1. Articles from Frédéric Lesage

    1-15 of 15

    1. Fully automated dual-resolution serial optical coherence tomography aimed at diffusion MRI validation in whole mouse brains

      Explore SPIE Digital Library Neurology
      Fully automated dual-resolution serial optical coherence tomography aimed at diffusion MRI validation in whole mouse brains

      An automated dual-resolution serial optical coherence tomography (2R-SOCT) scanner is developed. The serial histology system combines a low-resolution (25  μm  /  voxel) 3  ×   OCT with a high-resolution (1.5  μm  /  voxel) 40  ×   OCT to acquire whole mouse brains at low resolution and to target specific regions of interest (ROIs) at high resolution. The 40  ×   ROIs positions are selected either manually by the microscope operator or using an automated ROI positioning selection algorithm. Additionally, a multimodal and multiresolution registration pipeline is developed in order to align the 2R-SOCT data onto diffusion MRI (dMRI) data acquired in the same ex vivo mouse brains ...

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      Mentions: University of Montreal Polytechnique Montreal Frédéric Lesage

    2. Imaging whole mouse brains with a dual resolution serial swept-source optical coherence tomography scanner

      Explore SPIE Digital Library Developmental Biology , Neurology
      Imaging whole mouse brains with a dual resolution serial swept-source optical coherence tomography scanner

      High resolution imaging of whole rodent brains using serial OCT scanners is a promising method to investigate microstructural changes in tissue related to the evolution of neuropathologies. Although micron to sub-micron sampling resolution can be obtained by using high numerical aperture objectives and dynamic focusing, such an imaging system is not adapted to whole brain imaging. This is due to the large amount of data it generates and the significant computational resources required for reconstructing such volumes. To address this limitation, a dual resolution serial OCT scanner was developed. The optical setup consists in a swept-source OCT made of two ...

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      Mentions: Polytechnique Montreal Frédéric Lesage

    3. Comparing three-dimensional serial optical coherence tomography histology to MRI imaging in the entire mouse brain

      Explore SPIE Digital Library Neurology
      Comparing three-dimensional serial optical coherence tomography histology to MRI imaging in the entire mouse brain

      An automated serial histology setup combining optical coherence tomography (OCT) imaging with vibratome sectioning was used to image eight wild type mouse brains. The datasets resulted in thousands of volumetric tiles resolved at a voxel size of ( 4.9 × 4.9 × 6.5 ) μ m 3 (4.9×4.9×6.5)  μm3 stitched back together to give a three-dimensional map of the brain from which a template OCT brain was obtained. To assess deformation caused by tissue sectioning, reconstruction algorithms, and fixation, OCT datasets were compared to both in vivo and ex vivo magnetic resonance imaging (MRI) imaging. The OCT ...

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      Mentions: Polytechnique Montreal Frédéric Lesage

    4. Serial optical coherence scanning reveals an association between cardiac function and the heart architecture in the aging rodent heart

      Explore OSA | OSA Publishing
      Serial optical coherence scanning reveals an association between cardiac function and the heart architecture in the aging rodent heart

      Normal aging is accompanied by structural changes in the heart architecture. To explore this remodeling, we used a serial optical coherence tomography scanner to image entire mouse hearts at micron scale resolution. Ex vivo hearts of 7 young (4 months) and 5 old (24 months) C57BL/6 mice were acquired with the imaging platform. OCT of the myocardium revealed myofiber orientation changing linearly from the endocardium to the epicardium. In old mice, this rate of change was lower when compared to young mice while the average volume of old mice hearts was significantly larger (p<0.05). Myocardial wall thickening ...

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      Mentions: Polytechnique Montreal Frédéric Lesage

    5. Whole mouse brain imaging using optical coherence tomography: reconstruction, normalization, segmentation, and comparison with diffusion MRI

      Explore SPIE | Journal Developmental Biology , Neurology
      Whole mouse brain imaging using optical coherence tomography: reconstruction, normalization, segmentation, and comparison with diffusion MRI

      An automated massive histology setup combined with an optical coherence tomography (OCT) microscope was used to image a total of n = 5 n=5 whole mouse brains. Each acquisition generated a dataset of thousands of OCT volumetric tiles at a sampling resolution of 4.9 × 4.9 × 6.5    μ m 4.9×4.9×6.5  μm . This paper describes techniques for reconstruction and segmentation of the sliced brains. In addition to the measured OCT optical reflectivity, a single scattering photon model was used to compute the attenuation coefficients within each tissue slice. Average mouse brain templates were generated for ...

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      Mentions: Polytechnique Montreal Frédéric Lesage

    6. White matter segmentation by estimating tissue optical attenuation from volumetric OCT massive histology of whole rodent brains

      Explore Conference Proceedings Microscopy , Neurology
      White matter segmentation by estimating tissue optical attenuation from volumetric OCT massive histology of whole rodent brains

      A whole rodent brain was imaged using an automated massive histology setup and an Optical Coherence Tomography (OCT) microscope. Thousands of OCT volumetric tiles were acquired, each covering a size of about 2.5x2.5x0.8 mm3 with a sampling resolution of 4.9x4.9x6.5 microns. This paper shows the techniques for reconstruction, attenuation compensation and segmentation of the sliced brains. The tile positions within the mosaic were evaluated using a displacement model of the motorized stage and pairwise coregistration. Volume blending was then performed by solving the 3D Laplace equation, and consecutive slices were assembled using the cross-correlation ...

