Marinko V. Sarunic

Adaptive optics scanning laser ophthalmoscopy and optical coherence tomography (AO-SLO-OCT) system for in vivo mouse retina imaging

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Optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO) are imaging technologies invented in the 1980s that have revolutionized the field of in vivo retinal diagnostics and are now commonly used in ophthalmology clinics as well as in vision science research. Adaptive optics (AO) technology enables high-fidelity correction of ocular aberrations, resulting in improved resolution and sensitivity for both SLO and OCT systems. The potential of gathering multi-modal cellular-resolution information in a single instrument is of great interest to the ophthalmic imaging community. Although similar instruments have been developed for imaging the human retina, developing such a system for mice will benefit basic science research and should help with further dissemination of AO technology. Here, we present our work integrating OCT into an existing mouse retinal AO-SLO system, resulting in a multi-modal AO-enhanced imaging system of the living mouse eye. The new system allows e...

Pilot study of optical coherence tomography angiography-derived microvascular metrics in hands and feet of healthy and diabetic people

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Optical coherence tomography angiography (OCTA) is a non-invasive, high-resolution imaging modality with growing application in dermatology and microvascular assessment. Accepted reference values for OCTA-derived microvascular parameters in skin do not yet exist but need to be established to drive OCTA into the clinic. In this pilot study, we assess a range of OCTA microvascular metrics at rest and after post-occlusive reactive hyperaemia (PORH) in the hands and feet of 52 healthy people and 11 people with well-controlled type 2 diabetes mellitus (T2DM). We calculate each metric, measure test–retest repeatability, and evaluate correlation with demographic risk factors. Our study delivers extremity-specific, age-dependent reference values and coefficients of repeatability of nine microvascular metrics at baseline and at the maximum of PORH. Significant differences are not seen for age-dependent microvascular metrics in hand, but they are present for several metrics in the foot. Signi...

Pilot study of optical coherence tomography angiography-derived microvascular metrics in hands and feet of healthy and diabetic peopl

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Optical coherence tomography angiography (OCTA) is a non-invasive, high-resolution imaging modality with growing application in dermatology and microvascular assessment. Accepted reference values for OCTA-derived microvascular parameters in skin do not yet exist but need to be established to drive OCTA into the clinic. In this pilot study, we assess a range of OCTA microvascular metrics at rest and after post-occlusive reactive hyperaemia (PORH) in the hands and feet of 52 healthy people and 11 people with well-controlled type 2 diabetes mellitus (T2DM). We calculate each metric, measure test–retest repeatability, and evaluate correlation with demographic risk factors. Our study delivers extremity-specific, age-dependent reference values and coefficients of repeatability of nine microvascular metrics at baseline and at the maximum of PORH. Significant differences are not seen for age-dependent microvascular metrics in hand, but they are present for several metrics in the foot. Signi...

Senior Research Fellow in Optical Coherence Tomography, University College London

Location: London Salary: £47,414 inclusive of London Allowance Hours: Full Time Contract Type: Fixed-Term/Contract Placed On: 5th January 2023 Closes: 22nd January 2023 Job Ref: B02-04320 About us The post of Senior Research Fellow is for biophotonics research with a focus on optical coherence tomography (OCT). The research fellow will join Prof. Sarunic’s group, which is primarily based at UCL Institute of Ophthalmology and cross-appointed with the UCL Department of Medical Physics and Biomedical Engineering, for the development of novel ocular imaging technologies. The post of Senior Research Fellow offers an exciting opportunity for someone to play a key role in developing new OCT-based diagnostics in a highly successful and dynamic research Institute, as well as benefiting from the clinical collaborations and translational opportunities at the NIHR Moorfields Biomedical Research Centre. About the role The Senior Research Fellow role will combine practical re...

Spectral Bandwidth Recovery of Optical Coherence Tomography Images using Deep Learning

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Optical coherence tomography (OCT) captures cross-sectional data and is used for the screening, monitoring, and treatment planning of retinal diseases. Technological developments to increase the speed of acquisition often results in systems with a narrower spectral bandwidth, and hence a lower axial resolution. Traditionally, image-processing-based techniques have been utilized to reconstruct subsampled OCT data and more recently, deep-learning-based methods have been explored. In this study, we simulate reduced axial scan (A-scan) resolution by Gaussian windowing in the spectral domain and investigate the use of a learning-based approach for image feature reconstruction. In anticipation of the reduced resolution that accompanies wide-field OCT systems, we build upon super-resolution techniques to explore methods to better aid clinicians in their decision-making to improve patient outcomes, by reconstructing lost features using a pixel-to-pixel approach with an altered super-resol...

