1. Featured Articles

    25-48 of 74 « 1 2 3 »
    1. Engineering of Nanoscale Contrast Agents for Optical Coherence Tomography

      Engineering of Nanoscale Contrast Agents for Optical Coherence Tomography

      Optical coherence tomography has emerged as valuable imaging modality in ophthalmology and other fields by enabling high-resolution three-dimensional imaging of tissue. In this paper, we review recent progress in the field of contrast-enhanced optical coherence tomography (OCT). We discuss exogenous and endogenous sources of OCT contrast, focusing on their use with standard OCT systems as well as emerging OCT-based imaging modalities. We include advances in the processing of OCT data that generate improved tissue contrast, including spectroscopic OCT (SOCT), as well as work utilizing secondary light sources and/or detection mechanisms to create and detect enhanced contrast, including photothermal OCT ...

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    2. Optical Coherence Tomography: Age estimation of Calliphora vicina pupae in vivo?

      Optical Coherence Tomography: Age estimation of Calliphora vicina pupae in vivo?

      Necrophagous blowfly pupae are valuable contributors to the estimation of post-mortem interval, should an accurate age estimate be obtained. At present, this is reliant on a combination of rearing and destructive methods conducted on preserved samples, including morphological observation and gene expression analyses. This study demonstrates the use of optical coherence tomography (OCT) as a tool for in vivo morphological observation and pupal age estimation. Using a Michelson OCT microscope, alive and preserved four and ten-day old Calliphora vicina pupae were scanned in different orientations. Two and three-dimensional images were created. Morphological characteristics such as the brain, mouthparts and legs ...

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    3. Quantitative Assessment of Tissue Prolapse on Optical Coherence Tomography and its Relation with Underlying Plaque Morphologies and Clinical Outcome in Patients with Elective Stent Implantation

      Quantitative Assessment of Tissue Prolapse on Optical Coherence Tomography and its Relation with Underlying Plaque Morphologies and Clinical Outcome in Patients with Elective Stent Implantation

      Background Tissue prolapse (TP) is sometimes observed after percutaneous coronary intervention (PCI), but its clinical significance remains unclear. We investigated the relationship between TP volume on optical coherence tomography (OCT) after PCI and underlying plaque morphologies, and the impact of TP on clinical outcomes. Methods We investigated 178 native coronary lesions with normal pre-PCI creatine kinase-myocardial band (CK-MB) values (154 lesions with stable angina; 24 with unstable angina). TP was defined as tissue extrusion from stent struts throughout the stented segments. All lesions were divided into tertiles according to TP volume. The differences in plaque morphologies and 9-month clinical outcomes ...

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    4. The investigation of acute optic neuritis: a review and proposed protocol

      The investigation of acute optic neuritis: a review and proposed protocol

      Optic neuritis is an inflammatory optic neuropathy that affects many patients with multiple sclerosis (MS) at some point during their disease course. Differentiation of acute episodes of MS-associated optic neuritis from other autoimmune and inflammatory optic neuropathies is vital for treatment choice and further patient management, but is not always straightforward. Over the past decade, a number of new imaging, laboratory and electrophysiological techniques have entered the clinical arena. To date, however, no consensus guidelines have been devised to specify how and when these techniques can be most rationally applied for the diagnostic work-up of patients with acute optic neuritis ...

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    5. Multiwavelength phase unwrapping and aberration correction using depth filtered digital holography

      Multiwavelength phase unwrapping and aberration correction using depth filtered digital holography

      In this Letter, we present a new approach to processing data from a standard spectral domain optical coherence tomography (OCT) system using depth filtered digital holography (DFDH). Intensity-based OCT processing has an axial resolution of the order of a few micrometers. When the phase information is used to obtain optical path length differences, subwavelength accuracy can be achieved, but this limits the resolvable step heights to half of the wavelength of the system. Thus there is a metrology gap between phase- and intensity-based methods. Our concept addresses this metrology gap by combining DFHD with multiwavelength phase unwrapping. Additionally, the measurements ...

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    6. High-resolution images of inner ear could lead to new hearing loss therapies

      High-resolution images of inner ear could lead to new hearing loss therapies

      Understanding how hearing works has long been hampered by challenges associated with seeing inside the inner ear, but technology being developed by a team of researchers that includes a biomedical engineer from Texas A&M University is generating some of the most detailed images of the inner ear to date while offering new insight into the mechanics of hearing that could lead to new therapies for hearing loss. Employing a technique that generates high-resolution, three-dimensional images, Brian Applegate, associate professor in the Department of Biomedical Engineering at Texas A&M, and colleagues from Stanford University are mapping the tissues within ...

