1. 1-24 of 1527 1 2 3 4 ... 62 63 64 »
    1. Scanning optimization of an electrothermally-actuated MEMS mirror for applications in optical coherence tomography endoscopy

      Scanning optimization of an electrothermally-actuated MEMS mirror for applications in optical coherence tomography endoscopy

      Probe is an important component of the optical coherence tomography (OCT) system. Electrothermally-actuated micro-electromechanical (MEMS) mirrors are especially suitable for OCT endoscopic imaging due to their large scan angle, low driving voltage and high fill factor. However, endoscopic OCT imaging quality would be seriously affected by the nonlinear scanning characteristics of electrothermal MEMS mirrors as well as the distortion due to the need of placing the MEMS mirror on a 45 slope. In this work, an open-loop control method based on the transfer function of the MEMS mirror is proposed to optimize the overall optical trajectory scanned on the sample ...

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    2. Near-infrared active superparamagnetic iron oxide nanoparticles for magnetomotive optical coherence tomography imaging and magnetic hyperthermia therapeutic applications

      Near-infrared active superparamagnetic iron oxide nanoparticles for magnetomotive optical coherence tomography imaging and magnetic hyperthermia therapeutic applications

      A green chemistry-based approach to nanoparticle synthesis is an eco-friendly, simple, and cost-effective way to fabricate nanoparticles. This study aims at the biomedical applications of green synthesized near-infrared (NIR) active superparamagnetic iron oxide nanoparticles (SPIONs). The SPIONs obtained by the green synthesis route are non-toxic and their surface is free from any chemical impurity. The MTT [3-(4, 5-Dimethylthiazol-2-yl)-2, 5-Diphenyltetrazolium Bromide] assay was accomplished on human cervical cancer (HeLa) cells and shows that the SPIONs are biocompatible and thus safe for cells even at higher concentrations up to 500 μg/ml. The synthesized SPIONs display an absorbance in the ...

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    3. Detecting early osteoarthritis through changes in biomechanical properties – A review of recent advances in indentation technologies in a clinical arthroscopic setup

      Detecting early osteoarthritis through changes in biomechanical properties – A review of recent advances in indentation technologies in a clinical arthroscopic setup

      Osteoarthritis (OA) is a degenerative joint disease currently affecting half of all women and one-third of all men aged over 65 and it is predicted to even increase in the next decades. In the variety of causes leading to OA, the first common denominator are changes in the extracellular matrix of the cartilage. In later stages, OA affects the whole joint spreading to higher levels of tissue architecture causing irreversible functional and structural damage. To date, the diagnosis of OA is only formulated in the late stages of the disease. This is also, where most present therapies apply. Since a ...

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    4. In-vivo visualization of the photoreceptors using Spectralis High Magnification Module imaging in central serous chorioretinopath

      In-vivo visualization of the photoreceptors using Spectralis High Magnification Module imaging in central serous chorioretinopath

      Purpose To visualize photoreceptors using the Spectralis High Magnification Module (HMM) in a case of central serous chorioretinopathy (CSCR) and to correlate the findings with those of optical coherence tomography (OCT) and optical coherence tomography angiography (OCT-A). Observations A 35-year-old Caucasian male presenting with chronic CSCR in the left eye was examined using HMM, OCT and OCT-A. The photoreceptors mosaic was assessed both in diseased and apparently uninvolved areas. A partial topographic correlation between the loss of photoreceptors on HMM images and an altered reflectivity of the photoreceptor layer on en-face OCT was noted. Interestingly, a correlation between the photoreceptor ...

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    5. Microtensile bond strength to sealer-contaminated dentin after using different cleaning protocols

      Microtensile bond strength to sealer-contaminated dentin after using different cleaning protocols

      Background/purpose Sealer residues on dentin may affect bonding to restorative materials. This study aimed to evaluate the bond strength to sealer-contaminated dentin after using different cleaning protocols. Materials and methods Freshly extracted bovine incisors were prepared and exposed the buccal pulp chamber dentin, obtaining segments measuring 5 mm × 5 mm with a height of 3 mm. The segments were randomly distributed into 4 groups (n = 7) according to different protocols. Control group : no contamination was performed. In the three experimental groups, the segments were contaminated with epoxy resin-based sealer for 5 min, and different cleaning protocols were performed. Acetone ...