Effects of Myopia and Glaucoma on the Neural Canal and Lamina Cribrosa Using Optical Coherence Tomography

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Précis: Glaucoma was associated with axial bowing and rotation of Bruchs membrane opening (BMO) and anterior laminar insertion (ALI), skewed neural canal, and deeper anterior lamina cribrosa surface (ALCS). Longer axial length was associated with wider, longer, and more skewed neural canal and flatter ALCS. Purpose: Investigate the effects of myopia and glaucoma in the prelaminar neural canal and anterior lamina cribrosa using 1060-nm swept-source optical coherence tomography. Patients: 19 control (38 eyes) and 38 glaucomatous subjects (63 eyes). Materials and Methods: Participants were imaged with swept-source optical coherence tomography, and the images were analyzed for the BMO and ALI dimensions, prelaminar neural canal dimensions, and ALCS depth. Results: Glaucomatous eyes had more bowed and nasally rotated BMO and ALI, more horizontally skewed prelaminar neural canal, and deeper ALCS than the control eyes. Increased axial length was associated with a wider, long...

Senior Research Fellow Opening at Institute of Ophthalmology, University College London

      Location: London Salary: From £46,979 UCL Grade 8, per annum, inclusive of London Allowance Hours: Full Time Contract Type: Fixed-Term/Contract Placed On: 22nd September 2022 Closes: 18th October 2022 Job Ref: 1886911 Interview Date: TBC Full time, Fixed Term: The post is funded for 12 months (in the first instance).   Applications are invited for the post of Senior Research Fellow to join the research group of Professor Marinko Sarunic at the UCL Institute of Ophthalmology. The project involves developing adaptive optics optical coherence tomography (AOOCT) imaging systems. The duties include designing and building a user-friendly optical system that will correct for the eye’s optical imperfections and acquire high resolution structural and functional retinal images.   The post is funded for 12 months (in the first instance).   The successful candidate should have a first degree in physics, engineering or a related field, and a PhD in...

Effects of Myopia and Glaucoma on the Neural Canal and Lamina Cribrosa using Optical Coherence Tomography

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Précis: Glaucoma was associated with axial bowing and rotation of BMO and ALI, skewed neural canal, and deeper ALCS. Longer axial length was associated with wider, longer, and more skewed neural canal and flatter ALCS. Purpose: Investigate the effects of myopia and glaucoma in the prelaminar neural canal and anterior lamina cribrosa using 1060-nm swept-source optical coherence tomography . Patients: 19 control (38 eyes) and 38 glaucomatous subjects (63 eyes). Methods: Participants were imaged with swept-source optical coherence tomography and the images were analyzed for the Bruchs membrane opening (BMO) and anterior laminar insertion (ALI) dimensions, prelaminar neural canal dimensions, and anterior lamina cribrosa surface (ALCS) depth. Results: Glaucomatous eyes had more bowed and nasally rotated BMO and ALI, more horizontally skewed prelaminar neural canal, and deeper ALCS than the control eyes. Increased axial length was associated with a wider, longer, and more horizonta...

Numerical calibration method for a multiple spectrometer-based OCT system

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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 critical to achieve improved retinal image data without any artifacts caused by misalignment of the spectrometers. ( Read Full Article )

LF-UNet – A Novel Anatomical-Aware Dual-Branch Cascaded Deep Neural Network for Segmentation of Retinal Layers and Fluid from Optical Coherence Tomography Images

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Computer-assistant diagnosis of retinal disease relies heavily on the accurate detection of retinal boundaries and other pathological features such as fluid accumulation. Optical coherence tomography (OCT) is a non-invasive ophthalmological imaging technique that has become a standard modality in the field due to its ability to detect cross-sectional retinal pathologies at the micrometer level. In this work, we presented a novel framework to achieve simultaneous retinal layers and fluid segmentation. A dual-branch deep neural network, termed LF-UNet, was proposed which combines the expansion path of the U-Net and original fully convolutional network, with a dilated network. In addition, we introduced a cascaded network framework to include the anatomical awareness embedded in the volumetric image. Cross validation experiments showed that the proposed LF-UNet has superior performance compared to the state-of-the-art methods, and that incorporating the relative positional map structur...

