All Articles from Maciej Szkulmowski -Optical Coherence Tomography News

Articles from Maciej Szkulmowski

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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. Feature Of The Week 10/08/2017: Optical Coherence Microscopy as a Novel, Non-Invasive Method for the 4D Live Imaging of Early Mammalian Embryos
  
  Explore Optical Coherence Tomography News Oct 8 2017 Developmental Biology
  
  Imaging of living cells based on traditional fluorescence and confocal laser scanning microscopy has delivered an enormous amount of information critical for understanding biological processes in single cells. However, the requirement for a high numerical aperture and fluorescent markers still limits researchers’ ability to visualize the cellular architecture without causing short- and long-term photodamage. Optical coherence microscopy (OCM) is a promising alternative that circumvents the technical limitations of fluorescence imaging techniques and provides unique access to fundamental aspects of early embryonic development, without the requirement for sample pre-processing or labeling. In the present paper, we utilized the internal motion of ...
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  Mentions: Maciej Wojtkowski Nicolaus Copernicus University Maciej Szkulmowski
3. Optical coherence microscopy as a novel, non-invasive method for the 4D live imaging of early mammalian embryos
  
  Explore Nature Publishing Group Jun 29 2017 Developmental Biology , Microscopy
  
  Imaging of living cells based on traditional fluorescence and confocal laser scanning microscopy has delivered an enormous amount of information critical for understanding biological processes in single cells. However, the requirement for a high numerical aperture and fluorescent markers still limits researchers’ ability to visualize the cellular architecture without causing short- and long-term photodamage. Optical coherence microscopy (OCM) is a promising alternative that circumvents the technical limitations of fluorescence imaging techniques and provides unique access to fundamental aspects of early embryonic development, without the requirement for sample pre-processing or labeling. In the present paper, we utilized the internal motion of ...
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  Mentions: Maciej Wojtkowski Nicolaus Copernicus University Maciej Szkulmowski
4. Spectrometer calibration for spectroscopic Fourier domain optical coherence tomography
  
  Explore OSA | OSA Publishing Nov 15 2016
  
  We propose a simple and robust procedure for Fourier domain optical coherence tomography (FdOCT) that allows to linearize the detected FdOCT spectra to wavenumber domain and, at the same time, to determine the wavelength of light for each point of detected spectrum. We show that in this approach it is possible to use any measurable physical quantity that has linear dependency on wavenumber and can be extracted from spectral fringes. The actual values of the measured quantity have no importance for the algorithm and do not need to be known at any stage of the procedure. As example we calibrate ...
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  Mentions: Maciej Wojtkowski Nicolaus Copernicus University Maciej Szkulmowski
5. Extended-focus optical coherence microscopy for high-resolution imaging of the murine brain
  
  Explore OSA | OSA Publishing Oct 13 2016 Developmental Biology , Neurology
  
  We propose a new method and optical instrumentation for mouse brain imaging based on extended-focus optical coherence microscopy. This in vivo imaging technique allows the evaluation of the cytoarchitecture at cellular level and the circulation system dynamics in three dimensions. This minimally invasive and non-contact approach is performed without the application of contrasting agents. The optical design achieved a resolution of 2.2 μm over a distance of 800 μm, which was sufficient to obtain a detailed three-dimensional image of a wild-type mouse’s brain down to the layer III of the cortex. Intrinsically contrasted microvessels and structures similar to ...
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  Mentions: Maciej Wojtkowski Nicolaus Copernicus University Ecole Polytechnique Fédérale de Lausanne
6. Method and apparatus for imaging of semi-transparent matter
  
  Explore uspto.gov May 24 2016 Ophthalmology , Patents
  
  The invention relates to a method and apparatus for measuring the spatial and velocity distribution of scattering structures of a sample in semi-transparent matter. The acquired spectral data I(k, t) are transformed in two steps to image data I(z, v). A Doppler shift is imposed on the light to a separate real and mirror images in the v space to suppress the complex ambiguity artifact.
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  Mentions: Maciej Wojtkowski Tomasz Bajraszewski Maciej Szkulmowski
7. Image capturing apparatus, image capturing method, and storage medium
  