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    7. Investigating Recurrent Neural Networks for OCT A-scan Based Tissue Analysis

      Investigating Recurrent Neural Networks for OCT A-scan Based Tissue Analysis

      Objectives: Optical Coherence Tomography (OCT) has been proposed as a high resolution image modality to guide transbronchial biopsies. In this study we address the question, whether individual A-scans obtained in needle direction can contribute to the identification of pulmonary nodules. Methods: OCT A-scans from freshly resected human lung tissue specimen were recorded through a customized needle with an embedded optical fiber. Bidirectional Long Short Term Memory networks (BLSTMs) were trained on randomly distributed training and test sets of the acquired A-scans. Patient specific training and different pre-processing steps were evaluated. Results: Classification rates from 67.5% up to 76% were ...

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    8. Morphometric grading of osteoarthritis by optical coherence tomography - An ex vivo study

      Morphometric grading of osteoarthritis by optical coherence tomography - An ex vivo study

      Optical Coherence Tomography (OCT) yields microscopic cross-sectional images of cartilage in real time and at high resolution. As yet, comprehensive grading of degenerative cartilage changes based on OCT has rarely been performed. This study investigated the potential of quantitative OCT using algorithm-based image parameters such as irregularity (OII – Optical Irregularity Index), homogeneity (OHI – Optical Homogeneity Index) and attenuation (OAI – Optical Attenuation Index) in the objective grading of cartilage degeneration. Therefore, OCT was used to image and assess 113 human osteochondral samples obtained from total knee replacements. Processing included the analysis of OII (by calculation of the standard deviation with regards ...

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    9. Numerical focusing methods for full field OCT: a comparison based on a common signal model

      Numerical focusing methods for full field OCT: a comparison based on a common signal model

      In this paper a theoretical model of the full field swept source (FF SS) OCT signal is presented based on the angular spectrum wave propagation approach which accounts for the defocus error with imaging depth. It is shown that using the same theoretical model of the signal, numerical defocus correction methods based on a simple forward model (FM) and inverse scattering (IS), the latter being similar to interferometric synthetic aperture microscopy (ISAM), can be derived. Both FM and IS are compared quantitatively with sub-aperture based digital adaptive optics (DAO). FM has the least numerical complexity, and is the fastest in ...

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    10. Adaptive-Weighted Bilateral Filtering and Other Pre-processing Techniques for Optical Coherence Tomography

      Adaptive-Weighted Bilateral Filtering and Other Pre-processing Techniques for Optical Coherence Tomography

      This paper presents novel pre-processing image enhancement algorithms for retinal optical coherence tomography (OCT). These images contain a large amount of speckle causing them to be grainy and of very low contrast. To make these images valuable for clinical interpretation, we propose a novel method to remove speckle, while preserving useful information contained in each retinal layer. The process starts with multi-scale despeckling based on a dual-tree complex wavelet transform (DT-CWT). We further enhance the OCT image through a smoothing process that uses a novel adaptive-weighted bilateral filter (AWBF). This offers the desirable property of preserving texture within the OCT ...

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    11. A generic process platform for photonic integrated circuits

      A generic process platform for photonic integrated circuits

      A generic integration platform, analogous to that used in microelectronics, may reduce the cost of photonic integrated circuits and make this technology accessible to new sectors. Photonic integrated circuits (PICs) are used primarily in fiber-optic communications and telecommunications as signal encoders and decoders for systems operating at 100–400Gb/s. Furthermore, they have applications in fiber-based sensors as readout circuits, and in metrology and medicine (specifically, optical coherence tomography). PIC technology exploits light to achieve signal processing using predominantly indium phosphide (InP)-based materials (see Figure 1 ), which offer the required functionalities of emission, modulation, and detection. 1

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    12. Multifocal interferometric synthetic aperture microscopy

      Multifocal interferometric synthetic aperture microscopy

      There is an inherent trade-off between transverse resolution and depth of field (DOF) in optical coherence tomography (OCT) which becomes a limiting factor for certain applications. Multifocal OCT and interferometric synthetic aperture microscopy (ISAM) each provide a distinct solution to the trade-off through modification to the experiment or via post-processing, respectively. In this paper, we have solved the inverse problem of multifocal OCT and present a general algorithm for combining multiple ISAM datasets. Multifocal ISAM (MISAM) uses a regularized combination of the resampled datasets to bring advantages of both multifocal OCT and ISAM to achieve optimal transverse resolution, extended effective ...

