1. 1-24 of 456 1 2 3 4 ... 17 18 19 »
    1. Volumetric optical coherence microscopy with a high space-bandwidth-time product enabled by hybrid adaptive optics

      Volumetric optical coherence microscopy with a high space-bandwidth-time product enabled by hybrid adaptive optics

      Optical coherence microscopy (OCM) is a promising modality for high resolution imaging, but has limited ability to capture large-scale volumetric information about dynamic biological processes with cellular resolution. To enhance the throughput of OCM, we implemented a hybrid adaptive optics (hyAO) approach that combines computational adaptive optics with an intentionally aberrated imaging beam generated via hardware adaptive optics. Using hyAO, we demonstrate the depth-equalized illumination and collection ability of an astigmatic beam compared to a Gaussian beam for cellular-resolution imaging. With this advantage, we achieved volumetric OCM with a higher space-bandwidth- time product compared to Gaussian-beam acquisition that employed focus-scanning ...

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    2. Deep learning for the segmentation of preserved photoreceptors on en face optical coherence tomography in two inherited retinal diseases

      Deep learning for the segmentation of preserved photoreceptors on en face optical coherence tomography in two inherited retinal diseases

      The objective quantification of photoreceptor loss in inherited retinal degenerations (IRD) is essential for measuring disease progression, and is now especially important with the growing number of clinical trials. Optical coherence tomography (OCT) is a non-invasive imaging technology widely used to recognize and quantify such anomalies. Here, we implement a versatile method based on a convolutional neural network to segment the regions of preserved photoreceptors in two different IRDs (choroideremia and retinitis pigmentosa) from OCT images. An excellent segmentation accuracy (~90%) was achieved for both IRDs. Due to the flexibility of this technique, it has potential to be extended to ...

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    3. Realistic simulation and experiment reveals the importance of scatterer microstructure in optical coherence tomography image formation

      Realistic simulation and experiment reveals the importance of scatterer microstructure in optical coherence tomography image formation

      Realistic simulation of image formation in optical coherence tomography, based on Maxwell’s equations, has recently been demonstrated for sample volumes of practical significance. Yet, there remains a limitation whereby reducing the size of cells used to construct a computational grid, thus allowing for a more realistic representation of scatterer microstructure, necessarily reduces the overall sample size that can be modelled. This is a significant problem since, as is well known, the microstructure of a scatterer significantly influences its scattering properties. Here we demonstrate that an optimized scatterer design can overcome this problem resulting in good agreement between simulated and ...

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    4. Pixel-wise segmentation of severely pathologic retinal pigment epithelium and choroidal stroma using multi-contrast Jones matrix optical coherence tomography

      Pixel-wise segmentation of severely pathologic retinal pigment epithelium and choroidal stroma using multi-contrast Jones matrix optical coherence tomography

      Tissue segmentation of retinal optical coherence tomography (OCT) is widely used in ophthalmic diagnosis. However, its performance in severe pathologic cases is still insufficient. We propose a pixel-wise segmentation method that uses the multi-contrast measurement capability of Jones matrix OCT (JM-OCT). This method is applicable to both normal and pathologic retinal pigment epithelium (RPE) and choroidal stroma. In this method, “features,” which are sensitive to specific tissues of interest, are synthesized by combining the multi-contrast images of JM-OCT, including attenuation coefficient, degree-of-polarization-uniformity, and OCT angiography. The tissue segmentation is done by simple thresholding of the feature. Compared with conventional segmentation ...

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    5. Simulation of penetration depth of Bessel beams for multifocal optical coherence tomography

      Simulation of penetration depth of Bessel beams for multifocal optical coherence tomography

      Multifocal Bessel beam optical coherence tomography (MBOCT) combines the advantages of Bessel beam OCT and multifocal OCT to increase imaging depth. For MBOCT, the penetration depth of the Bessel beam in highly scattering biological tissue limits the final imaging depth. In this paper, we theoretically analyze the penetration depth of the Bessel beams with different parameters to explore which kind of Bessel beam is more suitable for MBOCT in a scattering medium. The finite-difference time-domain method is used to simulate the field distribution of Bessel beams in the medium. We find that the MBOCT for more focus based on a ...

