1. Articles from Boris Považay

    1-24 of 43 1 2 »
    1. Selective retina therapy enhanced with optical coherence tomography for dosimetry control and monitoring: a proof of concept study

      Selective retina therapy enhanced with optical coherence tomography for dosimetry control and monitoring: a proof of concept study

      Selective treatment of the retinal pigment epithelium (RPE) by using short-pulse lasers leads to a less destructive treatment for certain retinal diseases in contrast to conventional photocoagulation. The introduction of selective retina therapy (SRT) to clinical routine is still precluded by the challenges to reliably monitor treatment success and to automatically adjust dose within the locally varying therapeutic window. Combining micrometer-scale depth resolving capabilities of optical coherence tomography (OCT) with SRT can yield real-time information on the laser-induced changes within the RPE after a laser pulse or even during treatment with a laser pulse train. In the present study, SRT ...

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    2. Time-Resolved Ultra–High Resolution Optical Coherence Tomography for Real-Time Monitoring of Selective Retina Therapy

      Time-Resolved Ultra–High Resolution Optical Coherence Tomography for Real-Time Monitoring of Selective Retina Therapy

      Purpose : Selective retina therapy (SRT) is a novel treatment for retinal pathologies, solely targeting the RPE. During SRT, the detection of an immediate tissue reaction is challenging, as tissue effects remain limited to intracellular RPE photodisruption. Time-resolved ultra-high axial resolution optical coherence tomography (OCT) is thus evaluated for the monitoring of dynamic optical changes at and around the RPE during SRT. Methods : An experimental OCT system with an ultra-high axial resolution of 1.78 μm was combined with an SRT system and time-resolved OCT M-scans of the target area were recorded from four patients undergoing SRT. Optical coherence tomography scans ...

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    3. Single-pulse CARS based multimodal nonlinear optical microscope for bioimaging

      Single-pulse CARS based multimodal nonlinear optical microscope for bioimaging

      Noninvasive label-free imaging of biological systems raises demand not only for high-speed three-dimensional prescreening of morphology over a wide-field of view but also it seeks to extract the microscopic functional and molecular details within. Capitalizing on the unique advantages brought out by different nonlinear optical effects, a multimodal nonlinear optical microscope can be a powerful tool for bioimaging. Bringing together the intensity-dependent contrast mechanisms via second harmonic generation, third harmonic generation and four-wave mixing for structural-sensitive imaging, and single-beam/single-pulse coherent anti-Stokes Raman scattering technique for chemical sensitive imaging in the finger-print region, we have developed a simple and nearly ...

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    4. Automatic estimation of noise parameters in Fourier-domain optical coherence tomography cross sectional images using statistical information

      Automatic estimation of noise parameters in Fourier-domain optical coherence tomography cross sectional images using statistical information

      Steiner, Patrick; Kowal, Jens H; Pova?ay, Boris; Meier, Christoph; Sznitman, We present an application and sample independent method for the automatic discrimination of noise and signal in optical coherence tomography Bscans. The proposed algorithm models the observed noise probabilistically and allows for a dynamic determination of image noise parameters and the choice of appropriate image rendering parameters. This overcomes the observer variability and the need for a priori information about the content of sample images, both of which are challenging to estimate systematically with current systems. As such, our approach has the advantage of automatically determining crucial parameters for ...

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    5. Hybrid single-source online Fourier transform coherent anti-Stokes Raman scattering/optical coherence tomography

      Hybrid single-source online Fourier transform coherent anti-Stokes Raman scattering/optical coherence tomography

      We demonstrate a multimodal optical coherence tomography (OCT) and online Fourier transform coherent anti-Stokes Raman scattering (FTCARS) platform using a single sub-12 femtosecond (fs) Ti:sapphire laser enabling simultaneous extraction of structural and chemical (“morphomolecular”) information of biological samples. Spectral domain OCT prescreens the specimen providing a fast ultrahigh ( 4 × 12     μ m axial and transverse) resolution wide field morphologic overview. Additional complementary intrinsic molecular information is obtained by zooming into regions of interest for fast label-free chemical mapping with online FTCARS spectroscopy. Background-free CARS is based on a Michelson interferometer in combination with a highly linear piezo stage, which allows ...

