1. Articles from Marco Augustin

    1-23 of 23
    1. Polarization-sensitive imaging with simultaneous bright- and dark-field optical coherence tomography

      Polarization-sensitive imaging with simultaneous bright- and dark-field optical coherence tomography

      We present a polarization-sensitive (PS) extension for bright- and dark-field (BRAD) optical coherence tomography imaging. Using a few-mode fiber detection scheme, the light backscattered at different angles is separated, and the BRAD images of tissue scattering are generated. A calibration method to correct for the fiber birefringence is proposed. Since particle scattering profiles are polarization dependent, a PS detection extends the capabilities for investigating the scattering properties of biological tissues. Both phantoms consisting of different-sized microparticles and a brain tissue specimen were imaged to validate the system performance and demonstrate the complementary image contrast.

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    2. Comparison of Intensity- and Polarization-based Contrast in Amyloid-beta Plaques as Observed by Optical Coherence Tomography

      Comparison of Intensity- and Polarization-based Contrast in Amyloid-beta Plaques as Observed by Optical Coherence Tomography

      One key hallmark of Alzheimer’s disease (AD) is the accumulation of extracellular amyloid-beta protein in cortical regions of the brain. For a definitive diagnosis of AD, post-mortem histological analysis, including sectioning and staining of different brain regions, is required. Here, we present optical coherence tomography (OCT) as a tissue-preserving imaging modality for the visualization of amyloid-beta plaques and compare their contrast in intensity- and polarization-sensitive (PS) OCT. Human brain samples of eleven patients diagnosed with AD were imaged. Three-dimensional PS-OCT datasets were acquired and plaques were manually segmented in 500 intensity and retardation cross-sections per patient using the freely ...

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    3. Synthetic subaperture-based angle-independent Doppler flow measurements using single-beam line field optical coherence tomography in vivo

      Synthetic subaperture-based angle-independent Doppler flow measurements using single-beam line field optical coherence tomography in vivo

      We demonstrate a synthetic subaperture-based angle-independent Doppler flow calculation, using a line field spectral domain optical coherence tomography system. The high speed of the system features a high phase stability over the volume, which is necessary to apply synthetic subapertures in the aperture plane. Thus, the flow component for each subaperture can be reconstructed in postprocessing. Capillary phantom and in vivo retinal imaging experiments were performed to validate and demonstrate angle-independent Doppler flow calculation

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    4. Assessment of pathological features in Alzheimer’s disease brain tissue with a large field-of-view visible-light optical coherence microscope

      Assessment of pathological features in Alzheimer’s disease brain tissue with a large field-of-view visible-light optical coherence microscope

      We implemented a wide field-of-view visible-light optical coherence microscope (OCM) for investigating ex-vivo brain tissue of patients diagnosed with Alzheimer’s disease (AD) and of a mouse model of AD. A submicrometer axial resolution in tissue was achieved using a broad visible light spectrum. The use of various objective lenses enabled reaching micrometer transversal resolution and the acquisition of images of microscopic brain features, such as cell structures, vessels, and white matter tracts. Amyloid-beta plaques in the range of 10 to 70  μm were visualized. Large field-of-view images of young and old mouse brain sections were imaged using an automated ...

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    5. Beyond backscattering: optical neuroimaging by BRAD

      Beyond backscattering: optical neuroimaging by BRAD

      Optical coherence tomography (OCT) is a powerful technology for rapid volumetric imaging in biomedicine. The bright field imaging approach of conventional OCT systems is based on the detection of directly backscattered light, thereby waiving the wealth of information contained in the angular scattering distribution. Here we demonstrate that the unique features of few-mode fibers (FMF) enable simultaneous bright and dark field (BRAD) imaging for OCT. As backscattered light is picked up by the different modes of a FMF depending upon the angular scattering pattern, we obtain access to the directional scattering signatures of different tissues by decoupling illumination and detection ...