  Explore uspto.gov Apr 12 2016 Patents
  
  An image capturing apparatus includes a dividing unit configured to divide light from a light source into reference light and measurement light; a first dichroic mirror arranged in a measurement optical path for guiding the measurement light to an object to be examined; a second dichroic mirror arranged in a reference optical path for guiding the reference light to a reference object; and a light receiving unit configured to receive interference light between the measurement light passing through the first dichroic mirror and the reference light passing through the second dichroic mirror.
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  Mentions: Tomasz Bajraszewski Maciej Szkulmowski Canon Medical Systems
8. Imaging of the stroke-related changes in the vascular system of the mouse brain with the use of extended focus Optical Coherence Microscopy
  
  Explore Conference Proceedings Mar 13 2016 Developmental Biology , Microscopy
  
  We used Optical Coherence Microscopy (OCM) to monitor structural and functional changes due to ischemic stroke in small animals brains in vivo. To obtain lateral resolution of 2.2 μm over the range of 600 μm we used extended focus configuration of OCM instrument involving Bessel beam. It provided access to detailed 3D information about the changes in brain vascular system up to the level of capillaries across I and II/III layers of neocortex. We used photothrombotic stroke model involving photoactive application of rose bengal to assure minimal invasiveness of the procedure and precise localization of the clot distribution ...
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  Mentions: Maciej Wojtkowski Nicolaus Copernicus University Ecole Polytechnique Fédérale de Lausanne
9. Spectroscopy by joint spectral and time domain optical coherence tomography
  
  Explore Conference Proceedings Mar 10 2015
  
  We present the methodology for spectroscopic examination of absorbing media being the combination of Spectral Optical Coherence Tomography and Fourier Transform Spectroscopy. The method bases on the joint Spectral and Time OCT computational scheme and simplifies data analysis procedure as compared to the mostly used windowing-based Spectroscopic OCT methods. The proposed experimental setup is self-calibrating in terms of wavelength-pixel assignment. The performance of the method in measuring absorption spectrum was checked with the use of the reflecting phantom filled with the absorbing agent (indocyanine green). The results show quantitative accordance with the controlled exact results provided by the reference method.
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  Mentions: Maciej Wojtkowski Nicolaus Copernicus University Maciej Szkulmowski
10. Wavelength to pixel calibration for FdOCT
  
  Explore Conference Proceedings Mar 8 2015
  
  We show that in Fourier domain Optical Coherence Tomography (FdOCT) it is possible to determine the wavelength of light for each point of the detected spectrum using any measurable physical quantity that has linear dependency on wavenumber. The presented approach is robust as the actual values of the measured quantity have no importance for the algorithm. As example we calibrate a SOCT spectrometer using Doppler frequency induced in time-dependent spectral fringes by a mirror moving in one of the arm of the interferometer. The results of calibration are validated using narrow spectral lines generated by optical parametric oscillator
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  Mentions: Joseph A. Izatt James G. Fujimoto Maciej Wojtkowski
11. Multimodal instrument for high-sensitivity autofluorescence and spectral optical coherence tomography of the human eye fundus
  
  Explore opticsinfobase.org Oct 29 2013 Ophthalmology
  
  In this paper we present a multimodal device for imaging fundus of human eye in vivo which combines functionality of autofluorescence by confocal SLO with Fourier domain OCT. Native fluorescence of human fundus was excited by modulated laser beam (λ = 473 nm, 20 MHz) and lock-in detection was applied resulting in improving sensitivity. The setup allows for acquisition of high resolution OCT and high contrast AF images using fluorescence excitation power of 50-65 μW without averaging consecutive images. Successful functioning of constructed device have been demonstrated for 8 healthy volunteers of different age ranging from 24 to 83 years old.
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  Mentions: Maciej Wojtkowski Nicolaus Copernicus University Maciej Szkulmowski
12. Assessment of the flow velocity of blood cells in a microfluidic device using joint spectral and time domain optical coherence tomography
  
  Explore opticsinfobase.org Oct 6 2013
  
  Although Doppler optical coherence tomography techniques have enabled the imaging of blood flow in mid-sized vessels in biological tissues, the generation of velocity maps of capillary networks remains a challenge. To better understand the origin and information content of the Doppler signal from small vessels and limitations of such measurements, we used joint spectral and time domain optical coherence tomography to monitor the flow in a model, semitransparent microchannel device. The results obtained for Intralipid, whole blood, as well as separated red blood cells indicate that the technique is suitable to record velocity profiles in vitro , in a range of ...
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  Mentions: Maciej Wojtkowski Nicolaus Copernicus University Maciej Szkulmowski
13. Quantitative lateral and axial flow imaging with optical coherence microscopy and tomography
  