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    6. Optical coherence tomography angiography (OCTA) in differential diagnosis of aquaporin-4 antibody seronegative NMOSD and multiple sclerosis

      Optical coherence tomography angiography (OCTA) in differential diagnosis of aquaporin-4 antibody seronegative NMOSD and multiple sclerosis

      Backround Optic neuritis(ON) is a common feature of both relapsing-remitting multiple sclerosis(RRMS) and neuromyelitis optica spectrum disorders(NMOSD). It is crucial to early differentiate these two diseases, as they differ in pathophysiology and treatment. Objective To compare NMOSD and RRMS patients using optical coherence tomography(OCT) and OCT angiography(OCTA) to assess retinal microvascular network differences. Methods Fourteen RRMS (28 eyes) and 9 NMOSD patients(18 eyes), and 11 controls were enrolled. Seropositivity for aquaporin-4 antibody (anti-AQP4 Abs) was 44.4%. Peripapillary and macular retinal nerve fiber layer(RNFL) thickness, superficial peripapillary and macular vessel density(VD), area ...

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    7. Virtual intraoperative optical coherence tomography angiography integrated surgical microscope for simultaneous imaging of morphological structures and vascular maps in vivo

      Virtual intraoperative optical coherence tomography angiography integrated surgical microscope for simultaneous imaging of morphological structures and vascular maps in vivo

      Intraoperative surgical microscopy integrated with optical coherence tomography (OCT) has improved the accuracy and safety of surgeries by providing a visualization of the sub-surface tissue structure. Although intraoperative OCT has resolved the conventional limitations of the surgical microscope, it is still remained to provide additional informative blood vessel-related data that is required to enhance the stability of surgery by minimizing bleeding and tissue damage. In this paper, we developed a virtual intraoperative OCT angiography integrated surgical microscope (VI-OCTA-SM) to simultaneously visualize morphological tissue structure and microvasculature data of the surgical region including tumor margin and blood vessel map. In addition ...

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    8. Comprehensive Assessment of High-Risk Plaques by Dual-Modal Imaging Catheter in Coronary Artery

      Comprehensive Assessment of High-Risk Plaques by Dual-Modal Imaging Catheter in Coronary Artery

      Coronary plaque destabilization involves alterations in microstructure and biochemical composition; however, no imaging approach allows such comprehensive characterization. Herein, the authors demonstrated a simultaneous microstructural and biochemical assessment of high-risk plaques in the coronary arteries in a beating heart using a fully integrated optical coherence tomography and fluorescence lifetime imaging (FLIm). It was found that plaque components such as lipids, macrophages, lipids+macrophages, and fibrotic tissues had unique fluorescence lifetime signatures that were distinguishable using multispectral FLIm. Because FLIm yielded massive biochemical readouts, the authors incorporated machine learning framework into FLIm, and ultimately, their approach enabled an automated, quantitative imaging ...

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    9. Deep learning to detect optical coherence tomography-derived diabetic macular edema from retinal photographs: a multicenter validation study

      Deep learning to detect optical coherence tomography-derived diabetic macular edema from retinal photographs: a multicenter validation study

      Purpose: To validate the generalizability of a deep learning system (DLS) that detects diabetic macular edema (DME) from two-dimensional color fundus photography (CFP), where the reference standard for retinal thickness and fluid presence is derived from three-dimensional optical coherence tomography (OCT). Design: Retrospective validation of a DLS across international datasets. Participants: Paired CFP and OCT of patients from diabetic retinopathy (DR) screening programs or retina clinics. The DLS was developed using datasets from Thailand, the United Kingdom (UK) and the United States and validated using 3,060 unique eyes from 1,582 patients across screening populations in Australia, India and ...

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    10. Incidence and characteristics of incomplete stent apposition in calcified lesions: An optical coherence tomography study

      Incidence and characteristics of incomplete stent apposition in calcified lesions: An optical coherence tomography study

      Background: Persistent or late acquired incomplete stent apposition (ISA) may be associated with late or very late stent thrombosis following drug-eluting stent implantation. Presence of calcium at the target lesion may increase the risk of ISA even after rotational atherectomy (RA) followed by stenting with high pressure balloon inflation. The aim of this study is to examine the incidence and characteristics of ISA in heavily calcified lesions. Methods: A total of 52 heavily calcified coronary artery lesions requiring RA plus stenting were selected and studied. After successful ablation followed by stent implantation, optical coherence tomography (OCT) was performed to assess ...

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    11. Imaging biomarkers for Alzheimer’s disease and glaucoma: Current and future practices

      Imaging biomarkers for Alzheimer’s disease and glaucoma: Current and future practices

      Glaucoma is a leading cause of blindness worldwide. Although intraocular pressure is the main risk factor for glaucoma, several intraocular pressure independent factors have been associated with the risk of developing the disease and its progression. The diagnosis of glaucoma relies on clinical features of the optic nerve, visual field test, and optical coherence tomography. However, the multidisciplinary aspect of the disease suggests that other biomarkers may be useful for the diagnosis, thus underling the importance of novel imaging techniques supporting clinicians. This review analyzes the common pathogenic mechanisms between glaucoma and Alzheimer’s disease and the possible novel approaches ...

