1. Articles from Hrebesh Subhash

    1-17 of 17
    1. Semi-automated registration and segmentation for gingival tissue volume measurement on 3D OCT images

      Semi-automated registration and segmentation for gingival tissue volume measurement on 3D OCT images

      The change in gingival tissue volume may be used to indicate changes in gingival inflammation, which may be useful for the clinical assessment of gingival health. Properly quantifying gingival tissue volume requires a robust technique for accurate registration and segmentation of longitudinally captured 3-dimensional (3D) images. In this paper, a semi-automated registration and segmentation method for micrometer resolution measurement of gingival-tissue volume is proposed for 3D optical coherence tomography (OCT) imaging. For quantification, relative changes in gingiva tissue volume are measured based on changes in the gingiva surface height using the tooth surface as a reference. This report conducted repeatability ...

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    2. Split-spectrum amplitude-decorrelation angiography with optical coherence tomography

      Split-spectrum amplitude-decorrelation angiography with optical coherence tomography

      Amplitude decorrelation measurement is sensitive to transverse flow and immune to phase noise in comparison to Doppler and other phase-based approaches. However, the high axial resolution of OCT makes it very sensitive to the pulsatile bulk motion noise in the axial direction. To overcome this limitation, we developed split-spectrum amplitude-decorrelation angiography (SSADA) to improve the signal-to-noise ratio (SNR) of flow detection. The full OCT spectrum was split into several narrower bands. Inter-B-scan decorrelation was computed using the spectral bands separately and then averaged. The SSADA algorithm was tested on in vivo images of the human macula and optic nerve head ...

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    3. Nano-sensitive fourier-domain optical coherence tomography inspection system

      Nano-sensitive fourier-domain optical coherence tomography inspection system

      An OCT imaging system (100) comprising a radiation emitter (SLD), a radiation receiver CCD), an interferometer (FC, PC, X-Scan, Y-Scan), a controller (COMP) which controls the emitter and processes received radiation data according to OCT to provide an output image. The controller (COMP) forms a spectrum of spatial frequencies along the depth direction. It calculates from the spectrum local spectra of spatial frequencies or periods along the depth direction for individual volume elements along the depth direction. It translates the local spectra of spatial frequencies or periods along the depth direction into the OCT image domain. It maps the local ...

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    4. Feasibility study of phase-sensitive imaging based on multiple reference optical coherence tomography

      Feasibility study of phase-sensitive imaging based on multiple reference optical coherence tomography

      Multiple reference optical coherence tomography (MR-OCT) is a recently developed, low-cost and compact time-domain OCT solution for primary care and consumer level applications. A combination of a voice coil actuator and a partial mirror (PM) extends the scan range for imaging depths of approximately 1 mm in biological samples. Our previous research on MR-OCT is based only on intensity information obtained from the depth-resolved interference signal. In this Letter, we extract the phase information from the MR-OCT signal and, hence, provide an additional contrast modality. The phase sensitivity of the system is measured to be approximately 0.2 and 1 ...

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    5. Quantitative assessment of rat corneal thickness and morphology during stem cell therapy by high-speed optical coherence tomography

      Quantitative assessment of rat corneal thickness and morphology during stem cell therapy by high-speed optical coherence tomography

      Optical Coherence Tomography (OCT) is a non-invasive 3 dimensional optical imaging modality that enables high resolution cross sectional imaging in biological tissues and materials. Its high axial and lateral resolution combined with high sensitivity, imaging depth and wide field of view makes it suitable for wide variety of high resolution medical imaging applications at clinically relevant speed. With the advent of swept source lasers, the imaging speed of OCT has increased considerably in recent years. OCT has been used in ophthalmology to study dynamic changes occurring in the cornea and iris, thereby providing physiological and pathological changes that occur within ...

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    6. Optimization of modified scanning protocol based correlation mapping optical coherence tomography at 200 kHz VCSEL source for in vivo microcirculation imaging applications

      Optimization of modified scanning protocol based correlation mapping optical coherence tomography at 200 kHz VCSEL source for in vivo microcirculation imaging applications

      Optical Coherence Tomography (OCT) is a non-invasive 3 dimensional optical imaging modality that enables high resolution cross sectional imaging in biological tissues and materials. Unlike other 3 D medical imaging modalities, OCT provides high axial and lateral resolution combined with high sensitivity, imaging depth and wide field of view which makes it suitable for wide variety of medical imaging applications1. Apart from analysing the morphological characteristics of the biological organs with micron scale axial and lateral resolution, OCT also provides functional information from the biological sample. Among the various functional extensions of OCT, angiographic OCT that enables visualization of lumens ...

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    7. The impact of relative intensity noise on the signal in multiple reference optical coherence tomography

      The impact of relative intensity noise on the signal in multiple reference optical coherence tomography

      Multiple reference optical coherence tomography (MR-OCT) applies a unique low-cost solution to enhance the scanning depth of standard time domain OCT by inserting an partial mirror into the reference arm of the interferometric system. This novel approach achieves multiple reflections for different layers and depths of an sample with minimal effort of engineering and provides an excellent platform for low-cost OCT systems based on well understood production methods for micro-mechanical systems such as CD/DVD pick-up systems. The direct integration of a superluminescent light-emitting diode (SLED) is a preferable solution to reduce the form- factor of an MR-OCT system. Such ...

