1. Articles from Caroline Magnain

    1-16 of 16
    1. A novel algorithm for multiplicative speckle noise reduction in ex vivo human brain OCT images

      A novel algorithm for multiplicative speckle noise reduction in ex vivo human brain OCT images

      Optical coherence tomography (OCT) images of ex vivo human brain tissue are corrupted by multiplicative speckle noise that degrades the contrast to noise ratio (CNR) of microstructural compartments. This work proposes a novel algorithm to reduce noise corruption in OCT images that minimizes the penalized negative log likelihood of gamma distributed speckle noise. The proposed method is formulated as a majorize-minimize problem that reduces to solving an iterative regularized least squares optimization. We demonstrate the usefulness of the proposed method by removing speckle in simulated data, phantom data and real OCT images of human brain tissue. We compare the proposed ...

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    2. Volumetric characterization of microvasculature in ex vivo human brain samples by serial sectioning optical coherence tomography

      Volumetric characterization of microvasculature in ex vivo human brain samples by serial sectioning optical coherence tomography

      Objective: Serial sectioning optical coherence tomography (OCT) enables distortion-free volumetric reconstruction of several cubic centimeters of human brain samples. We aimed to identify anatomical features of the ex vivo human brain, such as intraparenchymal blood vessels and axonal fiber bundles, from the OCT data in 3D, using intrinsic optical contrast. Methods: We developed an automatic processing pipeline to enable characterization of the intraparenchymal microvascular network in human brain samples. Results: We demonstrated the automatic extraction of the vessels down to a 20 m in diameter using a filtering strategy followed by a graphing representation and characterization of the geometrical properties ...

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    3. Refractive-index matching enhanced polarization sensitive optical coherence tomography quantification in human brain tissue

      Refractive-index matching enhanced polarization sensitive optical coherence tomography quantification in human brain tissue

      The importance of polarization-sensitive optical coherence tomography (PS-OCT) has been increasingly recognized in human brain imaging. Despite the recent progress of PS-OCT in revealing white matter architecture and orientation, quantification of fine-scale fiber tracts in the human brain cortex has been a challenging problem, due to a low birefringence in the gray matter. In this study, we investigated the effect of refractive index matching by 2,2’-thiodiethanol (TDE) immersion on the improvement of PS-OCT measurements in ex vivo human brain tissue. We show that we can obtain fiber orientation maps of U-fibers that underlie sulci, as well as cortical ...

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    4. Scalable mapping of myelin and neuron density in the human brain with micrometer resolution

      Scalable mapping of myelin and neuron density in the human brain with micrometer resolution

      Optical coherence tomography (OCT) is an emerging 3D imaging technique that allows quantification of intrinsic optical properties such as scattering coefficient and back-scattering coefficient, and has proved useful in distinguishing delicate microstructures in the human brain. The origins of scattering in brain tissues are contributed by the myelin content, neuron size and density primarily; however, no quantitative relationships between them have been reported, which hampers the use of OCT in fundamental studies of architectonic areas in the human brain and the pathological evaluations of diseases. Here, we built a generalized linear model based on Mie scattering theory that quantitatively links ...

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    5. Refractive-index matching enhanced polarization-sensitive optical coherence tomography quantification in human brain tissue

      Refractive-index matching enhanced polarization-sensitive optical coherence tomography quantification in human brain tissue

      The importance of polarization-sensitive optical coherence tomography (PS-OCT) has been increasingly recognized in human brain imaging. Despite the recent progress of PS-OCT in revealing white matter architecture and orientation, quantification of fine-scale fiber tracts in the human brain cortex has been a challenging problem, due to a low birefringence in the gray matter. In this study, we investigated the effect of refractive index matching by 2,2'-thiodiethanol (TDE) immersion on the improvement of PS-OCT measurements in ex vivo human brain tissue. We obtain the cortical fiber orientation maps in the gray matter, which reveals the radial fibers in the ...

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    6. Scalable mapping of myelin and neuron density in the human brain with micrometer resolution

      Scalable mapping of myelin and neuron density in the human brain with micrometer resolution

      Optical Coherence Tomography (OCT) is an emerging 3D imaging technique that allows quantification of intrinsic optical properties such as scattering coefficient and back-scattering coefficient, and has proved useful in distinguishing delicate microstructures in the human brain. The origins of scattering in brain tissues are contributed by the myelin content, neuron size and density primarily; however, no quantitative relationships between them have been reported, which hampers the use of OCT in fundamental studies of architectonic areas in the human brain and the pathological evaluations of diseases. To date, histology remains the golden standard, which is prone to errors and can only ...

