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    1. Elimination of Artifacts Caused by the Nonidentity of Parallel Signal-Reception Channels in Spectral Domain Optical Coherence Tomography

      Elimination of Artifacts Caused by the Nonidentity of Parallel Signal-Reception Channels in Spectral Domain Optical Coherence Tomography

      We study the causes of artifact appearance in the images obtained by the method of spectral domain optical coherence tomography with parallel reception of the optical-spectrum components, which are manifested in repetition and overlay of the structural elements of the images of the studied medium with a shift in depth. It is shown that nonidentity of the transfer characteristics of the channels of the multichannel photoreceiving elements is one of the sources of such artifacts. A numerical method for eliminating such artifacts is proposed and experimentally verified. This method is based on using the models whose parameters are estimated by ...

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    2. Compensation for the Influence of Fluctuations in the Distance to the Object During Noncontact Probing in Spectral Domain Optical Coherence Tomography

      Compensation for the Influence of Fluctuations in the Distance to the Object During Noncontact Probing in Spectral Domain Optical Coherence Tomography

      We propose and experimentally test a numerical method for correction of the influence of fluctuations in the distance to objects during noncontact probing in optical coherence tomography. The method is based on the analysis of phase shifts of the neighboring scans, which are due to microscale displacements, and further compensation for these displacements by using phasefrequency correction in the spectral domain. Unlike the known correlation methods, the proposed method does not distort the represented shape of the object surface. Its operability is demonstrated in model experiments in the cases of harmonic and random types of the motion of the scattering ...

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    3. The broad spectrum of application of optical coherence tomography angiography to the anterior segment of the eye in inflammatory conditions: a review of the literature

      The broad spectrum of application of optical coherence tomography angiography to the anterior segment of the eye in inflammatory conditions: a review of the literature

      Background With an increased number of papers on how to interpret optical coherence tomography angiography (OCTA) findings in uveitis, the aim of this review is to assess its efficacy for the quantitative monitoring of structural and functional changes in inflamed conjunctiva and iris vessels in patients with acute anterior uveitis and iris neovascularization. Main body OCTA, currently designed as a retinal vascular imaging system, has been recently adapted for anterior segment and showed good potential for successful imaging of the conjunctiva, the cornea, and the iris. OCTA can successfully delineate corneal vessels with substantial image quality. At the same time ...

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    4. Widefield optical coherence tomography angiography in diabetic retinopathy

      Widefield optical coherence tomography angiography in diabetic retinopathy

      Aims To evaluate superficial capillary plexus (SCP), deep capillary plexus (DCP) and choriocapillaris (CC) perfusion in macular and near/mid periphery regions in diabetic patients using widefield swept-source optical coherence tomography angiography (WSS-OCTA). Methods Ninety-four diabetic patients (94 eyes) classified as diabetics without diabetic retinopathy (no DR) (25 eyes), mild DR (23 eyes), moderate/severe DR (26 eyes), proliferative DR (20 eyes) and a control group of 25 healthy subjects (25 eyes) were imaged with the WSS-OCTA system (PLEX Elite 9000, Carl Zeiss Meditec Inc., Dublin, CA, USA). Quantitative analysis was performed in the macular and peripheral regions. The main ...

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    5. Comparison between non-visualized polyps and visualized polyps on optical coherence tomography angiography in polypoidal choroidal vasculopathy

      Comparison between non-visualized polyps and visualized polyps on optical coherence tomography angiography in polypoidal choroidal vasculopathy

      Purpose To determine the underlying reasons for the non-visualization of polyps on en face optical coherence tomography angiography (OCTA) in patients with polypoidal choroidal vasculopathy (PCV). Methods A cross-sectional study of consecutive treatment-naïve 30 eyes with active PCV was included. Results of fundus photography, fundus fluorescein angiography (FFA), indocyanine green angiography (ICGA), spectral domain optical coherence tomography (SD-OCT), and en face OCTA were analyzed. Results A total of 64 active polyps were found on FFA and ICGA in 30 eyes. On OCTA, 42/64 (65.6%) polyps were visualized, while 22/64 (34.4%) polyps were non-visualized. There were ...

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    6. Research of Ocular Hemodynamics by Optical Coherence Tomography and Transpalpebral Rheoophthalmography Methods

      Research of Ocular Hemodynamics by Optical Coherence Tomography and Transpalpebral Rheoophthalmography Methods

      The main task of this work was to find the connection between ocular hemodynamic parameters and the lamina cribrosa parameters of the eyes with primary open angle glaucoma (POAG). The study was conducted on 51 eyes of 34 subjects, including 11 eyes without ophthalmopathology (control group, average age 49.4 ± ± 17.5 years), 15 eyes of patients with the 1st (initial) stage of POAG (group 1, average age 67.0 ± ± 7.6 years), 15 eyes with II (developed) stage of glaucoma (group 2, average age 75.4 ± ± 6.1 years) and 10 eyes with III (advanced) disease stage (group 3 ...