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      Mentions: Polytechnique Montreal Frédéric Lesage

    7. Validating Intravascular Imaging with Serial Optical Coherence Tomography and Confocal Fluorescence Microscopy

      Explore MDPI Open Access Journals Platform Cardiology
      Validating Intravascular Imaging with Serial Optical Coherence Tomography and Confocal Fluorescence Microscopy

      Atherosclerotic cardiovascular diseases are characterized by the formation of a plaque in the arterial wall. Intravascular ultrasound (IVUS) provides high-resolution images allowing delineation of atherosclerotic plaques. When combined with near infrared fluorescence (NIRF), the plaque can also be studied at a molecular level with a large variety of biomarkers. In this work, we present a system enabling automated volumetric histology imaging of excised aortas that can spatially correlate results with combined IVUS/NIRF imaging of lipid-rich atheroma in cholesterol-fed rabbits. Pullbacks in the rabbit aortas were performed with a dual modality IVUS/NIRF catheter developed by our group. Ex vivo ...

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      Mentions: University of Montreal Polytechnique Montreal National Research Council Canada

    8. Multimodal reconstruction of microvascular-flow distributions using combined two-photon microscopy and Doppler optical coherence tomography

      Explore SPIE | Journal
      Multimodal reconstruction of microvascular-flow distributions using combined two-photon microscopy and Doppler optical coherence tomography

      Computing microvascular cerebral blood flow ( μ CBF ) in real cortical angiograms is challenging. Here, we investigated whether the use of Doppler optical coherence tomography (DOCT) flow measurements in individual vessel segments can help in reconstructing μ CBF across the entire vasculature of a truncated cortical angiogram. A μ CBF computational framework integrating DOCT measurements is presented. Simulations performed on a synthetic angiogram showed that the addition of DOCT measurements, especially close to large inflowing or outflowing vessels, reduces the impact of pressure boundary conditions and estimated vessel resistances resulting in a more accurate reconstruction of μ CBF . Our technique was then applied to reconstruct ...

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      Mentions: Massachusetts General Hospital Harvard University Polytechnique Montreal

    9. Investigating the correlation between white matter and microvasculature changes in aging using large scale optical coherence tomography and confocal fluorescence imaging combined with tissue sectioning

      Explore Conference Proceedings Developmental Biology , Neurology
      Investigating the correlation between white matter and microvasculature changes in aging using large scale optical coherence tomography and confocal fluorescence imaging combined with tissue sectioning

      Here, we present a serial OCT/confocal scanner for histological study of the mouse brain. Three axis linear stages combined with a sectioning vibratome allows to cut thru the entire biological tissue and to image every section at a microscopic resolution. After acquisition, each OCT volume and confocal image is re-stitched with adjacent acquisitions to obtain a reconstructed, digital volume of the imaged tissue. This imaging platform was used to investigate correlations between white matter and microvasculature changes in aging mice. Three age groups were used in this study (4, 12, 24 months). At sacrifice, mice were transcardially perfused with ...

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      Mentions: Polytechnique Montreal Frédéric Lesage

    10. Ex-vivo multi-modal microscopy of healthy skin

      Explore Conference Proceedings Dermatology
      Ex-vivo multi-modal microscopy of healthy skin

      The thorough characterization of skin samples is a critical step in investigating dermatological diseases. The combination of depth-sensitive anatomical imaging with molecular imaging has the potential to provide vast information about the skin. In this proof-of-concept work we present high-resolution mosaic images of skin biopsies using Optical Coherence Tomography (OCT) manually co-registered with standard microscopy, bi-dimensional Raman spectral mapping and fluorescence imaging. A human breast skin sample, embedded in paraffin, was imaged with a swept-source OCT system at 1310 nm. Individual OCT volumes were acquired in fully automated fashion in order to obtain a large field-of-view at high resolution (~10 ...

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      Mentions: Polytechnique Montreal Frédéric Lesage

    11. Statistical intensity variation analysis for rapid volumetric imaging of capillary network flux

      Explore opticsinfobase.org
      Statistical intensity variation analysis for rapid volumetric imaging of capillary network flux

      We present a novel optical coherence tomography (OCT)-based technique for rapid volumetric imaging of red blood cell (RBC) flux in capillary networks. Previously we reported that OCT can capture individual RBC passage within a capillary, where the OCT intensity signal at a voxel fluctuates when an RBC passes the voxel. Based on this finding, we defined a metric of statistical intensity variation (SIV) and validated that the mean SIV is proportional to the RBC flux [RBC/s] through simulations and measurements. From rapidly scanned volume data, we used Hessian matrix analysis to vectorize a segment path of each capillary ...

