1. Articles from Yifan Jian

    1-25 of 25
    1. Directional optical coherence tomography reveals melanin concentration-dependent scattering properties of retinal pigment epithelium

      Directional optical coherence tomography reveals melanin concentration-dependent scattering properties of retinal pigment epithelium

      Optical coherence tomography (OCT) is a powerful tool in ophthalmology that provides in vivo morphology of the retinal layers and their light scattering properties. The directional (angular) reflectivity of the retinal layers was investigated with focus on the scattering from retinal pigment epithelium (RPE). The directional scattering of the RPE was studied in three mice strains with three distinct melanin concentrations: albino (BALB/c), agouti (129S1/SvlmJ), and strongly pigmented (C57BL/6J). The backscattering signal strength was measured with a directional OCT system in which the pupil entry position of the narrow OCT beam can be varied across the dilated ...

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    2. Multi-scale and -contrast sensorless adaptive optics optical coherence tomography

      Multi-scale and -contrast sensorless adaptive optics optical coherence tomography

      Background: The roles of the retinal microvasculature and the retinal pigment epithelium (RPE) in maintaining the health and metabolic activity of the retina lend great clinical value to their high-resolution visualization. Methods: By integrating polarization diversity detection (PDD) into multi-scale and -contrast sensorless adaptive optics optical coherence tomography (MSC-SAO-OCT), we have developed a novel multi-contrast SAO OCT system for imaging pigment in the RPE as well as flow in the retinal capillaries using OCT angiography (OCTA). Aberration correction was performed based on the image quality using transmissive deformable optical elements. Results: MSC-SAO-OCTA imaging was performed at multiple fields-of-view (FOVs) with ...

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    3. System and method for dynamic focus control

      System and method for dynamic focus control

      En face views of OCT volumes provide important and complementing visualizations of the retina and optic nerve head investigating biomarkers of diseases affecting the retina. We demonstrate the combination of real time processing of OCT volumetric data for axial tracking. In combination with a Controllable Optical Element (COE), this invention demonstrates acquisition, real time tracking, automated focus on depth resolved en face layers extracted from a volume, and focus stacked OCT volumes with high resolution throughout an extended depth range.

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    4. Aperture phase modulation with adaptive optics

      Aperture phase modulation with adaptive optics

      Speckle is an inevitable consequence of the use of coherent light in imaging and acts as noise that corrupts image formation in most applications. Optical coherence tomographic imaging, as a technique employing coherence time gating, suffers from speckle. We present here a novel method of suppressing speckle noise intrinsically compatible with adaptive optics (AO) for confocal coherent imaging: modulation of the phase in the system pupil aperture with a segmented deformable mirror (DM) to introduce minor perturbations in the point spread function. This approach creates uncorrelated speckle patterns in a series of images, enabling averaging to suppress speckle noise while ...

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    5. Visible light sensorless adaptive optics for retinal structure and fluorescence imaging

      Visible light sensorless adaptive optics for retinal structure and fluorescence imaging

      Optical coherence tomography (OCT) has emerged as a powerful imaging instrument and technology in biomedicine. OCT imaging is predominantly performed using wavelengths in the near infrared; however, visible light (VIS) has been recently employed in OCT systems with encouraging results for high-resolution retinal imaging. Using a broadband supercontinuum VIS source, we present a sensorless adaptive optics (SAO) multimodal imaging system driven by VIS-OCT for volumetric retinal structural imaging, followed by the acquisition of fluorescence emission. The coherence-gated, depth-resolved VIS-OCT images used for image-guided SAO aberration correction enable high-resolution structural and fluorescence imaging.

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    6. Aperture Phase Modulation with Adaptive Optics: A Novel Approach for Speckle Reduction and Structure Extraction in Optical Coherence Tomography

      Aperture Phase Modulation with Adaptive Optics: A Novel Approach for Speckle Reduction and Structure Extraction in Optical Coherence Tomography

      Speckle is an inevitable consequence of the use of coherent light in optical coherence tomography (OCT), and often acts as noise that obscures micro-structures of biological tissue. We here present a novel method of suppressing speckle noise intrinsically compatible with adaptive optics (AO) in OCT system: by modulating the phase inside the imaging system pupil aperture with a segmented deformable mirror, thus producing minor perturbations in the point spread function (PSF) to create un-correlated speckle pattern between B-scans, and further averaging to wash out the speckle but maintain the structures. It is a well-controlled and universal method which can efficiently ...

