All Articles from Iwona Gorczynska -Optical Coherence Tomography News

Articles from Iwona Gorczynska

1-24 of 35 1 2 »
1. Computationally effective 2D and 3D fast phase unwrapping algorithms and their applications to Doppler optical coherence tomography
  
  Explore OSA | OSA Publishing Feb 20 2019
  
  We propose a simplification for a robust and easy to implement fast phase unwrapping (FPU) algorithm that is used to solve the phase wrapping problem encountered in various fields of optical imaging and metrology. We show that the number of necessary computations using the algorithm can be reduced compared to its original version. FPU can be easily extended from two to three spatial dimensions. We demonstrate the applicability of the two- and three-dimensional FPU algorithm for Doppler optical coherence tomography (DOCT) in numerical simulations, and in the imaging of a flow phantom and blood flow in the human retina in ...
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  Mentions: Nicolaus Copernicus University Maciej Szkulmowski Iwona Gorczynska
2. Megahertz-rate optical coherence tomography angiography improves the contrast of the choriocapillaris and choroid in human retinal imaging
  
  Explore OSA | OSA Publishing Dec 5 2018 Ophthalmology
  
  Angiographic imaging of the human eye with optical coherence tomography (OCT) is becoming an increasingly important tool in the scientific investigation and clinical management of several blinding diseases, including age-related macular degeneration and diabetic retinopathy. We have observed that OCT angiography (OCTA) of the human choriocapillaris and choroid with a 1.64 MHz A-scan rate swept-source laser yields higher contrast images as compared to a slower rate system operating at 100 kHz. This result is unexpected because signal sensitivity is reduced when acquisition rates are increased, and the incident illumination power is kept constant. The contrast of angiography images generated ...
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  Mentions: John S. Werner Nicolaus Copernicus University UC Davis
3. Intraframe motion correction for raster-scanned adaptive optics images using strip-based cross-correlation lag biases
  
  Explore Journals | PLOS Oct 25 2018 Ophthalmology
  
  In retinal raster imaging modalities, fixational eye movements manifest as image warp, where the relative positions of the beam and retina change during the acquisition of single frames. To remove warp artifacts, strip-based registration methods–in which fast-axis strips from target images are registered to a reference frame–have been applied in adaptive optics (AO) scanning light ophthalmoscopy (SLO) and optical coherence tomography (OCT). This approach has enabled object tracking and frame averaging, and methods have been described to automatically select reference frames with minimal motion. However, inconspicuous motion artifacts may persist in reference frames and propagate themselves throughout the ...
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  Mentions: Thorlabs Dalsa Superlum
4. Challenges and advantages in wide-field optical coherence tomography angiography imaging of the human retinal and choroidal vasculature at 1.7-MHz A-scan rate
  
  Explore SPIE Digital Library Nov 16 2017 Ophthalmology
  
  We present noninvasive, three-dimensional, depth-resolved imaging of human retinal and choroidal blood circulation with a swept-source optical coherence tomography (OCT) system at 1065-nm center wavelength. Motion contrast OCT imaging was performed with the phase-variance OCT angiography method. A Fourier-domain mode-locked light source was used to enable an imaging rate of 1.7 MHz. We experimentally demonstrate the challenges and advantages of wide-field OCT angiography (OCTA). In the discussion, we consider acquisition time, scanning area, scanning density, and their influence on visualization of selected features of the retinal and choroidal vascular networks. The OCTA imaging was performed with a field of ...
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  Mentions: John S. Werner UC Davis Iwona Gorczynska
5. The Properties of Outer Retinal Band Three Investigated With Adaptive-Optics Optical Coherence Tomography
  
