1. Articles from michael a. choma

    1-19 of 19
    1. Optical coherence tomography and autofluorescence microscopy of respiratory ciliated epithelia

      Optical coherence tomography and autofluorescence microscopy of respiratory ciliated epithelia

      Efficient mucociliary clearance is necessary to protect the respiratory tract from infection. Mucociliary dysfunction is common in respiratory diseases including asthma, chronic obstructive pulmonary disease, and cystic fibrosis. Rescuing mucociliary clearance by stimulating the metabolism of respiratory ciliated epithelia could offer new treatments for respiratory diseases. However, the coupling between cellular metabolism and mechanical output in respiratory ciliated epithelia is poorly understood. We propose to study this coupling with autofluorescence microscopy and optical coherence tomography (OCT), to measure cellular metabolism and ciliary motility, respectively. The autofluorescent metabolic co-enzymes NAD(P)H and FAD provide non-invasive measures of metabolism through the ...

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    2. Visualization and quantification of injury to the ciliated epithelium using quantitative flow imaging and speckle variance optical coherence tomography

      Visualization and quantification of injury to the ciliated epithelium using quantitative flow imaging and speckle variance optical coherence tomography

      Mucociliary flow is an important defense mechanism in the lung to remove inhaled pathogens and pollutants. Disruption of ciliary flow can lead to respiratory infections. Multiple factors, from drugs to disease can cause an alteration in ciliary flow. However, less attention has been given to injury of the ciliated epithelium. In this study, we show how optical coherence tomography (OCT) can be used to investigate injury to the ciliated epithelium in a multi-contrast setting. We used particle tracking velocimetry (PTV-OCT) to investigate the cilia-driven flow field and 3D speckle variance imaging to investigate size and extent of injury caused to ...

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    3. Ex vivo visualization of human ciliated epithelium and quantitative analysis of induced flow dynamics by using optical coherence tomography

      Ex vivo visualization of human ciliated epithelium and quantitative analysis of induced flow dynamics by using optical coherence tomography

      Background and Objective Cilia-driven mucociliary clearance is an important self-defense mechanism of great clinical importance in pulmonary research. Conventional light microscopy possesses the capability to visualize individual cilia and its beating pattern but lacks the throughput to assess the global ciliary activities and flow dynamics. Optical coherence tomography (OCT), which provides depth-resolved cross-sectional images, was recently introduced to this area. Materials and Methods Fourteen de-identified human tracheobronchial tissues are directly imaged by two OCT systems: one system centered at 1,300 nm with 6.5 μm axial resolution and 15 μm lateral resolution, and the other centered at 800 nm ...

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    4. Analysis of Craniocardiac Malformations in Xenopus using Optical Coherence Tomography : Scientific Reports

      Analysis of Craniocardiac Malformations in Xenopus using Optical Coherence Tomography : Scientific Reports

      Birth defects affect 3% of children in the United States. Among the birth defects, congenital heart disease and craniofacial malformations are major causes of mortality and morbidity. Unfortunately, the genetic mechanisms underlying craniocardiac malformations remain largely uncharacterized. To address this, human genomic studies are identifying sequence variations in patients, resulting in numerous candidate genes. However, the molecular mechanisms of pathogenesis for most candidate genes are unknown. Therefore, there is a need for functional analyses in rapid and efficient animal models of human disease. Here, we coupled the frog Xenopus tropicalis with Optical Coherence Tomography (OCT) to create a fast and ...

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    5. Particle streak velocimetry-optical coherence tomography: a novel method for multidimensional imaging of microscale fluid flows

      Particle streak velocimetry-optical coherence tomography: a novel method for multidimensional imaging of microscale fluid flows

      We present a new OCT method for flow speed quantification and directional velocimetry: particle streak velocimetry-OCT (PSV-OCT). PSV-OCT generates two-dimensional, 2.5-vector component ( v x ,| v y |, v z ) maps of microscale flow velocity fields. Knowledge of 2.5-vector components also enables the estimation of total flow speed. The enabling insight behind PSV-OCT is that tracer particles in sparsely-seeded fluid flow trace out streaks in ( x,z,t )-space. The streak orientations in x-t and z-t yield v x and v z , respectively. The in-plane ( x-z plane) residence time yields the out-of-plane speed | v y |. Vector component values are generated ...