  Explore opticsinfobase.org Aug 5 2013 Microscopy
  
  Optical coherence tomography (OCT) and optical coherence microscopy (OCM) allow the acquisition of quantitative three-dimensional axial flow by estimating the Doppler shift caused by moving scatterers. Measuring the velocity of red blood cells is currently the principal application of these methods. In many biological tissues, blood flow is often perpendicular to the optical axis, creating the need for a quantitative measurement of lateral flow. Previous work has shown that lateral flow can be measured from the Doppler bandwidth, albeit only for simplified optical systems. In this work, we present a generalized model to analyze the influence of relevant OCT/OCM ...
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  Mentions: Maciej Wojtkowski Nicolaus Copernicus University Ecole Polytechnique Fédérale de Lausanne
14. Averaging techniques for OCT imaging
  
  Explore opticsinfobase.org Apr 15 2013
  
  State-of-the-art Fourier-domain optical coherence tomography (OCT) allows for the acquisition of up to millions of spectral fringes per second. This large amount of data can be used to improve the quality of structural tomograms after effective averaging. Here, we compare three OCT image improvement techniques: magnitude averaging, complex averaging, and spectral and time domain OCT (STdOCT). We evaluate the performance for images on both linear and logarithmic intensity scales and discuss their advantages and disadvantages. We propose the use of the STdOCT approach as it offers the best advantages. Applications to in vivo imaging and speckle reduction are presented.
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  Mentions: Maciej Wojtkowski Nicolaus Copernicus University Maciej Szkulmowski
15. 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
16. Improved measurement of vibration amplitude in dynamic optical coherence elastography
  
  Explore opticsinfobase.org Nov 12 2012
  
  Optical coherence elastography employs optical coherence tomography (OCT) to measure the displacement of tissues under load and, thus, maps the resulting strain into an image, known as an elastogram. We present a new improved method to measure vibration amplitude in dynamic optical coherence elastography. The tissue vibration amplitude caused by sinusoidal loading is measured from the spread of the Doppler spectrum, which is extracted using joint spectral and time domain signal processing. At low OCT signal-to-noise ratio (SNR), the method provides more accurate vibration amplitude measurements than the currently used phase-sensitive method. For measurements performed on a mirror at OCT ...
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  Mentions: Maciej Wojtkowski David D. Sampson Nicolaus Copernicus University
17. 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
18. 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
19. 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
20. 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
21. 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
22. 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
23. Corneal topography from spectral optical coherence tomography (sOCT)
  
  Explore opticsinfobase.org Nov 4 2011 Ophthalmology
  
  We present a method to obtain accurate corneal topography from a spectral optical coherence tomography (sOCT) system. The method includes calibration of the device, compensation of the fan (or field) distortion introduced by the scanning architecture, and image processing analysis for volumetric data extraction, segmentation and fitting. We present examples of three-dimensional (3-D) surface topography measurements on spherical and aspheric lenses, as well as on 10 human corneas in vivo. Results of sOCT surface topography (with and without fan-distortion correction) were compared with non-contact profilometry (taken as reference) on a spherical lens, and with non-contact profilometry and state-of-the art commercial ...
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  Mentions: Maciej Wojtkowski Nicolaus Copernicus University Maciej Szkulmowski
24. Corneal topography with high-speed swept source OCT in clinical examination
  
  Explore opticsinfobase.org Aug 29 2011 Ophthalmology
  
  We present the applicability of high-speed swept source (SS) optical coherence tomography (OCT) for quantitative evaluation of the corneal topography. A high-speed OCT device of 108,000 lines/s permits dense 3D imaging of the anterior segment within a time period of less than one fourth of second, minimizing the influence of motion artifacts on final images and topographic analysis. The swept laser performance was specially adapted to meet imaging depth requirements. For the first time to our knowledge the results of a quantitative corneal analysis based on SS OCT for clinical pathologies such as keratoconus, a cornea with superficial ...
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  Mentions: Maciej Wojtkowski Nicolaus Copernicus University Maciej Szkulmowski
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