1. Articles from Hrebesh M. Subhash

    1-24 of 38 1 2 »
    1. Postdoctoral Research Scientist Position at Colgate-Palmolive Company in Piscataway New Jersey

      Postdoctoral Research Scientist Position at Colgate-Palmolive Company in Piscataway New Jersey

      Colgate-Palmolive is a leading global consumer products company, tightly focused on Oral Care, Personal Care, Home Care and Pet Nutrition. Colgate sells its products in over 200 countries and territories around the world under such internationally recognized brand names as Colgate, Palmolive, Speed Stick, Lady Speed Stick, Softsoap, Irish Spring, Protex, Sorriso, Kolynos, elmex, Tom’s of Maine, Sanex, Ajax, Axion, Fabuloso, Soupline and Suavitel, as well as Hill’s Science Diet, Hill’s Prescription Diet and Hill’s Ideal Balance. For more information about Colgate’s global business, visit the Company’s web site at http://www.colgatepalmolive.com ...

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    2. Comparing an FFT filter for multiple reference optical coherence tomography (MR-OCT) with an Chebychev and an elliptic filter

      Comparing an FFT filter for multiple reference optical coherence tomography (MR-OCT) with an Chebychev and an elliptic filter

      Portable and low-cost optical coherence tomography (OCT) is increasingly used to improve the accuracy of point-of-care applications. The increasing research efforts to use photonics integrated circuits (PIC) is without doubts the future for highest packaging densities in miniature optical systems. MR-OCT is another technology that is using the advantages of well known CD/DVD-ROM technology to build miniaturized and low-cost OCT systems and may be more readily available before PICs reach their full potential. For MR-OCT it is essential to separate the the multiple signals originating from the multiple reflections of the partial mirror in the reference arm of Michelson ...

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    3. Catoptric Objective Based HighSensitive Fourier-Domain Optical Coherence Tomography

      Catoptric Objective Based HighSensitive Fourier-Domain Optical Coherence Tomography

      We introduce a novel catoptric objective based high sensitive Fourier Domain Optical Coherence Tomography (FD-OCT) system for enhanced structural and functional imaging of cochlear microstructures. Unlike the conventional refractive type microscopic objective, catoptric objectives are well-known for their chromatic aberrations free operation and high light gathering efficiency for a broad range of wavelengths. In this study, we present the feasibility of a commercially available catoptric type objective to obtain high-sensitivity structural and functional imaging of cochlear microstructures of an excised guinea pig through intact temporal bone.

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    4. 3D nondestructive testing system with an affordable multiple reference optical-delay-based optical coherence tomography

      3D nondestructive testing system with an affordable multiple reference optical-delay-based optical coherence tomography

      Optical coherence tomography (OCT) is emerging as a powerful noncontact imaging technique, allowing high-quality cross-sectional imaging of scattering specimens nondestructively. However, the complexity and cost of current embodiments of an OCT system limit its use in various nondestructive testing (NDT) applications at resource-limited settings. In this paper, we demonstrate the feasibility of a novel low-cost OCT system for a range of nondestructive testing (NDT) applications. The proposed imaging system is based on an enhanced time-domain OCT system with a low cost and small form factor reference arm optical delay, called multiple reference OCT (MR-OCT), which uses a miniature voice coil ...

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    5. Multiple-reference optical coherence tomography for smartphone applications

      Multiple-reference optical coherence tomography for smartphone applications

      As a multifunctional clinical diagnostic and monitoring technique, optical coherence tomography (OCT) 1 has become a well-established tool in many areas, including ophthalmology, dermatology, gastrointestinal endoscopy, intravascular imaging, and oncology. OCT is a low-coherence, interferometric-based imaging modality that can be implemented using either time-domain (TD) or frequency-domain (FD) methods in which the interference signals generated by combining reference signals with light scattered by the target are detected. Early OCT systems are based on TD technology, and they use a bulky scanning reference arm optical delay to sequentially generate the axial scans (A-scans). TD systems require an inherently long acquisition time ...

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    6. Developing cross-correlation as a method for microvessel imaging using clinical intravascular optical coherence tomography systems

      Developing cross-correlation as a method for microvessel imaging using clinical intravascular optical coherence tomography systems

      Current clinical intravascular optical coherence tomography (IV-OCT) imaging systems have limited in-vivo flow imaging capability because of non-uniform catheter rotation and inadequate A-line scan density. Thus any flow-localisation method that seeks to identify sites of variation within the OCT image data-sets, whether that is in amplitude or phase, produces non-representative correlation (or variance) maps. In this study, both mean and the variation within a set of cross-correlation maps, for static OCT imaging was used to differentiate flow from nonflow regions. Variation was quantified by use of standard deviation. The advantage of this approach is its ability to image flow, even ...

