1. Articles from frédérique vanholsbeeck

    1-26 of 26
    1. Quantum Optical Coherence Tomography using two photon joint spectrum detection (JS-Q-OCT)

      Quantum Optical Coherence Tomography using two photon joint spectrum detection (JS-Q-OCT)

      Quantum Optical Coherence Tomography (Q-OCT) is the non-classical counterpart of Optical Coherence Tomography (OCT) - a high-resolution 3D imaging technique based on white-light interferometry. Because Q-OCT uses a source of frequency-entangled photon pairs, not only is the axial resolution not affected by dispersion mismatch in the interferometer, but is also inherently improved by a factor of square root of two. Unfortunately, practical applications of QOCT are hindered by image-scrambling artefacts and slow acquisition times. Here, we present a theoretical analysis of a novel approach that is free of these problems: Q-OCT with joint spectrum detection (JS-Q-OCT). Based on a photon pair ...

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    2. Quantum-inspired detection for Spectral Domain Optical Coherence Tomography

      Quantum-inspired detection for Spectral Domain Optical Coherence Tomography

      The intensity levels allowed by safety standards (ANSI or ICNIRP) limit the amount of light that can be used in a clinical setting to image highly scattering or absorptive tissues with Optical Coherence Tomography (OCT). To achieve high-sensitivity imaging at low intensity levels, we adapt a detection scheme - which is used in quantum optics for providing information about spectral correlations of photons - into a standard spectral domain OCT system. This detection scheme is based on the concept of Dispersive FourierTransformation, where a fibre introduces a wavelength-dependent time delay measured by a single-pixel detector, usually a high-speed photoreceiver. Here, we use ...

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    3. Optical coherence tomography complements confocal microscopy for investigation of multicellular tumour spheroids

      Optical coherence tomography complements confocal microscopy for investigation of multicellular tumour spheroids

      Knowledge of optical properties, such as the refractive index (RI), of biological tissues is important in optical imaging, as they influence the distribution and propagation of light in tissue. To accurately study the response of cancerous cells to drugs, optimised imaging protocols are required. This study uses a simple custom-built spectral domain optical coherence tomography (OCT) system to conduct RI measurements of multicellular spheroids, three-dimensional (3D) in-vitro culture systems, of the cell line HCT116. The spheroid RIs are compared to study the effect of growth over time. To improve confocal microscopy imaging protocols, two immersion media (glycerol and ScaleView-A2) matching ...

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    4. Refractive index measurements of multicellular tumour spheroids using optical coherence tomography: dependence on growth phase and size

      Refractive index measurements of multicellular tumour spheroids using optical coherence tomography: dependence on growth phase and size

      Knowledge of optical properties, such as the refractive index (RI), of biological tissues is important in optical imaging, as they influence the distribution and propagation of light in tissue. To accurately study the response of cancerous cells to drugs, optimised imaging protocols are required. This study uses a simple custom-built spectral domain optical coherence tomography (OCT) system to conduct RI measurements of multicellular spheroids, three-dimensional in-vitro culture systems, of the cell line HCT116. The spheroid RIs are compared to study the effect of growth time. To improve confocal microscopy imaging protocols, two immersion media (glycerol and ScaleView-A2) matching the spheroid ...

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    5. Quantifying birefringence in the bovine model of early osteoarthritis using polarisation-sensitive optical coherence tomography and mechanical indentation

      Quantifying birefringence in the bovine model of early osteoarthritis using polarisation-sensitive optical coherence tomography and mechanical indentation

      Recent studies have shown potential for using polarisation sensitive optical coherence tomography (PS-OCT) to study cartilage morphology, and to be potentially used as an in vivo , non-invasive tool for detecting osteoarthritic changes. However, there has been relatively limited ability of this method to quantify the subtle changes that occur in the early stages of cartilage degeneration. An established mechanical indenting technique that has previously been used to examine the microstructural response of articular cartilage was employed to fix the bovine samples in an indented state. The samples were subject to creep loading with a constant compressive stress of 4.5 ...

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    6. Using polarisation-sensitive optical coherence tomography and mechanical indentation to assess cartilage degeneration in the bovine model of early osteoarthritis

      Using polarisation-sensitive optical coherence tomography and mechanical indentation to assess cartilage degeneration in the bovine model of early osteoarthritis

      Recent studies have shown potential for using polarisation sensitive optical coherence tomography (PS-OCT) to study cartilage morphology, and this presents a useful real-time non-invasive tool for detecting osteoarthritic changes. However, there has been relatively limited ability of this method to quantify the subtle changes in the early stages of joint degeneration. In this study, we investigate the ability of PS-OCT to detect microscale degenerative changes in cartilage, following compression, using a validated animal model of early cartilage degeneration, and a special indentation technique. It was found that PS-OCT was able to detect and quantify microstructural changes between healthy and early ...