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    7. High Resolution Imaging in Microscopy and Ophthalmology New Frontiers in Biomedical Optics (Textbook)

      High Resolution Imaging in Microscopy and Ophthalmology New Frontiers in Biomedical Optics (Textbook)

      Optical coherence tomography (OCT) is a non-invasive technique for cross-sectional tissue imaging. It typically uses light in the near-infrared spectral range which has a penetration depth of several hundred microns in tissue. The backscattered light is measured with an interferometric set-up to reconstruct the depth profile of the sample at the selected location. A scanning OCT beam allows for acquisition of cross-sectional images of the tissue structure. Different technical methods are introduced and compared regarding their properties like sensitivity, imaging speed and penetration depth. Regardless of the technical realization, axial resolution and imaging range of an OCT system are determined ...

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    8. What’s New in Optical Coherence Tomography Angiography for Glaucoma (Book Chapter)

      What’s New in Optical Coherence Tomography Angiography for Glaucoma (Book Chapter)

      Glaucoma is one of the main clinical areas where OCT angiography is used. In contrast to medical retinal application, where qualitative image analysis and semiquantitative measurements are frequently satisfactory for clinical decision-making, in glaucoma the exact quantitative measurements provide the useful information. Therefore both general ophthalmologists who treat glaucoma patients and glaucoma subspecialists need to be familiar with the measurement details of OCT angiography, the types of complementary structural information necessary to clinical decision-making, and the current limitations of the technology. This chapter attempts to guide the reader through all aspects of glaucoma-related OCT angiography in a stepwise manner.

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    9. Speckle denoising in optical coherence tomography images using residual deep convolutional neural network

      Speckle denoising in optical coherence tomography images using residual deep convolutional neural network

      Optical Coherence Tomography (OCT) is an emerging imaging modality used for diagnosis of ocular diseases like age-related macular degeneration (AMD) and macular edema. OCT imaging is a non-invasive technique to capture cross-sectional volumes of the retinal areas of human eye. Due to coherent nature of image acquisition process, OCT images suffer from granular multiplicative speckle noise. Presence of speckle noise in OCT images makes its clinical analysis difficult for the experts. The same is the problem with the development of computer aided diagnosis (CAD) systems for detection of ocular diseases. Speckle noise is granular in nature and interferes with the ...

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    10. Prognostic role of optical coherence tomography after switch to dexamethasone in diabetic macular edema

      Prognostic role of optical coherence tomography after switch to dexamethasone in diabetic macular edema

      Aims To analyze the visual outcome after early switch to dexamethasone (DEX) in eyes with diabetic macular edema previously treated with ranibizumab (RNB), based on structural spectral-domain optical coherence tomography (SD-OCT) features. Methods Retrospective study of data from 28 eyes which underwent a loading dose of three monthly RNB injections and were then shifted to DEX implant injection. SD-OCT analysis was performed before switch to DEX (week 12, 12W) according to the presence of integrity of ellipsoid zone (EZ) and external limiting membrane (ELM), disorganization of retinal inner layers (DRIL), and quantity of hyper-reflective spots (HRS). Best-corrected visual acuity (BCVA ...

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    11. Optical coherence tomography and cognitive dysfunction in Parkinson disease

      Optical coherence tomography and cognitive dysfunction in Parkinson disease

      Background Parkinson’s disease (PD) is a progressive neurodegenerative disease of aging. Optical coherence tomography (OCT) is a simple noninvasive imaging technique to estimate the retinal nerve fiber layer (RNFL) thickness. The aim of this study is to measure the changes of the RNFL thickness in patients with Parkinson disease in comparison with the control group and to detect the relationship between these changes in RNFL with cognitive functions and physical disability in Parkinson patients. Methods 20 PD patients (40 eyes) and 20 healthy persons (40 eyes) were enrolled according to the defined criteria. The diagnosis of the patient's ...