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    6. Real-time visualization and interaction with static and live optical coherence tomography volumes in immersive virtual reality

      Real-time visualization and interaction with static and live optical coherence tomography volumes in immersive virtual reality

      Virtual reality (VR) head-mounted displays are an attractive technology for viewing intrasurgical optical coherence tomography (OCT) volumes because they liberate surgeons from microscope oculars. We demonstrate real-time, interactive viewing of OCT volumes in a commercial HTC Vive immersive VR system using previously reported ray casting techniques. Furthermore, we show interactive manipulation and sectioning of volumes using handheld controllers and guidance of mock surgical procedures in porcine eyes exclusively within VR. To the best of our knowledge, we report the first immersive VR-OCT viewer with stereo ray casting volumetric renders, arbitrary sectioning planes, and live acquisition support. We believe VR-OCT volume ...

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    7. Deep longitudinal transfer learning-based automatic segmentation of photoreceptor ellipsoid zone defects on optical coherence tomography images of macular telangiectasia type 2

      Deep longitudinal transfer learning-based automatic segmentation of photoreceptor ellipsoid zone defects on optical coherence tomography images of macular telangiectasia type 2

      Photoreceptor ellipsoid zone (EZ) defects visible on optical coherence tomography (OCT) are important imaging biomarkers for the onset and progression of macular diseases. As such, accurate quantification of EZ defects is paramount to monitor disease progression and treatment efficacy over time. We developed and trained a novel deep learning-based method called Deep OCT Atrophy Detection (DOCTAD) to automatically segment EZ defect areas by classifying 3-dimensional A-scan clusters as normal or defective. Furthermore, we introduce a longitudinal transfer learning paradigm in which the algorithm learns from segmentation errors on images obtained at one time point to segment subsequent images with higher ...

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    8. Photothermal optical coherence tomography of indocyanine green in ex vivo eyes

      Photothermal optical coherence tomography of indocyanine green in ex vivo eyes

      Indocyanine green (ICG) is routinely used during surgery to stain the inner limiting membrane (ILM) and provide contrast on white light surgical microscopy. While translation of optical coherence tomography (OCT) for intraoperative imaging during ophthalmic surgery has enhanced visualization, the ILM remains difficult to distinguish from underlying retinal structures and ICG does not provide additional OCT contrast. We present photothermal OCT (PT-OCT) for high-specificity detection of ICG on retinal OCT images. We demonstrate our technique by performing an ILM peel in ex vivo eyes using low ICG concentrations and laser powers. These results establish the feasibility of PT-OCT for intraoperative ...

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    9. Wide dynamic range high-speed three-dimensional quantitative OCT angiography with a hybrid-beam scan

      Wide dynamic range high-speed three-dimensional quantitative OCT angiography with a hybrid-beam scan

      We demonstrate a novel hybrid-beam scanning-based quantitative optical coherence tomography angiography (OCTA) that provides high-speed wide dynamic range blood flow speed imaging. The hybrid-beam scanning scheme enables multiple OCTA image acquisitions with a wide range of multiple time intervals simultaneously providing wide dynamic range blood flow speed imaging independent of the blood vessel orientation, which was quantified over a speed range of 0.6 ∼ 104    mm / s 0.6∼104  mm/s through the blood flow phantom experiments. A fully automated high-speed hybrid-beam scanning-based quantitative OCTA system demonstrates visualization of blood flow speeds in various vessels from the main arteries ...