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    7. Effective bidirectional scanning pattern for optical coherence tomography angiography

      Effective bidirectional scanning pattern for optical coherence tomography angiography

      We demonstrate the utility of a novel scanning method for optical coherence tomography angiography (OCTA). Although raster scanning is commonly used for OCTA imaging, a bidirectional approach would lessen the distortion caused by galvanometer-based scanners as sources continue to increase sweep rates. As shown, a unidirectional raster scan approach has a lower effective scanning time than bidirectional approaches; however, a strictly bidirectional approach causes contrast variation along the B-scan direction due to the non-uniform time interval between B-scans. Therefore, a stepped bidirectional approach is introduced and successfully applied to retinal imaging in normal controls and in a pathological subject with ...

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    8. Investigation of the effect of directional (off-axis) illumination on the reflectivity of retina layers in mice using swept-source optical coherence tomography

      Investigation of the effect of directional (off-axis) illumination on the reflectivity of retina layers in mice using swept-source optical coherence tomography

      Changes in visibility of the Henle fiber layer and photoreceptor bands of the human retina with illumination directionality have been reported in OCT clinical imaging. These are a direct consequence of the changes in back scattering due to fibrous tissue orientation and to waveguiding properties of the photoreceptors respectively. Here we report the preliminary results of a study on the effects of retinal images acquired with OCT of illumination directionality in the mouse retina. The quantitative assessment of the reflectivity of retinal layers of a BALB/c and WT pigmented mice was performed in-vivo using a swept-source optical coherence tomography ...

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    9. Multiscale sensorless adaptive optics OCT angiography system for in vivo human retinal imaging

      Multiscale sensorless adaptive optics OCT angiography system for in vivo human retinal imaging

      We present a multiscale sensorless adaptive optics (SAO) OCT system capable of imaging retinal structure and vasculature with various fields-of-view (FOV) and resolutions. Using a single deformable mirror and exploiting the polarization properties of light, the SAO-OCT-A was implemented in a compact and easy to operate system. With the ability to adjust the beam diameter at the pupil, retinal imaging was demonstrated at two different numerical apertures with the same system. The general morphological structure and retinal vasculature could be observed with a few tens of micrometer-scale lateral resolution with conventional OCT and OCT-A scanning protocols with a 1.7-mm-diameter ...

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    10. Strip-based registration of serially acquired optical coherence tomography angiography

      Strip-based registration of serially acquired optical coherence tomography angiography

      The visibility of retinal microvasculature in optical coherence tomography angiography (OCT-A) images is negatively affected by the small dimension of the capillaries, pulsatile blood flow, and motion artifacts. Serial acquisition and time-averaging of multiple OCT-A images can enhance the definition of the capillaries and result in repeatable and consistent visualization. We demonstrate an automated method for registration and averaging of serially acquired OCT-A images. Ten OCT-A volumes from six normal control subjects were acquired using our prototype 1060-nm swept source OCT system. The volumes were divided into microsaccade-free en face angiogram strips, which were affine registered using scale-invariant feature transform ...

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    11. Lens-based wavefront sensorless adaptive optics swept source OCT

      Lens-based wavefront sensorless adaptive optics swept source OCT

      Optical coherence tomography (OCT) has revolutionized modern ophthalmology, providing depth resolved images of the retinal layers in a system that is suited to a clinical environment. Although the axial resolution of OCT system, which is a function of the light source bandwidth, is sufficient to resolve retinal features at a micrometer scale, the lateral resolution is dependent on the delivery optics and is limited by ocular aberrations. Through the combination of wavefront sensorless adaptive optics and the use of dual deformable transmissive optical elements, we present a compact lens-based OCT system at an imaging wavelength of 1060 nm for high ...

