1. Articles from Tilman Schmoll

    1-24 of 33 1 2 »
    1. Holographic line field en-face OCT with digital adaptive optics in the retina in vivo

      Holographic line field en-face OCT with digital adaptive optics in the retina in vivo

      We demonstrate a high-resolution line field en-face time domain optical coherence tomography (OCT) system using an off-axis holography configuration. Line field en-face OCT produces high speed en-face images at rates of up to 100 Hz. The high frame rate favors good phase stability across the lateral field-of-view which is indispensable for digital adaptive optics (DAO). Human retinal structures are acquired in-vivo with a broadband light source at 840 nm, and line rates of 10 kHz to 100 kHz. Structures of different retinal layers, such as photoreceptors, capillaries, and nerve fibers are visualized with high resolution of 2.8 µm and ...

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    2. Systems and methods for spectrally dispersed illumination optical coherence tomography

      Systems and methods for spectrally dispersed illumination optical coherence tomography

      Systems and methods are presented for acquisition and processing of spectrally dispersed illumination optical coherence tomographic data. Light from a source is distributed spectrally on the sample, and each acquisition simultaneously provides partial spectral interference information from multiple locations in the sample. Thus for a given spatial point, a single observation will be of a partial spectrum A-scan. When multiple partial spectrum A-scan observations are made at the same point by shifting the spectrum of light on to the tissue, the point can be observed by the entire broadband spectrum of the light source, thereby making it possible to create ...

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    3. Analysis and visualization of OCT angiography data

      Analysis and visualization of OCT angiography data

      Methods for analyzing and visualizing OCT angiography data are presented. In one embodiment, an automated method for identifying the foveal avascular zone in a two dimensional en face image generated from motion contrast data is presented. Several 3D visualization techniques are presented including one in which a particular vessel is selected in a motion contrast image and all connected vessels are highlighted. A further embodiment includes a stereoscopic visualization method. In addition, a variety of metrics for characterizing OCT angiography image data are described.

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    4. Systems and methods for improved acquisition of ophthalmic optical coherence tomography data

      Systems and methods for improved acquisition of ophthalmic optical coherence tomography data

      Systems and methods for improved acquisition of ophthalmic optical coherence tomography data are presented, allowing for enhanced ease of use and higher quality data and analysis functionality. Embodiments include automated triggering for detecting and initiating collection of OCT ophthalmic data, an automated technique for determining the optimal number of B-scans to be collected to create the highest quality image and optimize speckle reduction, automated review of fundus images collected with an adjunct imaging modality to guide the OCT data collection, a single scan protocol in which a large field of view is collected with HD B-scans embedded at different locations ...

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    5. Line-field parallel swept source interferometric imaging at up to 1  MHz

      Line-field parallel swept source interferometric imaging at up to 1  MHz

      We present a novel medical imaging modality based on optical coherence tomography (OCT) that enables in vivo 3D tomography at acquisition rates up to 1 MHz. Line field parallel swept source interferometric imaging (LPSI) combines line-field swept source OCT with modulation of the interferometric signal in spatial direction for full range imaging. This method enables high speed imaging with cost-effective and commercially available technology. We explain the realization of the LPSI setup, acquisition, and postprocessing and finally demonstrate 3D in vivo imaging of human nail fold. To the best of our knowledge, sensitivity and depth penetration are competitive with respective ...

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    6. Intra- and Inter-Frame Differential Doppler Optical Coherence Tomography

      Intra- and Inter-Frame Differential Doppler Optical Coherence Tomography

      Spectrometer based optical coherence tomography suffers from fringe washout for fast flow, a drawback for flow visualization, which is of interest for both lable-free optical angiography and flow quantification. We presented a method, which can be used to contrast very fast flows, while maintaining relatively low A-scan rates. It is based on introducing a phase shift of during acquisition such that the interference fringes associated to moving sample structures are recovered depending on the axial velocity. This enables the use of slower line scan cameras for measuring the fast blood flows within the large vessels in the region of the ...

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    7. Line-field parallel swept source MHz OCT for structural and functional retinal imaging

      Line-field parallel swept source MHz OCT for structural and functional retinal imaging

      We demonstrate three-dimensional structural and functional retinal imaging with line-field parallel swept source imaging (LPSI) at acquisition speeds of up to 1 MHz equivalent A-scan rate with sensitivity better than 93.5 dB at a central wavelength of 840 nm. The results demonstrate competitive sensitivity, speed, image contrast and penetration depth when compared to conventional point scanning OCT. LPSI allows high-speed retinal imaging of function and morphology with commercially available components. We further demonstrate a method that mitigates the effect of the lateral Gaussian intensity distribution across the line focus and demonstrate and discuss the feasibility of high-speed optical angiography ...