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    7. Dispersion mapping as a simple postprocessing step for Fourier domain Optical Coherence Tomography data

      Dispersion mapping as a simple postprocessing step for Fourier domain Optical Coherence Tomography data

      Optical Coherence Tomography (OCT) was originally conceived as a volumetric imaging method. Quickly, OCT images went beyond structural data and started to provide functional information about an object enabling for example visualization of blood flow or tissue elasticity. Minimal or no need for system alterations make functional OCT techniques useful in performing multimodal imaging, where differently contrasted images are produced in a single examination. We propose a method that further extends the current capabilities of OCT and requires no modifications to the system. Our algorithm provides information about the sample’s Group Velocity Dispersion (GVD) and can be easily applied ...

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    8. Dispersion measurements in ocular media using a dual-wavelength swept source optical coherence tomography system

      Dispersion measurements in ocular media using a dual-wavelength swept source optical coherence tomography system

      Optical coherence tomography (OCT) has proved to be a powerful tool for the detection of microstructure in tissue. Label-free tissue differentiation on a micron scale is a promising and powerful technique for segmentation. This Letter describes a technique using a dual-wavelength OCT system to image the eye. We measure the walk-off between interfaces in A-scans, taken at two different wavelengths, to calculate the average group velocity dispersion parameter of each segment of the eye. We present measurements of the dispersion of the cornea and the aqueous humour in rat eyes.

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    9. 4D imaging of cardiac trabeculae contracting in vitro using gated OCT

      4D imaging of cardiac trabeculae contracting in vitro using gated OCT

      Cardiac trabeculae are widely used as experimental muscle preparations for studying heart muscle. However, their geometry (diameter, length, and shape) can vary not only amongst samples, but also within a sample, leading to inaccuracies in estimating their stress production, volumetric energy output, and/or oxygen consumption. Hence, it is desirable to have a system that can accurately image each trabecula in vitro during an experiment. To this end, we constructed an optical coherence tomography (OCT) system and implemented a gated imaging procedure to image actively contracting trabeculae and reconstruct their time-varying geometry. By imaging a single cross section while monitoring ...

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    10. Simple and versatile long range swept source for optical coherence tomography applications

      Simple and versatile long range swept source for optical coherence tomography applications

      We present a versatile long coherence length swept-source laser design for optical coherence tomography applications. This design consists of a polygonal spinning mirror and an optical gain chip in a modified Littman–Metcalf cavity. A narrowband intra-cavity filter is implemented through multiple passes off a diffraction grating set at grazing incidence. The key advantage of this design is that it can be readily adapted to any wavelength regions for which broadband gain chips are available. We demonstrate this by implementing sources at 1650 nm, 1550 nm, 1310 nm and 1050 nm. In particular, we present a 1310 nm swept source ...

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    11. Optical coherence tomography imaging of cardiac trabeculae

      Optical coherence tomography imaging of cardiac trabeculae

      An integrated instrument is being developed to study live cardiac trabeculae, which is capable of stimulating the muscle under controlled conditions while measuring the heat production, force, and sarcomere length distribution. To improve the accuracy of estimation of stress, strain, and volumetric heat production, the geometry of the muscle must be known. A spectral domain optical coherence tomography system (SD-OCT) has been constructed and calibrated to image the trabecula mounted inside the instrument. This system was mounted above the muscle chamber and a series of equally-spaced cross-sectional images were obtained. These were processed using a workflow developed to extract cross-sectional ...

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    12. Dispersion mapping at the micrometer scale using tri-band optical frequency domain imaging

      Dispersion mapping at the micrometer scale using tri-band optical frequency domain imaging

      Techniques to differentiate between materials are a powerful addition to the structural information traditionally available from optical coherence tomography images. We present label-free detection of water and lipid at a micrometer scale by evaluating their unique dispersion properties. Using a tri-band swept source configuration, we measure both β 2 and β 3 and show how to identify the two materials at sample thicknesses of 40 and 90 μm, respectively.

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    13. Speckle suppression in Fourier domain optical coherence tomography by fractional Fourier domain compounding

      Speckle suppression in Fourier domain optical coherence tomography by fractional Fourier domain compounding

      We propose a new numerical method for speckle reduction in Fourier domain OCT based on incoherent averaging of fractional Fourier domains of a single A-scan. Fractional Fourier transforms represent projections in the time-frequency space and thus, this method simultaneously compensates for group velocity dispersion.