  Explore IOVS Journal Sep 12 2017 Ophthalmology
  
  Purpose : Optical coherence tomography's (OCT) third outer retinal band has been attributed to the zone of interdigitation between RPE cells and cone outer segments. The purpose of this paper is to investigate the structure of this band with adaptive optics (AO)-OCT. Methods : Using AO-OCT, images were obtained from two subjects. Axial structure was characterized by measuring band 3 thickness and separation between bands 2 and 3 in segmented cones. Lateral structure was characterized by correlation of band 3 with band 2 and comparison of their power spectra. Band thickness and separation were also measured in a clinical OCT ...
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  Mentions: John S. Werner UC Davis Robert J. Zawadzki
6. Comparison of amplitude-decorrelation, speckle-variance and phase-variance OCT angiography methods for imaging the human retina and choroid
  
  Explore OSA | OSA Publishing Feb 25 2016 Ophthalmology
  
  We compared the performance of three OCT angiography (OCTA) methods: speckle variance, amplitude decorrelation and phase variance for imaging of the human retina and choroid. Two averaging methods, split spectrum and volume averaging, were compared to assess the quality of the OCTA vascular images. All data were acquired using a swept-source OCT system at 1040 nm central wavelength, operating at 100,000 A-scans/s. We performed a quantitative comparison using a contrast-to-noise (CNR) metric to assess the capability of the three methods to visualize the choriocapillaris layer. For evaluation of the static tissue noise suppression in OCTA images we proposed ...
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  Mentions: John S. Werner UC Davis Robert J. Zawadzki
7. En face projection imaging of the human choroidal layers with tracking SLO and swept source OCT angiography methods
  
  Explore Conference Proceedings Jul 28 2015 Ophthalmology
  
  We tested and compared the capability of multiple optical coherence tomography (OCT) angiography methods: phase variance, amplitude decorrelation and speckle variance, with application of the split spectrum technique, to image the choroiretinal complex of the human eye. To test the possibility of OCT imaging stability improvement we utilized a real-time tracking scanning laser ophthalmoscopy (TSLO) system combined with a swept source OCT setup. In addition, we implemented a post- processing volume averaging method for improved angiographic image quality and reduction of motion artifacts. The OCT system operated at the central wavelength of 1040nm to enable sufficient depth penetration into the ...
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  Mentions: John S. Werner UC Davis Robert J. Zawadzki
8. Feature Of The Week 11/25/12: Nicolaus Copernicus University Presents Work on Four-Dimensional OCT Imaging Using Graphics Processing Units
  
  Explore Optical Coherence Tomography News Nov 25 2012
  
  Nicolaus Copernicus University present the application of graphics processing unit (GPU) programming for real-time three-dimensional (3-D) Fourier domain optical coherence tomography (FdOCT) imaging with implementation of flow visualization algorithms. One of the limitations of FdOCT is data processing time, which is generally longer than data acquisition time. Utilizing additional algorithms, such as Doppler analysis, further increases computation time. The general purpose computing on GPU (GPGPU) has been used successfully for structural OCT imaging, but real-time 3-D imaging of flows has so far not been presented. NCU has developed software for structural and Doppler OCT processing capable of visualization of two-dimensional ...
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  Mentions: Maciej Wojtkowski Nicolaus Copernicus University Maciej Szkulmowski
9. Four-dimensional structural and Doppler optical coherence tomography imaging on graphics processing units
  
  Explore SPIE | Journal Oct 12 2012
  
  The authors present the application of graphics processing unit (GPU) programming for real-time three-dimensional (3-D) Fourier domain optical coherence tomography (FdOCT) imaging with implementation of flow visualization algorithms. One of the limitations of FdOCT is data processing time, which is generally longer than data acquisition time. Utilizing additional algorithms, such as Doppler analysis, further increases computation time. The general purpose computing on GPU (GPGPU) has been used successfully for structural OCT imaging, but real-time 3-D imaging of flows has so far not been presented. We have developed software for structural and Doppler OCT processing capable of visualization of two-dimensional (2-D ...
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  Mentions: Maciej Wojtkowski Nicolaus Copernicus University Maciej Szkulmowski
10. Optical Coherence Tomography Apparatus And Method With Speckle Suppression
  