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    8. Wide-Field OCT Angiography at 400 kHz Utilizing Spectral Splitting

      Wide-Field OCT Angiography at 400 kHz Utilizing Spectral Splitting

      Optical angiography systems based on optical coherence tomography (OCT) require dense sampling in order to maintain good vascular contrast. We demonstrate a way to gain acquisition speed and spatial sampling by using spectral splitting with a swept source OCT system. This method splits the recorded spectra into two to several subspectra. Using continuous lateral scanning, the lateral sampling is then increased by the same factor. This allows increasing the field of view of OCT angiography, while keeping the same transverse resolution and measurement time. The performance of our method is demonstrated in vivo at different locations of the human retina ...

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    9. Line-field parallel swept source interferometric imaging at up to 1MHz

      Line-field parallel swept source interferometric imaging at up to 1MHz

      We present a novel medical imaging modality based on optical coherence tomography (OCT) that enables in vivo 3D tomography at acquisition rates up to 1 MHz. Line field parallel swept source interferometric imaging (LPSI) combines line-field swept source OCT with modulation of the interferometric signal in spatial direction for full range imaging. This method enables high speed imaging with cost-effective and commercially available technology. We explain the realization of the LPSI setup, acquisition, and postprocessing and finally demonstrate 3D in vivo imaging of human nail fold. To the best of our knowledge, sensitivity and depth penetration are competitive with respective ...

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    10. Measuring pulse-induced natural relative motions within human ocular tissue in vivo using phase-sensitive optical coherence tomography

      Measuring pulse-induced natural relative motions within human ocular tissue in vivo using phase-sensitive optical coherence tomography

      We use phase-sensitive optical coherence tomography to measure relative motions within the human eye. From a sequence of tomograms, the phase difference between successive tomograms reveals the local axial motion of the tissue at every location within the image. The pulsation of the retina and of the lamina cribrosa amounts to, at most, a few micrometers per second, while the bulk velocity of the eye, even with the head resting in an ophthalmic instrument, is a few orders of magnitude faster. The bulk velocity changes continuously as the tomograms are acquired, whereas localized motions appear at acquisition times determined by ...

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    11. Measurement of Tear Film Thickness Using Ultrahigh Resolution Optical Coherence Tomography

      Measurement of Tear Film Thickness Using Ultrahigh Resolution Optical Coherence Tomography

      Purpose: To visualize the pre-corneal tear film with high resolution spectral domain optical coherence tomography, enabling quantification of tear film thickness in healthy subjects. Methods: A custom built spectral domain optical coherence tomography system comprising a broad band Ti:Sapphire laser operating at 800 nm and a high speed CCD camera with a read out rate of 47 kHz was used for measurement of pre-corneal tear film thickness. The system provides an axial resolution of 1.2 µm in tissue. A total of 26 healthy subjects were included in this study. Measurement was started immediately after blinking and averaged over ...

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    12. Natural motion of the optic nerve head revealed by high speed phase-sensitive OCT

      Natural motion of the optic nerve head revealed by high speed phase-sensitive OCT

      We use phase-sensitive optical coherence tomography (OCT) to measure the deformation of the optic nerve head during the pulse cycle, motivated by the possibility that these deformations might be indicative of the progression of glaucoma. A spectral-domain OCT system acquired 100k A-scans per second, with measurements from a pulse-oximeter recorded simultaneously, correlating OCT data to the subject’s pulse. Data acquisition lasted for 2 seconds, to cover at least two pulse cycles. A frame-rate of 200–400 B-scans per second results in a sufficient degree of correlated speckle between successive frames that the phase-differences between fames can be extracted. Bulk ...

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    13. Ultrahigh-speed non-invasive widefield angiography

      Ultrahigh-speed non-invasive widefield angiography

      tinal and choroidal vascular imaging is an important diagnostic benefit for ocular diseases such as age-related macular degeneration. The current gold standard for vessel visualization is fluorescence angiography. We present a potential non-invasive alternative to image blood vessels based on functional Fourier domain optical coherence tomography (OCT). For OCT to compete with the field of view and resolution of angiography while maintaining motion artifacts to a minimum, ultrahigh-speed imaging has to be introduced. We employ Fourier domain mode locking swept source technology that offers high quality imaging at an A-scan rate of up to 1.68 MHz. We present retinal ...