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    6. Fiber-optically integrated cost-effective spectrometer for optical coherence tomography

      Fiber-optically integrated cost-effective spectrometer for optical coherence tomography

      A tilted fiber Bragg grating (TFBG) was integrated as the dispersive element in a high performance biomedical imaging system. The spectrum emitted by the 23 mm long active region of the fiber is projected through custom designed optics consisting of a cylindrical lens for vertical beam collimation and successively by an achromatic doublet onto a linear detector array. High resolution tomograms of biomedical samples were successfully acquired by the frequency domain OCT-system. Tomograms of ophthalmic and dermal samples obtained by the frequency domain OCT-system were obtained achieving 2.84 μm axial and 10.2 μm lateral resolution. The miniaturization reduces ...

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    7. Non-Invasive Detection of Early Retinal Neuronal Degeneration by Ultrahigh Resolution Optical Coherence Tomography

      Non-Invasive Detection of Early Retinal Neuronal Degeneration by Ultrahigh Resolution Optical Coherence Tomography

      Optical coherence tomography (OCT) has revolutionises the diagnosis of retinal disease based on the detection of microscopic rather than subcellular changes in retinal anatomy. However, currently the technique is limited to the detection of microscopic rather than subcellular changes in retinal anatomy. However, coherence based imaging is extremely sensitive to both changes in optical contrast and cellular events at the micrometer scale, and can generate subtle changes in the spectral content of the OCT image. Here we test the hypothesis that OCT image speckle (image texture) contains information regarding otherwise unresolvable features such as organelle changes arising in the early ...

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    8. Photonic integrated Mach-Zehnder interferometer with an on-chip reference arm for optical coherence tomography

      Photonic integrated Mach-Zehnder interferometer with an on-chip reference arm for optical coherence tomography

      Optical coherence tomography (OCT) is a noninvasive, three-dimensional imaging modality with several medical and industrial applications. Integrated photonics has the potential to enable mass production of OCT devices to significantly reduce size and cost, which can increase its use in established fields as well as enable new applications. Using silicon nitride (Si 3 N 4 ) and silicon dioxide (SiO 2 ) waveguides, we fabricated an integrated interferometer for spectrometer-based OCT. The integrated photonic circuit consists of four splitters and a 190 mm long reference arm with a foot-print of only 10 × 33 mm 2 . It is used as the core of ...

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    9. Cost-effective optical coherence tomography spectrometer based on a tilted fiber Bragg grating

      Cost-effective optical coherence tomography spectrometer based on a tilted fiber Bragg grating

      A compact, fiber-based spectrometer for biomedical application utilizing a tilted fiber Bragg grating (TFBG) as integrated dispersive element is demonstrated. Based on a 45° UV-written PS750 TFBG a refractive spectrometer with 2.06 radiant/μm dispersion and a numerical aperture of 0.1 was set up and tested as integrated detector for an optical coherence tomography (OCT) system. Featuring a 23 mm long active region at the fiber the spectrum is projected via a cylindrical lens for vertical beam collimation and focused by an achromatic doublet onto the detector array. Covering 740 nm to 860 nm the spectrometer was optically ...

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    10. Choroidal Thinning in Diabetes Type 1 Detected by 3-Dimensional 1060 nm Optical Coherence Tomography

      Choroidal Thinning in Diabetes Type 1 Detected by 3-Dimensional 1060 nm Optical Coherence Tomography
      Purpose. To map choroidal (ChT) and retinal thickness (RT) in patients with diabetes type 1 with and without maculopathy and retinopathy in order to compare them with healthy subjects using high speed 3-dimensional (3D) 1060 nm optical coherence tomography (OCT). Methods. Thirty-three eyes from 33 diabetes type 1 subjects (23–57 years, 15 male) divided into groups of without pathology (NDR) and with pathology (DR; including microaneurysms, exudates, clinically significant macular-oedema and proliferative retinopathy) were compared with 20 healthy axial eye length and age-matched subjects (24–57 years, 9 male), imaged by high speed (60.000 A-scans/s) 3D 1060 ...
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    11. Graphics processing unit-based dispersion encoded full-range frequency-domain optical coherence tomography

      Graphics processing unit-based dispersion encoded full-range frequency-domain optical coherence tomography

      Dispersion encoded full-range (DEFR) frequency-domain optical coherence tomography (FD-OCT) and its enhanced version, fast DEFR, utilize dispersion mismatch between sample and reference arm to eliminate the ambiguity in OCT signals caused by non-complex valued spectral measurement, thereby numerically doubling the usable information content. By iteratively suppressing asymmetrically dispersed complex conjugate artifacts of OCT-signal pulses the complex valued signal can be recovered without additional measurements, thus doubling the spatial signal range to cover the full positive and negative sampling range. Previously the computational complexity and low processing speed limited application of DEFR to smaller amounts of data and did not allow ...