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    7. Measuring myelin content and cell density in the human brain using optical coherence tomography

      Measuring myelin content and cell density in the human brain using optical coherence tomography

      Serial Sectioning Optical Coherence Tomography(serial sectioning OCT) has been widely used to investigate the structural and pathological features of brain samples. OCT is an optical imaging technique that provides both the 3D structure of the tissue as well as the optical properties including the scattering coefficient (μ s ) and back-scattering coefficient (μ b ). Serial sectioning OCT allows the reconstruction of distortion-free volumetric images at high contrast and high resolution, which has proven to be useful for the detection of cancerous tissue boundaries, visualizing 3D vascular structures and measuring neuron density. The tissue optical properties extracted from the OCT depth profile has ...

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    8. Human Brain Imaging by Optical Coherence Tomography (Book Chapter)

      Human Brain Imaging by Optical Coherence Tomography (Book Chapter)

      The Handbook of Neurophotonics provides a dedicated overview of neurophotonics, covering the use of advanced optical technologies to record, stimulate, and control the activity of the brain, yielding new insight and advantages over conventional tools due to the adaptability and non-invasive nature of light. Including 30 colour figures, this book addresses functional studies of neurovascular signaling, metabolism, electrical excitation, and hemodynamics, as well as clinical applications for imaging and manipulating brain structure and function. The unifying theme throughout is not only to highlight the technology, but to show how these novel methods are becoming critical to breakthroughs that will lead ...

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    9. Insight into the fundamental trade-offs of diffusion MRI from polarization-sensitive optical coherence tomography in ex vivo human brain

      Insight into the fundamental trade-offs of diffusion MRI from polarization-sensitive optical coherence tomography in ex vivo human brain

      In the first study comparing high angular resolution diffusion MRI (dMRI) in the human brain to axonal orientation measurements from polarization-sensitive optical coherence tomography (PSOCT), we compare the accuracy of orientation estimates from various dMRI sampling schemes and reconstruction methods. We find that, if the reconstruction approach is chosen carefully, single-shell dMRI data can yield the same accuracy as multi-shell data, and only moderately lower accuracy than a full Cartesian-grid sampling scheme. Our results suggest that current dMRI reconstruction approaches do not benefit substantially from ultra-high b-values or from very large numbers of diffusion-encoding directions. We also show that accuracy ...

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    10. Colocalization of neurons in optical coherence microscopy and Nissl-stained histology in Brodmann’s area 32 and area 21

      Colocalization of neurons in optical coherence microscopy and Nissl-stained histology in Brodmann’s area 32 and area 21

      Optical coherence tomography is an optical technique that uses backscattered light to highlight intrinsic structure, and when applied to brain tissue, it can resolve cortical layers and fiber bundles. Optical coherence microscopy (OCM) is higher resolution (i.e., 1.25 µm) and is capable of detecting neurons. In a previous report, we compared the correspondence of OCM acquired imaging of neurons with traditional Nissl stained histology in entorhinal cortex layer II. In the current method-oriented study, we aimed to determine the colocalization success rate between OCM and Nissl in other brain cortical areas with different laminar arrangements and cell packing ...

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    11. Characterizing the optical properties of human brain tissue with high numerical aperture optical coherence tomography

      Characterizing the optical properties of human brain tissue with high numerical aperture optical coherence tomography

      Quantification of tissue optical properties with optical coherence tomography (OCT) has proven to be useful in evaluating structural characteristics and pathological changes. Previous studies primarily used an exponential model to analyze low numerical aperture (NA) OCT measurements and obtain the total attenuation coefficient for biological tissue. In this study, we develop a systematic method that includes the confocal parameter for modeling the depth profiles of high NA OCT, when the confocal parameter cannot be ignored. This approach enables us to quantify tissue optical properties with higher lateral resolution. The model parameter predictions for the scattering coefficients were tested with calibrated ...

