1. Articles from Martin J. Leahy

    1-20 of 20
    1. Feasibility of Intracoronary Frequency Domain Optical Coherence Tomography Derived Fractional Flow Reserve for the Assessment of Coronary Artery Stenosis

      Feasibility of Intracoronary Frequency Domain Optical Coherence Tomography Derived Fractional Flow Reserve for the Assessment of Coronary Artery Stenosis

      Frequency domain optical coherence tomography (FD-OCT) provides cross-sectional images of coronary arteries and deployed stents with micron resolution and measures lumen dimensions with excellent reproducibility. FD-OCT combined with a blood flow resistances model can overcome many limitations of conventional measures of stenosis severity based on quantitative coronary angiography (QCA) and intravascular ultrasound (IVUS). The aim of this feasibility study was to investigate the relationship between pressure derived fractional flow reserve (FFR) and FD-OCT derived FFR, a new method for quantitative measure of stenosis severity that estimates the blood flow resistance and microvascular resistance of the vessel segments imaged by FD-OCT ...

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    2. Comparison of frequency domain optical coherence tomography and quantitative coronary angiography for the assessment of coronary lesions

      Comparison of frequency domain optical coherence tomography and quantitative coronary angiography for the assessment of coronary lesions

      Quantitative coronary angiography (QCA) has been used as a standard technique for the evaluation of coronary artery disease for many years. Intracoronary optical coherence tomography (OCT) offers higher resolution, faster image acquisition speeds and greater sensitivity than the intravascular ultrasound (IVUS). Recently developed frequency domain OCT (FD-OCT) systems overcome many technical limitations of conventional time domain OCT systems (TDOCT). The main objective of this study was to compare the FD-OCT and QCA measurements for the assessment of coronary lesions. A total of 21 stenoses in 18 patients were analysed using QCA and FD-OCT. The average minimum lumen diameter (MLD) and ...

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    3. Imaging mesenchymal stem cells containing single wall nanotube nanoprobes in a 3D scaffold using photo-thermal optical coherence tomography

      Imaging mesenchymal stem cells containing single wall nanotube nanoprobes in a 3D scaffold using photo-thermal optical coherence tomography

      Despite the fact, that a range of clinically viable imaging modalities, such as magnetic resonance imaging (MRI), computed tomography (CT), photo emission tomography (PET), ultrasound and bioluminescence imaging are being optimised to track cells in vivo, many of these techniques are subject to limitations such as the levels of contrast agent required, toxic effects of radiotracers, photo attenuation of tissue and backscatter. With the advent of nanotechnology, nanoprobes are leading the charge to overcome these limitations. In particular, single wall nanotubes (SWNT) have been shown to be taken up by cells and as such are effective nanoprobes for cell imaging ...

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    4. Nano-sensitive optical coherence tomography

      Nano-sensitive optical coherence tomography

      Depth resolved label-free detection of structural changes with nanoscale sensitivity is an outstanding problem in the biological and physical sciences and has significant applications in both the fundamental research and healthcare diagnostics arenas. Here we experimentally demonstrate a novel label-free depth resolved sensing technique based on optical coherence tomography (OCT) to detect structural changes at the nanoscale. Structural components of the 3D object, spectrally encoded in the remitted light, are transformed from the Fourier domain into each voxel of the 3D OCT image without compromising sensitivity. Spatial distribution of the nanoscale structural changes in the depth direction is visualized in ...

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    5. Feature Of The Week 1/19/14: Feature Of The Week: Irish Researchers Investigate Correlation of FFR and OCT Measured Parameters for Identifying Coronary Stenosis

      Feature Of The Week 1/19/14: Feature Of The Week: Irish Researchers Investigate Correlation of FFR and OCT Measured Parameters for Identifying Coronary Stenosis

      The usefulness of fractional flow reserve (FFR) in the functional evaluation of intermediate coronary stenosis is well established. Similarly, intracoronary optical coherence tomography (OCT) continues to be a promising imaging technique for the assessment of coronary artery disease. The frequency domain OCT (FD-OCT) provides faster image acquisition speeds, higher frame rates and greater scan depths as compared to time domain OCT while preserving the image quality. The main aim of this study was to determine the correlation between FFR and frequency domain OCT (FD-OCT) measured anatomical parameters that include minimal lumen area (MLA), minimal lumen diameter (MLD) and percent lumen ...