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    6. In Vivo Characterization of Spontaneous Retinal Neovascularization in the Mouse Eye by Multifunctional Optical Coherence Tomography

      In Vivo Characterization of Spontaneous Retinal Neovascularization in the Mouse Eye by Multifunctional Optical Coherence Tomography

      Purpose : To investigate the early development of spontaneous retinal neovascularization in the murine retina by a multifunctional optical coherence tomography approach. To characterize involved tissue changes in vivo and describe structural and functional changes over time. Methods : A multifunctional optical coherence tomography (OCT) system providing 3-fold contrast comprising reflectivity, polarization sensitivity, and OCT angiography (OCTA) was utilized to image very-low-density lipoprotein receptor (VLDLR) knockout mice. Baseline measurements were acquired as early as postnatal day 14 and a follow-up of neovascularization development was performed until the age of 3 months. Control mice were imaged accordingly and a multiparametric image analysis was ...

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    7. Compact akinetic swept source optical coherence tomography angiography at 1060 nm supporting a wide field of view and adaptive optics imaging modes of the posterior eye

      Compact akinetic swept source optical coherence tomography angiography at 1060 nm supporting a wide field of view and adaptive optics imaging modes of the posterior eye

      Imaging of the human retina with high resolution is an essential step towards improved diagnosis and treatment control. In this paper, we introduce a compact, clinically user-friendly instrument based on swept source optical coherence tomography (SS-OCT). A key feature of the system is the realization of two different operation modes. The first operation mode is similar to conventional OCT imaging and provides large field of view (FoV) images (up to 45° × 30°) of the human retina and choroid with standard resolution. The second operation mode enables it to optically zoom into regions of interest with high transverse resolution using adaptive ...

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    8. White light polarization sensitive optical coherence tomography for sub-micron axial resolution and spectroscopic contrast in the murine retina

      White light polarization sensitive optical coherence tomography for sub-micron axial resolution and spectroscopic contrast in the murine retina

      A white light polarization sensitive optical coherence tomography system has been developed, using a supercontinuum laser as the light source. By detecting backscattered light from 400–700 nm, an axial resolution of 1.0 µm in air was achieved. The system consists of a free-space interferometer and two homemade spectrometers that detect orthogonal polarization states. Following system specifications, images of a healthy murine retina as acquired by this non-contact system are presented, showing high resolution reflectivity images as well as spectroscopic and polarization sensitive contrast. Additional images of the very-low-density-lipoprotein-receptor (VLDLR) knockout mouse model were acquired. The high resolution allows ...

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    9. Visualization of neuritic plaques in Alzheimer’s disease by polarization-sensitive optical coherence microscopy

      Visualization of neuritic plaques in Alzheimer’s disease by polarization-sensitive optical coherence microscopy

      One major hallmark of Alzheimer’s disease (AD) and cerebral amyloid angiopathy (CAA) is the deposition of extracellular senile plaques and vessel wall deposits composed of amyloid-beta (A β ). In AD, degeneration of neurons is preceded by the formation of A β plaques, which show different morphological forms. Most of them are birefringent owing to the parallel arrangement of amyloid fibrils. Here, we present polarization sensitive optical coherence microscopy (PS-OCM) for imaging mature neuritic A β plaques based on their birefringent properties. Formalin-fixed, post-mortem brain samples of advanced stage AD patients were investigated. In several cortical brain regions, neuritic A β plaques were successfully ...

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    10. Ocular fundus pulsations within the posterior rat eye: Chorioscleral motion and response to elevated intraocular pressure

      Ocular fundus pulsations within the posterior rat eye: Chorioscleral motion and response to elevated intraocular pressure

      A multi-functional optical coherence tomography (OCT) approach is presented to determine ocular fundus pulsations as an axial displacement between the retina and the chorioscleral complex in the albino rat eye. By combining optical coherence elastography and OCT angiography (OCTA), we measure subtle deformations in the nanometer range within the eye and simultaneously map retinal and choroidal perfusion. The conventional OCT reflectivity contrast serves as a backbone to segment the retina and to define several slabs which are subsequently used for quantitative ocular pulsation measurements as well as for a qualitative exploration of the multi-functional OCT image data. The proposed concept ...