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    6. Improved velocimetry in optical coherence tomography using Bayesian analysis

      Improved velocimetry in optical coherence tomography using Bayesian analysis

      OCT is a popular cross-sectional microscale imaging modality in medicine and biology. While structural imaging using OCT is a mature technology in many respects, flow and motion estimation using OCT remains an intense area of research. In particular, there is keen interest in maximizing information extraction from the complex-valued OCT signal. Here, we introduce a Bayesian framework into the data workflow in OCT-based velocimetry. We demonstrate that using prior information in this Bayesian framework can significantly improve velocity estimate precision in a correlation-based, model-based framework for Doppler and transverse velocimetry. We show results in calibrated flow phantoms as well as ...

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    7. Three-dimensional, three-vector-component velocimetry of cilia-driven fluid flow using correlation-based approaches in optical coherence tomography

      Three-dimensional, three-vector-component velocimetry of cilia-driven fluid flow using correlation-based approaches in optical coherence tomography

      Microscale quantification of cilia-driven fluid flow is an emerging area in medical physiology, including pulmonary and central nervous system physiology. Cilia-driven fluid flow is most completely described by a three-dimensional, three-component (3D3C) vector field. Here, we generate 3D3C velocimetry measurements by synthesizing higher dimensional data from lower dimensional measurements obtained using two separate optical coherence tomography (OCT)-based approaches: digital particle image velocimetry (DPIV) and dynamic light scattering (DLS)-OCT. Building on previous work, we first demonstrate directional DLS-OCT for 1D2C velocimetry measurements in the sub-1 mm/s regime (sub-2.5 inch/minute regime) of cilia-driven fluid flow in Xenopus ...

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    8. Quantifying hyperoxia-mediated damage to mammalian respiratory cilia-driven fluid flow using particle tracking velocimetry optical coherence tomography

      Quantifying hyperoxia-mediated damage to mammalian respiratory cilia-driven fluid flow using particle tracking velocimetry optical coherence tomography

      Oxygen supplementation [hyperoxia, increased fraction of inspired oxygen ( FiO 2 )] is an indispensable treatment in the intensive care unit for patients in respiratory failure. Like other treatments or drugs, hyperoxia has a risk-benefit profile that guides its clinical use. While hyperoxia is known to damage respiratory epithelium, it is unknown if damage can result in impaired capacity to generate cilia-driven fluid flow. Here, we demonstrate that quantifying cilia-driven fluid flow velocities in the sub - 100   μ m / s regime (sub-0.25 in./min regime) reveals hyperoxia-mediated damage to the capacity of ciliated respiratory mucosa to generate directional flow. Flow quantification was ...

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    9. Low-spatial-coherence broadband fiber source for speckle free imaging

      Low-spatial-coherence broadband fiber source for speckle free imaging

      We designed and demonstrate a fiber-based amplified spontaneous emission (ASE) source with low spatial coherence, low temporal coherence, and high power per mode. ASE is produced by optically pumping a large gain core multimode fiber while minimizing optical feedback to avoid lasing. The fiber ASE source provides 270 mW of continuous wave emission, centered at λ=1055 nm with a full-width half-maximum bandwidth of 74 nm. The emission is distributed among as many as ~70 spatial modes, enabling efficient speckle suppression when combined with spectral compounding. Finally, we demonstrate speckle-free full field imaging using the fiber ASE source. The fiber ASE ...

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      Mentions: Michael A. Choma
    10. Quantitative optical coherence tomography imaging of intermediate flow defect phenotypes in ciliary physiology and pathophysiology

      Quantitative optical coherence tomography imaging of intermediate flow defect phenotypes in ciliary physiology and pathophysiology

      Cilia-driven fluid flow is a critical yet poorly understood aspect of pulmonary physiology. Here, we demonstrate that optical coherence tomography-based particle tracking velocimetry can be used to quantify subtle variability in cilia-driven flow performance in Xenopus , an important animal model of ciliary biology. Changes in flow performance were quantified in the setting of normal development, as well as in response to three types of perturbations: mechanical (increased fluid viscosity), pharmacological (disrupted serotonin signaling), and genetic (diminished ciliary motor protein expression). Of note, we demonstrate decreased flow secondary to gene knockdown of kif3a , a protein involved in ciliogenesis, as well as ...