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    6. Feature Of The Week 1/6/14: In Vivo Full-Field En Face Optical Coherence Tomography

      Feature Of The Week 1/6/14: In Vivo Full-Field En Face Optical Coherence Tomography

      The correlation mapping processing algorithm was developed by our group and utilises the time varying speckle effect produced from moving scatterers to provide contrast against static tissue. The technique has previously been applied to images acquired with frequency-domain OCT systems and hence in a cross-sectional geometry. In this work, a full-field optical coherence tomography system has been developed for the purpose of performing non-scanning en face flow imaging. The light source is centred at 840 nm with a bandwidth of 50 nm resulting in an axial resolution of 8 µm in air. Microscope objectives with a numerical aperture of 0 ...

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    7. Evaluation of hemodynamically severe coronary stenosis as determined by fractional flow reserve with frequency domain optical coherence tomography measured anatomical parameters

      Evaluation of hemodynamically severe coronary stenosis as determined by fractional flow reserve with frequency domain optical coherence tomography measured anatomical parameters

      Objectives The main objective of this study is to determine the correlation between fractional flow reserve (FFR)- and frequency domain optical coherence tomography (FD-OCT)-measured lumen parameters, and to determine the diagnostic competence of FD-OCT concerning the identification of severe coronary stenosis. Methods A total of 41 coronary stenoses in 30 patients were assessed consecutively by quantitative coronary angiography (QCA), FFR, and FD-OCT. Stenoses were labeled severe if FFR ≤ 0.80. The minimal lumen area (MLA), minimal lumen diameter (MLD), and percent lumen area stenosis (%AS) were measured using FD-OCT. Results FFR was ≤0.80 in 10 stenoses (24.4 ...

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    8. In vivo full-field en face correlation mapping optical coherence tomography

      In vivo full-field en face correlation mapping optical coherence tomography

      A full-field optical coherence tomography (OCT) system has been developed for the purpose of performing nonscanning en face flow imaging. The light source is centered at 840 nm with a bandwidth of 50 nm resulting in an axial resolution of 8 μ m in air. Microscope objectives with a numerical aperture of 0.1 were incorporated giving a transverse resolution of 5 μ m. A magnification of 5.65 was measured, resulting in a field of view of 1260 × 945     μ m . Pairs of interference fringe images are captured with opposing phase and a two-step phase image reconstruction method is applied to reconstruct ...

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    9. Optimization and extraction of functional information from in vitro flow models using dual-beam spectral-domain optical coherence tomography cross-correlation analysis

      Optimization and extraction of functional information from in vitro flow models using dual-beam spectral-domain optical coherence tomography cross-correlation analysis

      As in vivo flow behavior can be pulsatile, intermittent, and/or otherwise changeable with time, the ability to provide clinicians with a means of real-time visualization and functional assessment of structures is of particular importance. The discernment of pulsatile flow behavior using a dual-beam spectral domain optical coherence tomography system (db-SdOCT) by quasi-simultaneous measurement by two planes of illumination is demonstrated. By cross-correlation analysis, it is possible to compute velocity metrics pertaining to flowing particle motion, without a priori angular knowledge. This is the first application of cross-correlation-based dynamic assessment for the extraction of pulsatile behavior in an in vitro ...

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    10. Microcirculation imaging based on full-range high-speed spectral domain correlation mapping optical coherence tomography

      Microcirculation imaging based on full-range high-speed spectral domain correlation mapping optical coherence tomography

      Microcirculation imaging is a key parameter for studying the pathophysiological processes of various disease conditions, in both clinical and fundamental research. A full-range spectral-domain correlation mapping optical coherence tomography (cm-OCT) method to obtain a complex-conjugate-free, full-range depth-resolved microcirculation map is presented. The proposed system is based on a high-speed spectrometer at 91 kHz with a modified scanning protocol to achieve higher acquisition speed to render cm-OCT images with high-speed and wide scan range. The mirror image elimination is based on linear phase modulation of B-frames by introducing a slight off-set of the probe beam with respect to the lateral scanning ...

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    11. Feature Of The Week 5/19/13: Using Optical Coherence Tomography For Anti-Spoof Fingerprint Detection

      Feature Of The Week 5/19/13: Using Optical Coherence Tomography For Anti-Spoof Fingerprint Detection

      Fingerprint biometrics, including automated fingerprint identification systems (AFIS), currently occupy two-thirds of the biometric market and are expected to remain the dominant player in this area. The technology can be integrated into small, compact devices and the instruments are relatively fast. However, the overall success of using fingerprints for identification and verification purposes greatly depends upon the quality of the fingerprints initially enrolled. For example, fingerprints captured from older people are significantly lower quality than those from younger people due primarily to ridge-wearing and difficulty of interacting effectively with conventional fingerprint scanners. The ramification is that the problem of obtaining ...

