1. Articles from Stefan Zotter

    1-22 of 22
    1. Automated Identification and Quantification of Subretinal Fibrosis in Neovascular Age-Related Macular Degeneration Using Polarization-Sensitive OCT

      Automated Identification and Quantification of Subretinal Fibrosis in Neovascular Age-Related Macular Degeneration Using Polarization-Sensitive OCT

      Purpose : To identify and quantify subretinal fibrosis in eyes with advanced neovascular age-related macular degeneration (nAMD) using polarization-sensitive optical coherence tomography (PS-OCT). Methods : Eyes of patients with subretinal fibrosis secondary to nAMD were included in this case series. All patients underwent a complete ophthalmic examination to clearly identify advanced nAMD lesions with fibrosis. Examinations of PS-OCT were performed using a novel system with an integrated eye tracker. Areas of fibrosis in PS-OCT, automatically segmented using a custom-built algorithm, were compared with conventional imaging modalities including spectral-domain OCT, fluorescein angiography, and color fundus photography in their potential to visualize fibrosis in ...

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    2. Method and apparatus for processing polarization data of polarization sensitive optical coherence tomography

      Method and apparatus for processing polarization data of polarization sensitive optical coherence tomography

      A method for processing polarization data includes steps of acquiring a plurality of sets of polarization data items, converting the set of polarization data items into a representation including parameters of amplitude and phase, and averaging the converted set of polarization data items.

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    3. Spectral degree of polarization uniformity for polarization-sensitive OCT

      Spectral degree of polarization uniformity for polarization-sensitive OCT

      Depolarization of light can be measured by polarization-sensitive optical coherence tomography (PS-OCT) and has been used to improve tissue discrimination as well as segmentation of pigmented structures. Most approaches to depolarization assessment for PS-OCT – such as the degree of polarization uniformity (DOPU) – rely on measuring the uniformity of polarization states using spatial evaluation kernels. In this article, we present a different approach which exploits the spectral dimension. We introduce the spectral DOPU for the pixelwise analysis of polarization state variations between sub-bands of the broadband light source spectrum. Alongside a comparison with conventional spatial and temporal DOPU algorithms, we demonstrate ...

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    4. Polarization-Sensitive Optical Coherence Tomography and Conventional Retinal Imaging Strategies in Assessing Foveal Integrity in Geographic Atrophy

      Polarization-Sensitive Optical Coherence Tomography and Conventional Retinal Imaging Strategies in Assessing Foveal Integrity in Geographic Atrophy

      Purpose : To compare current imaging methods with respect to their ability to detect the condition of the fovea in patients with geographic atrophy (GA). Methods : The retinas of 176 eyes with GA were imaged using two spectral-domain optical coherence tomography (SD-OCT) systems, Cirrus HD-OCT and Spectralis HRA+OCT, and fundus autofluorescence (FAF) and infrared imaging (IR) was used in the scanning laser ophthalmoscope (SLO) mode. Polarization-sensitive OCT (PS-OCT), which selectively visualizes the RPE in addition to SD-OCT features, was used to image 95 eyes. Geographic atrophy lesions were categorized as fovea spared, involved, or not quantifiable (grades 0, 1, and ...

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    5. POLARIZATION-SENSITIVE Optical Coherence Tomography System

      POLARIZATION-SENSITIVE Optical Coherence Tomography System

      In a polarization-sensitive optical coherence tomography system, an interferometer includes single mode fibers and a plurality of polarization controllers. At least one of the plurality of polarization controllers is disposed on each of the fibers of the interferometer. The fibers include a fiber for sample light beam, a fiber for reference light beam, and a fiber for detection light beam. An image forming unit determines a pixel value from a data set consists of two orthogonal polarization components simultaneously obtained at substantially identical spatial positions of a test sample, wherein a measurement light beam has static single polarization state.

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    6. Analysis of optimum conditions of depolarization imaging by polarization-sensitive optical coherence tomography in the human retina

      Analysis of optimum conditions of depolarization imaging by polarization-sensitive optical coherence tomography in the human retina

      Measurement and imaging of depolarization by polarization-sensitive optical coherence tomography (PS-OCT) requires averaging of Stokes vector elements within two- or three-dimensional (3-D) evaluation windows to obtain the degree of polarization uniformity (DOPU). By use of a PS-OCT system with an integrated retinal tracker, we analyze optimum conditions for depolarization imaging, data processing, and segmentation of depolarizing tissue in the human retina. The trade-offs between figures of merit like DOPU imaging sensitivity, efficiency, and susceptibility are evaluated in terms of 3-D resolution. The results are used for a new, detailed interpretation of PS-OCT high-resolution images of the human retinal pigment epithelium ...