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    10. Automatic analysis of bioresorbable vascular scaffolds in intravascular optical coherence tomography images

      Automatic analysis of bioresorbable vascular scaffolds in intravascular optical coherence tomography images

      The bioresorbable vascular scaffold (BVS) is a new generation of bioresorbable scaffold (BRS) for the treatment of coronary artery disease. A potential challenge of BVS is malapposition, which may possibly lead to late stent thrombosis. It is therefore important to conduct malapposition analysis right after stenting. Since an intravascular optical coherence tomography (IVOCT) image sequence contains thousands of BVS struts, manual analysis is labor intensive and time consuming. Computer-based automatic analysis is an alternative, but faces some difficulties due to the interference of blood artifacts and the uncertainty of the struts number, position and size. In this paper, we propose ...

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    11. Multimodality endoscopic optical coherence tomography and fluorescence imaging technology for visualization of layered architecture and subsurface microvasculature

      Multimodality endoscopic optical coherence tomography and fluorescence imaging technology for visualization of layered architecture and subsurface microvasculature

      Endoscopic imaging technologies, such as endoscopic optical coherence tomography (OCT) and near-infrared fluorescence, have been used to investigate vascular and morphological changes as hallmarks of early cancer in the gastrointestinal tract. Here we developed a high-speed multimodality endoscopic OCT and fluorescence imaging system. Using this system, the architectural morphology and vasculature of the rectum wall were obtained simultaneously from a Sprague Dawley rat in vivo . This multimodality imaging strategy in a single imaging system permits the use of a single imaging probe, thereby improving prognosis by early detection and reducing costs.

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    12. Fast and robust standard-deviation-based method for bulk motion compensation in phase-based functional OCT

      Fast and robust standard-deviation-based method for bulk motion compensation in phase-based functional OCT

      Phase-based optical coherence tomography (OCT), such as OCT angiography (OCTA) and Doppler OCT, is sensitive to the confounding phase shift introduced by subject bulk motion. Traditional bulk motion compensation methods are limited by their accuracy and computing cost-effectiveness. In this Letter, to the best of our knowledge, we present a novel bulk motion compensation method for phase-based functional OCT. Bulk motion associated phase shift can be directly derived by solving its equation using a standard deviation of phase-based OCTA and Doppler OCT flow signals. This method was evaluated on rodent retinal images acquired by a prototype visible light OCT and ...

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    13. Effective bidirectional scanning pattern for optical coherence tomography angiography

      Effective bidirectional scanning pattern for optical coherence tomography angiography

      We demonstrate the utility of a novel scanning method for optical coherence tomography angiography (OCTA). Although raster scanning is commonly used for OCTA imaging, a bidirectional approach would lessen the distortion caused by galvanometer-based scanners as sources continue to increase sweep rates. As shown, a unidirectional raster scan approach has a lower effective scanning time than bidirectional approaches; however, a strictly bidirectional approach causes contrast variation along the B-scan direction due to the non-uniform time interval between B-scans. Therefore, a stepped bidirectional approach is introduced and successfully applied to retinal imaging in normal controls and in a pathological subject with ...

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    14. Speckle noise reduction of multi-frame optical coherence tomography data using multi-linear principal component analysis

      Speckle noise reduction of multi-frame optical coherence tomography data using multi-linear principal component analysis

      Optical coherence tomography (OCT) is an important interferometric diagnostic technique extensively applied in medical sciences. However, OCT images inevitably suffer from speckle noise, which reduces the accuracy of the diagnosis of ocular diseases. To deal with this problem, a speckle noise reduction method based on multi-linear principal component analysis (MPCA) is presented to denoise multi-frame OCT data. To well preserve local image features, nonlocal similar 3D blocks extracted from the data are first grouped using k-means++ clustering method. MPCA transform is then performed on each group and the transform coefficients are shrunk to remove speckle noise. Finally, the filtered OCT ...