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    12. Feasibility of correlation mapping optical coherence tomography (cmOCT) for anti-spoof sub-surface fingerprinting

      Feasibility of correlation mapping optical coherence tomography (cmOCT) for anti-spoof sub-surface fingerprinting

      We propose the use of correlation mapping optical coherence tomography (cmOCT) to deliver additional biometrics associated with the finger that could complement existing fingerprint technology for law enforcement applications. The current study extends the existing fingerprint paradigm by measuring additional biometrics associated with sub-surface finger tissue such as sub-surface fingerprints, sweat glands, and the pattern of the capillary bed to yield a user-friendly cost effective and anti-spoof multi-mode biometric solution associated with the finger. To our knowledge no other method has been able to capture sub-surface fingerprint, papillary pattern and horizontal vessel pattern in a single scan or to show ...

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    13. Blood optical clearing by optical coherence tomography

      Blood optical clearing by optical coherence tomography

      The main limitation of optical imaging techniques for studying biological tissues is light scattering leading to decreasing of transmittance, which lowers the imaging quality. In this case, an immersion method for optical clearing of biological tissues can provide a possible solution to this problem, because the application of biocompatible clearing agents can reduce light scattering. Optical clearing represents a promising approach to increasing the imaging depth for various techniques, for example, various spectroscopy and fluorescent methods, and optical coherence tomography (OCT). We investigate the improvement of light penetration depth in blood after application of polyethylene glycol, polypropylene glycol, propylene glycol ...

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    14. Feasibility of capillary velocity assessment by statistical means using dual-beam spectral-domain Optical Coherence Tomography: a preliminary study

      Feasibility of capillary velocity assessment by statistical means using dual-beam spectral-domain Optical Coherence Tomography: a preliminary study

      The assessment of vascular dynamics has been shown to yield both qualitative and quantitative metrics and thus play a pivotal role in the diagnosis and prognosis of various diseases, which may manifest as microcirculatory irregularities. Optical Coherence Tomography (OCT) is an established imaging modality which utilises the principle of optical interferometry to distinguish between spatial changes in refractive index and thus formulate a multi-dimensional representation of a specimen in vivo . Nonetheless, difficulties remain in obtaining accurate data (morphological and/or transient) in an environment which is subject to such large biological variability. In an effort to address the issue of ...

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    15. PhD Studentships Optical Coherence Tomography (OCT)/Tissue Optics/Photoacoustics School of Physics NUI Galway University

      PhD Studentships Optical Coherence Tomography (OCT)/Tissue Optics/Photoacoustics School of Physics NUI Galway University

      Ref. No. NUIG TOMI PhD 02-12 Applications are invited from suitably qualified candidates for PhD studentships with the School of Physics, National University of Ireland, Galway. We are looking for highly motivated students who wish to hone their knowledge of physics, engineering and/or software development to deliver new tools for clinical and pre-clinical investigation of the eye, skin and brain. Further details about the Tissue Optics and Microcirculation Imaging Group may be found at: http://tomi.nuigalway.ie/ and the National Biophotonics and Imaging Platform Ireland at www.nbipireland.ie Example project: The focus of this studentship is to ...

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    16. Microcirculation Imaging (Book)

      Microcirculation Imaging (Book)

      Adopting a multidisciplinary approach with input from physicists, researchers and medical professionals, this is the first book to introduce many different technical approaches for the visualization of microcirculation, including laser Doppler and laser speckle, optical coherence tomography and photo-acoustic tomography. It covers everything from basic research to medical applications, providing the technical details while also outlining the respective strengths and weaknesses of each imaging technique. Edited by an international team of top experts, this is the ultimate handbook for every clinician and researcher relying on microcirculation imaging.