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    7. MR-OCT: Affordable Tomographic Imaging Applications

      MR-OCT: Affordable Tomographic Imaging Applications

      The application of optical coherence tomography (OCT) in the field of biomedical imaging has increased rapidly in recent years and may continue on this trajectory with growth potential in clinical diagnostics. 1 Integration of OCT for affordable point-of-care (POC) diagnostic applications and personal-care monitoring should lead to miniature, inexpensive, portable, robust optical instrumentation that is accurate and simple to use. However, the current embodiments of OCT systems are highly expensive, utilize large-form-factor optical design, and require accurate alignment of complex optics, making them impractical for the POC environment. In recent years, there has been an increasing interest in the development ...

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    8. High resolution coherence domain depth-resolved nailfold capillaroscopy based on correlation mapping optical coherence tomography

      High resolution coherence domain depth-resolved nailfold capillaroscopy based on correlation mapping optical coherence tomography

      In this paper we demonstrate a novel application of correlation mapping optical coherence tomography (cm-OCT) for volumetric nailfold capillaroscopy (NFC). NFC is a widely used non-invasive diagnostic method to analyze capillary morphology and microvascular abnormalities of nailfold area for a range of disease conditions. However, the conventional NFC is incapable of providing volumetric imaging, when volumetric quantitative microangiopathic parameters such as plexus morphology, capillary density, and morphologic anomalies of the end row loops most critical. cm-OCT is a recently developed well established coherence domain magnitude based angiographic modality, which takes advantage of the time-varying speckle effect, which is normally dominant ...

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    9. High-sensitive full-range optical vibrometry based on Fourier-domain optical coherence tomography

      High-sensitive full-range optical vibrometry based on Fourier-domain optical coherence tomography

      Optical vibrometery based on low coherence Fourier-domain optical coherence tomography (FD-OCT) technique are well capable for providing depth resolved vibration information in comparison with conventional laser based vibrometery. Recently, there has been growing interest in developing coherence-domain vibrometry for various clinical and pre-clinical applications. However, a major drawback of the conventional vibrometer based on Fourier-domain low coherence interferometry is the complex-conjugate ambiguity. This is because in FD-OCT, the detected real valued spectral interferogram is Fourier transformed to localize the scatter within the sample. The Fourier transform of a real valued function is Hermitian, so the reconstructed image is symmetric with ...

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    10. Variation in cross-correlation as a discriminator for microvessel imaging using clinical intravascular optical coherence tomography systems

      Variation in cross-correlation as a discriminator for microvessel imaging using clinical intravascular optical coherence tomography systems

      Cross-correlation of Intravascular Optical Coherence Tomography (IV-OCT) images is affected by image distortion due to the non-uniform rotational velocity of the imaging catheter. It results in non-representative cross-correlation maps such that for a static scan, the coefficients fluctuate from high to low correlation values. The variation in cross-correlation at flow locations is muted, in comparison to stationary regions. In the present study, the variation of correlation values and its standard deviation (SD) is used to suppress the distortion related noise effects and to extract flow maps from static scan images. The standard deviation of the cross-correlation variation can distinguish flow ...

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    11. Photothermal optical coherence tomography for depth-resolved imaging of mesenchymal stem cells via single wall carbon nanotube

      Photothermal optical coherence tomography for depth-resolved imaging of mesenchymal stem cells via single wall carbon nanotube

      The progress in stem cell research over the past decade holds promise and potential to address many unmet clinical therapeutic needs. Tracking stem cell with modern imaging modalities are critically needed for optimizing stem cell therapy, which offers insight into various underlying biological processes such as cell migration, engraftment, homing, differentiation, and functions etc. In this study we report the feasibility of photothermal optical coherence tomography (PT-OCT) to image human mesenchymal stem cells (hMSCs) labeled with single-walled carbon nanotubes (SWNTs) for in vitro cell tracking in three dimensional scaffolds. PT-OCT is a functional extension of conventional OCT with extended capability ...

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    12. 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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    13. 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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    14. 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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    15. 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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    16. Feature Of The Week: High-speed full-range spectral domain correlation mapping optical coherence tomography for in vivo microcirculation imaging applications

      Feature Of The Week: High-speed full-range spectral domain correlation mapping optical coherence tomography for in vivo microcirculation imaging applications

      Microcirculation imaging is a key parameter for studying the pathophysiological processes of various disease conditions, in both clinical and fundamental research. Recently, the functional extension of the OCT technique to image depth-resolved microcirculation has become a very promising area of research. There is a growing interest in the field of development of various types of OCT-based angiographic techniques, which aims to visualize the lumens and architecture of blood vessels in many clinical and fundamental areas of research, including cardiology, dermatology, neurology, ophthalmology, small animal imaging studies, and so forth. OCT-based angiography techniques utilize the red blood cell scattering dynamics as ...

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    17. 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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    18. 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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    19. 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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    20. Reflective type objective based spectral-domain phase-sensitive optical coherence tomography for high-sensitive structural and functional imaging of cochlear microstructures through intact bone of an excised guinea pig cochlea

      Reflective type objective based spectral-domain phase-sensitive optical coherence tomography for high-sensitive structural and functional imaging of cochlear microstructures through intact bone of an excised guinea pig cochlea

      Most of the optical coherence tomographic (OCT) systems for high resolution imaging of biological specimens are based on refractive type microscope objectives, which are optimized for specific wave length of the optical source. In this study, we present the feasibility of using commercially available reflective type objective for high sensitive and high resolution structural and functional imaging of cochlear microstructures of an excised guinea pig through intact temporal bone. Unlike conventional refractive type microscopic objective, reflective objective are free from chromatic aberrations due to their all-reflecting nature and can support a broadband of spectrum with very high light collection efficiency.