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      Mentions: Thorlabs Massachusetts General Hospital Harvard University

    12. Multiple-capillary measurement of RBC speed, flux, and density with optical coherence tomography

      Explore Nature Publishing Group Neurology
      Multiple-capillary measurement of RBC speed, flux, and density with optical coherence tomography

      As capillaries exhibit heterogeneous and fluctuating dynamics even during baseline, a technique measuring red blood cell (RBC) speed and flux over many capillaries at the same time is needed. Here, we report that optical coherence tomography can capture individual RBC passage simultaneously over many capillaries located at different depths. Further, we demonstrate the ability to quantify RBC speed, flux, and linear density. This technique will provide a means to monitor microvascular flow dynamics over many capillaries at different depths at the same time.

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      Mentions: Massachusetts General Hospital Harvard University Frédéric Lesage

    13. Catechin prevents severe dyslipidemia-associated changes in wall biomechanics of cerebral arteries in LDLr-/-:hApoB+/+ mice and improves cerebral blood flow

      Explore AJP - Heart and Circulatory Physiology
      Catechin prevents severe dyslipidemia-associated changes in wall biomechanics of cerebral arteries in LDLr-/-:hApoB+/+ mice and improves cerebral blood flow

      Endothelial dysfunction and oxidative stress contribute to the atherosclerotic process that includes stiffening of large peripheral arteries. In contrast, we previously reported a paradoxical increase in cerebrovascular compliance in LDLr-/-: hApoB+/+ atherosclerotic (ATX) mice. We hypothesized that prevention of cerebral artery endothelial function with a chronic dietary antioxidant intake would normalize the changes in cerebral artery wall structure and biomechanics and prevent the decline in basal cerebral blood flow (CBF) associated with atherosclerosis. Three-month old ATX mice were treated, or not, for 3 months with the polyphenol (+)-catechin (CAT, 30 mg/kg/day) and compared to wild-type (WT) controls. In ...

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      Mentions: University of Montreal Polytechnique Montreal Frédéric Lesage

    14. Imaging Biomarkers in Atherosclerosis Trials

      Explore Circulation Cardiology
      Imaging Biomarkers in Atherosclerosis Trials
      Atherosclerosis and its thrombotic complications are the leading cause of morbidity and mortality in developed countries, and the burden of atherosclerotic disease is expected to increase even further in the coming decades due to soaring obesity rates that feed the diabetes epidemic. There is, therefore, a clear need for new drugs targeting atherosclerosis to add to our current therapeutic armamentarium. Drug approval currently is based on multicenter, randomized, placebo-controlled trials with long-term follow-up in thousands of patients to demonstrate clear benefits in mortality and cardiovascular events and to allow adequate assessment of safety. Cardiovascular drug development has become a hostage ...
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      Mentions: University of Montreal Frédéric Lesage

    15. Catechin treatment improves cerebrovascular flow-mediated dilation and learning abilities in atherosclerotic mice

      Explore AJP - Heart and Circulatory Physiology Cardiology
      Catechin treatment improves cerebrovascular flow-mediated dilation and learning abilities in atherosclerotic mice

      Severe dyslipidemia and the associated oxidative stress, could accelerate the age-related decline in cerebrovascular endothelial function and cerebral blood flow (CBF), leading to neuronal loss and impaired learning abilities. We hypothesized that a chronic treatment with the polyphenol catechin would prevent endothelial dysfunction, maintain CBF responses and protect learning abilities in atherosclerotic (ATX) mice. We treated ATX (C57Bl/6-LDLR-/-hApoB+/+; 3 month-old, m/o) mice with catechin (30 mg/kg/day) for 3 months, and C57Bl/6 (WT, 3 and 6-m/o) mice were used as controls. ACh- and flow-mediated dilations (FMD) were recorded in pressurized cerebral arteries. Basal CBF ...

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      Mentions: Polytechnique Montreal Frédéric Lesage
    1-15 of 15
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    1. (15 articles) Frédéric Lesage
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    Catechin treatment improves cerebrovascular flow-mediated dilation and learning abilities in atherosclerotic mice Imaging Biomarkers in Atherosclerosis Trials Catechin prevents severe dyslipidemia-associated changes in wall biomechanics of cerebral arteries in LDLr-/-:hApoB+/+ mice and improves cerebral blood flow Multiple-capillary measurement of RBC speed, flux, and density with optical coherence tomography Statistical intensity variation analysis for rapid volumetric imaging of capillary network flux Ex-vivo multi-modal microscopy of healthy skin Investigating the correlation between white matter and microvasculature changes in aging using large scale optical coherence tomography and confocal fluorescence imaging combined with tissue sectioning Multimodal reconstruction of microvascular-flow distributions using combined two-photon microscopy and Doppler optical coherence tomography White matter segmentation by estimating tissue optical attenuation from volumetric OCT massive histology of whole rodent brains Whole mouse brain imaging using optical coherence tomography: reconstruction, normalization, segmentation, and comparison with diffusion MRI Moody's says Excelitas' proposed $80 million first lien term loan facility to acquire Axsun is a moderate credit negative; ratings unaffected Estimation of refractive index for biological tissue using micro-optical coherence tomography