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    11. Polarization-sensitive optical coherence tomography in the anterior mouse eye

      Polarization-sensitive optical coherence tomography in the anterior mouse eye

      Polarization-sensitive optical coherence tomography (PS-OCT) provides intrinsic contrast related to tissue microstructure. In the past, PS-OCT has been successfully used for imaging the anterior eye of humans in a variety of pathologic conditions. Here, we present PS-OCT imaging of the anterior eye in mice. Spectral domain PS-OCT centered at a wavelength of 840 nm was performed in anaesthetized laboratory mice. Three dimensional data sets were acquired at a 70 kHz A-line rate. PS-OCT images displaying phase retardation, birefringent axis orientation and degree of polarization uniformity (DOPU) were computed. Similar to human anterior segments, depolarization was observed in the corneal stroma ...

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    12. Beyond backscattering: Optical neuroimaging by BRAD

      Beyond backscattering: Optical neuroimaging by BRAD

      Optical coherence tomography (OCT) is a powerful technology for rapid volumetric imaging in biomedicine. The bright field imaging approach of conventional OCT systems is based on the detection of directly backscattered light, thereby waiving the wealth of information contained in the angular scattering distribution. Here we demonstrate that the unique features of few-mode fibers (FMF) enable simultaneous bright and dark field (BRAD) imaging for OCT. As backscattered light is picked up by the different modes of a FMF depending upon the angular scattering pattern, we obtain access to the directional scattering signatures of different tissues by decoupling illumination and detection ...

      Read Full Article
    13. Multi-directional optical coherence tomography for retinal imaging

      Multi-directional optical coherence tomography for retinal imaging

      We introduce multi-directional optical coherence tomography (OCT), a technique for investigation of the scattering properties of directionally reflective tissue samples. By combining the concepts of multi-channel and directional OCT, this approach enables simultaneous acquisition of multiple reflectivity depth-scans probing a mutual sample location from differing angular orientations. The application of multi-directional OCT in retinal imaging allows for in-depth investigations on the directional reflectivity of the retinal nerve fiber layer, Henle’s fiber layer and the photoreceptor layer. Major ophthalmic diseases (such as glaucoma or age-related macular degeneration) have been reported to alter the directional reflectivity properties of these retinal layers ...

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    14. Feature Of The Week 09/03/2017: Spectroscopic imaging with spectral domain visible light optical coherence microscopy in Alzheimer’s disease brain samples

      Feature Of The Week 09/03/2017: Spectroscopic imaging with spectral domain visible light optical coherence microscopy in Alzheimer’s disease brain samples

      A visible light spectral domain optical coherence microscopy system was developed. A high axial resolution of 0.88 μm in tissue was achieved using a broad visible light spectrum (425 – 685 nm). Healthy human brain tissue was imaged to quantify the difference between white (WM) and grey matter (GM) in intensity and attenuation. The high axial resolution enables the investigation of amyloid-beta plaques of various sizes in human brain tissue and animal models of Alzheimer’s disease (AD). By performing a spectroscopic analysis of the OCM data, differences in the characteristics for WM, GM, and neuritic amyloid-beta plaques were found ...

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    15. Spectroscopic imaging with spectral domain visible light optical coherence microscopy in Alzheimer’s disease brain samples

      Spectroscopic imaging with spectral domain visible light optical coherence microscopy in Alzheimer’s disease brain samples

      A visible light spectral domain optical coherence microscopy system was developed. A high axial resolution of 0.88 µm in tissue was achieved using a broad visible light spectrum (425 − 685 nm). Healthy human brain tissue was imaged to quantify the difference between white (WM) and grey matter (GM) in intensity and attenuation. The high axial resolution enables the investigation of amyloid-beta plaques of various sizes in human brain tissue and animal models of Alzheimer’s disease (AD). By performing a spectroscopic analysis of the OCM data, differences in the characteristics for WM, GM, and neuritic amyloid-beta plaques were found ...