Phase-corrected buffer averaging for enhanced OCT angiography using FDML laser

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Megahertz-rate optical coherence tomography angiography (OCTA) is highly anticipated as an ultrafast imaging tool in clinical settings. However, shot-noise-limited sensitivity is inevitably reduced in high-speed imaging systems. In this Letter, we present a coherent buffer averaging technique for use with a Fourier-domain mode-locked (FDML) laser to improve OCTA contrast at 1060 nm MHz-rate retinal imaging. Full characterization of spectral variations among the FDML buffers and a numerical correction method are also presented, with the results demonstrating a 10-fold increase in the phase alignment among buffers. Coherent buffer averaging provided better OCTA contrast than the conventional multi-frame averaging approach with a faster acquisition time. ( Read Full Article )

Quantitative Optical Coherence Tomography Angiography in Patients with Moyamoya Vasculopathy: A Pilot Study

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Moyamoya (MM) disease is a chronic cerebrovascular disease that can lead to progressive stenosis of the terminal portions of the internal carotid arteries and their proximal branches. We sought to investigate and quantify retinal vascular changes in patients with MM vasculopathy (MMV) using optical coherence tomography angiography (OCTA) compared to healthy controls. Our findings reveal retinal microvascular changes in patients with MMV and highlights the potential of OCTA imaging for the detection of subclinical retinal pathology. ( Read Full Article )

Domain Adaptation via CycleGAN for Retina Segmentation in Optical Coherence Tomography

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With the FDA approval of Artificial Intelligence (AI) for point-of-care clinical diagnoses, model generalizability is of the utmost importance as clinical decision-making must be domain-agnostic. A method of tackling the problem is to increase the dataset to include images from a multitude of domains; while this technique is ideal, the security requirements of medical data is a major limitation. Additionally, researchers with developed tools benefit from the addition of open-sourced data, but are limited by the difference in domains. Herewith, we investigated the implementation of a Cycle-Consistent Generative Adversarial Networks (CycleGAN) for the domain adaptation of Optical Coherence Tomography (OCT) volumes. This study was done in collaboration with the Biomedical Optics Research Group and Functional & Anatomical Imaging & Shape Analysis Lab at Simon Fraser University. In this study, we investigated a learning-based approach of adapting the domain of a publicly availabl...

Investigating Microangiopathy using Swept-Source Optical Coherence Tomography Angiography in Patients with Susac Syndrome

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Purpose: To determine whether optical coherence tomography angiography is of diagnostic utility for Susac syndrome (SuS) by quantifying microvascular retinal changes. Methods: We enrolled 18 eyes of 9 healthy controls and 18 eyes of 9 patients with chronic SuS (12 had previous branch retinal artery occlusions and 6 were clinically unaffected). Images of the fovea were taken using an optical coherence tomography angiography system. Analysis included vessel density, fractal dimension, vessel diameter and measurements of the foveal avascular zone (area, eccentricity, acircularity index, axis ratio) in deep and superficial retinal layers. Results: Skeleton density and inner ring vessel density was significantly lower in patients with SuS (SD: Susac 0.11±0.01 vs. controls 0.12±0.01, p=0.027. VD: SuS 0.39±0.04 vs. controls 0.42±0.02, p=0.041). Eccentricity and axis ratio were significantly higher in patients with SuS (EC: Susac 0.61±0.11, controls 0.51&p...

Optimizing 3D retinal vasculature imaging in diabetic retinopathy using registration and averaging of OCT-A

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High resolution visualization of optical coherence tomography (OCT) and OCT angiography (OCT-A) data is required to fully take advantage of the imaging modality's three-dimensional nature. However, artifacts induced by patient motion often degrade OCT-A data quality. This is especially true for patients with deteriorated focal vision, such as those with diabetic retinopathy (DR). We propose a novel methodology for software-based OCT-A motion correction achieved through serial acquisition, volumetric registration, and averaging. Motion artifacts are removed via a multi-step 3D registration process, and visibility is significantly enhanced through volumetric averaging. We demonstrate that this method permits clear 3D visualization of retinal pathologies and their surrounding features, 3D visualization of inner retinal capillary connections, as well as reliable visualization of the choriocapillaris layer. ( Read Full Article )

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