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    12. Graphics processing unit based dispersion encoded full-range frequency domain OCT

      Graphics processing unit based dispersion encoded full-range frequency domain OCT

      Standard FD-OCT systems suffer from a limited useful depth range due to the inherent complex conjugate artifacts and continuous fall-off in sensitivity with distance from the zero delay. The techniques of dispersion encoded full range (DEFR) frequency-domain optical coherence tomography (FD-OCT) and its enhanced version fast DEFR use the dispersion mismatch between sample and reference arm to double the imaging depth range by iteratively suppressing complex conjugate artifacts. Previously the computational complexity of DEFR prevented its application to fields where real-time visualization or large volumetric datasets are needed. A graphics processing unit (GPU) with hundreds of processing cores provides highly ...

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    13. Three-dimensional calibration targets for optical coherence tomography

      Three-dimensional calibration targets for optical coherence tomography

      The recent expansion of clinical applications for optical coherence tomography (OCT) is driving the development of approaches for consistent image acquisition. There is a simultaneous need for time-stable, easy-to-use imaging targets for calibration and standardization of OCT devices. We present calibration targets consisting of three-dimensional structures etched into nanoparticle-embedded resin. Spherical iron oxide nanoparticles with a predominant particle diameter of 400 nm were homogeneously dispersed in a two part polyurethane resin and allowed to harden overnight. These samples were then etched using a precision micromachining femtosecond laser with a center wavelength of 1026 nm, 100kHz repetition rate and 450 fs ...

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    14. Automated choroidal segmentation of 1060 nm OCT in healthy and pathologic eyes using a statistical model

      Automated choroidal segmentation of 1060 nm OCT in healthy and pathologic eyes using a statistical model
      A two stage statistical model based on texture and shape for fully automatic choroidal segmentation of normal and pathologic eyes obtained by a 1060 nm optical coherence tomography (OCT) system is developed. A novel dynamic programming approach is implemented to determine location of the retinal pigment epithelium/ Bruch’s membrane /choriocapillaris (RBC) boundary. The choroid–sclera interface (CSI) is segmented using a statistical model. The algorithm is robust even in presence of speckle noise, low signal (thick choroid), retinal pigment epithelium (RPE) detachments and atrophy, drusen, shadowing and other artifacts. Evaluation against a set of 871 manually segmented cross-sectional scans ...
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    15. 3D optical coherence tomography for clinical diagnosis of nonmelanoma skin cancers

      3D optical coherence tomography for clinical diagnosis of nonmelanoma skin cancers

      High-resolution frequency domain optical coherence tomography (OCT) stands out amongst a range of novel dermatologic imaging technologies, with its good detection sensitivity around -100 dB, high measurement speeds allowing real-time image acquisition and its ability to acquire high definition cross-sectional and 3D tomograms of regions greater than 1 cm2, providing tissue information comparable to conventional histopathology without the need for any contrast agents. Typical axial and transverse resolutions of state-of-the-art OCT systems range between 1–10 µm and approximately 20 µm, respectively, depending on the employed wavelength region. This review investigates the significant progress accomplished in the field of dermatologic ...

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    16. Feature Of The Week 10/2/11: Heritability of Ocular Component Dimensions in Mice Phenotyped using Depth-Enhanced SS-OCT

      Feature Of The Week 10/2/11: Heritability of Ocular Component Dimensions in Mice Phenotyped using Depth-Enhanced SS-OCT
      Researchers based at Cardiff University and the Medical University of Vienna have taken advantage of the extended depth range delivered by swept source OCT to measure the eye size of mice with unprecedented precision [1].Measurement of eye size in humans is a standard medical procedure carried out before cataract removal surgery, which is perhaps the most commonly performed surgical operation in the world. The eye measurements are acquired using a laser Doppler interferometry (LDI) technique [2] closely related to time domain OCT.The length of the eye along its visual axis determines the refractive error of the eye. Myopia ...
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    17. Retinal and Choroidal Thickness in Early Age-Related Macular Degeneration