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    12. Deep Learning Based Fluid Segmentation in Retinal Optical Coherence Tomography Images

      Deep Learning Based Fluid Segmentation in Retinal Optical Coherence Tomography Images

      Macular Edema (ME) is the accumulation of fluid in the macular region of the eye, and it may lead to the distortion of center vision. It often occurs in diabetic retinopathy. It is important to measure fluid accumulation in ME patients for disease monitor. Segmentation of the fluid region in the retinal layer is an essential step for quantitatively analysis. However, manual segmentation is time consuming and also subjective. In this paper, a new deep learning based segmentation method is proposed. The attention mechanism is introduced to automatically locate the fluid region, which can reduce the number of parameters compared ...

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    13. Impact of lesion angle on optical coherence tomography findings and clinical outcomes after drug-eluting stent implantation in curved vessels

      Impact of lesion angle on optical coherence tomography findings and clinical outcomes after drug-eluting stent implantation in curved vessels

      Tortuous coronary lesions are associated with adverse outcomes after implantation of bare metal or first-generation drug-eluting stents (DESs). We investigated the impact of lesion angle on vessel wall injuries and stent apposition as assessed by optical coherence tomography (OCT) after second- and newer-generation DES implantation. We investigated 95 de novo lesions treated with a single DES (62 platinum-chromium everolimus-eluting stents and 33 bioresorbable-polymer sirolimus-eluting stents). Post-intervention OCT findings were compared between angled lesions (≥ 45°; n = 33) and non-angled lesions (< 45°; n = 62). The 12-month clinical outcomes were also compared between the groups. Cross-sectional OCT analysis revealed that compared to non-angled ...

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    14. Swept-source optical coherence tomographic observation on prevalence and variations of cemento-enamel junction morphology

      Swept-source optical coherence tomographic observation on prevalence and variations of cemento-enamel junction morphology

      To investigate the prevalence of different patterns of cemento-enamel junction (CEJ) morphology under swept-source optical coherence tomography (SS-OCT). One hundred extracted human teeth were used consisting of incisors, premolars, and molars. Each sample was observed for every 500 μm circumferentially along CEJ and OCT images of the pattern were noted. Microscopic observations were done for the representative sample using confocal laser scanning microscope (CLSM) and transmission electron microscope (TEM). The OCT images exhibited four CEJ patterns: edge-to-edge (type I), exposed dentin (type II), cementum overlapping enamel (type III), and enamel overlapping cementum (type IV). The prevalence of CEJ patterns was ...

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    15. Effect of topical steroids on recently developed incomplete nasolacrimal duct obstruction: optical coherence tomography study

      Effect of topical steroids on recently developed incomplete nasolacrimal duct obstruction: optical coherence tomography study

      Purpose To evaluate the effect of a topical steroid instillation on recently developed incomplete nasolacrimal duct obstruction (NLDO) evaluated by using anterior segment optical coherence tomography (ASOCT). Methods Forty-nine eyes of 31 patients with incomplete NLDO who developed epiphora within 3 months were recruited and treated with a topical steroid for 3 months. Tear meniscus height (TMH) and area (TMA) were measured by ASOCT. The treatment was considered to be effective when there was improvement of subjective epiphora, normal tear meniscus on slit lamp examination, a fluorescein dye disappearance test with grade 0 or 1, and TMH < 250 μm on ...

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    16. Optical coherence tomography in forensic sciences: a review of the literature

      Optical coherence tomography in forensic sciences: a review of the literature

      Optical coherence tomography (OCT) is an interferometric imaging technique that has revolutionized clinical ophthalmology since the first half of the 1990’s. Despite this approach being successfully employed in ophthalmology and having great potential in forensic cases, its use in different forensic fields appears to be quite limited. In this review we reviewed the scientific literature regarding the application of OCT in forensic science and legal medicine from 1995 to 2019. Our research showed the usefulness of this approach for the study of coronary injuries, postmortem ocular changes, forensic entomology, and several other applications of specific forensic interest (the study ...

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    17. Assessment of tear meniscus by optical coherence tomography in patients with canalicular laceration repair

      Assessment of tear meniscus by optical coherence tomography in patients with canalicular laceration repair

      Purpose To analyze tear meniscus measurements with optical coherence tomography (OCT) in patients with canalicular laceration repair. Methods Thirty-four consecutive patients who underwent unilateral canalicular repair due to canalicular laceration between January 2014 and December 2018 were included. All patients had canalicular repair followed by monocanalicular or annular silicone tube intubation. Anatomic patency of canalicular system was tested with probing and irrigation, while functional patency was evaluated with Munk score. Tear meniscus measurements of all patients were obtained following tube removal by spectral OCT. Tear meniscus height (TMH), tear meniscus depth (TMD) and tear meniscus area (TMA) of eyes with ...