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    7. Single input state polarization sensitive swept source optical coherence tomography based on an all single mode fiber interferometer

      Single input state polarization sensitive swept source optical coherence tomography based on an all single mode fiber interferometer

      We present a newly developed single mode fiber based swept source polarization sensitive optical coherence tomography system using a single input state at 1040 nm. Two non-polarizing fiber based beam splitters are combined to form a Mach-Zehnder interferometer, while two polarizing beam splitters are used to obtain a polarization sensitive detection. Both types of beam splitters solely feature conventional single mode fibers. Polarization control paddles are used to set and maintain the polarization states in the fibers of the interferometer and detection unit. By use of a special paddle alignment scheme we are able to eliminate any bulk optic wave ...

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    8. RETINAL PIGMENT EPITHELIUM FINDINGS IN PATIENTS WITH ALBINISM USING WIDE-FIELD POLARIZATION-SENSITIVE OPTICAL COHERENCE TOMOGRAPHY

      RETINAL PIGMENT EPITHELIUM FINDINGS IN PATIENTS WITH ALBINISM USING WIDE-FIELD POLARIZATION-SENSITIVE OPTICAL COHERENCE TOMOGRAPHY

      Purpose: To investigate pigmentation characteristics of the retinal pigment epithelium (RPE) in patients with albinism using wide-field polarization-sensitive optical coherence tomography compared with intensity-based spectral domain optical coherence tomography and fundus autofluorescence imaging. Methods: Five patients (10 eyes) with previously genetically diagnosed albinism and 5 healthy control subjects (10 eyes) were imaged by a wide-field polarization-sensitive optical coherence tomography system (scan angle: 40 x 40[degrees] on the retina), sensitive to melanin contained in the RPE, based on the polarization state of backscattered light. Conventional intensity-based spectral domain optical coherence tomography and fundus autofluorescence examinations were performed. Retinal pigment epithelium-pigmentation ...

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    9. Adaptive optics SLO/OCT for 3D imaging of human photoreceptors in vivo

      Adaptive optics SLO/OCT for 3D imaging of human photoreceptors in vivo

      We present a new instrument that is capable of imaging human photoreceptors in three dimensions. To achieve high lateral resolution, the system incorporates an adaptive optics system. The high axial resolution is achieved through the implementation of optical coherence tomography (OCT). The instrument records simultaneously both, scanning laser ophthalmoscope (SLO) and OCT en-face images, with a pixel to pixel correspondence. The information provided by the SLO is used to correct for transverse eye motion in post-processing. In order to correct for axial eye motion, the instrument is equipped with a high speed axial eye tracker. In vivo images of foveal ...

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    10. Motion artifact and speckle noise reduction in polarization sensitive optical coherence tomography by retinal tracking

      Motion artifact and speckle noise reduction in polarization sensitive optical coherence tomography by retinal tracking

      We present a novel polarization sensitive optical coherence tomography (PS-OCT) system with an integrated retinal tracker. The tracking operates at up to 60 Hz, correcting PS-OCT scanning positions during the acquisition to avoid artifacts caused by eye motion. To demonstrate the practical performance of the system, we imaged several healthy volunteers and patients with AMD both with B-scan repetitions for frame averaging and with 3D raster scans. Under large retinal motions with up to 1 mm amplitude at 0.5 ~a few Hz frequency range, motion artifact suppression in the PS-OCT images as well as standard deviation noise reduction in ...

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    11. In vitro and in vivo three-dimensional velocity vector measurement by three-beam spectral-domain Doppler optical coherence tomography

      In vitro and in vivo three-dimensional velocity vector measurement by three-beam spectral-domain Doppler optical coherence tomography

      We developed a three-beam Doppler optical coherence tomography (OCT) system that enables measurement of the velocity vector of moving particles in three-dimensions (3-D). The spatial orientation as well as the magnitude of motion can be determined without prior knowledge of the geometry of motion. The system combines three spectral-domain OCT interferometers whose sample beams are focused at the sample by a common focusing lens at three different angles. This provides three spatially independent velocity components simultaneously from which the velocity vector can be reconstructed. We demonstrate the system in a simple test object (rotating disc), a flow phantom, and for ...

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    12. Characterization of Stargardt disease using polarisation-sensitive optical coherence tomography and fundus autofluorescence imaging

      Characterization of Stargardt disease using polarisation-sensitive optical coherence tomography and fundus autofluorescence imaging

      Purpose: To identify disease-specific changes in Stargardt disease (STGD) based on imaging with polarisation-sensitive spectral-domain optical coherence tomography (PS-OCT) and to compare structural changes to those visible on blue light fundus autofluorescence (FAF)imaging. Methods: 28 eyes of 14 patients diagnosed with STGD were imaged using a novel high-speed, large-field PS-OCT system and FAF (Heidelberg Retina Angiograph/Spectralis, Heidelberg Engineering, Germany; excitation 488nm, emission >500nm). The ophthalmoscopic phenotype was classified into 3 groups as suggested by Fishman et al. ABCA4 mutation testing detected 15 STGD alleles, 6 of which harbour novel mutations. Results: STGD phenotype 1 (12 eyes) showed sharply ...