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    12. Retinal optical coherence tomography at 1  μm with dynamic focus control and axial motion tracking

      Retinal optical coherence tomography at 1  μm with dynamic focus control and axial motion tracking

      High-resolution optical coherence tomography (OCT) retinal imaging is important to noninvasively visualize the various retinal structures to aid in better understanding of the pathogenesis of vision-robbing diseases. However, conventional OCT systems have a trade-off between lateral resolution and depth-of-focus. In this report, we present the development of a focus-stacking OCT system with automatic focus optimization for high-resolution, extended-focal-range clinical retinal imaging by incorporating a variable-focus liquid lens into the sample arm optics. Retinal layer tracking and selection was performed using a graphics processing unit accelerated processing platform for focus optimization, providing real-time layer-specific en face visualization. After optimization, multiple volumes ...

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    13. In vivo wide-field multispectral scanning laser ophthalmoscopy–optical coherence tomography mouse retinal imager: longitudinal imaging of ganglion cells, microglia, and Müller glia, and mapping of the mouse retinal and choroidal vasculature

      In vivo wide-field multispectral scanning laser ophthalmoscopy–optical coherence tomography mouse retinal imager: longitudinal imaging of ganglion cells, microglia, and Müller glia, and mapping of the mouse retinal and choroidal vasculature

      Scanning laser ophthalmoscopy (SLO) and optical coherence tomography (OCT) provide complementary views of the retina, with the former collecting fluorescence data with good lateral but relatively low-axial resolution, and the latter collecting label-free backscattering data with comparable lateral but much higher axial resolution. To take maximal advantage of the information of both modalities in mouse retinal imaging, we have constructed a compact, four-channel, wide-field ( ∼ 50     deg ) system that simultaneously acquires and automatically coregisters three channels of confocal SLO and Fourier domain OCT data. The scanner control system allows “zoomed” imaging of a region of interest identified in a wide-field image ...

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    14. En face projection imaging of the human choroidal layers with tracking SLO and swept source OCT angiography methods

      En face projection imaging of the human choroidal layers with tracking SLO and swept source OCT angiography methods

      We tested and compared the capability of multiple optical coherence tomography (OCT) angiography methods: phase variance, amplitude decorrelation and speckle variance, with application of the split spectrum technique, to image the choroiretinal complex of the human eye. To test the possibility of OCT imaging stability improvement we utilized a real-time tracking scanning laser ophthalmoscopy (TSLO) system combined with a swept source OCT setup. In addition, we implemented a post- processing volume averaging method for improved angiographic image quality and reduction of motion artifacts. The OCT system operated at the central wavelength of 1040nm to enable sufficient depth penetration into the ...

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    15. Enhancing the visualization of human retina vascular networks by Graphics Processing Unit accelerated speckle variance OCT and graph cut retinal layer segmentation

      Enhancing the visualization of human retina vascular networks by Graphics Processing Unit accelerated speckle variance OCT and graph cut retinal layer segmentation

      We present a Graph Cut based image segmentation that was implemented on a Graphics Processing Unit for acceleration of processing retinal images acquired with OCT. We applied this work to generate a retinal thickness map, and for retinal layer segmentation to enhance the visualization of vasculature networks from distinct retinal capillary beds during acquisition using speckle variance OCT.

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    16. Progress on developing wavefront sensorless adaptive optics optical coherence tomography for in vivo retinal imaging in mice

      Progress on developing wavefront sensorless adaptive optics optical coherence tomography for in vivo retinal imaging in mice

      We present a new design for a wavefront sensorless adaptive optics (WS-AO) Fourier domain optical coherence tomography (FD-OCT) system for small animal retinal imaging in vivo. Without the optical complications necessary for inclusion of a wavefront sensor in the optical system, this version of WS-AO FD-OCT system has a simplified optical design, including elimination of long focal length scanning optics and optical conjugation of vertical and horizontal scanners. This modification provides a modular large Field of View for retinal screening (25 degree visual angle), while also allowing a “zoom” capability for allocating all the scanning resources to a smaller region ...