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    11. Microscale imaging of cilia-driven fluid flow

      Microscale imaging of cilia-driven fluid flow

      Cilia-driven fluid flow is important for multiple processes in the body, including respiratory mucus clearance, gamete transport in the oviduct, right–left patterning in the embryonic node, and cerebrospinal fluid circulation. Multiple imaging techniques have been applied toward quantifying ciliary flow. Here, we review common velocimetry methods of quantifying fluid flow. We then discuss four important optical modalities, including light microscopy, epifluorescence, confocal microscopy, and optical coherence tomography, that have been used to investigate cilia-driven flow.

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    12. Postdoctoral Opening at Biophotonics Laboratory at Yale University

      Postdoctoral Opening at Biophotonics Laboratory at Yale University

      There is an immediate opening at Yale University for a postdoctoral associate to work on a newly-funded research project entitled “Massively parallel interferometric confocal microscopy using degenerate lasers.” The postdoctoral associate will be supervised by Michael A. Choma, MD, PhD (Yale Diagnostic Radiology) in collaboration with Hui Cao, PhD (Yale Applied Physics). The postdoctoral associate will work in a highly collaborative and interdisciplinary environment to develop next-generation laser technologies to enable new kinds of biomedical optical imaging systems. We are particularly interested in candidates who have experience in designing and building solid-state lasers, but candidates with excellent skills in designing ...

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    13. Resolving directional ambiguity in dynamic light scattering-based transverse motion velocimetry in optical coherence tomography

      Resolving directional ambiguity in dynamic light scattering-based transverse motion velocimetry in optical coherence tomography

      Dynamic light scattering-based optical coherence tomography approaches have been successfully implemented to measure total transverse ( x y ) flow speed, but are unable to resolve directionality. We propose a method to extract directional velocity in the transverse plane by introducing a variable scan bias to our system. Our velocity estimation, which yields the directional velocity component along the scan axis, is also independent of any point-spread function calibration. By combining our approach with Doppler velocimetry, we show three-component velocimetry that is appropriately dependent on latitudinal and longitudinal angle ]

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    14. Microfluidic Phenotyping of Cilia-Driven Mixing for the Assessment of Respiratory Diseases

      Microfluidic Phenotyping of Cilia-Driven Mixing for the Assessment of Respiratory Diseases

      The function of ciliated surfaces to clear mucus from the respiratory system is important for many respiratory diseases and, therefore, has a high impact on public health. In this work, we present a quantitative method to evaluate mixing efficiency of cilia-driven microfluidic flow based on front line deformation as an integrated measurement of cilia function. So far, mixing efficiency has been used mainly for analyzing artificial cilia. Most of this work, however, was either bound to specific imaging modalities or done on simulated data. In this simulations, mixing efficiency has been quantified as the change in length of a virtual ...

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    15. Feature Of The Week 2/12/12: Researchers at Yale University use OCT to Characterize Microfluidic Ciliary Induced Fluid Flow

      Feature Of The Week 2/12/12: Researchers at Yale University use OCT to Characterize Microfluidic Ciliary Induced Fluid Flow

      Recently researchers at Yale University demonstrated a very novel application of optical coherence tomography using a Thorlabs OCT system.  The research involved characterizing microfluidic flow of fluid driven by cilia.  Below is a summary of this interesting novel application of OCT.Motile cilia are fingerlike projections from different epithelial surfaces that move in a periodic manner to generate directional fluid flow. For example, respiratory cilia generate a microfluidic-scale flow that moves pathogen and allergen-containing mucus out of the lungs. Defects in motile cilia lead to recurrent respiratory infections. Despite the importance of cilia in rare disease such as primary ciliary ...