      Retinal and Choroidal Thickness in Early Age-Related Macular Degeneration
      Purpose To compare retinal thickness and choroidal thickness at increasing retinal eccentricity in individuals with early age-related macular degeneration (AMD) and in healthy controls using enhanced choroidal penetration, 3-dimensional optical coherence tomography at 1060 nm. Design Cross-sectional study. Methods Individuals with early AMD (n = 16; mean age, 71.6 ± 8.5 years) and a comparison group of healthy controls (n = 16; 67.6 ± 5.4 years) were recruited. Three-dimensional (20 degrees × 20 degrees) long-wavelength optical coherence tomography (1060 nm) images (approximately 8-μm axial resolution; 47 000 A scans/second, centered on the fovea) were obtained from all participants after pupil ...
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    18. Mapping Choroidal and Retinal Thickness Variation in Type 2 Diabetes using Three-Dimensional 1060-nm Optical Coherence Tomography

      Mapping Choroidal and Retinal Thickness Variation in Type 2 Diabetes using Three-Dimensional 1060-nm Optical Coherence Tomography
      Purpose. To map choroidal (ChT) and retinal thickness (RT) in healthy subjects and patients with diabetes with and without maculopathy using three dimensional 1060-nm optical coherence tomography (3D-1060nm-OCT). Methods. Sixty-three eyes from 42 diabetic subjects (41–82 years of age; 11 females) grouped according to a custom scheme using Early Treatment Diabetic Retinopathy Study definitions for pathology within 1 disc-diameter of fovea (without pathology [NDR], microaneurysms [M1], exudates [M2], clinically significant macular edema [CSME]) and 16 eyes from 16 healthy age matched subjects (38–79 years of age; 11 females) were imaged by 3D-1060nm-OCT performed over a 36° × 36° field ...
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    19. Multimodal photoacoustic and optical coherence tomography scanner using an all optical detection scheme for 3D morphological skin imaging

      Multimodal photoacoustic and optical coherence tomography scanner using an all optical detection scheme for 3D morphological skin imaging

      A noninvasive, multimodal photoacoustic and optical coherence tomography (PAT/OCT) scanner for three-dimensional in vivo (3D) skin imaging is described. The system employs an integrated, all optical detection scheme for both modalities in backward mode utilizing a shared 2D optical scanner with a field-of-view of ~13 × 13 mm2. The photoacoustic waves were detected using a Fabry Perot polymer film ultrasound sensor placed on the surface of the skin. The sensor is transparent in the spectral range 590-1200 nm. This permits the photoacoustic excitation beam (670-680 nm) and the OCT probe beam (1050 nm) to be transmitted through the sensor head ...

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    20. Heritability of ocular component dimensions in mice phenotyped using depth-enhanced swept source optical coherence tomography

      Heritability of ocular component dimensions in mice phenotyped using depth-enhanced swept source optical coherence tomography
      The range of genetic and genomic resources available makes the mouse a powerful model for the genetic dissection of complex traits. Because accurate, high-throughput phenotypic characterisation is crucial to the success of such endeavours, we recently developed an optical coherence tomography (OCT) system with extended depth range scanning capability for measuring ocular component dimensions in mice. In order to test whether the accuracy and reproducibility of our OCT system was sufficient for gene mapping studies, we carried out an experiment designed to estimate the heritability of mouse ocular component dimensions. High-resolution, two dimensional tomograms were obtained for both eyes of ...
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    21. In vivo response of GsdmA3Dfl/+ mice to topically applied anti-psoriatic agents: effects on epidermal thickness, as determined by optical coherence tomography and H&E staining.

      In vivo response of GsdmA3Dfl/+ mice to topically applied anti-psoriatic agents: effects on epidermal thickness, as determined by optical coherence tomography and H&E staining.

      This study evaluated in vivo the potential of optical coherence tomography (OCT) to determine changes in thickness of the epidermis in response to the topically applied anti-psoriatics betamethasone dipropionate (BD), salicylic acid (SA) and also fish oil (FO). GsdmA3Dfl/+ mice have an inflammatory hair loss phenotype that includes hyperproliferation and epidermal thickening, hence a potential psoriasis model. Changes in epidermal thickness were evaluated over a period of 10 days, with the mice treated with combined BD + SA, FO + SA and BD + FO + SA. The data were validated with conventional measurement using H&E staining coupled with microscopy. Initial baseline measurement ...