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    17. In-vivo assessment of cleavage line orientation in human skin using optical coherence tomography

      In-vivo assessment of cleavage line orientation in human skin using optical coherence tomography
      Collagen and elastin fibers are generally arranged in parallel bundles within the dermis. These bundles are oriented such that they can most efficiently resist the stress and strain that normally occurs on the skin during movement. The pattern of these fiber bundles establishes the lines of cleavage of the skin. Knowledge of the orientation of these is of key importance for surgical procedures. When incisions are cut parallel to the cleavage line orientation the incision will heal better and produce less scaring. In this work we report a novel application of Optical coherence tomography for the determination of cleavage line ...
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    18. Correlation mapping method for generating microcirculation morphology from optical coherence tomography (OCT) intensity images

      Correlation mapping method for generating microcirculation morphology from optical coherence tomography (OCT) intensity images
      Standard optical coherence tomography (OCT) in combination with software tools can be harnessed to generate vascular maps in vivo. In this study we have successfully combined a software algorithm based on correlation statistic to reveal microcirculation morphology on OCT intensity images of a mouse brain in vivo captured trans-cranially and through a cranial window. We were able to estimate vessel geometry at bifurcation as well as along vessel segments down-to mean diameters of about 24 μm. Our technique has potential applications in cardiovascular-related parameter measurements such as volumetric flow as well as in assessing vascular density of normal and diseased ...
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    19. A new device for assessing changes in skin viscoelasticity using indentation and optical measurement

      A new device for assessing changes in skin viscoelasticity using indentation and optical measurement
      Skin is a viscoelastic material, comprised of fluidic and fibrous components. Changes in viscoelasticity can arise due to a number of conditions including dehydration, swelling (associated with injury or disease), impaired heart function, rehydration therapy, ageing, scarring, sun exposure and genetic conditions affecting connective tissue. Quantification of changes in skin viscoelasticity due to these processes is of great clinical interest in the fields of therapy monitoring, wound healing and disease screening. However, devices currently available to measure aspects of the mechanical properties of skin have limitations in ease-of-use, accessibility, and depth of measurement. This paper describes a new technique to ...
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    20. A gel-based skin and blood flow model for a Doppler optical coherence tomography (DOCT) imaging system

      A gel-based skin and blood flow model for a Doppler optical coherence tomography (DOCT) imaging system
      Since its discovery in 1842 by Christian Johann Doppler, the Doppler Effect has had many applications in the scientific world. In recent years, the phenomenon has been integrated with Optical Coherence Tomography (OCT) yielding Doppler Optical Coherence Tomography (DOCT), a technique that is useful for high-resolution imaging of the skin microcirculation. However, interpretation of DOCT images is rather challenging. Thus, our study aims to aid understanding of DOCT images with respect to parameters of microcirculation components such as blood vessel size, depth and angular position. To this end, we have constructed a gel-based tissue and blood-flow model for performing DOCT ...
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    1-20 of 20
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    1. (20 articles) Martin J. Leahy
    2. (17 articles) National University of Ireland, Galway
    3. (7 articles) University of Limerick
    4. (7 articles) Hrebesh M. Subhash
    5. (4 articles) Haroon Zafar
    6. (4 articles) Carl Zeiss Meditec
    7. (4 articles) Zeiss Cirrus HD-OCT
    8. (3 articles) Azhar Zam
    9. (3 articles) Harvard University
    10. (2 articles) University of Houston
    11. (2 articles) Roshan Dsouza
    12. (2 articles) Paul M. McNamara
    13. (2 articles) Kirill V. Larin
    14. (2 articles) Massachusetts Eye and Ear Infirmary
    15. (2 articles) UCLA
    16. (2 articles) Srinivas R. Sadda
    17. (2 articles) Vikas Chopra
    18. (1 articles) Sherif S. Sherif
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    A gel-based skin and blood flow model for a Doppler optical coherence tomography (DOCT) imaging system A new device for assessing changes in skin viscoelasticity using indentation and optical measurement Correlation mapping method for generating microcirculation morphology from optical coherence tomography (OCT) intensity images In-vivo assessment of cleavage line orientation in human skin using optical coherence tomography Microcirculation Imaging (Book) PhD Studentships Optical Coherence Tomography (OCT)/Tissue Optics/Photoacoustics School of Physics NUI Galway University Feasibility of correlation mapping optical coherence tomography (cmOCT) for anti-spoof sub-surface fingerprinting Feature Of The Week 5/19/13: Using Optical Coherence Tomography For Anti-Spoof Fingerprint Detection Microcirculation imaging based on full-range high-speed spectral domain correlation mapping optical coherence tomography Feature Of The Week 1/19/14: Feature Of The Week: Irish Researchers Investigate Correlation of FFR and OCT Measured Parameters for Identifying Coronary Stenosis University of Maryland Receives NIH Grant for Monitoring Photo-Immunotherapy Using Multi-Channel Multi-Modal Imaging Needles Pediatric Sleep-Related Breathing Disorders: Advances in imaging and computational modeling.