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    17. Multispectral scanning laser ophthalmoscopy combined with optical coherence tomography for simultaneous in vivo mouse retinal imaging

      Multispectral scanning laser ophthalmoscopy combined with optical coherence tomography for simultaneous in vivo mouse retinal imaging

      A compact, non-invasive multi-modal system has been developed for in vivo mouse retina imaging. It is configured for simultaneously detecting green and red fluorescent protein signals with scanning laser ophthalmoscopy (SLO) back-scattered light from the SLO illumination beam, and depth information about different retinal layers by means of Optical Coherence Tomography (OCT). Simultaneous assessment of retinal characteristics with different modalities can provide a wealth of information about the structural and functional changes in the retinal neural tissue and chorio-retinal vasculature in vivo. Additionally, simultaneous acquisition of multiple channels facilitates analysis of the data of different modalities by automatic temporal and ...

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    18. In vivo imaging of human photoreceptor mosaic with wavefront sensorless adaptive optics optical coherence tomography

      In vivo imaging of human photoreceptor mosaic with wavefront sensorless adaptive optics optical coherence tomography

      Wavefront sensorless adaptive optics optical coherence tomography (WSAO-OCT) is a novel imaging technique for in vivo high-resolution depth-resolved imaging that mitigates some of the challenges encountered with the use of sensor-based adaptive optics designs. This technique replaces the Hartmann Shack wavefront sensor used to measure aberrations with a depth-resolved image-driven optimization algorithm, with the metric based on the OCT volumes acquired in real-time. The custom-built ultrahigh-speed GPU processing platform and fast modal optimization algorithm presented in this paper was essential in enabling real-time, in vivo imaging of human retinas with wavefront sensorless AO correction. WSAO-OCT is especially advantageous for developing ...

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    19. Adaptive optics optical coherence tomography for in vivo retinal imaging (Thesis)

      Adaptive optics optical coherence tomography for in vivo retinal imaging (Thesis)

      Optical coherence tomography (OCT) is a non-invasive micrometer-resolution volumetric imaging modality that has been employed in diverse applications. In this thesis, we first describe a GPU accelerated program to perform FDOCT data processing and real time 3D volumetric rendering. The real time visualization of volumetric images provided by the GPU acceleration was essential to the rest of the work described in this thesis. Small animal models of retinal diseases serve as a vital component in vision research, and non-invasive in vivo imaging is becoming an increasingly important tool in the field. We describe the first adaptive optics optical coherence tomography ...

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    20. Real-time acquisition and display of flow contrast using speckle variance optical coherence tomography in a graphics processing unit

      Real-time acquisition and display of flow contrast using speckle variance optical coherence tomography in a graphics processing unit

      In this report, we describe a graphics processing unit (GPU)-accelerated processing platform for real-time acquisition and display of flow contrast images with Fourier domain optical coherence tomography (FDOCT) in mouse and human eyes in vivo . Motion contrast from blood flow is processed using the speckle variance OCT (svOCT) technique, which relies on the acquisition of multiple B-scan frames at the same location and tracking the change of the speckle pattern. Real-time mouse and human retinal imaging using two different custom-built OCT systems with processing and display performed on GPU are presented with an in-depth analysis of performance metrics. The ...

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    21. Wavefront sensorless adaptive optics optical coherence tomography for in vivo retinal imaging in mice

      Wavefront sensorless adaptive optics optical coherence tomography for in vivo retinal imaging in mice

      e present wavefront sensorless adaptive optics (WSAO) Fourier domain optical coherence tomography (FD-OCT) for in vivo small animal retinal imaging. WSAO is attractive especially for mouse retinal imaging because it simplifies optical design and eliminates the need for wavefront sensing, which is difficult in the small animal eye. GPU accelerated processing of the OCT data permitted real-time extraction of image quality metrics (intensity) for arbitrarily selected retinal layers to be optimized. Modal control of a commercially available segmented deformable mirror (IrisAO Inc.) provided rapid convergence using a sequential search algorithm. Image quality improvements with WSAO OCT are presented for both ...