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    14. Dispersion mapping at the micron scale using tri-band optical frequency domain imaging

      Dispersion mapping at the micron scale using tri-band optical frequency domain imaging

      We present detection of water and lipid at a micron scale by evaluating their unique dispersion properties. Using a triband swept source configuration, we measure β2 and β3 and show how to identify the two materials at a sample thickness of 40μm and 90μm, respectively. This report reveals exciting new prospects for label free differentiation and segmentation using optical coherence tomography.

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    15. Single-shot speckle reduction and dispersion compensation in optical coherence tomography by compounding fractional Fourier domains

      Single-shot speckle reduction and dispersion compensation in optical coherence tomography by compounding fractional Fourier domains

      We present speckle suppression and dispersion compensation for Fourier-domain optical coherence tomography based on fractional Fourier transforms of a single A scan. A 1.54-fold reduction in speckle contrast was achieved with group velocity dispersion compensation. The method is demonstrated on biological samples using a swept source configuration at 1310 nm and a spectral-domain system at 840 nm

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    16. Dispersion compensation in Fourier domain optical coherence tomography using the fractional Fourier transform

      Dispersion compensation in Fourier domain optical coherence tomography using the fractional Fourier transform

      We address numerical dispersion compensation based on the use of the fractional Fourier transform (FrFT). The FrFT provides a new fundamental perspective on the nature and role of group-velocity dispersion in Fourier domain OCT. The dispersion induced by a 26 mm long water cell was compensated for a spectral bandwidth of 110 nm, allowing the theoretical axial resolution in air of 3.6 μm to be recovered from the dispersion degraded point spread function. Additionally, we present a new approach for depth dependent dispersion compensation based on numerical simulations. Finally, we show how the optimized fractional Fourier transform order parameter ...

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    17. Instantaneous quadrature components or Jones vector retrieval using the Pancharatnam–Berry phase in frequency domain low-coherence interferometry

      Instantaneous quadrature components or Jones vector retrieval using the Pancharatnam–Berry phase in frequency domain low-coherence interferometry

      We use the Pancharatnam–Berry phase as a multifunctional tool for low-coherence interferometry. This geometric phase shift enables instantaneous retrieval of the quadrature components of the complex interferometric signal. The phase shift is independent of wavelength and allows for a complex conjugate suppression of 40 dB for an optical bandwidth of 115 nm. Furthermore, this paper investigates the versatility of the geometric phase to perform polarization sensitive measurements. The Jones vector of the sample was obtained numerically, allowing sample birefringence and optical axis calculation.

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    18. Complex conjugate term manipulation in optical frequency-domain imaging using the time-frequency distribution

      Complex conjugate term manipulation in optical frequency-domain imaging using the time-frequency distribution

      We discuss two methods which use the intrinsic dispersion imbalance between interferometer arms in order to address and manipulate the complex conjugate terms in spectral domain optical coherence tomography. Using projections of the time-frequency plane, we can manipulate small induced dispersion and obtain similar modification of the complex conjugate term as large amount of chromatic dispersion. The algorithm described spreads the energy of the complex conjugate term over the entire A-scan. The method is applied to simulated OCT depth signals and offered a mirror term suppression of 20 dB. The second method shows how we can use the time-frequency distribution ...

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    19. Chromatic dispersion compensation of an OCT system with a programmable spectral filter

      Chromatic dispersion compensation of an OCT system with a programmable spectral filter
      We demonstrate the use of a programmable optical spectral filter to compensate all orders of chromatic dispersion in an all-fibre Fourier-domain optical coherence tomography system at 1550 nm. The pointspread- function, originally 58 μm wide, asymmetric, with strong sidelobes, is successfully made symmetric and recompressed to 37 μm, close to the theoretical limit of 36 μm.
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    20. Dispersion compensation in spectral domain optical coherence tomography in the continuum of fractional Fourier domains

      Dispersion compensation in spectral domain optical coherence tomography in the continuum of fractional Fourier domains
      We present a new method of numerical dispersion compensation in spectral domain optical coherence tomography based on the fractional Fourier transform. The dispersion induced by a 26 mm length water cell was compensated for a spectral bandwidth of 110 nm, allowing the theoretical axial resolution in air of 3.6 μm to be recovered from the dispersion degraded point spread function of 49 μm.
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    21. Dual-fibre stretcher and coma as tools for independent 2nd and 3rd order tunable dispersion compensation in a fibre-based ‘scan-free’ time domain optical coherence tomography system