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    22. Highly reproducible swept-source, dispersion-encoded full-range biometry and imaging of the mouse eye

      Highly reproducible swept-source, dispersion-encoded full-range biometry and imaging of the mouse eye
      We report a high-speed, dispersion-encoded, full-range (DEFR) swept-source optical coherence tomography system for in vivo ocular imaging and biometry of small animals. The fast DEFR algorithm removes the depth ambiguity, gives access to objects located at the zero delay position, and doubles the sampling depth to 2×5.0 mm (at −101 to −71 dB sensitivity) in a single scan using 2048 samples/depth scan 0.43 nm line width of a light source operating at 1056 nm with 70 nm tuning range. The acquisition speed (frames of 512 depth scans in 18.3 ms) permits precise on-line monitoring during ...
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    23. Robust segmentation of intraretinal layers in the normal human fovea using a novel statistical model based on texture and shape analysis

      Robust segmentation of intraretinal layers in the normal human fovea using a novel statistical model based on texture and shape analysis
      A novel statistical model based on texture and shape for fully automatic intraretinal layer segmentation of normal retinal tomograms obtained by a commercial 800nm optical coherence tomography (OCT) system is developed. While existing algorithms often fail dramatically due to strong speckle noise, non-optimal imaging conditions, shadows and other artefacts, the novel algorithm’s accuracy only slowly deteriorates when progressively increasing segmentation task difficulty. Evaluation against a large set of manual segmentations shows unprecedented robustness, even in the presence of additional strong speckle noise, with dynamic range tested down to 12dB, enabling segmentation of almost all intraretinal layers in cases previously ...
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    24. In Vivo, In Situ Imaging of Microneedle Insertion into the Skin of Human Volunteers Using Optical Coherence Tomography

      In Vivo, In Situ Imaging of Microneedle Insertion into the Skin of Human Volunteers Using Optical Coherence Tomography

      Purpose  To gather sub-surface in situ images of microneedle-treated human skin, in vivo, using optical coherence tomography (OCT). This is the first study to utilise OCT to investigate the architectural changes that are induced in skin following microneedle application. Methods  Steel, silicon and polymer microneedle devices, with different microneedle arrangements and morphologies, were applied to two anatomical sites in human volunteers following appropriate ethical approval. A state-of-the-art ultrahigh resolution OCT imaging system operating at 800 nm wavelength and <3 µm effective axial resolution was used to visualise the microneedle-treated area during insertion and/or following removal of the device, without ...

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    1-24 of 43 1 2 »
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    1. (43 articles) Boris Považay
    2. (36 articles) Wolfgang Drexler
    3. (30 articles) Cardiff University
    4. (28 articles) Bernd M. Hofer
    5. (24 articles) Medical University of Vienna
    6. (16 articles) Boris Hermann
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    Multimodal simultaneous photoacoustic tomography, optical resolution microscopy, and OCT system Fast dispersion encoded full range optical coherence tomography for retinal imaging at 800 nm and 1060 nm Multispectral in vivo three-dimensional optical coherence tomography of human skin In Vivo, In Situ Imaging of Microneedle Insertion into the Skin of Human Volunteers Using Optical Coherence Tomography Robust segmentation of intraretinal layers in the normal human fovea using a novel statistical model based on texture and shape analysis Highly reproducible swept-source, dispersion-encoded full-range biometry and imaging of the mouse eye Feature Of The Week 10/2/11: Heritability of Ocular Component Dimensions in Mice Phenotyped using Depth-Enhanced SS-OCT Evaluation of Age-related Skin Changes and Instrument Reliability Using Clinical Probe Measurements and Imaging Modalities HP-OCT™ wins Victorian AEEA award – nominated for Sir William Hudson award Postdoctoral Scholar in High Resolution Retinal Imaging at The Ohio State University Cone Photoreceptor Integrity assessed with Adaptive Optics Imaging after Laser-Pointer-Induced Retinal Injury Quantitative assessment of macular microvasculature and radial peripapillary capillary plexus in the fellow eyes of patients with retinal vein occlusion using OCT angiography