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    15. Feature issue of Biomedical Optics Express: Progress in Multimodal En-Face Imaging

      Feature issue of Biomedical Optics Express: Progress in Multimodal En-Face Imaging

      Biomedical Optics Express welcomes submissions to a feature issue on "Progress in Multimodal En-Face Imaging". Multimodal optical imaging certainly enriches the amount of information that can be retrieved from biological tissue. For this purpose, many different approaches have been combined, including optical coherence tomography (OCT), microscopy, scanning laser ophthalmoscopy (SLO), fluorescence imaging, multi-photon imaging, Raman spectroscopy, photoacoustics, and many more. This year marks 20 years from the publication of a first report on a combination of the old SLO, dating back from 1980, and of OCT, at that time a rather novel imaging technique as it was just invented in ...

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    16. Extending axial focus of optical coherence tomography using parallel multiple aperture synthesis

      Extending axial focus of optical coherence tomography using parallel multiple aperture synthesis

      Compromising the inherent trade-off between transverse resolution and depth of focus (DOF) remains a long-standing issue in optical coherence tomography (OCT). In this work, we report a novel technique—parallel multiple aperture synthesis (pMAS) to simultaneously generate multiple optical apertures in an OCT sample arm by employing a two-surface coated mirror. In the proposed pMAS, the DOF is extended by a factor of 16.49 without sacrificing the transverse resolution for proof-of-concept experiments when multiple distinctive apertures are digitally synthesized. The microparticles and tissue experiments demonstrate the feasibility of pMAS to address the fundamental problem of limited DOF in high-resolution ...

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    17. A handheld microscope integrating photoacoustic microscopy and optical coherence tomography

      A handheld microscope integrating photoacoustic microscopy and optical coherence tomography

      The combination of optical resolution photoacoustic microscopy (ORPAM) and optical coherence tomography (OCT) is capable of providing complementary imaging contrasts. Unfortunately, the miniaturization of ORPAM remains a major challenge in the development of a handheld dual-modality imaging microscope with OCT. Here, we report the design and evaluation of an integrated ORPAM and OCT imaging probe using a two-dimensional MEMS (micro-electro-mechanical-system)-based optical scanner. This microscope, weighting 35.4 g, has an ultracompact size of 65×30×18 mm 3 , and an effective imaging area of 2×2 mm 2 . The experimental lateral resolutions are 3.7 μm (ORPAM) and 5 ...

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    18. Endoscopic optical coherence tomography enables morphological and subnanometer vibratory imaging of the porcine cochlea through the round window

      Endoscopic optical coherence tomography enables morphological and subnanometer vibratory imaging of the porcine cochlea through the round window

      A highly phase stable hand-held (HH) endoscopic system has been developed for optical coherence tomography and vibrometry. Designed to transit the ear canal to the middle ear space and peer through the round window (RW), it is capable of imaging the vibratory function of the cochlear soft tissues with subnanometer scale sensitivity. A side-looking, 9 cm long rigid endoscope with a distal diameter of 1.2 mm, was able to fit within the RW niche and provide imaging access. The phase stability was achieved in part by fully integrating a Michelson interferometer into the HH device. Ex vivo imaging of ...

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    19. Sub-clinical assessment of atopic dermatitis severity using angiographic optical coherence tomography

      Sub-clinical assessment of atopic dermatitis severity using angiographic optical coherence tomography

      Measurement of sub-clinical atopic dermatitis (AD) is important for determining how long therapies should be continued after clinical clearance of visible AD lesions. An important biomarker of subclinical AD is epidermal hypertrophy, the structural measures of which often make optical coherence tomography (OCT) challenging due to the lack of a clearly delineated dermal-epidermal junction in AD patients. Alternatively, angiographic OCT measurements of vascular depth and morphology may represent a robust biomarker for quantifying the severity of clinical and sub clinical AD. To investigate this, angiographic data sets were acquired from 32 patients with a range of AD severities. Deeper vascular ...

