1. Articles from Maciej Wojtkowski

    1-24 of 91 1 2 3 4 »
    1. Non invasive optical cellular imaging in humans

      Non invasive optical cellular imaging in humans

      One of the most appealing and still unsolved problems in biological and medical imaging is the possibility of noninvasive visualization of tissue in vivo with an accuracy of microscopic examination. A major difficulty to solve in biomedical imaging is a degradation of image quality caused by the presence of optical inhomogeneity of tissue. Is there any chance to develop a microscopic method that allows non-invasive observation of cells in living tissue? Classical optical microscopy requires first to retrieve, then to process and finally to stain the sample, which is usually not possible to be performed in vivo. One of the ...

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    2. Assessment of the influence of viscoelasticity of cornea in animal ex vivo model using air‐puff optical coherence tomography and corneal hysteresis

      Assessment of the influence of viscoelasticity of cornea in animal ex vivo model using air‐puff optical coherence tomography and corneal hysteresis

      Application of the air‐puff swept source OCT (SS‐OCT) instrument to determine the influence of viscoelasticity on the relation between overall the air‐puff force and corneal apex displacement of porcine corneas ex vivo is demonstrated. Simultaneous recording of time‐evolution of the tissue displacement and air pulse stimulus allows obtaining valuable information related in part to the mechanical properties of the cornea. A novel approach based on quantitative analysis of the corneal hysteresis of OCT data is presented. The corneal response to the air pulse is assessed for different well‐controlled IOP levels and for the progression of ...

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    3. 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

      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

      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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    4. Classification of biological micro-objects using optical coherence tomography

      Classification of biological micro-objects using optical coherence tomography

      We report on the development of a technique for differentiating between biological micro-objects using a rigorous, full-wave model of OCT image formation. We model an existing experimental prototype which uses OCT to interrogate a microfluidic chip containing the blood cells. A full-wave model is required since the technique uses light back-scattered by a scattering substrate, rather than by the cells directly. The light back-scattered by the substrate is perturbed upon propagation through the cells, which flow between the substrate and imaging system’s objective lens. We present the key elements of the 3D, Maxwell equation-based computational model, the key findings ...

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    5. Optical coherence microscopy as a novel, non-invasive method for the 4D live imaging of early mammalian embryos

      Optical coherence microscopy as a novel, non-invasive method for the 4D live imaging of early mammalian embryos

      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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    6. Twenty-five years of optical coherence tomography: the paradigm shift in sensitivity and speed provided by Fourier domain OCT

      Twenty-five years of optical coherence tomography: the paradigm shift in sensitivity and speed provided by Fourier domain OCT

      Optical coherence tomography (OCT) has become one of the most successful optical technologies implemented in medicine and clinical practice mostly due to the possibility of non-invasive and non-contact imaging by detecting back-scattered light. OCT has gone through a tremendous development over the past 25 years. From its initial inception in 1991 [Science 254 , 1178 (1991)] it has become an indispensable medical imaging technology in ophthalmology. Also in fields like cardiology and gastro-enterology the technology is envisioned to become a standard of care. A key contributor to the success of OCT has been the sensitivity and speed advantage offered by Fourier ...

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    7. Spectrometer calibration for spectroscopic Fourier domain optical coherence tomography

      Spectrometer calibration for spectroscopic Fourier domain optical coherence tomography

      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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    8. Extended-focus optical coherence microscopy for high-resolution imaging of the murine brain

      Extended-focus optical coherence microscopy for high-resolution imaging of the murine brain

      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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    9. Non-contact investigation of the corneal biomechanics with air-puff swept source optical coherence tomography

      Non-contact investigation of the corneal biomechanics with air-puff swept source optical coherence tomography

      In this paper, we use swept source optical coherence tomography combined with air-puff module (air-puff SS-OCT) to investigate the properties of the cornea. During OCT measurement the cornea was stimulated by short, air pulse, and corneal response was recorded. In this preliminary study, the air-puff SS-OCT instrument was applied to measure behavior of the porcine corneas under varied, well-controlled intraocular pressure conditions. Additionally, the biomechanical response of the corneal tissue before, during and after crosslinking procedure (CXL) was assessed. Air-puff swept source OCT is a promising tool to extract information about corneal behavior as well as to monitor and assess ...

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    10. Method and apparatus for imaging of semi-transparent matter

      Method and apparatus for imaging of semi-transparent matter

      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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    11. Coherence properties of fast frequency swept lasers revealed via full electric field reconstruction

      Coherence properties of fast frequency swept lasers revealed via full electric field reconstruction

      A novel, time-resolved interferometric technique is presented allowing the reconstruction of the complex electric field output of a fast frequency swept laser in a single-shot measurement. The power of the technique is demonstrated by examining a short cavity swept source designed for optical coherence tomography applications, with a spectral bandwidth of 18 THz. This novel analysis of the complete electric field reveals the modal structure and modal evolution of the device as well as providing a time-resolved real-time characterization of the optical spectrum, linewidth and coherence properties of a dynamic rapidly swept laser.