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    16. Visible light spectral domain optical coherence microscopy system for ex vivo imaging

      Visible light spectral domain optical coherence microscopy system for ex vivo imaging

      A visible light spectral domain optical coherence microscopy system operating in the wavelength range of 450-680 nm was developed. The resulting large wavelength range of 230 nm enabled an ultrahigh axial resolution of 0.88μm in tissue. The setup consisted of a Michelson interferometer combined with a homemade spectrometer with a spectral resolution of 0.03 nm. Scanning of 1 x 1 mm 2 and 0.5 x 0.5 mm 2 areas was performed by an integrated microelectromechanical mirror. After scanning the light beam is focused onto the tissue by a commercial objective with a 10 x magnification ...

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    17. Posterior rat eye during acute intraocular pressure elevation studied using polarization sensitive optical coherence tomography

      Posterior rat eye during acute intraocular pressure elevation studied using polarization sensitive optical coherence tomography

      Polarization sensitive optical coherence tomography (PS-OCT) operating at 840 nm with axial resolution of 3.8 µm in tissue was used for investigating the posterior rat eye during an acute intraocular pressure (IOP) increase experiment. IOP was elevated in the eyes of anesthetized Sprague Dawley rats by cannulation of the anterior chamber. Three dimensional PS-OCT data sets were acquired at IOP levels between 14 mmHg and 105 mmHg. Maps of scleral birefringence, retinal nerve fiber layer (RNFL) retardation and relative RNFL/retina reflectivity were generated in the peripapillary area and quantitatively analyzed. All investigated parameters showed a substantial correlation with ...

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    18. Visualization of micro-capillaries using optical coherence tomography angiography with and without adaptive optics

      Visualization of micro-capillaries using optical coherence tomography angiography with and without adaptive optics

      The purpose of this work is to investigate the benefits of adaptive optics (AO) technology for optical coherence tomography angiography (OCTA). OCTA has shown great potential in non-invasively enhancing the contrast of vessels and small capillaries. Especially the capability of the technique to visualize capillaries with a lateral extension that is below the transverse resolution of the system opens unique opportunities in diagnosing retinal vascular diseases. However, there are some limitations of this technology such as shadowing and projection artifacts caused by overlying vasculature or the inability to determine the true extension of a vessel. Thus, the evaluation of the ...

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    19. Multi-Functional OCT Enables Longitudinal Study of Retinal Changes in a VLDLR Knockout Mouse Model

      Multi-Functional OCT Enables Longitudinal Study of Retinal Changes in a VLDLR Knockout Mouse Model

      We present a multi-functional optical coherence tomography (OCT) imaging approach to study retinal changes in the very-low-density-lipoprotein-receptor (VLDLR) knockout mouse model with a threefold contrast. In the retinas of VLDLR knockout mice spontaneous retinal-chorodoidal neovascularizations form, having an appearance similar to choroidal and retinal neovascularizations (CNV and RNV) in neovascular age-related macular degeneration (AMD) or retinal angiomatous proliferation (RAP). For this longitudinal study, the mice were imaged every 4 to 6 weeks starting with an age of 4 weeks and following up to the age of 11 months. Significant retinal changes were identified by the multi-functional imaging approach offering a ...

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    20. Polarization properties of single layers in the posterior eyes of mice and rats investigated using high resolution polarization sensitive optical coherence tomography

      Polarization properties of single layers in the posterior eyes of mice and rats investigated using high resolution polarization sensitive optical coherence tomography

      We present a high resolution polarization sensitive optical coherence tomography (PS-OCT) system for ocular imaging in rodents. The system operates at 840 nm and uses a broadband superluminescent diode providing an axial resolution of 5.1 µm in air. PS-OCT data was acquired at 83 kHz A-scan rate by two identical custom-made spectrometers for orthogonal polarization states. Pigmented (Brown Norway, Long Evans) and non-pigmented (Sprague Dawley) rats as well as pigmented mice (C57BL/6) were imaged. Melanin pigment related depolarization was analyzed in the retinal pigment epithelium (RPE) and choroid of these animals using the degree of polarization uniformity (DOPU ...