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    20. Robust wavenumber and dispersion calibration for Fourier-domain optical coherence tomography

      Robust wavenumber and dispersion calibration for Fourier-domain optical coherence tomography

      Many Fourier-domain optical coherence tomography (FD-OCT) systems sample the interference fringes with a non-uniform wavenumber ( k ) interval, introducing a chirp to the signal that depends on the path length difference underlying each fringe. A dispersion imbalance between sample and reference arms also generates a chirp in the fringe signal which, in contrast, is independent of depth. Fringe interpolation to obtain a signal linear in k and compensate dispersion imbalance is critical to achieving bandwidth-limited axial resolution. In this work, we propose an optimization-based algorithm to perform robust and automated calibration of FD-OCT systems, recovering both the interpolation function and the ...

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    21. Multispectral analog-mean-delay fluorescence lifetime imaging combined with optical coherence tomography

      Multispectral analog-mean-delay fluorescence lifetime imaging combined with optical coherence tomography

      The pathophysiological progression of chronic diseases, including atherosclerosis and cancer, is closely related to compositional changes in biological tissues containing endogenous fluorophores such as collagen, elastin, and NADH, which exhibit strong autofluorescence under ultraviolet excitation. Fluorescence lifetime imaging (FLIm) provides robust detection of the compositional changes by measuring fluorescence lifetime, which is an inherent property of a fluorophore. In this paper, we present a dual-modality system combining a multispectral analog-mean-delay (AMD) FLIm and a high-speed swept-source optical coherence tomography (OCT) to simultaneously visualize the cross-sectional morphology and biochemical compositional information of a biological tissue. Experiments using standard fluorescent solutions showed ...

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    22. Compact akinetic swept source optical coherence tomography angiography at 1060 nm supporting a wide field of view and adaptive optics imaging modes of the posterior eye

      Compact akinetic swept source optical coherence tomography angiography at 1060 nm supporting a wide field of view and adaptive optics imaging modes of the posterior eye

      Imaging of the human retina with high resolution is an essential step towards improved diagnosis and treatment control. In this paper, we introduce a compact, clinically user-friendly instrument based on swept source optical coherence tomography (SS-OCT). A key feature of the system is the realization of two different operation modes. The first operation mode is similar to conventional OCT imaging and provides large field of view (FoV) images (up to 45° × 30°) of the human retina and choroid with standard resolution. The second operation mode enables it to optically zoom into regions of interest with high transverse resolution using adaptive ...

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    23. Circumferential-scanning endoscopic optical coherence tomography probe based on a circular array of six 2-axis MEMS mirrors

      Circumferential-scanning endoscopic optical coherence tomography probe based on a circular array of six 2-axis MEMS mirrors

      We present a novel circumferential-scan endoscopic optical coherence tomography (OCT) probe by using a circular array of six electrothermal microelectromechanical (MEMS) mirrors and six C-lenses. The MEMS mirrors have a 0.5 mm × 0.5 mm mirror plate and a chip size of 1.5 mm × 1.3 mm. Each MEMS mirror can scan up to 45° at a voltage of less than 12 V. Six of those mirrors have been successfully packaged to a probe head; full circumferential scans have been demonstrated. Furthermore, each scan unit is composed of a MEMS mirror and a C-lens and the six scan ...

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      Mentions: Huikai K. Xie
    24. Automated spectroscopic retinal oximetry with visible-light optical coherence tomography

      Automated spectroscopic retinal oximetry with visible-light optical coherence tomography

      Accurate, quantitative assessment of retinal blood oxygen saturation ( sO 2 ) may provide a useful early indicator of pathophysiology in several ocular diseases. Here, with visible-light optical coherence tomography (OCT), we demonstrate an automated spectroscopic retinal oximetry algorithm to measure the sO 2 within the retinal arteries (A- sO 2 ) and veins (V- sO 2 ) in rats by automatically detecting the vascular posterior boundary on cross-sectional structural OCT. The algorithm was validated in vitro with flow phantoms and in vivo in rats by comparing the sO 2 results, respectively, to those obtained using a blood gas analyzer and pulse oximetry. We ...

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