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    12. Bietti crystalline dystrophy: Role of multimodal imaging and optical coherence tomography angiography

      Bietti crystalline dystrophy: Role of multimodal imaging and optical coherence tomography angiography

      Bietti crystalline dystrophy (BCD) is a rare inherited chorioretinal degenerative disease due to pathogenic variants in the CYP4V2 gene [1]. It is characterized by the presence of shimmering crystalline deposits in the posterior pole of the retina and/or the corneal limbus, pigment clumps, and sclerosis of choroidal vessels. Onset is typically in the third decade of life with clinical manifestations of reduced visual acuity, visual field loss, night blindness and impaired color vision. BCD leads to legal blindness by the age of 40 to 50 years.

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    13. The Optical Coherence Tomography Angiography study on Paediatric COVID-19 cases

      The Optical Coherence Tomography Angiography study on Paediatric COVID-19 cases

      Dear Editor, We read with interest the research article entitled “Retinal microvascular and perfusional disruption in paediatric COVID-19: A case-control optical coherence tomography angiography study”, [1] it was a cross-sectional study on choroidal structural and vascular changes on paediatric COVID-19 subjects. We are particularly interested in the possible confounding on the optical coherence tomography angiography (OCT-A) measurements. Firstly, we appreciated Zengin and Güven for recording the autorefraction measurement values of all patients, [1] however these data were not presented. High myopia subjects were not excluded according to the primary study's methodology. [1] Refraction, with and without cycloplegic, or ...

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    14. Localized vibrations incorporated thickness assessment of cadaveric tympanic membranes using Doppler-optical coherence tomography

      Localized vibrations incorporated thickness assessment of cadaveric tympanic membranes using Doppler-optical coherence tomography

      Vibrations of the tympanic membrane (TM) play a key role in the diagnosis of the middle ear in hearing research. The thickness is one of the factors that determines performance analysis of the TM and plays an important role in forming vibration patterns. When the thickness of TM is changed for various reasons, the vibration pattern is also changed, which interferes with sound transmission. The previously reported studies of measuring TM obtained the response of the entire or at a single point to understand the characteristics of the TM, which is limited to providing detailed information for the region of ...

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    15. Optical coherence tomography versus angiography guided magnesium bioresorbable scaffold implantation in NSTEMI patients

      Optical coherence tomography versus angiography guided magnesium bioresorbable scaffold implantation in NSTEMI patients

      Background: The purpose of a bioresorbable scaffold (BRS) is to provide radial support during coronary healing. In this study, coronary artery healing after optical coherence tomography (OCT)- versus angiography-guided magnesium BRS (MBRS) implantation in patients with non-ST-segment-elevation myocardial infarction (NSTEMI) is compared. Methods: 75 patients were randomized 1:1 to OCT- or angiography-guided implantation of a MBRS with protocolled pre- and post-dilation. In the OCT-guided group, prespecified criteria indicating additional intervention were (1) scaffold under-expansion, (2) strut malapposition, (3) edge dissection, and (4) residual stenosis at distal or proximal reference segments. The primary endpoint was OCT-derived healing stage at 6 ...

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    16. An outer hair cell-powered global hydromechanical mechanism for cochlear amplification

      An outer hair cell-powered global hydromechanical mechanism for cochlear amplification

      It is a common belief that the mammalian cochlea achieves its exquisite sensitivity, frequency selectivity, and dynamic range through an outer hair cell-based active process, or cochlear amplification. As a sound-induced traveling wave propagates from the cochlear base toward the apex, outer hair cells at a narrow region amplify the low level sound-induced vibration through a local feedback mechanism. This widely accepted theory has been tested by measuring sound-induced sub-nanometer vibrations within the organ of Corti in the sensitive living cochleae using heterodyne low-coherence interferometry and optical coherence tomography. The aim of this short review is to summarize experimental findings ...

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    17. Assessment of Tacrolimus Neurotoxicity Measured by Retinal OCT

      Assessment of Tacrolimus Neurotoxicity Measured by Retinal OCT

      Background Neurotoxicity secondary to anticalcineurinics is a prevalent side effect in transplant recipients. Optical coherence tomography (OCT) scans the central nervous system by direct access to the retina. OCT assesses central nervous system involvement by measuring the thickness of the retinal layers, especially the ganglion cell layer (GCL). The retinal scan divides the scanned area into affected and unaffected segments, which can be quantified for each eye. The aim of this study was to determine retinal GCL thickness by means of OCT, analyzing the proportion of affected segments in individuals exposed to tacrolimus compared with a control group. Materials and ...