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    13. Bayesian maximum likelihood estimator of phase retardation for quantitative polarization-sensitive optical coherence tomography

      Bayesian maximum likelihood estimator of phase retardation for quantitative polarization-sensitive optical coherence tomography

      This paper presents the theory and numerical implementation of a maximum likelihood estimator for local phase retardation (i.e., birefringence) measured using Jones-matrix-based polarization sensitive optical coherence tomography. Previous studies have shown conventional mean estimations of phase retardation and birefringence are significantly biased in the presence of system noise. Our estimator design is based on a Bayes’ rule that relates the distributions of the measured birefringence under a particular true birefringence and the true birefringence under a particular measured birefringence. We used a Monte-Carlo method to calculate the likelihood function that describes the relationship between the distributions and numerically implement ...

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    14. Comparison by Optical Coherence Tomography of the Frequency of Lipid Coronary Plaques in Current Smokers, Former Smokers, and Non-smokers

      Comparison by Optical Coherence Tomography of the Frequency of Lipid Coronary Plaques in Current Smokers, Former Smokers, and Non-smokers

      Smoking is associated with high incidence of cardiovascular events including acute coronary syndrome (ACS). We sought to characterize coronary plaques in patients with ongoing smoking using optical coherence tomography (OCT) compared to former smokers and nonsmokers. We identified 465 coronary plaques from 182 subjects who underwent OCT imaging for all three coronary arteries. Subjects were divided into 3 groups: current smokers (n=41), former smokers (n=67) and nonsmokers (n=74). OCT analysis included the presence of lipid rich plaque, thin-cap fibroatheroma (TCFA), calcification, maximum lipid arc, lipid core length, lipid index, and fibrous cap thickness (FCT). Lipid index was ...

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    15. Polarization Sensitive Multimodal Imaging for Detecting Breast Cancer

      Polarization Sensitive Multimodal Imaging for Detecting Breast Cancer

      Intra-operative delineation of breast cancer is a significant problem in surgical oncology. A reliable method for demarcation of malignant breast tissue during surgery would reduce the re-excision rate due to positive margins. We present a novel method of identifying breast cancer margins using combined dye-enhanced wide-field fluorescence polarization (FP) imaging for en face cancer margins and polarization sensitive (PS) optical coherence tomography (OCT) for cross-sectional evaluation. Tumor specimens were collected following breast surgery, stained with methylene blue, and imaged. Wide-field FP images were excited at 640 nm and registered between 660 and 750 nm. Standard and PS OCT images were ...

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    16. Optical coherence tomography for the evaluation of asymmetric cardiac allograft vasculopathy in a child

      Optical coherence tomography for the evaluation of asymmetric cardiac allograft vasculopathy in a child

      We present an unusual case of CAV in a child with isolated disease in the LAD coronary artery. Initial progression of the disease appeared to have been halted by the use of sirolimus, but the assessment of disease in other vessels (particularly the RCA) was of particular importance in deciding whether or not to relist this patient for transplantation. Due to the known limitations of coronary angiography, we used OCT to assess for angiographically silent CAV. The normal intravascular appearance of the RCA by OCT was reassuring, and the child was not relisted for transplantation. OCT offers multiple advantages for ...

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    17. Cross-validation of serial optical coherence scanning and diffusion tensor imaging: A study on neural fiber maps in human medulla oblongata

      Cross-validation of serial optical coherence scanning and diffusion tensor imaging: A study on neural fiber maps in human medulla oblongata

      We established a strategy to perform cross-validation of serial optical coherence scanner imaging (SOCS) and diffusion tensor imaging (DTI) on a postmortem human medulla. Following DTI, the sample was serially scanned by SOCS, which integrates a vibratome slicer and a multi-contrast optical coherence tomography rig for large-scale three-dimensional imaging at microscopic resolution. The DTI dataset was registered to the SOCS space. An average correlation coefficient of 0.9 was found between the co-registered fiber maps constructed by fractional anisotropy and retardance contrasts. Pixelwise comparison of fiber orientations demonstrated good agreement between the DTI and SOCS measures. Details of the comparison ...

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    18. Observing cochlear function

      Observing cochlear function

      Phase-sensitive optical coherence tomography measures the morphology and functional vibratory response in the mouse cochlea and helps decipher the complex mechanical processes responsible for hearing.  Hearing loss is the most common sensory health issue due to the multiple effects of noise, aging, disease, and heredity. According to the World Health Organization, more than 360 million people worldwide suffer from disabling hearing loss. 1 Current therapies for hearing loss treat some of the symptoms by providing volume amplification, but there are no curative therapies. The development of effective therapies significantly depends upon a detailed understanding of the complex mechanisms of the ...