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    14. Heart-beat-phase-coherent Doppler optical coherence tomography for measuring pulsatile ocular blood flow

      Heart-beat-phase-coherent Doppler optical coherence tomography for measuring pulsatile ocular blood flow

      We introduce a Doppler OCT (DOCT) platform that is fully synchronized with the heart-beat via a pulse oximeter. The system allows reconstructing heart-beat-phase-coherent quantitative DOCT volumes. The method is to acquire a series of DOCT volumes and to record the pulse in parallel. The heartbeat data is used for triggering the start of each DOCT volume acquisition. The recorded volume series is registered to the level of capillaries using a cross-volume registration. The information of the pulse phase is used to rearrange the tomograms in time, to obtain a series of phase coherent DOCT volumes over a pulse. We present ...

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    15. Precise Thickness Measurements of Bowman's Layer, Epithelium, and Tear Film

      Precise Thickness Measurements of Bowman's Layer, Epithelium, and Tear Film

      Purpose. To visualize corneal microstructure such as tear film, epithelium, and Bowman's layer in three dimensions with spectral domain optical coherence tomography (SDOCT) exhibiting 1.3 [mu]m axial resolution at 100,000 A-scans/s. This enables measurement of epithelial and Bowman layer thickness across an area of 8.4 mm x 8.4 mm and measuring the tear film thickness at the central cornea.Methods. We designed a high-performance SDOCT system, which uses a broad bandwidth TiSapph Laser and a high-speed complementary metal-oxide-semiconductor detector technology, providing a resolution in tissue of 1.3 [mu]m and an acquisition ...

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    16. Feature Of The Week 10/30/11: Medical University of Vienna Researchers Investigate Segmentation of Doppler OCT Signatures Using a Support-Vector Machine

      Feature Of The Week 10/30/11: Medical University of Vienna Researchers Investigate Segmentation of Doppler OCT Signatures Using a Support-Vector Machine
      Researchers from the Medical University of Vienna have been prolific contributors to the field of Optical Coherence Tomography for many years. Their pioneering work started back in the late 1980’s and early 1990’s and the group has published over 165 articles since OCT News started in late 2007 (Reference). Recently the group published interesting work on segmentation of Doppler optical coherence tomography signatures using a support-vector machine. Below is a summary of that work. Analysis of tissue perfusion offers direct access to tissue nutrition, its health, or any pathologic alterations that affect the vascular system. Doppler OCT (DOCT ...
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    17. Speckle noise reduction in high speed polarization sensitive spectral domain optical coherence tomography

      Speckle noise reduction in high speed polarization sensitive spectral domain optical coherence tomography
      We present a high speed polarization sensitive spectral domain optical coherence tomography system based on polarization maintaining fibers and two high speed CMOS line scan cameras capable of retinal imaging with up to 128 k A-lines/s. This high imaging speed strongly reduces motion artifacts and therefore averaging of several B-scans is possible, which strongly reduces speckle noise and improves image quality. We present several methods for averaging retardation and optic axis orientation, the best one providing a 5 fold noise reduction. Furthermore, a novel scheme of calculating images of degree of polarization uniformity is presented. We quantitatively compare the ...
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    18. Automated extraction of 3D Doppler OCT signatures using a support vector machine

      Automated extraction of 3D Doppler OCT signatures using a support vector machine
      We present a method for the automated extraction of Doppler OCT flow information by using a support vector machine that combines different features for classification. We employ histogram equalization that makes it possible to distinguish vessels from bulk tissue by texture analysis. This method is particularly applicable to settings with significant phase noise as it is more robust to multiple scattering components than simple threshold-based methods.
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    19. Segmentation of Doppler optical coherence tomography signatures using a support-vector machine

      Segmentation of Doppler optical coherence tomography signatures using a support-vector machine
      When processing Doppler optical coherence tomography images, there is a need to segment the Doppler signatures of the vessels. This can be used for visualization, for finding the center point of the flow areas or to facilitate the quantitative analysis of the vessel flow. We propose the use of a support-vector machine classifier in order to segment the flow. It uses the phase values of the Doppler image as well as texture information. We show that superior results compared to conventional simple threshold-based methods can be achieved in conditions of significant phase noise, which inhibit the use of a simple ...
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    20. Imaging of the parafoveal capillary network and its integrity analysis using fractal dimension

      Imaging of the parafoveal capillary network and its integrity analysis using fractal dimension

      Using a spectral domain OCT system, equipped with a broadband Ti:sapphire laser, we imaged the human retina with 5 µm x 1.3 µm transverse and axial resolution at acquisition rate of 100 kHz. Such imaging speed significantly reduces motion artifacts. Combined with the ultra-high resolution, this allows observing microscopic retinal details with high axial definition without the help of adaptive optics. In this work we apply our system to image the parafoveal capillary network. We demonstrate how already on the intensity level the parafoveal capillaries can be segmented by a simple structural high pass filtering algorithm. This data ...