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    18. Optical coherence tomography-based patient-specific coronary artery reconstruction and fluid–structure interaction simulation

      Optical coherence tomography-based patient-specific coronary artery reconstruction and fluid–structure interaction simulation

      Plaque rupture is related to the mechanical stress it suffered. The value and distribution of the mechanical stress in plaque could help on assessing plaque vulnerability. To look into the stress conditions in the coronary artery, a patient-specific coronary model was created by using optical coherence tomography (OCT) and angiography imaging data. The reconstructed coronary model consisted of the structure of the lumen, the arterial wall and plaque components. Benefited by the high resolution of OCT, detailed structures such as the thin fibrous cap could be observed and built into the geometry. On this reconstructed coronary model, a fully coupled ...

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    19. Comparison of conjunctival vascularity changes using optical coherence tomography angiography after trabeculectomy and phacotrabeculectomy

      Comparison of conjunctival vascularity changes using optical coherence tomography angiography after trabeculectomy and phacotrabeculectomy

      Purpose To compare bleb vascularity changes using optical coherence tomography angiography (OCT-A) between mitomycin-C (MMC)-augmented trabeculectomy and phacotrabeculectomy and to determine whether bleb vascularity measurements during preoperative and early postoperative periods could act as surrogate parameters to predict surgical outcomes. Methods We retrospectively reviewed data for 72 eyes from 72 glaucoma patients who underwent MMC-augmented trabeculectomy with/without cataract surgery. Bleb area scans were obtained using OCT-A during the preoperative period; 1, 2, 4, and 6 weeks postoperatively; and 2, 4, and 6 months postoperatively. For conjunctival vascularity analysis, a semi-automated program was used to calculate color and brightness ...

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    20. Retinal Optical Coherence Tomography Image Analysis (Textbook)

      Retinal Optical Coherence Tomography Image Analysis (Textbook)

      This book introduces the latest optical coherence tomography (OCT) imaging and computerized automatic image analysis techniques, and their applications in the diagnosis and treatment of retinal diseases. Discussing the basic principles and the clinical applications of OCT imaging, OCT image preprocessing, as well as the automatic detection and quantitative analysis of retinal anatomy and pathology, it includes a wealth of clinical OCT images, and state-of-the-art research that applies novel image processing, pattern recognition and machine learning methods to real clinical data. It is a valuable resource for researchers in both medical image processing and ophthalmic imaging.

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    21. Analysis of retinal nerve fiber layer thickness in anisometropic amblyopia via optic coherence tomography

      Analysis of retinal nerve fiber layer thickness in anisometropic amblyopia via optic coherence tomography

      Objective To detect retinal nerve fiber layer thickness differences of ambylopic and fellow eyes and ambylopic and control eyes. Methods The study comprised a total of 152 eyes recruited from Erzurum Region Training and Research Hospital, Turkey, between January 2018 and May 2018. Anisometropic amblyopia was the only cause of disability (visual acuity ≤ 6/12 and a difference in best-corrected visual acuity (BCVA) between the two eyes of 0.20 logMAR (2 lines on an acuity chart) in amblyopic eyes ( n , 74) whereas normal eyes had a best-corrected visual acuity of 6/6 and no morbidities ( n , 78). Anisometropic patients ...

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    22. Optical coherence tomography angiography in preclinical neuroimaging

      Optical coherence tomography angiography in preclinical neuroimaging

      Preclinical neuroimaging allows for the assessment of brain anatomy, connectivity, and function in laboratory animals, such as mice and this imaging field has been a rapidly growing aimed at bridging the translation gap between animal and human research. The progress in the animal research could be accelerated by high-resolution in vivo optical imaging technologies. Optical coherence tomography-based angiography (OCTA) estimates the scattering from moving red blood cells, providing the visualization of functional micro-vessel networks within tissue beds in vivo without a need for exogenous contrast agents. Recent advancement of OCTA methods have expanded its application to neuroimaging of small animal ...

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      Mentions: Woo June Choi
    23. An Experimentally Trained Noise Filtration Method of Optical Coherence Tomography Signals

      An Experimentally Trained Noise Filtration Method of Optical Coherence Tomography Signals

      A method for wavelet filtration procedure training for optical coherence tomography (OCT) images using the experimental measurements of test objects that were constructed by means of water solutions of monodisperse nanoparticles and several microscopic inclusions has been described in the present paper. The choice of test-object parameters (concentration of water solution, size of nanoparticles, and shape, dimensions, and mutual position of inclusions) has allowed the modeling of various working conditions of OCT and setting different criteria for estimation of filtration efficiency. In the present work, the optimal filter for the considered example of a test object has been selected among ...

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