All Articles from Frédéric Lesage -Optical Coherence Tomography News

Articles from Frédéric Lesage

1-18 of 18
1. Validation of red blood cell flux and velocity estimations based on optical coherence tomography intensity fluctuations
  
  Explore Nature Publishing Group Nov 13 2020 Neurology
  
  We present a validation of red blood cell flux and speed measurements based on the passage of erythrocytes through the OCT’s focal volume. We compare the performance of the so-called RBC-passage OCT technique to co-localized and simultaneously acquired two-photon excitation fluorescence microscopy (TPEF) measurements. Using concurrent multi-modal imaging, we show that fluctuations in the OCT signal display highly similar features to TPEF time traces. Furthermore, we demonstrate an overall difference in RBC flux and speed of 2.5 ± 3.27 RBC/s and 0.12 ± 0.67 mm/s (mean ± S.D.), compared to TPEF. The analysis also revealed ...
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  Mentions: Frédéric Lesage
2. Cerebral tissue pO2 response to treadmill exercise in awake mice
  
  Explore Nature Publishing Group Aug 10 2020 Developmental Biology , Neurology
  
  We exploited two-photon microscopy and Doppler optical coherence tomography to examine the cerebral blood flow and tissue pO 2 response to forced treadmill exercise in awake mice. To our knowledge, this is the first study performing both direct measure of brain tissue pO 2 during acute forced exercise and underlying microvascular response at capillary and non-capillary levels. We observed that cerebral perfusion and oxygenation are enhanced during running at 5 m/min compared to rest. At faster running speeds (10 and 15 m/min), decreasing trends in arteriolar and capillary flow speed were observed, which could be due to cerebral ...
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  Mentions: Polytechnique Montreal Frédéric Lesage
3. Longitudinal optical coherence tomography imaging of tissue repair and microvasculature regeneration and function after targeted cerebral ischemia
  
  Explore SPIE Digital Library Apr 17 2020 Cardiology
  
  Significance: Understanding how the brain recovers from cerebral tissue and vascular damage after an ischemic event can help develop new therapeutic strategies for the treatment of stroke. Aim: We investigated cerebral tissue repair and microvasculature regeneration and function after a targeted ischemic stroke. Approach: Following photothrombosis occlusion of microvasculature, chronic optical coherence tomography (OCT)-based angiography was used to track ischemic tissue repair and microvasculature regeneration at three different cortical depths and up to 28 days in awake animals. Capillary network orientation analysis was performed to study the structural pattern of newly formed microvasculature. Based on the time-resolved OCT-angiography, we ...
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  Mentions: University of Montreal Polytechnique Montreal Frédéric Lesage
4. Fully automated dual-resolution serial optical coherence tomography aimed at diffusion MRI validation in whole mouse brains
  
  Explore SPIE Digital Library Nov 8 2018 Neurology
  
  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
5. Imaging whole mouse brains with a dual resolution serial swept-source optical coherence tomography scanner
  
  Explore SPIE Digital Library Feb 17 2018 Developmental Biology , Neurology
  
  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
6. Comparing three-dimensional serial optical coherence tomography histology to MRI imaging in the entire mouse brain
  
  Explore SPIE Digital Library Jan 13 2018 Neurology
  
  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
7. Serial optical coherence scanning reveals an association between cardiac function and the heart architecture in the aging rodent heart
  
  Explore OSA | OSA Publishing Oct 22 2017
  
  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
8. Whole mouse brain imaging using optical coherence tomography: reconstruction, normalization, segmentation, and comparison with diffusion MRI
  
  Explore SPIE | Journal Jul 21 2017 Developmental Biology , Neurology
  
  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
9. White matter segmentation by estimating tissue optical attenuation from volumetric OCT massive histology of whole rodent brains
  
  Explore Conference Proceedings Mar 1 2017 Microscopy , Neurology
  
  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
10. Validating Intravascular Imaging with Serial Optical Coherence Tomography and Confocal Fluorescence Microscopy
  
  Explore MDPI Open Access Journals Platform Dec 15 2016 Cardiology
  
  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
11. Multimodal reconstruction of microvascular-flow distributions using combined two-photon microscopy and Doppler optical coherence tomography
  
  Explore SPIE | Journal Mar 18 2015
  
  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
12. 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 Mar 8 2015 Developmental Biology , Neurology
  
  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
13. Ex-vivo multi-modal microscopy of healthy skin
  
  Explore Conference Proceedings Oct 1 2014 Dermatology
  
  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
14. Statistical intensity variation analysis for rapid volumetric imaging of capillary network flux
  
  Explore opticsinfobase.org Mar 13 2014
  
  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
15. Multiple-capillary measurement of RBC speed, flux, and density with optical coherence tomography
  
  Explore Nature Publishing Group Sep 15 2013 Neurology
  
  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
16. 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 Jan 26 2012
  
  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
17. Imaging Biomarkers in Atherosclerosis Trials
  
  Explore Circulation May 18 2011 Cardiology
  
  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
18. Catechin treatment improves cerebrovascular flow-mediated dilation and learning abilities in atherosclerotic mice
  
  Explore AJP - Heart and Circulatory Physiology Dec 24 2010 Cardiology
  
  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
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