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    12. Imaging of the stroke-related changes in the vascular system of the mouse brain with the use of extended focus Optical Coherence Microscopy

      Imaging of the stroke-related changes in the vascular system of the mouse brain with the use of extended focus Optical Coherence 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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    13. Tissue thickness calculation in ocular optical coherence tomography

      Tissue thickness calculation in ocular optical coherence tomography

      Thickness measurements derived from optical coherence tomography (OCT) images of the eye are a fundamental clinical and research metric, since they provide valuable information regarding the eye’s anatomical and physiological characteristics, and can assist in the diagnosis and monitoring of numerous ocular conditions. Despite the importance of these measurements, limited attention has been given to the methods used to estimate thickness in OCT images of the eye. Most current studies employing OCT use an axial thickness metric, but there is evidence that axial thickness measures may be biased by tilt and curvature of the image. In this paper, standard ...

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    14. Optical Coherence Tomography of the Labial Salivary Glands Reveals Age-Related Differences in Women

      Optical Coherence Tomography of the Labial Salivary Glands Reveals Age-Related Differences in Women

      The labial minor salivary glands (LSGs) play a role in medical research and practice due to their superficial location and involvement in both systemic and localized diseases. Swept-source optical coherence tomography (OCT) is a noninvasive modality that enables in vivo , micrometer resolution, wide-field three-dimensional imaging in seconds. A purpose-built swept-source OCT instrument was employed to acquire three-dimensional datasets covering the area of 2.43 cm 2 of the mucosa of the lower lip to the depth of 3.4 mm in young ( n = 14; mean age ± SD: 27 ± 3 years; body mass index [BMI] 20.4 ± 2.3 kg/m ...

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    15. Differentiation of morphotic elements in human blood using optical coherence tomography and a microfluidic setup

      Differentiation of morphotic elements in human blood using optical coherence tomography and a microfluidic setup

      We demonstrate a novel optical method for the detection and differentiation between erythrocytes and leukocytes that uses amplitude and phase information provided by optical coherence tomography (OCT). Biological cells can introduce significant phase modulation with substantial scattering anisotropy and dominant forward-scattered light. Such physical properties may favor the use of a trans-illumination imaging technique. However, an epi-illumination mode may be more practical and robust in many applications. This study describes a new way of measuring the phase modulation introduced by flowing microobjects. The novel part of this invention is that it uses the backscattered signal from the substrate located below ...

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    16. Blue-light Fourier-domain optical-coherence microscopy with linear k-sampling using second-harmonic generation

      Blue-light Fourier-domain optical-coherence microscopy with linear k-sampling using second-harmonic generation

      We demonstrate Fourier-domain optical-coherence microscopy (OCM) method that uses blue light for high-resolution microscopic imaging. Spectrally broad bandwidth is obtained by means of second-harmonic generation of Ti:sapphire laser light on the nonlinear crystal. Angular scanning of the crystal performed by a resonant scanner results in second-harmonic generation for a broad range of frequencies producing blue light with central wavelength of 402 nm and bandwidth of 35 nm in one cycle. The axial resolution of the new setup is 3.5 μm in air, and the transverse resolution for Olympus 40 × objective lens is 2.7 μm in X direction ...

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    17. Spectroscopy by joint spectral and time domain optical coherence tomography

      Spectroscopy by joint spectral and time domain optical coherence tomography

      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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    18. Wavelength to pixel calibration for FdOCT

      Wavelength to pixel calibration for FdOCT

      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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    19. Detection of small biological objects by phase-sensitive optical coherence tomography

      Detection of small biological objects by phase-sensitive optical coherence tomography

      We demonstrate a novel label-free OCT method allowing optical detection and differentiation of moving micro-objects, such as blood cells. In this study we use phase-sensitive Fd-OCT/OCM system with broadband light source (axial resolution: 3 μm in tissue and lateral resolution 4−8 μm) and fluidic sample setup. The novel part of this method is that the optical identification is based on optical signal coming from optically uniform scattering media localized beneath the flowing/moving objects and not from the objects itself. This signal reveals as an enhancement in speckle pattern on intensity images and non-zero phase change on phase ...

