images were processed with ...

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    6. Homotopic, non-local sparse reconstruction of optical coherence tomography imagery

      Homotopic, non-local sparse reconstruction of optical coherence tomography imagery

      The resolution in optical coherence tomography imaging is an important parameter which determines the size of the smallest features that can be visualized. Sparse sampling approaches have shown considerable promise in producing high resolution OCT images with fewer camera pixels, reducing both the cost and the complexity of an imaging system. In this paper, we propose a non-local approach to the reconstruction of high resolution OCT images from sparsely sampled measurements. An iterative strategy is introduced for minimizing a homotopic, non-local regularized functional in the spatial domain, subject to data fidelity constraints in the k-space domain. The novel algorithm was ...

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    1-6 of 6
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  2. Topics in the News

    1. (6 articles) University of Waterloo
    2. (6 articles) Kostadinka K. Bizheva
    3. (2 articles) Sepideh Hariri
    4. (2 articles) Alireza A. Moayed
    5. (1 articles) Sun Yat-Sen University
    6. (1 articles) National Institutes of Health
    7. (1 articles) University of Illinois at Urbana-Champaign
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    Homotopic, non-local sparse reconstruction of optical coherence tomography imagery Stimulus Specific Pupil Dynamics Measured in Birds (Gallus Gallus Domesticus) in vivo with Ultrahigh Resolution Optical Coherence Tomography Stimulus-Specific Pupil Dynamics Measured in Birds (Gallus gallus domesticus) In Vivo with Ultrahigh Resolution Optical Coherence Tomography Energy-guided learning approach to compressive FD-OCT Automatic tracking of pupillary dynamics from in vivo functional optical coherence tomography images Noise-compensated Homotopic Non-local Regularized Reconstruction for Rapid Retinal Optical Coherence Tomography Image Acquisitions Optical coherence tomography angiography in glaucoma Handheld optical coherence tomography for clinical assessment of dental plaque and gingiva Characterisation of macular superficial vessel density alteration in preclinical ethambutol-induced optic neuropathy using optical coherence tomography angiography Three-dimensional spatial reconstruction of coronary arteries based on fusion of intravascular optical coherence tomography and coronary angiography Dynamic-range compression and contrast enhancement in swept-source optical coherence tomography systems with a frequency gain compensation amplifier Healing and early stent coverage after ultrathin strut biodegradable polymer-coated sirolimus-eluting stent implantation: SiBi optical coherence tomography study