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    21. Melanin Pigmentation in Rat Eyes: In Vivo Imaging by Polarization-Sensitive Optical Coherence Tomography and Comparison to Histology

      Melanin Pigmentation in Rat Eyes: In Vivo Imaging by Polarization-Sensitive Optical Coherence Tomography and Comparison to Histology

      Purpose : The purpose of this study was to demonstrate polarization-sensitive optical coherence tomography (PS-OCT) for imaging pigmented structures in the posterior eye segments of albino and pigmented rats and to correlate depolarization contrast of the retinal pigment epithelium (RPE) and choroid in in vivo PS-OCT to melanin pigmentation detected in postmortem histologic serial sections. Methods : In vivo three-dimensional PS-OCT imaging was performed in adult albino and pigmented rat eyes at 70-kHz A-line rate. Degree of polarization uniformity (DOPU) fundus maps and radial DOPU profiles were generated. Postmortem histomorphologic analysis was performed in order to investigate melanin pigmentation of the RPE ...

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    22. Comparison of the polarization properties in the retinas of different rodents using high resolution polarization sensitive OCT

      Comparison of the polarization properties in the retinas of different rodents using high resolution polarization sensitive OCT

      Animal models play an important role for understanding the pathophysiology of glaucoma and age-related macular degeneration. With these models, longitudinal studies can be performed and therefore there is need for non-invasive evaluation of disease progress. For that purpose optical coherence tomography (OCT) can be used. Since tissues with different polarization properties are important in these diseases, polarization sensitive OCT (PS-OCT) could be a valuable tool in preclinical research. In this work a high resolution PS-OCT (HR-PS-OCT) system was used in-vivo for rodent retinal imaging. A super luminescent diode with a bandwidth of 100 nm was used as a light source ...

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    23. In vivo imaging of retinal and choroidal vasculature in the rodent eye using optical coherence tomography

      In vivo imaging of retinal and choroidal vasculature in the rodent eye using optical coherence tomography

      In vivo imaging technologies such as optical coherence tomography (OCT) and rodent models enable longitudinal studies of different ophthalmic pathologies and their underlying physiological changes. In this work a custom-made high resolution polarization sensitive OCT system is used to image the posterior eye of small rodents like mice and rats. Enface projections at certain depths/levels in the three-dimensional (3D) reflectivity images enable to visualize different vascular structures in the retina as well as in the choroid. Further, phase resolved motion contrast based OCT angiography allows to create vascular maps with a high contrast to distinguish between static tissue and ...

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    1-23 of 23
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    In vivo imaging of retinal and choroidal vasculature in the rodent eye using optical coherence tomography Comparison of the polarization properties in the retinas of different rodents using high resolution polarization sensitive OCT Posterior rat eye during acute intraocular pressure elevation studied using polarization sensitive optical coherence tomography Visible light spectral domain optical coherence microscopy system for ex vivo imaging Spectroscopic imaging with spectral domain visible light optical coherence microscopy in Alzheimer’s disease brain samples Feature Of The Week 09/03/2017: Spectroscopic imaging with spectral domain visible light optical coherence microscopy in Alzheimer’s disease brain samples Beyond backscattering: Optical neuroimaging by BRAD Ocular fundus pulsations within the posterior rat eye: Chorioscleral motion and response to elevated intraocular pressure Visualization of neuritic plaques in Alzheimer’s disease by polarization-sensitive optical coherence microscopy Compact akinetic swept source optical coherence tomography angiography at 1060 nm supporting a wide field of view and adaptive optics imaging modes of the posterior eye Optical coherence tomography angiography of foveal neovascularisation in proliferative diabetic retinopathy Treating port wine stain birthmarks using dynamic optical coherence tomography-guided setting