1. Articles from Ringo Ng

    1-7 of 7
    1. Numerical calibration method for a multiple spectrometer-based OCT system

      Numerical calibration method for a multiple spectrometer-based OCT system

      The present paper introduces a numerical calibration method for the easy and practical implementation of multiple spectrometer-based spectral-domain optical coherence tomography (SD-OCT) systems. To address the limitations of the traditional hardware-based spectrometer alignment across more than one spectrometer, we applied a numerical spectral calibration algorithm where the pixels corresponding to the same wavelength in each unit are identified through spatial- and frequency-domain interferometric signatures of a mirror sample. The utility of dual spectrometer-based SD-OCT imaging is demonstrated through in vivo retinal imaging at two different operation modes with high-speed and dual balanced acquisitions, respectively, in which the spectral alignment is ...

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    2. Volumetric directional optical coherence tomography

      Volumetric directional optical coherence tomography

      Photoreceptor loss and resultant thinning of the outer nuclear layer (ONL) is an important pathological feature of retinal degenerations and may serve as a useful imaging biomarker for age-related macular degeneration. However, the demarcation between the ONL and the adjacent Henle’s fiber layer (HFL) is difficult to visualize with standard optical coherence tomography (OCT). A dedicated OCT system that can precisely control and continuously and synchronously update the imaging beam entry points during scanning has not been realized yet. In this paper, we introduce a novel imaging technology, Volumetric Directional OCT (VD-OCT), which can dynamically adjust the incident beam ...

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    3. 105° field of view non-contact handheld swept-source optical coherence tomography

      105° field of view non-contact handheld swept-source optical coherence tomography

      We demonstrate a handheld swept-source optical coherence tomography (OCT) system with a 400 kHz vertical-cavity surface-emitting laser (VCSEL) light source, a non-contact approach, and an unprecedented single shot 105° field of view (FOV). We also implemented a spiral scanning pattern allowing real-time visualization with improved scanning efficiency. To the best of our knowledge, this is the widest FOV achieved in a portable non-contact OCT retinal imaging system to date. Improvements to the FOV may aid the evaluation of retinal diseases such as retinopathy of prematurity, where important vitreoretinal changes often occur in the peripheral retina.

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    4. High-speed and widefield handheld swept-source OCT angiography with a VCSEL light source

      High-speed and widefield handheld swept-source OCT angiography with a VCSEL light source

      Optical coherence tomography (OCT) and OCT angiography (OCTA) enable noninvasive structural and angiographic imaging of the eye. Portable handheld OCT/OCTA systems are required for imaging patients in the supine position. Examples include infants in the neonatal intensive care unit (NICU) and operating room (OR). The speed of image acquisition plays a pivotal role in acquiring high-quality OCT/OCTA images, particularly with the handheld system, since both the operator hand tremor and subject motion can cause significant motion artifacts. In addition, having a large field of view and the ability of real-time data visualization are critical elements in rapid disease ...

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    5. Quantitative multi-contrast in vivo mouse imaging with polarization diversity optical coherence tomography and angiography

      Quantitative multi-contrast in vivo mouse imaging with polarization diversity optical coherence tomography and angiography

      Retinal microvasculature and the retinal pigment epithelium (RPE) play vital roles in maintaining the health and metabolic activity of the eye. Visualization of these retina structures is essential for pre-clinical studies of vision-robbing diseases, such as age-related macular degeneration (AMD). We have developed a quantitative multi-contrast polarization diversity OCT and angiography (QMC-PD-OCTA) system for imaging and visualizing pigment in the RPE using degree of polarization uniformity (DOPU), along with flow in the retinal capillaries using OCT angiography (OCTA). An adaptive DOPU averaging kernel was developed to increase quantifiable values from visual data, and QMC en face images permit simultaneous visualization ...

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    6. Depth-resolved optimization of a real-time sensorless adaptive optics optical coherence tomography

      Depth-resolved optimization of a real-time sensorless adaptive optics optical coherence tomography

      Sensorless adaptive optics optical coherence tomography (AO-OCT) is a technology to image retinal tissue with high resolution by compensating ocular aberrations without wavefront sensors. In this Letter, a fast and robust hill-climbing algorithm is developed to optimize five Zernike modes in AO-OCT with a numerical aperture between that of conventional AO and commercial OCT systems. The merit function is generated in real time using graphics processing unit while axially tracking the retinal layer of interest. A new method is proposed to estimate the largest achievable field of view for which aberrations are corrected uniformly in sensorless AO-OCT.

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    7. Pseudo-real-time retinal layer segmentation for high-resolution adaptive optics optical coherence tomography

      Pseudo-real-time retinal layer segmentation for high-resolution adaptive optics optical coherence tomography

      We present a pseudo-real-time retinal layer segmentation for high-resolution Sensorless Adaptive Optics-Optical Coherence Tomography (SAO-OCT). Our pseudo-real-time segmentation method is based on Dijkstra’s algorithm that uses the intensity of pixels and the vertical gradient of the image to find the minimum cost in a geometric graph formulation within a limited search region. It segments six retinal layer boundaries in an iterative process according to their order of prominence. The segmentation time is strongly correlated to the number of retinal layers to be segmented. Our program permits en face images to be extracted during data acquisition to guide the depth ...

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    1-7 of 7
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  2. Topics in the News

    1. (6 articles) Simon Fraser University
    2. (5 articles) Oregon Health & Science University
    3. (3 articles) Center for Ophthalmic Optics and Lasers
    4. (2 articles) University of British Columbia
    5. (2 articles) National Institutes of Health
    6. (1 articles) University of Tsukuba
    7. (1 articles) University College London
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    Pseudo-real-time retinal layer segmentation for high-resolution adaptive optics optical coherence tomography Depth-resolved optimization of a real-time sensorless adaptive optics optical coherence tomography Quantitative multi-contrast in vivo mouse imaging with polarization diversity optical coherence tomography and angiography High-speed and widefield handheld swept-source OCT angiography with a VCSEL light source 105° field of view non-contact handheld swept-source optical coherence tomography Volumetric directional optical coherence tomography Numerical calibration method for a multiple spectrometer-based OCT system Optical coherence tomography findings in patients with transfusion-dependent β-thalassemia Higher-order regression three-dimensional motion-compensation method for real-time optical coherence tomography volumetric imaging of the cornea Optical coherence tomography image based eye disease detection using deep convolutional neural network Optical Coherence Tomography Biomarkers in Predicting Treatment Outcomes of Diabetic Macular Edema After Dexamethasone Implants Macular and Optic Disc Parameters in Children with Amblyopic and Nonamblyopic Eyes under Optical Coherence Tomography Fundus Images