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    16. Microfluidic characterization of cilia-driven fluid flow using optical coherence tomography-based particle tracking velocimetry

      Microfluidic characterization of cilia-driven fluid flow using optical coherence tomography-based particle tracking velocimetry
      Motile cilia are cellular organelles that generate directional fluid flow across various epithelial surfaces including the embryonic node and respiratory mucosa. The proper functioning of cilia is necessary for normal embryo development and, for the respiratory system, the clearance of mucus and potentially harmful particulate matter. Here we show that optical coherence tomography (OCT) is well-suited for quantitatively characterizing the microfluidic-scale flow generated by motile cilia. Our imaging focuses on the ciliated epithelium of Xenopus tropicalis embryos, a genetically manipulable and experimentally tractable animal model of human disease. We show qualitative flow profile characterization using OCT-based particle pathline imaging. We ...
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    17. Physiological homology between Drosophila melanogaster and vertebrate cardiovascular systems

      Physiological homology between Drosophila melanogaster and vertebrate cardiovascular systems
      The physiology of the Drosophila melanogaster cardiovascular system remains poorly characterized compared with its vertebrate counterparts. Basic measures of physiological performance remain unknown. It also is unclear whether subtle physiological defects observed in the human cardiovascular system can be reproduced in D. melanogaster. Here we characterize the cardiovascular physiology of D. melanogaster in its pre-pupal stage by using high-speed dye angiography and optical coherence tomography. The heart has vigorous pulsatile contractions that drive intracardiac, aortic and extracellular-extravascular hemolymph flow. Several physiological measures, including weight-adjusted cardiac output, body-length-adjusted aortic velocities and intracardiac shear forces, are similar to those in the closed ...
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    18. Heart wall velocimetry and exogenous contrast-based cardiac flow imaging in Drosophila melanogaster using Doppler optical coherence tomography

      Heart wall velocimetry and exogenous contrast-based cardiac flow imaging in Drosophila melanogaster using Doppler optical coherence tomography
      Drosophila melanogaster (fruit fly) is a central organism in biology and is becoming increasingly important in the cardiovascular sciences. Prior work in optical imaging of the D. melanogaster heart has focused on static and dynamic structural anatomy. In the study, it is demonstrated that Doppler optical coherence tomography can quantify dynamic heart wall velocity and hemolymph flow in adult D. melanogaster. Since hemolymph is optically transparent, a novel exogenous contrast technique is demonstrated to increase the backscatter-based intracardiac Doppler flow signal. The results presented here open up new possibilities for functional cardiovascular phenotyping of normal and mutant D. melanogaster.
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    19. Method for optical coherence tomography imaging with molecular contrast

      Spatial information, such as concentration and displacement, about a specific molecular contrast agent, may be determined by stimulating a sample containing the agent, thereby altering an optical property of the agent. A plurality of optical coherence tomography (OCT) images may be acquired, at least some of which are acquired at different stimulus intensities. The acquired images are used to profile the molecular contrast agent concentration distribution of the sample.
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    1-19 of 19
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    1. (19 articles) Michael A. Choma
    2. (16 articles) Yale University
    3. (2 articles) Harvard University
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    6. (2 articles) Brett E. Bouma
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    Heart wall velocimetry and exogenous contrast-based cardiac flow imaging in Drosophila melanogaster using Doppler optical coherence tomography Physiological homology between Drosophila melanogaster and vertebrate cardiovascular systems Microfluidic characterization of cilia-driven fluid flow using optical coherence tomography-based particle tracking velocimetry Feature Of The Week 2/12/12: Researchers at Yale University use OCT to Characterize Microfluidic Ciliary Induced Fluid Flow Microfluidic Phenotyping of Cilia-Driven Mixing for the Assessment of Respiratory Diseases Resolving directional ambiguity in dynamic light scattering-based transverse motion velocimetry in optical coherence tomography Postdoctoral Opening at Biophotonics Laboratory at Yale University Particle streak velocimetry-optical coherence tomography: a novel method for multidimensional imaging of microscale fluid flows Analysis of Craniocardiac Malformations in Xenopus using Optical Coherence Tomography : Scientific Reports Non-local Weighted Sparse Representation for OCT Reconstruction Multimodality Imaging to Detect Vulnerable Plaque in Coronary Arteries and Its Clinical Application (Book Chapter) Characterization of Soft Contact Lens Edge Fitting during Daily Wear Using Ultrahigh-Resolution Optical Coherence Tomography