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    8. Depth-dependent displacement sensitivity analysis and the influence of Doppler angle for quantitative assessment of mechanical properties using phase-sensitive spectral domain optical coherence tomography

      Depth-dependent displacement sensitivity analysis and the influence of Doppler angle for quantitative assessment of mechanical properties using phase-sensitive spectral domain optical coherence tomography

      Optical coherence elastography (OCE) asesses the mechanical properties of samples by applying a mechanical stimulation and detecting the resulting sample displacement using optical coherence tomography (OCT). OCE methods which utilise the phase of the OCT signal offer the potential to detect displacements on the sub-nanometre scale. However, the displacement sensitivity achieveable is directly related to the signal-to-noise ratio and phase stability of the underlying OCT system. Furthermore, the estimation of Doppler angle is imperative in accurately measuring the sample displacement. This work evaluates the contributions of each of these parameters for quantitative assessment of mechanical properties using phase-sensitive spectral domain ...

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    9. Assessment of curing behavior of light-activated dental composites using intensity correlation based multiple reference optical coherence tomography

      Assessment of curing behavior of light-activated dental composites using intensity correlation based multiple reference optical coherence tomography

      Background and Objectives Monitoring the curing kinetics of light-activated resin is a key area of research. These resins are used in restorative applications and particularly in dental applications. They can undergo volumetric shrinkage due to poor control of the depth dependent curing process, modulated by the intensity and duration of the curing light source. This often results in the formation of marginal gaps, causing pain and damage to the restoration site. In this study, we demonstrate the capabilities of a correlation method applied using a multiple references optical coherence tomography (MR-OCT) architecture to monitor the curing of the resin. Study ...

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    10. A NANO-SENSITIVE FOURIER-DOMAIN Optical Coherence Tomography Inspection System

      A NANO-SENSITIVE FOURIER-DOMAIN Optical Coherence Tomography Inspection System

      ntroduction The invention relates to inspection of a variety of objects, including body tissue (also in vivo), cell cultures, materials for material science, and micro and nano electronics components, for example. Most of the fundamental pathological processes in living tissues, including cancer, exhibit changes at the nanoscale level. Recently the diffraction resolution limit has been broken and optical nanoscale microscopy has led to creation of nanoscopic medicine. However, nanoscopy largely requires labelling, is limited to superficial 2D imaging, and is not in general suitable for in vivo applications. Furthermore, it is currently believed that in many cases 2D biology does ...

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    11. Characterization of light distribution and optimization of detector position for multiple reference optical coherence tomography

      Characterization of light distribution and optimization of detector position for multiple reference optical coherence tomography

      A time-domain optical coherence tomography system with respect to multiple reflections in the reference arm is simulated with Zemax and the optimal detector position is discussed based on the wavefront error. Multiple reference optical coherence tomography (MR-OCT) is a novel optical imaging platform using a single miniature actuator and partial mirror to recirculate light multiple times within the interferometric system. The recirculation corresponds to multiple path delays extending effectively the axial scan-range. The simulation of MR-OCT with lenses of 5 mm diameter shows that it is suitable to build a compact system using low-cost components. Subsequently MR-OCT enables an affordable ...

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    12. Signal simulation and signal processing for multiple reference optical coherence tomography

      Signal simulation and signal processing for multiple reference optical coherence tomography

      The generation of a synthetic MR-OCT signal is presented and compared to a real acquired signal. Multiple reference optical coherence tomography (MR-OCT) is a novel time-domain interferometric system. The MR-OCT principle is adding a partial mirror to extend the axial scan range, which effectively extends the scan depth for imaging. The actuation of the scan mirror required for time-domain OCT, was demonstrated to operate with a low cost miniature voice coil, such as a speaker extracted from a smartphone or CD/DVD pick-up system. Building a compact and cost-effective optical imaging system will enable affordable medical diagnosis at low-resource setting ...

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    13. Dermascope guided multiple reference optical coherence tomography

      Dermascope guided multiple reference optical coherence tomography

      In this paper, we report the feasibility of integrating a novel low cost optical coherence tomography (OCT) system with a dermascope for point-of-care applications. The proposed OCT system is based on an enhanced time-domain optical coherence tomographic system, called multiple reference OCT (MR-OCT), which uses a single miniature voice coil actuator and a partial mirror for extending the axial scan range. The system can simultaneously register both the superficial dermascope image and the depth-resolved OCT sub-surface information by an interactive beam steering method. A practitioner is able to obtain the depth resolved information of the point of interest by simply ...