  Explore patentscope.wipo.int Aug 2 2012 Patents
  
  The invention relates to an optical coherence tomography apparatus and method. It improves speckle suppression by modifying the scanning trajectory (18) of the probing light beam so that groups of A scans close to the imaged segments (22) can be recorded and averaged. The invention facilitates effective speckle suppression combined with high resolution and little dependence of sample motions during the measurement.
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  Mentions: Maciej Wojtkowski Nicolaus Copernicus University Andrzej A. Kowalczyk
11. Multi-parametric imaging of murine brain using spectral and time domain optical coherence tomography
  
  Explore Linking to Scitation Content Jun 14 2012 Neurology
  
  Examination of brain functions in small animal models may help improve the diagnosis and treatment of neurological conditions. Transcranial imaging of small rodents’ brains poses a major challenge for optical microscopy. Another challenge is to reduce the measurement time. We describe methods and algorithms for three-dimensional assessment of blood flow in the brains of small animals, through the intact skull, using spectral and time domain optical coherence tomography. By introducing a resonant scanner to the optical setup of the optical coherence tomography (OCT) system, we have developed and applied a high-speed spectral OCT technique that allows us to vary the ...
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  Mentions: Maciej Wojtkowski Nicolaus Copernicus University Maciej Szkulmowski
12. Fourier domain OCT imaging of American cockroach nervous system
  
  Explore Linking to Scitation Content Feb 9 2012 Neurology
  
  In this pilot study we demonstrate results of structural Fourier domain OCT imaging of the nervous system of Periplaneta americana L. (American cockroach). The purpose of this research is to develop an OCT apparatus enabling structural imaging of insect neural system. Secondary purpose of the presented research is to develop methods of the sample preparation and handling during the OCT imaging experiments. We have performed imaging in the abdominal nerve cord excised from the American cockroach. For this purpose we have developed a Fourier domain / spectral OCT system operating at 820 nm wavelength range.
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  Mentions: Maciej Wojtkowski Nicolaus Copernicus University Andrzej A. Kowalczyk
13. Microfluidics analysis of blood using joint spectral and time domain optical coherence tomography
  
  Explore SPIE Digital Library Feb 9 2012
  
  Although the Doppler Optical Coherence Tomography techniques have already enabled imaging of blood flow in large vessels in biological tissues, the generation of velocity maps of the capillary network is still a challenge. Since several important physiological and pathological phenomena occur in the microcirculation, the possibility of flow imaging and velocity assessment in microcapillaries may be important for medical diagnostics. Understanding of the origin of the Doppler signal in capillary vessels and limitations of such measurements is essential for further development of Doppler OCT methods. In the OCT flow maps of a microcapillary network randomly varying Doppler signals are observed ...
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  Mentions: Maciej Wojtkowski Nicolaus Copernicus University Andrzej A. Kowalczyk
14. Angiogram visualization and total velocity blood flow assessment based on intensity information analysis of OCT data
  
  Explore SPIE Digital Library Feb 9 2012 Ophthalmology
  
  We propose two independent OCT data processing methods allowing visualization and analysis of the blood flow. These methods utilize variations in the OCT intensity images caused by flowing blood. The first method calculates standard deviation of intensity to generate retinal OCT angiograms. We present algorithm of this method and results of application for visualization of the microvasculature in the macular area of the human eye in vivo. The second method calculates cross power spectra of the volumetric intensity images to assess blood flow velocity in three dimensions. Validation of this method for OCT imaging was performed in a flow phantom.
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  Mentions: Maciej Wojtkowski Nicolaus Copernicus University Maciej Szkulmowski
15. Efficient reduction of speckle noise in Optical Coherence Tomography
  
  Explore opticsinfobase.org Jan 6 2012
  
  Speckle pattern, which is inherent in coherence imaging, influences significantly axial and transversal resolution of Optical Coherence Tomography (OCT) instruments. The well known speckle removal techniques are either sensitive to sample motion, require sophisticated and expensive sample tracking systems, or involve sophisticated numerical procedures. As a result, their applicability to in vivo real-time imaging is limited. In this work, we propose to average multiple A-scans collected in a fully controlled way to reduce the speckle contrast. This procedure involves non-coherent averaging of OCT A-scans acquired from adjacent locations on the sample. The technique exploits scanning protocol with fast beam deflection ...
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  Mentions: Maciej Wojtkowski Nicolaus Copernicus University Andrzej A. Kowalczyk
16. Segmented scanning protocols for speckle contrast reduction in Spectral OCT images
  
