1. Articles from Ratheesh K. Meleppat

    1-5 of 5
    1. Temporal speckle-averaging of optical coherence tomography volumes for in-vivo cellular resolution neuronal and vascular retinal imaging

      Temporal speckle-averaging of optical coherence tomography volumes for in-vivo cellular resolution neuronal and vascular retinal imaging

      It has been recently demonstrated that structures corresponding to the cell bodies of highly transparent cells in the retinal ganglion cell layer could be visualized noninvasively in the living human eye by optical coherence tomography (OCT) via temporal averaging. Inspired by this development, we explored the application of volumetric temporal averaging in mice, which are important models for studying human retinal diseases and therapeutic interventions. A general framework of temporal speckle-averaging (TSA) of OCT and optical coherence tomography angiography (OCTA) is presented and applied to mouse retinal volumetric data. Based on the image analysis, the eyes of mice under anesthesia ...

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    2. 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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    3. 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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    4. 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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    5. Adaptive optics with combined optical coherence tomography and scanning laser ophthalmoscopy for in vivo mouse retina imaging

      Adaptive optics with combined optical coherence tomography and scanning laser ophthalmoscopy for in vivo mouse retina imaging

      Optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO) are two state-of-the-art imaging technologies commonly used to study retina. Adaptive Optics (AO) methodologies enable high-fidelity correction of ocular aberrations, resulting in improved resolution and sensitivity for both SLO and OCT systems. Here we present work integrating OCT into a previously described mouse retinal AO-SLO system, allowing simultaneous reflectance and fluorescence imaging. The new system allows simultaneous data acquisition of AO-SLO and AO-OCT, facilitating registration and comparison of data from both modalities. The system has data acquisition speed of 200 kHz A-scans/pixel, and high volumetric resolution.

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    1-5 of 5
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  2. Topics in the News

    1. (5 articles) UC Davis
    2. (5 articles) Robert J. Zawadzki
    3. (4 articles) Simon Fraser University
    4. (4 articles) Marinko V. Sarunic
    5. (4 articles) Pengfei Zhang
    6. (2 articles) Oregon Health & Science University
    7. (2 articles) Yifan Jian
    8. (1 articles) Myeong Jin Ju
    9. (1 articles) University Hospital Zurich
    10. (1 articles) Harvard University
    11. (1 articles) Massachusetts General Hospital
    12. (1 articles) University of Athens
    13. (1 articles) L V Prasad Eye Institute
    14. (1 articles) Leiden University
    15. (1 articles) Massachusetts Institute of Technology
    16. (1 articles) Gijs van Soest
    17. (1 articles) Brett E. Bouma
    18. (1 articles) Evelyn Regar
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    Adaptive optics with combined optical coherence tomography and scanning laser ophthalmoscopy for in vivo mouse retina imaging Investigation of the effect of directional (off-axis) illumination on the reflectivity of retina layers in mice using swept-source optical coherence tomography 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 Temporal speckle-averaging of optical coherence tomography volumes for in-vivo cellular resolution neuronal and vascular retinal imaging Sequential imaging of a case of choroidal osteoma using swept-source OCT and optical coherence tomography angiography: A 4-year follow-up study Optical coherence tomography angiography–based analysis of intrinsic vasculature in juxtapapillary melanoma after ruthenium-106 plaque brachytherapy Understanding the structural changes following photodynamic and transpupillary thermotherapy for choroidal hemangioma using optical coherence tomography and optical coherence tomography angiography Swept-source optical coherence tomography features of regressed macular retinoblastoma Intravascular Polarimetry in Patients With Coronary Artery Disease AI More than Human in Healthcare First-in-human imaging study shows improved heart attack prediction