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    13. Retinal polarization-sensitive optical coherence tomography at 1060 nm with 350 kHz A-scan rate using an Fourier domain mode locked laser

      Retinal polarization-sensitive optical coherence tomography at 1060 nm with 350 kHz A-scan rate using an Fourier domain mode locked laser

      We present a novel, high-speed, polarization-sensitive, optical coherence tomography set-up for retinal imaging operating at a central wavelength of 1060 nm which was tested for in vivo imaging in healthy human volunteers. We use the system in combination with a Fourier domain mode locked laser with active spectral shaping which enables the use of forward and backward sweep in order to double the imaging speed without a buffering stage. With this approach and with a custom designed data acquisition system, we show polarization-sensitive imaging with an A-scan rate of 350 kHz. The acquired three-dimensional data sets of healthy human volunteers ...

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    14. Measuring Retinal Nerve Fiber Layer Birefringence, Retardation, and Thickness Using Wide-Field, High-Speed Polarization Sensitive Spectral Domain OCT

      Measuring Retinal Nerve Fiber Layer Birefringence, Retardation, and Thickness Using Wide-Field, High-Speed Polarization Sensitive Spectral Domain OCT

      Purpose. We presented a novel polarization sensitive optical coherence tomography (PS-OCT) system for measuring retinal nerve fiber layer (RNFL) birefringence, retardation, and thickness, and report on the repeatability of acquiring these quantities. Methods. A new PS-OCT system, measuring at 840 nm, was developed that supports scan angles of up to 40° × 40° with an A-scan rate of 70 kHz. To test the performance and reproducibility, we measured 10 eyes of 5 healthy human volunteers five times each. All volunteers were imaged further with scanning laser polarimetry (SLP). The obtained RNFL birefringence, retardation, and thickness maps were averaged, and standard deviation ...

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    15. High-speed polarization sensitive optical coherence tomography scan engine based on Fourier domain mode locked laser

      High-speed polarization sensitive optical coherence tomography scan engine based on Fourier domain mode locked laser

      We report on a new swept source polarization sensitive optical coherence tomography scan engine that is based on polarization maintaining (PM) fiber technology. The light source is a Fourier domain mode locked laser with a PM cavity that operates in the 1300 nm wavelength regime. It is equipped with a PM buffer stage that doubles the fundamental sweep frequency of 54.5 kHz. The fiberization allows coupling of the scan engine to different delivery probes. In a first demonstration, we use the system for imaging human skin at an A-scan rate of 109 kHz. The system illuminates the sample with ...

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    16. Large-field high-speed polarization sensitive spectral domain OCT and its applications in ophthalmology

      Large-field high-speed polarization sensitive spectral domain OCT and its applications in ophthalmology
      We present a novel spectral domain polarization sensitive OCT system (PS-OCT) that operates at an A-scan rate of 70 kHz and supports scan angles of up to 40° × 40°. The high-speed imaging allows the acquisition of up to 1024 × 250 A-scans per 3D scan, which, together with the large field of view, considerably increases the informative value of the images. To demonstrate the excellent performance of the new PS-OCT system, we imaged several healthy volunteers and patients with various diseases such as glaucoma, AMD, Stargardt’s disease, and albinism. The results are compared with clinically established methods such as scanning ...
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    17. High-speed polarization-sensitive OCT at 1060 nm using a Fourier domain mode-locked swept source

      High-speed polarization-sensitive OCT at 1060 nm using a Fourier domain mode-locked swept source

      Optical coherence tomography (OCT) in the 1060nm range is interesting for in vivo imaging of the human posterior eye segment (retina, choroid, sclera), as it permits a long penetration depth. Complementary to structural images, polarization-sensitive OCT (PS-OCT) images visualize birefringent, polarization-maintaining or depolarizing areas within the sample. This information can be used to distinguish retinal layers and structures with different polarization properties. High imaging speed is crucial for imaging ocular structures in vivo in order to minimize motion artifacts while acquiring sufficiently large datasets. Here, we demonstrate PS-OCT imaging at 350 kHz A-scan rate using a two-channel PS-OCT system in ...