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    18. Evaluations of the radial peripapillary, macular and choriocapillaris microvasculature using optical coherence tomography angiography in patients with systemic sclerosis

      Evaluations of the radial peripapillary, macular and choriocapillaris microvasculature using optical coherence tomography angiography in patients with systemic sclerosis

      Purpose: To analyze the macular microvascular (MMV) architecture, radial peripapillary capillary (RPC) network and choriocapillaris using optical coherence tomography angiography (OCT-A) in patients with systemic sclerosis (SSc) without systemic comorbidities. Methods: The vessel densities (VDs) of the MMV, foveal avascular zone (FAZ) parameters, choriocapillaris flow areas (CCFAs), RPC VDs, and optic nerve head (ONH) parameters were measured by OCT-A. Retinal thickness and subfoveal choroidal thickness (SFCT) were measured by spectral-domain optical coherence tomography (SD-OCT). The SD-OCT and OCT-A measurements of 53 eyes of 30 SSc patients were compared with 61 eyes of 33 healthy controls. Results: In the MMV analysis ...

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    19. Intramural hematoma burrowing behind a coronary stent: Optical coherence tomography findings

      Intramural hematoma burrowing behind a coronary stent: Optical coherence tomography findings

      A 47-year-old patient underwent elective percutaneous coronary intervention for two separate lesions in left circumflex artery with a intervening normal segment. After completion of the procedure, there was abrupt vessel closure in the intervening normal segment. Intracoronary imaging using optical coherence tomography (OCT) demonstrated a large intramural hematoma (IMH) extending distally behind the stent. We describe the OCT findings of IMH using cross-sectional, longitudinal and stent-rendered images, and discuss its management.

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    20. Benchmarking automated detection of the retinal external limiting membrane in a 3D spectral domain optical coherence tomography image dataset of full thickness macular holes

      Benchmarking automated detection of the retinal external limiting membrane in a 3D spectral domain optical coherence tomography image dataset of full thickness macular holes

      In this article, we present a new benchmark for the segmentation of the retinal external limiting membrane (ELM) using an image dataset of spectral domain optical coherence tomography (OCT) scans in a patient population with idiopathic full-thickness macular holes. Specifically, the dataset used contains OCT images from one eye of 107 patients with an idiopathic full-thickness macular hole. In total, the dataset contains 5243 individual 2-dimensional (2-D) OCT image slices, with each patient contributing 49 individual spectral-domain OCT tagged image slices. We display precise image-wise binary annotations to segment the ELM line. The OCT images present high variations in image ...

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    21. Comparison of similar Mueller and Jones matrix method in catheter based polarization sensitive optical coherence tomography

      Comparison of similar Mueller and Jones matrix method in catheter based polarization sensitive optical coherence tomography

      Catheter based polarization sensitive optical coherence tomography (PS-OCT) can provide composition information of coronary atherosclerotic plaque beyond the intensity based OCT, but it encounters a notable challenge that is how to reduce polarization properties variations owing to a rapidly rotating optical fiber in the catheter. Similar Jones matrix (SJM) and similar Mueller matrix (SMM) based polarization determination methods can provide a stable phase retardation imaging in a catheter based PS-OCT. In this paper, we systematically contrast SJM and SMM methods. Firstly, we theoretically illustrate the discrepancy between the eigenvalue decomposition in SJM and the polar decomposition in SMM. We find ...

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    22. Optical coherence tomography and visual evoked potential and its relationship with neurological disability in patients with relapsing-remitting multiple sclerosis

      Optical coherence tomography and visual evoked potential and its relationship with neurological disability in patients with relapsing-remitting multiple sclerosis

      Introduction : To evaluate the relationship between retinal nerve fiber layer involvement and visual evoked potential with the neurological disability scale in relapsing remitting multiple sclerosis. Methods : Fifty-two patients diagnosed with relapsing-remitting multiple sclerosis were evaluated for the study. Optical coherence tomography (retinal nerve fiber layer or RNFL and macular volume or MV), pattern visual evoked potential or VEP (latency and P100 wave amplitude), and neurological disability scale (EDSS) were performed. A baseline evaluation was carried out and it was repeated after one year and two years. Results : The baseline values ​​in the retinal nerve fiber layer were 82.5 (75-93 ...

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