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    21. Feature Of The Week 3/17/13: Using Optical Coherence Tomography to Study Mechanisms of Hearing

      Feature Of The Week 3/17/13: Using Optical Coherence Tomography to Study Mechanisms of Hearing

      The Oregon Hearing Research Centre (OHRC) at the Oregon Health and Science University (OHSU), Portland, Oregon is one of the strongest hearing research groups in the world, and one of the early adopters of optical coherence tomography technology in the field of hearing research. Researchers at OHRC have developed a couple of novel OCT based imaging technologies for functional imaging of middle and inner ear. This includes high-speed OCT system for in vivo imaging of microstructural morphology and micvascular perfusion within the cochlea [1,2], phase-sensitive time-domain and Fourier domain OCT for studying cochlear micromechanics [3,4] and middle ear ...

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    22. Measurement of in vivo basal-turn vibrations of the organ of Corti using phase-sensitive Fourier domain optical coherence tomography

      Measurement of in vivo basal-turn vibrations of the organ of Corti using phase-sensitive Fourier domain optical coherence tomography

      A major reason we can perceive faint sounds and communicate in noisy environments is that the outer hair cells of the organ of Corti enhance the sound-evoked motions inside the cochlea. To understand how the organ of Corti works, we have built and tested the phase-sensitive Fourier domain optical coherence tomography (PSFDOCT) system. This system has key advantages over our previous time domain OCT system [1]. The PSFDOCT system has better signal to noise and simultaneously acquires vibration data from all points along the optical-axis [2]. Feasibility of this system to measure in vitro cochlear vibrations in the apex was ...

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    23. High-speed full-range spectral-domain correlation mapping optical coherence tomography

      High-speed full-range spectral-domain correlation mapping optical coherence tomography

      We present a full range spectral-domain correlation mapping optical coherence tomography (cm-OCT) method to obtain complex conjugate free, full-range correlation mapping angiography. 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 fast mirror’s pivot axis. An algorithm that exploits Hilbert transform to obtain complex-conjugate free image in conjunction with the cm-OCT algorithm is used to obtain full-range imaging of microcirculation within tissue beds in vivo. The proposed system is based on a high speed spectrometer at 92kHz with a modified scanning ...

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    24. In vivo microcirculation imaging of the sub surface fingertip using correlation mapping optical coherence tomography (cmOCT)

      In vivo microcirculation imaging of the sub surface fingertip using correlation mapping optical coherence tomography (cmOCT)

      We describe a novel application of correlation mapping optical coherence tomography (cmOCT) for sub-surface fingerprint biometric identification. Fingerprint biometrics including automated fingerprint identification systems, are commonly used to recognise the fingerprint, since they constitute simple, effective and valuable physical evidence. Spoofing of biometric fingerprint devices can be easily done because of the limited information obtained from the surface topography. In order to overcome this limitation a potentially more secure source of information is required for biometric identification applications. In this study, we retrieve the microcirculation map of the subsurface fingertip by use of the cmOCT technique. To increase probing depth ...

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    1-24 of 38 1 2 »
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    1. (38 articles) Hrebesh M. Subhash
    2. (19 articles) National University of Ireland, Galway
    3. (19 articles) Martin J. Leahy
    4. (17 articles) Oregon Health & Science University
    5. (13 articles) Ruikang K. Wang
    6. (11 articles) Alfred L. Nuttall
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    Ultra-high speed full range complex spectral domain optical coherence tomography for volumetric imaging at 140,000 A scans per second Volumetric in vivo imaging of intracochlear microstructures in mice by high-speed spectral domain optical coherence tomography Volumetric In Vivo Imaging of Microvascular Perfusion Within the Intact Cochlea in Mice Using Ultra-High Sensitive Optical Microangiography Optical characterization and feasibility study of multifunctional polylactic-co-glycolic acid (PLGA) nanoparticles designed for photo-thermal optical coherence tomography Simultaneous depth-resolved imaging of sub-nanometer scale ossicular vibrations and morphological features of the human-cadaver middle ear with spectral-domain phase-sensitive optical coherence tomography Feature Of The Week 6/17/12: Middle Ear Vibrometry of Human Cadaver Temporal Bone with Spectral Domain Phase-Sensitive Optical Coherence Tomography Feature Of The Week 3/17/13: Using Optical Coherence Tomography to Study Mechanisms of Hearing 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 Postdoctoral Research Scientist Position at Colgate-Palmolive Company in Piscataway New Jersey Review: Optical Scanning Probe for Optical Coherence Tomography Gastrointestinal Endoscopy Editorial Board top 10 topics: advances in GI endoscopy in 2017