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    18. Feature Of The Week 4/29/12: Medical University of Vienna Demonstrates Automated Measurement of Choroidal Thickness in the Human Eye by PS-OCT

      Feature Of The Week 4/29/12: Medical University of Vienna Demonstrates Automated Measurement of Choroidal Thickness in the Human Eye by PS-OCT

      Researchers at the Medical University of Vienna have a long history of outstanding contributions to the field of Optical Coherence Tomography dating back 25 years.  This week work by Dr. Hitzenberger, one of the pioneers of the field, and his colleagues is featured demonstrating automated measurement of choroidal thickness in the human eye by polarization sensitive optical coherence tomography. Below is a summary of their work.Imaging of retinal layers and quantitative measurements of their thickness are among the most important applications of OCT. E.g., the total retinal thickness is an important quantity for diagnosis of diabetic retinopathy, the ...

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    19. High-Speed Retinal Imaging with Polarization-Sensitive OCT at 1040 nm

      High-Speed Retinal Imaging with Polarization-Sensitive OCT at 1040 nm

      Purpose. To demonstrate the ability of a new high-speed polarization-sensitive optical coherence tomography (PS-OCT) system for retinal imaging at 1040 nm. Methods. A new polarization-sensitive swept source OCT system in the 1 [mu]m wavelength range is used to image the retina of healthy volunteers. The instrument is operated at an A-scan rate of 100 kHz which is about three times faster than previously reported PS-OCT instruments in this wavelength region. The increased imaging speed can be used to record densely sampled volumes of the retina. Moreover, it enables averaging of several B-scans recorded at the same location to obtain ...

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    20. Automated measurement of choroidal thickness in the human eye by polarization sensitive optical coherence tomography

      Automated measurement of choroidal thickness in the human eye by polarization sensitive optical coherence tomography

      We present a new method to automatically segment the thickness of the choroid in the human eye by polarization sensitive optical coherence tomography (PS-OCT). A swept source PS-OCT instrument operating at a center wavelength of 1040 nm is used. The segmentation method is based entirely on intrinsic, tissue specific polarization contrast mechanisms. In a first step, the anterior boundary of the choroid, the retinal pigment epithelium, is segmented based on depolarization. In a second step, the choroid-sclera interface is found by using the birefringence of the sclera. The method is demonstrated in five healthy eyes. The mean repeatability (standard deviation ...

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    21. Visualization of microvasculature by dual-beam phase-resolved Doppler optical coherence tomography

      Visualization of microvasculature by dual-beam phase-resolved Doppler optical coherence tomography

      We present a dual-beam Doppler optical coherence tomography system for visualizing the microvasculature within the retina. The sample arm beams from two identical spectral domain optical coherence tomography (SD-OCT) systems are combined such that there is a small horizontal offset between them at the retina. Thereby we record two tomograms which are slightly separated in time. Phase-resolved Doppler analysis is performed between these two data sets. This system allows blood capillary imaging with high flow sensitivity and variable velocity range. To demonstrate the performance of our system we present images of the microvascular network around the fovea and around the ...

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    22. Sample motion-insensitive, full-range, complex, spectral-domain optical-coherence tomography

      Sample motion-insensitive, full-range, complex, spectral-domain optical-coherence tomography

      We present a full-range, complex, spectral-domain optical-coherence-tomography (SD-OCT) system that is based on a double-beam scanning approach. The sample beams of two identical SD-OCT setups are combined collinearly by a bulk optic beam splitter before illuminating the object. The required phase shift for the complex signal reconstruction comes from the phase difference between both interferometers. Because of the double-beam scanning approach, our system is completely insensitive to sample motion. To demonstrate the performance of our setup, we present images of the human optic nerve head in vivo and of a human tooth.

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    1-22 of 22
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    1. (22 articles) Michael Pircher
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    Sample motion-insensitive, full-range, complex, spectral-domain optical-coherence tomography Visualization of microvasculature by dual-beam phase-resolved Doppler optical coherence tomography Automated measurement of choroidal thickness in the human eye by polarization sensitive optical coherence tomography High-Speed Retinal Imaging with Polarization-Sensitive OCT at 1040 nm Feature Of The Week 4/29/12: Medical University of Vienna Demonstrates Automated Measurement of Choroidal Thickness in the Human Eye by PS-OCT High-speed polarization-sensitive OCT at 1060 nm using a Fourier domain mode-locked swept source Large-field high-speed polarization sensitive spectral domain OCT and its applications in ophthalmology Retinal polarization-sensitive optical coherence tomography at 1060 nm with 350 kHz A-scan rate using an Fourier domain mode locked laser In vitro and in vivo three-dimensional velocity vector measurement by three-beam spectral-domain Doppler optical coherence tomography Motion artifact and speckle noise reduction in polarization sensitive optical coherence tomography by retinal tracking Diagnostic Performance of Deep Learning for Angle Closre Wide-field Optical Coherence Tomography Imaging of Excised Breast Tissue.