  Explore SPIE Digital Library Feb 10 2011 Ophthalmology
  
  Recently introduced smart scanning protocols called segmented protocols offer possibility to create Spectral Optical Coherence Tomography images with strongly reduced speckle contrast. The algorithm is fast, robust and gives cross-sectional images with preserved high lateral resolution. To obtain efficient speckle reduction only slight modification to the optical setup is required. Cross-sectional images of anterior and posterior parts of the human eye with reduced speckle noise are presented.
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  Mentions: Maciej Wojtkowski Nicolaus Copernicus University Andrzej A. Kowalczyk
17. Intact Retinal Tissue and Retinal Pigment Epithelium Identified Within A Coloboma By High-Speed, Ultrahigh-Resolution Optical Coherence Tomography
  
  Explore LWW Online Jan 20 2011 Ophthalmology
  
  Purpose: The purpose of this study was to report on a posterior segment coloboma manifesting unusual morphology as determined by high-speed, ultrahigh-resolution optical coherence tomography imaging. Methods: A 47-year-old woman with bilateral colobomas was evaluated by fundus examination and high-speed, ultrahigh-resolution optical coherence tomography imaging. Results: Imaging with high-speed, ultrahigh-resolution optical coherence tomography showed intact retinal pigment epithelium within the posterior segment coloboma. Most of the retinal layers seemed to continue into the coloboma, although they exhibited slight attenuation. The external limiting membrane was clearly visible continuing within the coloboma, suggesting that Müller cells and the inner segments of the ...
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  Mentions: Massachusetts Institute of Technology James G. Fujimoto Vivek J. Srinivasan
18. Microvascular oxygen tension and flow measurements in rodent cerebral cortex during baseline conditions and functional activation
  
  Explore Nature Publishing Group Dec 24 2010 Neurology
  
  Measuring cerebral oxygen delivery and metabolism microscopically is important for interpreting macroscopic functional magnetic resonance imaging (fMRI) data and identifying pathological changes associated with stroke, Alzheimer's disease, and brain injury. Here, we present simultaneous, microscopic measurements of cerebral blood flow (CBF) and oxygen partial pressure (pO(2)) in cortical microvessels of anesthetized rats under baseline conditions and during somatosensory stimulation. Using a custom-built imaging system, we measured CBF with Fourier-domain optical coherence tomography (OCT), and vascular pO(2) with confocal phosphorescence lifetime microscopy. Cerebral blood flow and pO(2) measurements displayed heterogeneity over distances irresolvable with fMRI and positron ...
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  Mentions: Massachusetts Institute of Technology James G. Fujimoto Vivek J. Srinivasan
19. Ultrahigh-speed volumetric ophthalmic OCT imaging at 800nm and 1050nm
  
  Explore SPIE Digital Library Mar 2 2010 Ophthalmology , Tunable Sources
  
  The performance and imaging characteristics of ultrahigh speed ophthalmic optical coherence tomography (OCT) are investigated. In vivo imaging results are obtained at 850nm and 1050nm using different configurations of spectral and swept source / Fourier domain OCT. A spectral / Fourier domain instrument using a high speed CMOS linescan camera with SLD light source centered at 850nm achieves speeds of ~91,000 axial scans per second with ~3µm axial resolution in tissue. A spectral / Fourier domain instrument using an InGaAs linescan camera with SLD light source centered at 1050nm achieves ~47,000 axial scans per second with ~7µm resolution in tissue. A ...
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  Mentions: Massachusetts Institute of Technology James G. Fujimoto Thorlabs
20. True velocity mapping using joint spectral and time domain optical coherence tomography
  