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    19. Wide and fast wavelength-swept fiber lasers based on dispersion tuning for real-time OCT

      Wide and fast wavelength-swept fiber lasers based on dispersion tuning for real-time OCT

      Swept-Source Optical coherence tomography (SS-OCT) is a powerful tool for fast medical imaging. For the real-time 3D imaging, the wide tuning range over 100 nm and fast sweep rate over 100 kHz are typically required. We recently proposed a new wavelength-swept laser for SS-OCT. It is based on a principle called dispersion tuning. Since the cavity contains no mechanical components, such as tunable filters, we could achieve the very high sweep rate. In this review paper, we describe the principle of the dispersion-tuned swept lasers in detail and present our recent works on the application to the SS-OCT system.

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    20. Quality control for retinal OCT in multiple sclerosis: validation of the OSCAR-IB criteria

      Quality control for retinal OCT in multiple sclerosis: validation of the OSCAR-IB criteria

      Background: Retinal optical coherence tomography (OCT) permits quantification of retinal layer atrophy relevant to assessment of neurodegeneration in multiple sclerosis (MS). Measurement artefacts may limit the use of OCT to MS research. Objective: An expert task force convened with the aim to provide guidance on the use of validated quality control (QC) criteria for the use of OCT in MS research and clinical trials. Methods: A prospective multi-centre ( n = 13) study. Peripapillary ring scan QC rating of an OCT training set ( n = 50) was followed by a test set ( n = 50). Inter-rater agreement was calculated using kappa statistics. Results were ...

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    21. Validation of Airway Wall Measurements by Optical Coherence Tomography in Porcine Airways

      Validation of Airway Wall Measurements by Optical Coherence Tomography in Porcine Airways

      Examining and quantifying changes in airway morphology is critical for studying longitudinal pathogenesis and interventions in diseases such as chronic obstructive pulmonary disease and asthma. Here we present fiber-optic optical coherence tomography (OCT) as a nondestructive technique to precisely and accurately measure the 2-dimensional cross-sectional areas of airway wall substructure divided into the mucosa (WA muc ), submucosa (WA sub ), cartilage (WA cart ), and the airway total wall area (WAt). Porcine lung airway specimens were dissected from freshly resected lung lobes (N = 10). Three-dimensional OCT imaging using a fiber-optic rotary-pullback probe was performed immediately on airways greater than 0.9 mm ...

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    22. Perspectives of mid-infrared optical coherence tomography for inspection and micrometrology of industrial ceramics

      Perspectives of mid-infrared optical coherence tomography for inspection and micrometrology of industrial ceramics

      Optical coherence tomography (OCT) is a promising tool for detecting micro channels, metal prints, defects and delaminations embedded in alumina and zirconia ceramic layers at hundreds of micrometers beneath surfaces. The effect of surface roughness and scattering of probing radiation within sample on OCT inspection is analyzed from the experimental and simulated OCT images of the ceramic samples with varying surface roughnesses and operating wavelengths. By Monte Carlo simulations of the OCT images in the mid-IR the optimal operating wavelength is found to be 4 µm for the alumina samples and 2 µm for the zirconia samples for achieving sufficient ...

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    23. Reproducibility of the Carpet View system: a novel technical solution for display and off line analysis of OCT images

      Reproducibility of the Carpet View system: a novel technical solution for display and off line analysis of OCT images

      The optical coherence tomography (OCT) evaluation of the stent anatomy requires the inspection of sequential cross section (CS). However stent coils cannot be appreciated in the conventional format as the OCT CS simply display stent struts, that are poorly representative of the stent architecture. The aim of the present study was to validate a new software ( Carpet View ), which unfolds the stented segment, reconstructing it as an open structure and displaying the stent meshwork. 21 patients were studied with frequency domain OCT after the deployment of different stents: seven bio-absorbable scaffolds (Dream), seven bare metal stent (Vision/Multilink8), seven drug ...

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      Mentions: Francesco Prati
    24. Coherence revival multiplexed, buffered swept source optical coherence tomography: 400  kHz imaging with a 100  kHz source

      Coherence revival multiplexed, buffered swept source optical coherence tomography: 400  kHz imaging with a 100  kHz source

      The effective speed of a swept source optical coherence tomography (SSOCT) imaging system was quadrupled using efficient sweep buffering along with coherence revival and spatial multiplexing. A polarizing beam splitter and fold mirror assembly were used to create a dual spot sample arm with a common objective designed for near-diffraction-limited retinal imaging. Using coherence revival, a variable optical delay line allowed for separate locations within a sample to be simultaneously imaged and frequency encoded by carefully controlling the optical path length of each sample path. This method can be used to efficiently quadruple the imaging speed of any SSOCT system ...

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    25-48 of 74 « 1 2 3 »
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