1. Articles from Marco Augustin

    1-24 of 28 1 2 »
    1. Improved Diagnostic Imaging of Brain Tumors by Multimodal Microscopy and Deep Learning

      Improved Diagnostic Imaging of Brain Tumors by Multimodal Microscopy and Deep Learning

      Fluorescence-guided surgery is a state-of-the-art approach for intraoperative imaging during neurosurgical removal of tumor tissue. While the visualization of high-grade gliomas is reliable, lower grade glioma often lack visible fluorescence signals. Here, we present a hybrid prototype combining visible light optical coherence microscopy (OCM) and high-resolution fluorescence imaging for assessment of brain tumor samples acquired by 5-aminolevulinic acid (5-ALA) fluorescence-guided surgery. OCM provides high-resolution information of the inherent tissue scattering and absorption properties of tissue. We here explore quantitative attenuation coefficients derived from volumetric OCM intensity data and quantitative high-resolution 5-ALA fluorescence as potential biomarkers for tissue malignancy including otherwise ...

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    2. Indocyanine green provides absorption and spectral contrast for optical coherence tomography at 840  nm in vivo

      Indocyanine green provides absorption and spectral contrast for optical coherence tomography at 840  nm in vivo

      In recent years, there has been growing interest in the application of exogenous contrast agents to supplement the traditional strengths of optical coherence tomography (OCT) and provide additional biological information. In this Letter, we present how indocyanine green, a common fluorescent contrast agent approved by the United States Food and Drug Administration, can provide absorption and spectral contrast for OCT imaging in the mouse eye in vivo . We further demonstrate high stability of spectral contrast measurements for the long-term monitoring of contrast agents in spite of fluctuations in intensity.

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    3. Three-dimensional visualization of opacifications in the murine crystalline lens by in vivo optical coherence tomography

      Three-dimensional visualization of opacifications in the murine crystalline lens by in vivo optical coherence tomography

      Diagnostic classification techniques used to diagnose cataracts, the world’s leading cause of blindness, are currently based on subjective methods. Here, we present optical coherence tomography as a noninvasive tool for volumetric visualization of lesions formed in the crystalline lens. A custom-made swept-source optical coherence tomography (SS-OCT) system was utilized to investigate the murine crystalline lens. In addition to imaging cataractous lesions in aged wildtype mice, we studied the structure and shape of cataracts in a mouse model of Alzheimer’s disease. Hyperscattering opacifications in the crystalline lens were observed in both groups. Post mortem histological analysis were performed to ...

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    4. Optical Coherence Tomography Findings in the Retinas of SOD1 Knockout Mice

      Optical Coherence Tomography Findings in the Retinas of SOD1 Knockout Mice

      Purpose : The retinal phenotype of popular mouse models mimicking ophthalmic diseases, such as the superoxide dismutase 1 (SOD1) knockout (KO) mouse model, has mainly been assessed by ex vivo histology and in vivo fundus photography. We used multifunctional optical coherence tomography (OCT) to characterize the retinas of SOD1 KO mice in vivo. Methods : The custom-made ophthalmoscope featured a combination of conventional OCT, polarization-sensitive OCT, and OCT angiography. Seven SOD1 KO mice and nine age-matched controls were imaged between 6 and 17 months of age. A postprocessing framework was used to analyze total and outer retinal thickness changes. Drusenlike lesions were ...

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    5. Changes in Retinal Blood Flow in Response to an Experimental Increase in IOP in Healthy Participants as Assessed With Doppler Optical Coherence Tomography

      Changes in Retinal Blood Flow in Response to an Experimental Increase in IOP in Healthy Participants as Assessed With Doppler Optical Coherence Tomography

      Purpose : Blood flow autoregulation is an intrinsic mechanism of the healthy retinal vasculature to keep blood flow constant when ocular perfusion pressure (OPP) is changed. In the present study, we set out to investigate retinal blood flow in response to an experimental decrease in OPP in healthy participants using Doppler optical coherence tomography. Methods : Fifteen healthy participants aged between 22 and 31 years (mean, 27 ± 3 years) were included in the present open study. IOP was increased stepwise via the suction cup method to induce a decrease in OPP. Retinal blood flow in arteries and veins was assessed using a ...

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    6. 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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    7. 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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    8. 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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    9. 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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    10. 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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    11. 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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    12. 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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    13. 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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    14. 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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    15. 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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    16. 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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    17. 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
    18. 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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    19. 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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    20. 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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    21. 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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    22. 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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    23. 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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    24. 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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    1-24 of 28 1 2 »
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    In vivo imaging of retinal and choroidal vasculature in the rodent eye using optical coherence tomography Visualization of micro-capillaries using optical coherence tomography angiography with and without adaptive optics 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 Vitreous Seeding in Retinocytoma: Importance of Optical Coherence Tomography Utility of Spectral-Domain Optical Coherence Tomography in Differentiating Papilledema From Pseudopapilledema: A Prospective Longitudinal Study