1. Articles from Sergey Alexandrov

    1-10 of 10
    1. Nanosensitive optical coherence tomography to assess wound healing within the cornea

      Nanosensitive optical coherence tomography to assess wound healing within the cornea

      Optical Coherence Tomography (OCT) is a non-invasive depth resolved optical imaging modality, that enables high resolution, cross-sectional imaging in biological tissues and materials at clinically relevant depths. Though OCT offers high resolution imaging, the best ultra-high-resolution OCT systems are limited to imaging structural changes with a resolution of one micron on a single B-scan within very limited depth. Nanosensitive OCT (nsOCT) is a recently developed technique that is capable of providing enhanced sensitivity of OCT to structural changes. Improving the sensitivity of OCT to detect structural changes at the nanoscale level, to a depth typical for conventional OCT, could potentially ...

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    2. Spatial frequency domain correlation mapping optical coherence tomography for nanoscale structural characterization

      Spatial frequency domain correlation mapping optical coherence tomography for nanoscale structural characterization

      Most of the fundamental pathological processes in living tissues exhibit changes at the nanoscale. Noninvasive, label-free detection of structural changes in biological samples pose a significant challenge to both researchers and healthcare professionals. It is highly desirable to be able to resolve these structural changes, during physiological processes, both spatially and temporally. Modern nanoscopy largely requires labeling, is limited to superficial 2D imaging, and is generally not suitable for in vivo applications. Furthermore, it is becoming increasingly evident that 2D biology often does not translate into the real 3D situation. Here, we present a method, spatial frequency domain correlation mapping ...

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    3. Feasibility of correlation mapping optical coherence tomography angiographic technique using a 200  kHz vertical-cavity surface-emitting laser source for in vivo microcirculation imaging applications

      Feasibility of correlation mapping optical coherence tomography angiographic technique using a 200  kHz vertical-cavity surface-emitting laser source for in vivo microcirculation imaging applications

      Optical coherence tomography (OCT) angiography is a well-established in vivo imaging technique to assess the overall vascular morphology of tissues and is an emerging field of research for the assessment of blood flow dynamics and functional parameters such as oxygen saturation. In this study, we present a modified scanning-based correlation mapping OCT using a 200 kHz high-speed swept-source OCT system operating at 1300 nm and demonstrate its wide field-imaging capability in ocular angiographic studies.

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    4. Characterization of an amplified piezoelectric actuator for multiple-reference optical coherence tomography

      Characterization of an amplified piezoelectric actuator for multiple-reference optical coherence tomography

      The characterization of an amplified piezoelectric actuator (APA) as a new axial scanning method for multiple-reference optical coherence tomography (MR-OCT) is described. MR-OCT is a compact optical imaging device based on a recirculating reference-arm-scanning optical delay using a partial mirror that can enhance the imaging depth range by more than 10 times the reference mirror’s scanning amplitude. The scanning amplitude of the used APA was varied between 30 μm and 250 μm, depending on the scanning frequency of between 0.8 kHz and 1.2 kHz. A silver-coated miniature mirror was attached to the APA via ultraviolet-cured optical adhesive ...

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    5. 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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    6. 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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    7. 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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    8. 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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    9. 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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    10. 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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    1-10 of 10
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    1. (10 articles) National University of Ireland, Galway
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    Nano-sensitive optical coherence tomography Nano-sensitive optical coherence tomography (nsOCT) for depth resolved characterization of 3D submicron structure A NANO-SENSITIVE FOURIER-DOMAIN Optical Coherence Tomography Inspection System 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 The impact of relative intensity noise on the signal in multiple reference optical coherence tomography Comparing an FFT filter for multiple reference optical coherence tomography (MR-OCT) with an Chebychev and an elliptic filter Characterization of an amplified piezoelectric actuator for multiple-reference optical coherence tomography Feasibility of correlation mapping optical coherence tomography angiographic technique using a 200  kHz vertical-cavity surface-emitting laser source for in vivo microcirculation imaging applications Spatial frequency domain correlation mapping optical coherence tomography for nanoscale structural characterization Nanosensitive optical coherence tomography to assess wound healing within the cornea In vivo dynamic characterization of the human tympanic membrane using pneumatic optical coherence tomography Negative Vessel Remodeling in Stargardt Disease Quantified with Volume-Rendered Optical Coherence Tomography Angiography