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    22. Feature Of The Week 6/16/13: Using Adaptive Optics Optical Coherence Tomography for in vivo Mouse Retinal Imaging

      Feature Of The Week 6/16/13: Using Adaptive Optics Optical Coherence Tomography for in vivo Mouse Retinal Imaging

      Small animal models of human diseases serve as a vital component in modern medical research, including eye-related research, where they facilitate the understanding of the underlying biological processes of human disorders, and development of novel therapies against vision-robbing diseases. Non-invasive ophthalmic imaging modalities such as optical coherence tomography have become an important tool for small animal vision research programs and has greatly accelerated numerous preclinical studies. OCT offers the ability to perform longitudinal in vivo studies which are not feasible with more invasive imaging techniques such as immunohistology. However, to better visualize the retinal cellular microstructure and understand the molecular ...

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    23. Adaptive optics optical coherence tomography for in vivo mouse retinal imaging

      Adaptive optics optical coherence tomography for in vivo mouse retinal imaging

      Small animal models of retinal diseases are important to vision research, and noninvasive high resolution in vivo rodent retinal imaging is becoming an increasingly important tool used in this field. We present a custom Fourier domain optical coherence tomography (FD-OCT) instrument for high resolution imaging of mouse retina. In order to overcome aberrations in the mouse eye, we incorporated a commercial adaptive optics system into the sample arm of the refractive FD-OCT system. Additionally, a commercially available refraction canceling lens was used to reduce lower order aberrations and specular back-reflection from the cornea. Performance of the adaptive optics (AO) system ...

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    24. Graphics processing unit accelerated optical coherence tomography processing at megahertz axial scan rate and high resolution video rate volumetric rendering

      Graphics processing unit accelerated optical coherence tomography processing at megahertz axial scan rate and high resolution video rate volumetric rendering

      In this report, we describe how to highly optimize a computer unified device architecture based platform to perform real-time processing of optical coherence tomography interferometric data and three-dimensional (3-D) volumetric rendering using a commercially available, cost-effective, graphics processing unit (GPU). The maximum complete attainable axial scan processing rate, including memory transfer and displaying B-scan frame, was 2.24 MHz for 16 bits pixel depth and 2048 fast Fourier transform size; the maximum 3-D volumetric rendering rate, including B-scan, en face view display, and 3-D rendering, was ∼ 23     volumes / second (volume size: 1024 × 256 × 200 ). To the best of our knowledge ...

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    25. Real-time high-speed volumetric imaging using compressive sampling optical coherence tomography

      Real-time high-speed volumetric imaging using compressive sampling optical coherence tomography

      Volumetric imaging of the Optic Nerve Head (ONH) morphometry with Optical Coherence Tomography (OCT) requires dense sampling and relatively long acquisition times. Compressive Sampling (CS) is an emerging technique to reduce volume acquisition time with minimal image degradation by sparsely sampling the object and reconstructing the missing data in software. In this report, we demonstrated real-time CS-OCT for volumetric imaging of the ONH using a 1060nm Swept-Source OCT prototype. We also showed that registration and averaging of CS-recovered volumes enhanced visualization of deep structures of the sclera and lamina cribrosa. This work validates CS-OCT as a means for reducing volume ...

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    1-25 of 25
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    Real-time high-speed volumetric imaging using compressive sampling optical coherence tomography Graphics processing unit accelerated optical coherence tomography processing at megahertz axial scan rate and high resolution video rate volumetric rendering Adaptive optics optical coherence tomography for in vivo mouse retinal imaging Feature Of The Week 6/16/13: Using Adaptive Optics Optical Coherence Tomography for in vivo Mouse Retinal Imaging Wavefront sensorless adaptive optics optical coherence tomography for in vivo retinal imaging in mice Real-time acquisition and display of flow contrast using speckle variance optical coherence tomography in a graphics processing unit In vivo imaging of human photoreceptor mosaic with wavefront sensorless adaptive optics optical coherence tomography Multispectral scanning laser ophthalmoscopy combined with optical coherence tomography for simultaneous in vivo mouse retinal imaging En face projection imaging of the human choroidal layers with tracking SLO and swept source OCT angiography methods Retinal optical coherence tomography at 1  μm with dynamic focus control and axial motion tracking AI-Assisted In Situ Detection of Human Glioma Infiltration Using a Novel Computational Method for Optical Coherence Tomography Motorized capsule for shadow-free OCT imaging and synchronous beam control