      Dual-fibre stretcher and coma as tools for independent 2nd and 3rd order tunable dispersion compensation in a fibre-based ‘scan-free’ time domain optical coherence tomography system
      Dispersion compensation up to the third order is experimentally demonstrated by using a dual-fibre stretcher combined with the coma of an imaging lens, in a fibre-based scan-free time domain optical coherence tomography system, leading to an axial resolution of less than 3 μm.
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    22. Improving the efficiency of optical coherence tomography by using the non-ideal behaviour of a polarising beam splitter

      Improving the efficiency of optical coherence tomography by using the non-ideal behaviour of a polarising beam splitter
      We present a new way of improving the efficiency of optical coherence tomography by using the polarisation crosstalk of a polarising beam splitter to direct most of the available source optical power to the sample. The use of a quarter wave plate in both the reference and the sample arms allows most of the sample power to be directed to the detector while adjusting the reference arm to ensure noise optimised operation. As a result, the sensitivity of such a system can be improved by 6 dB, or alternatively the acquisition time can be improved by a factor of 4 ...
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    23. Dual-fiber stretcher as a tunable dispersion compensator for an all-fiber optical coherence tomography system

      Dual-fiber stretcher as a tunable dispersion compensator for an all-fiber optical coherence tomography system
      We present an all-fiber tunable dispersion compensator based on a pair of fiber stretchers made with different fiber types in which the group delay and the second-order dispersion can be tuned independently. Its efficiency is demonstrated in a fiber-based optical coherence tomography (OCT) system operating in the 800 nm wavelength range. The average sample dispersion in OCT imaging or the dispersion of transmission lines could also be compensated by our system.
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    24. Time and spectral domain all-fiber optical coherence tomography systems with variable dispersion compensators

      We use variable dispersion compensators to build time (TD-OCT) and spectral (SD-OCT) domain all-fiber optical coherence tomography systems operating in the 800 nm wavelength range. The all-fiber tunable dispersion compensator is based on a pair of fiber stretchers made with different fiber types in which the group delay and the 2nd-order dispersion can be tuned independently. Their abilities are demonstrated in biological tissues with the TD-OCT system reaching a significant sensitivity of 86 dB.
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    25. Efficiency and contrast enhancement in full-field OCT using non-ideal polarization behavior

      We present how to improve the efficiency and dynamic range for interferometric systems by taking advantage of the finite extinction ratio of a polarizing beam splitter. The technique has been demonstrated on a full-field OCT system by imaging of surfaces as well as transparent and turbid media.
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    26. All-fiber optical coherence tomography system incorporating a dual fiber stretcher dispersion compensator

      Sairam Iyer, Stephane Coen, and Frederique Vanholsbeeck We report on the design and experimental demonstration of an all-fiber optical coherence tomography system in which residual chromatic dispersion is compensated for by a pair of fiber stretchers made with different fiber types. Both the dispersion variations resulting from fiber inhomogeneities and ... [Proc. SPIE 7004, 700434 (2008)] published Fri May 16, 2008.
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    1-26 of 26
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    1. (25 articles) University of Auckland
    2. (25 articles) Frederique Vanholsbeeck
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    Dual-fiber stretcher as a tunable dispersion compensator for an all-fiber optical coherence tomography system Dual-fibre stretcher and coma as tools for independent 2nd and 3rd order tunable dispersion compensation in a fibre-based ‘scan-free’ time domain optical coherence tomography system Dispersion compensation in spectral domain optical coherence tomography in the continuum of fractional Fourier domains Chromatic dispersion compensation of an OCT system with a programmable spectral filter Complex conjugate term manipulation in optical frequency-domain imaging using the time-frequency distribution Instantaneous quadrature components or Jones vector retrieval using the Pancharatnam–Berry phase in frequency domain low-coherence interferometry Dispersion compensation in Fourier domain optical coherence tomography using the fractional Fourier transform Evaluation of Age-related Skin Changes and Instrument Reliability Using Clinical Probe Measurements and Imaging Modalities HP-OCT™ wins Victorian AEEA award – nominated for Sir William Hudson award Postdoctoral Scholar in High Resolution Retinal Imaging at The Ohio State University Cone Photoreceptor Integrity assessed with Adaptive Optics Imaging after Laser-Pointer-Induced Retinal Injury Quantitative assessment of macular microvasculature and radial peripapillary capillary plexus in the fellow eyes of patients with retinal vein occlusion using OCT angiography