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    21. Ultra-high-speed polarization sensitive OCT in the human retina using a single spectrometer

      Ultra-high-speed polarization sensitive OCT in the human retina using a single spectrometer

      We present a single spectrometer functional spectral domain optical coherence tomography system, which allows for encoding additional information within the spatial frequencies. The method is based on a differentiation between orthogonal polarization channels through spatial modulation introduced by an electro-optic modulator. This method is used to perform Ultrahigh- speed retinal polarization sensitive optical coherence tomography (PSOCT). With this setup, we realized for the first time polarization sensitive OCT measurements of the human retina in-vivo, with camera line rates of up to 160.000 A-scans per second. Compared to PSOCT systems, operating at traditional line rates, this significantly improves patient comfort ...

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    22. Stable absolute flow estimation with Doppler OCT based on virtual circumpapillary scans

      Stable absolute flow estimation with Doppler OCT based on virtual circumpapillary scans
      We propose an algorithm to extract the angles of vessels for the correction of flow measurements in circumpapillary Doppler OCT scans. Firstly, we register a volume to two reference scans in order to determine the physiologically correct structure of the volume. Then, vessels are segmented in the volume and the angles are calculated and stored in a look-up table. After having registered the circular scan to the volume by using the projection along the z-axis, the angles can be extracted from the look-up table. Repeatability measurements of flow parameters on 5 vessels of a healthy subject are presented.
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    23. Stable absolute flow estimation with Doppler OCT based on virtual circumpapillary scans

      Stable absolute flow estimation with Doppler OCT based on virtual circumpapillary scans
      Doppler optical coherence tomography has the capability to measure blood flow quantitatively and in vivo. As only the axial component of the velocity can be assessed, the measurements have to be corrected for the angle of the vessels. We present a novel approach to extract quantitative flow data from circumpapillary scans in vivo on the human retina by registering the circular scan to a reference volume scan and extracting the angle directly from the volume. In addition, we perform phase unwrapping and interpolation of the flow under the assumption of a parabolic flow profile. We demonstrate the repeatability of the ...
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    1-24 of 33 1 2 »
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  2. Topics in the News

    1. (33 articles) Tilman Schmoll
    2. (29 articles) Medical University of Vienna
    3. (29 articles) Rainer A. Leitgeb
    4. (7 articles) Amardeep S. G. Singh
    5. (5 articles) Cedric Blatter
    6. (5 articles) Carl Zeiss Meditec
    7. (4 articles) Wolfgang Drexler
    8. (4 articles) Erich Götzinger
    9. (4 articles) Christoph K. Hitzenberger
    10. (4 articles) Branislav Grajciar
    11. (1 articles) Medical University of Vienna
    12. (1 articles) University of Florence
    13. (1 articles) UCLA
    14. (1 articles) National Institutes of Health
    15. (1 articles) Shanghai Jiao Tong University
    16. (1 articles) Srinivas R. Sadda
    17. (1 articles) Xincheng Yao
    18. (1 articles) Bo Yu
    19. (1 articles) Qian Li
    20. (1 articles) Heidelberg Engineering
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    Single-camera polarization-sensitive spectral-domain OCT by spatial frequency encoding In vivo functional retinal optical coherence tomography Stable absolute flow estimation with Doppler OCT based on virtual circumpapillary scans Ultra-high-speed polarization sensitive OCT in the human retina using a single spectrometer Imaging of the parafoveal capillary network and its integrity analysis using fractal dimension Segmentation of Doppler optical coherence tomography signatures using a support-vector machine Speckle noise reduction in high speed polarization sensitive spectral domain optical coherence tomography Feature Of The Week 10/30/11: Medical University of Vienna Researchers Investigate Segmentation of Doppler OCT Signatures Using a Support-Vector Machine Ultrahigh-speed non-invasive widefield angiography In-stent restenosis and longitudinal stent deformation: a case report Microvascular Features of Treated Retinoblastoma Tumors in Children Assessed Using OCTA OCTA characterisation of microvascular retinal alterations in patients with central serous chorioretinopathy