  Explore SPIE Digital Library Mar 2 2010 Ophthalmology
  
  We present both axial and transverse components estimation using joint Spectral and Time domain Optical Coherence Tomography (STdOCT) method. Whereas axial component of velocity vector can be determined from the time-dependent Doppler beating frequency, the transverse component can be assessed by the analysis of the broadening of flow velocity profiles (Doppler bandwidth). This enables us to quantitatively determine the absolute value of the velocity vector. The accurate analyses are performed using well-defined flow of Intralipid solution in the glass capillary. This enables performing in vivo imaging and allows to calculate velocity maps of the retinal vasculature
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  Mentions: Maciej Wojtkowski Nicolaus Copernicus University Andrzej A. Kowalczyk
21. Quantitative cerebral blood flow with Optical Coherence Tomography
  
  Explore opticsinfobase.org Jan 22 2010
  
  Vivek J. Srinivasan, Sava Sakadžić, Iwona Gorczynska, Svetlana Ruvinskaya, Weicheng Wu, James G. Fujimoto, David A. BoasAbsolute measurements of cerebral blood flow (CBF) are an important endpoint in studies of cerebral pathophysiology. Currently no accepted method exists for in vivo longitudinal monitoring of CBF with high resolution in rats and mice. Using three-dimensional Doppler Optical Coherence Tomography and ... [Opt. Express 18, 2477-2494 (2010)]
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  Mentions: Massachusetts Institute of Technology James G. Fujimoto Vivek J. Srinivasan
22. Scanning protocols dedicated to smart velocity ranging in Spectral OCT
  
  Explore opticsinfobase.org Dec 11 2009 Ophthalmology
  
  We introduce a new type of scanning protocols, called segmented protocols, which enable extracting multi-range flow velocity information from a single Spectral OCT data set. The protocols are evaluated using a well defined flow in a glass capillary. As an example of in vivo studies, we demonstrate two- and three-dimensional imaging of the retinal vascular system in the eyes of healthy volunteers. The flow velocity detection is performed using a method of Joint Spectral and Time domain OCT. Velocity ranging is demonstrated in imaging of retinal vasculature in the macular region and in the optic disk area characterized by different ...
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  Mentions: Rainer A. Leitgeb Maciej Wojtkowski Medical University of Vienna
23. COMPARISON OF SPECTRAL/FOURIER DOMAIN OPTICAL COHERENCE TOMOGRAPHY INSTRUMENTS FOR ASSESSMENT OF NORMAL MACULAR THICKNESS
  
  Explore LWW Online Dec 3 2009 Ophthalmology
  
  Purpose: The purpose of this study was to report normal macular thickness measurements and assess reproducibility of retinal thickness measurements acquired by a time-domain optical coherence tomography (OCT) (Stratus, Carl Zeiss Meditec, Inc., Dublin, CA) and three commercially available spectral/Fourier domain OCT instruments (Cirrus HD-OCT, Carl Zeiss Meditec, Inc.; RTVue-100, Optovue, Inc., Fremont, CA; 3D OCT-1000, Topcon, Inc., Paramus, NJ). Methods: Forty randomly selected eyes of 40 normal, healthy volunteers were imaged. Subjects were scanned twice during one visit and a subset of 25 was scanned again within 8 weeks. Retinal thickness measurements were automatically generated by OCT software ...
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  Mentions: University of Pittsburgh Massachusetts Institute of Technology James G. Fujimoto
24. Depth-resolved microscopy of cortical hemodynamics with optical coherence tomography
  
  Explore opticsinfobase.org Oct 6 2009 Microscopy
  
  We describe depth-resolved microscopy of cortical hemodynamics with high-speed spectral/Fourier domain optical coherence tomography (OCT). Stimulus-evoked changes in blood vessel diameter, flow, and total hemoglobin were measured in the rat somatosensory cortex. The results show OCT measurements of hemodynamic changes during functional activation and represent an important step toward understanding functional hyperemia at the microscopic level.
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  Mentions: Massachusetts Institute of Technology James G. Fujimoto Vivek J. Srinivasan
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