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    12. Polarization-sensitive optical coherence tomography of the human brain connectome

      Polarization-sensitive optical coherence tomography of the human brain connectome

      The human brain is composed of approximately 100 billion neurons that ‘communicate’ through an intricate network of axons and dendrites. 1 The difficulty of tracing these 3D neuronal pathways, however, has been a critical barrier for standard histology (the study of microscopic anatomy) over the past 100 years. Indeed, there is still no technology that can be used to acquire microscopic images in undistorted 3D space for mapping human brain connectivity. Currently available techniques for 3D brain mapping include histological staining and polarized light imaging. 2, 3 In these approaches, 2D image slices are obtained, but these must be physically ...

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    13. Polarization sensitive optical coherence microscopy for brain imaging

      Polarization sensitive optical coherence microscopy for brain imaging

      Optical coherence tomography (OCT) and optical coherence microscopy (OCM) have demonstrated the ability to investigate cyto- and myelo-architecture in the brain. Polarization-sensitive OCT provides sensitivity to additional contrast mechanisms, specifically the birefringence of myelination and, therefore, is advantageous for investigating white matter fiber tracts. In this Letter, we developed a polarization-sensitive optical coherence microscope (PS-OCM) with a 3.5 μm axial and 1.3 μm transverse resolution to investigate fiber organization and orientation at a finer scale than previously demonstrated with PS-OCT. In a reconstructed mouse brain section, we showed that at the focal depths of 20–70 μm, the ...

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    14. Optical coherence tomography visualizes neurons in human entorhinal cortex

      Optical coherence tomography visualizes neurons in human entorhinal cortex

      The cytoarchitecture of the human brain is of great interest in diverse fields: neuroanatomy, neurology, neuroscience, and neuropathology. Traditional histology is a method that has been historically used to assess cell and fiber content in the ex vivo human brain. However, this technique suffers from significant distortions. We used a previously demonstrated optical coherence microscopy technique to image individual neurons in several square millimeters of en-face tissue blocks from layer II of the human entorhinal cortex, over 50     μ m in depth. The same slices were then sectioned and stained for Nissl substance. We registered the optical coherence tomography (OCT) images ...

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    15. Blockface histology with optical coherence tomography: A comparison with Nissl staining

      Blockface histology with optical coherence tomography: A comparison with Nissl staining

      Spectral domain optical coherence tomography (SD-OCT) is a high resolution imaging technique that generates excellent contrast based on intrinsic optical properties of the tissue, such as neurons and fibers. The SD-OCT data acquisition is performed directly on the tissue block, diminishing the need for cutting, mounting and staining. We utilized SD-OCT to visualize the laminar structure of the isocortex and compared cortical cytoarchitecture with the gold standard Nissl staining, both qualitatively and quantitatively. In histological processing, distortions routinely affect registration to the blockface image and prevent accurate 3D reconstruction of regions of tissue. We compared blockface registration to SD-OCT and ...

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    16. Contribution of surface state characterization to studies of works of art

      Contribution of surface state characterization to studies of works of art
      This paper has two purposes. The first one underlines that qualitative and quantitative studies of surface states lead to relevant information for analyzing works of art, with lots of potential for art history, restorers, and curators. The discrimination between different artistic techniques and the influence of a varnish on the leveling of paint surfaces are presented. The second purpose is the comparison between different nondestructive optical topographic methods, i.e., goniophotometry, optical coherence topography, and confocal microscopy, according to their accuracy, their discriminatory ability, their practicability inside a museum, and the size limits of the studied objects.
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    1-16 of 16
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    1. (13 articles) Massachusetts General Hospital
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    Contribution of surface state characterization to studies of works of art Blockface histology with optical coherence tomography: A comparison with Nissl staining Optical coherence tomography visualizes neurons in human entorhinal cortex Polarization sensitive optical coherence microscopy for brain imaging Polarization-sensitive optical coherence tomography of the human brain connectome Characterizing the optical properties of human brain tissue with high numerical aperture optical coherence tomography Colocalization of neurons in optical coherence microscopy and Nissl-stained histology in Brodmann’s area 32 and area 21 Insight into the fundamental trade-offs of diffusion MRI from polarization-sensitive optical coherence tomography in ex vivo human brain Human Brain Imaging by Optical Coherence Tomography (Book Chapter) Refractive-index matching enhanced polarization-sensitive optical coherence tomography quantification in human brain tissue PREcise Percutaneous Coronary Intervention for Stent OptimizatION in Treatment of COMPLEX Lesion (PRECISION-COMPLEX) Real-Time Risk Score for Glaucoma Mass Screening by Spectral Domain Optical Coherence Tomography: Development and Validation