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    14. Nano-sensitive optical coherence tomography (nsOCT) for depth resolved characterization of 3D submicron structure

      Nano-sensitive optical coherence tomography (nsOCT) for depth resolved characterization of 3D submicron structure

      Nowadays optical coherence tomography (OCT) is a rapidly developing technique with various applications, including biomedical imaging and diagnosis. One of the main shortcomings of current OCT techniques is low resolution and sensitivity to structural changes (typically about 10 microns). The best ultra-high resolution OCT techniques demonstrate sensitivity to structural changes and depth resolution of about 1 micron. Since many applications of interest (such as cancer) depend on structural changes at the nanoscale, OCT would definitely benefit from improved structural resolution and sensitivity. A new spectral encoding of spatial frequency (SESF) approach for quantitative characterization of the structure with nanoscale sensitivity ...

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    15. Dermascope assisted interactive patient interface for multiple reference optical coherence tomography

      Dermascope assisted interactive patient interface for multiple reference optical coherence tomography

      There has been a growing interest in the development of a low cost depth-resolved non-invasive dermis imaging tool for both clinical and fundamental investigations of skin diseases. Multiple reference optical coherence tomography (MR-OCT) is a recently developed miniature time-domain low coherence interferometeric imaging platform, which promises to fit into robust, cost-effective designs that are virtually solid state, typical of handheld devices. In this paper we demonstrate the feasibility of MR-OCT for dermis imaging applications by incorporating it in a dermascope, which provides simultaneous imaging of dermis and an interactive tool for beam steering and registration of the OCT imaging beam ...

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    16. Voice coil based robust and miniature optical delay for multiple reference optical coherence tomography

      Voice coil based robust and miniature optical delay for multiple reference optical coherence tomography

      Multiple reference optical coherence tomography (MR-OCT) is a recently developed time-domain interferometeric imaging platform, which promises to fit into robust, cost-effective designs that are virtually solid state. An optical delay is created by the reference mirror which is mounted on a piezo-electric transducer (PZT) and the key element of MR-OCT technology is the presence of a partial mirror in front of the reference mirror. However, the limited axial displacement range at higher scanning-frequencies are a limitation of a PZT-based optical delay. Moreover, PZT-based actuators require a relatively high operational voltage and are expensive. In this paper we present a voice ...

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    17. Split-spectrum amplitude-decorrelation angiography with optical coherence tomography

      Split-spectrum amplitude-decorrelation angiography with optical coherence tomography

      Amplitude decorrelation measurement is sensitive to transverse flow and immune to phase noise in comparison to Doppler and other phase-based approaches. However, the high axial resolution of OCT makes it very sensitive to the pulsatile bulk motion noise in the axial direction. To overcome this limitation, we developed split-spectrum amplitude-decorrelation angiography (SSADA) to improve the signal-to-noise ratio (SNR) of flow detection. The full OCT spectrum was split into several narrower bands. Inter-B-scan decorrelation was computed using the spectral bands separately and then averaged. The SSADA algorithm was tested on in vivo images of the human macula and optic nerve head ...

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    1-17 of 17
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  2. Topics in the News

    1. (16 articles) Hrebesh M. Subhash
    2. (14 articles) National University of Ireland, Galway
    3. (14 articles) Martin J. Leahy
    4. (8 articles) Roshan Dsouza
    5. (3 articles) James G. Fujimoto
    6. (3 articles) Azhar Zam
    7. (3 articles) Compact Imaging, Inc
    8. (2 articles) Massachusetts Institute of Technology
    9. (2 articles) David Huang
    10. (2 articles) Thorlabs
    11. (1 articles) Cardiovascular Research Foundation
    12. (1 articles) University of Tsukuba
    13. (1 articles) Wakayama Medical University
    14. (1 articles) Georgetown University
    15. (1 articles) Takashi Tanimoto
    16. (1 articles) Gary S. Mintz
    17. (1 articles) Atsushi Tanaka
    18. (1 articles) Takashi Akasaka
    19. (1 articles) Hector M. Garcia-Garcia
    20. (1 articles) Takashi Kubo
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    Split-spectrum amplitude-decorrelation angiography with optical coherence tomography Voice coil based robust and miniature optical delay for multiple reference optical coherence tomography Dermascope assisted interactive patient interface for multiple reference optical coherence tomography Nano-sensitive optical coherence tomography (nsOCT) for depth resolved characterization of 3D submicron structure Dermascope guided multiple reference optical coherence tomography Signal simulation and signal processing for multiple reference optical coherence tomography A NANO-SENSITIVE FOURIER-DOMAIN Optical Coherence Tomography Inspection System Assessment of curing behavior of light-activated dental composites using intensity correlation based multiple reference optical coherence tomography Depth-dependent displacement sensitivity analysis and the influence of Doppler angle for quantitative assessment of mechanical properties using phase-sensitive spectral domain optical coherence tomography Quantitative assessment of rat corneal thickness and morphology during stem cell therapy by high-speed optical coherence tomography Deep learning differentiates between healthy and diabetic mouse ears from optical coherence tomography angiography images Spectral-Domain Optical Coherence Tomography For Evaluating Palisades of Vogt in Ocular Surface Disorders With Limbal Involvement