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    20. Optical Coherence Tomography Identifies Lower Labial Salivary Gland Surface Density in Cystic Fibrosis

      Optical Coherence Tomography Identifies Lower Labial Salivary Gland Surface Density in Cystic Fibrosis

      The labial minor salivary glands (LSGs) are easily accessible mucus-secreting structures of the alimentary tract that may provide new information on the basis of gastrointestinal complications of cystic fibrosis (CF). It was shown that they are destructed in the course of cystic fibrosis. We employed wide-field, micrometer resolution in vivo optical coherence tomography to assess the surface density of LSGs in 18 patients with CF and 18 healthy subjects. The median LSGs’ surface densities in CF patients, and in the control group were 4.32 glands/cm2 and 6.58 glands/cm2, respectively (p = 0.006; Mann-Whitney U test). A ...

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    21. Optical Coherence Tomography Identifies Lower Labial Salivary Gland Surface Density in Cystic Fibrosis

      Optical Coherence Tomography Identifies Lower Labial Salivary Gland Surface Density in Cystic Fibrosis

      The labial minor salivary glands (LSGs) are easily accessible mucus-secreting structures of the alimentary tract that may provide new information on the basis of gastrointestinal complications of cystic fibrosis (CF). It was shown that they are destructed in the course of cystic fibrosis. We employed wide-field, micrometer resolution in vivo optical coherence tomography to assess the surface density of LSGs in 18 patients with CF and 18 healthy subjects. The median LSGs’ surface densities in CF patients, and in the control group were 4.32 glands/cm 2 and 6.58 glands/cm 2 , respectively (p = 0.006; Mann-Whitney U ...

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    22. Microscopic OCT imaging with focus extension by ultrahigh-speed acousto-optic tunable lens and stroboscopic illumination

      Microscopic OCT imaging with focus extension by ultrahigh-speed acousto-optic tunable lens and stroboscopic illumination

      We develop high-resolution optical coherence tomography (OCT) system with high-speed acousto-optic tunable lens. Stroboscopic pulsed illumination is used for the first time to perform time-resolved OCT imaging with acousto-optic tunable focusing. The operation of ultrahigh-speed tunable acousto-optic lens is demonstrated theoretically and experimentally. Focal position tuning at MHz frequency range is experimentally shown in the imaging system leading to OCT images with extended depth of focus. Imaging with active optical elements is helpful for improvement of photon collection efficiency, depth of focus and enhancement of the image quality.

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    23. Feature Of The Week 11/9/14: Dynamics of a Short Cavity Swept Source OCT Laser

      Feature Of The Week 11/9/14: Dynamics of a Short Cavity Swept Source OCT Laser

      Great advances in OCT speed and sensitivity have been possible due to the introduction of fast frequency swept laser sources. One of the most commonly used swept source devices is a short (~5 cm) cavity Fabry-Perot laser. We present both experimental characterisation and numerical modelling of such an OCT swept source and also analyse the underlying physics to better understand how such sources may be optimised. For the experimental characterisation we use a high-speed digital oscilloscope for real time analysis of the fast temporal intensity and frequency evolution. For the theoretical analysis we use a set of delay differential equations ...

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    24. Quantitative optical inspection of contact lenses immersed in wet cell using swept source OCT

      Quantitative optical inspection of contact lenses immersed in wet cell using swept source OCT

      We demonstrate swept source optical coherence tomography (OCT) imaging of contact lenses (CLs) in a wet cell and comprehensive quantitative characterization of CLs from volumetric OCT datasets. The approach is based on a technique developed for lens autopositioning and autoleveling enabled by lateral capillary interactions between the wet cell wall and the lens floating on the liquid surface. The demonstrated OCT imaging has enhanced contrast due to the application of a scattering medium and it improves visualization of both CL interfaces and edges. We also present precise and accurate three-dimensional metrology of soft and rigid CLs based on the OCT ...

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    1-24 of 91 1 2 3 4 »
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    1. (89 articles) Maciej Wojtkowski
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    Flow velocity estimation using joint Spectral and Time domain Optical Coherence Tomography Comparison of reflectivity maps and outer retinal topography in retinal disease by 3-D Fourier domain optical coherence tomography Ultra high-speed swept source OCT imaging of the anterior segment of human eye at 200 kHz with adjustable imaging range High-speed optical coherence tomography: basics and applications 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 Faster, wider, deeper: imaging advances in focus at Hot Topics session University of Alabama Receives NIH Grant for In Vivo Ultrastructure of Chorioretinal Disease UC Davis Receives NIH Grant for Studying Properties of Photoreceptors and Muller Cells Investigated with AO-OCT Convolutional Mixture of Experts Model: A Comparative Study on Automatic Macular Diagnosis in Retinal Optical Coherence Tomography Imaging Intracameral air injection after completion of phacoemulsification cataract surgery: Evaluation of corneal incisions with optical coherence tomography Structure-function relationships in glaucoma using enhanced depth imaging optical coherence tomography-derived parameters: a cross-sectional observational study Impact of Accumulated Serum Uric Acid on Coronary Culprit Lesion Morphology Determined by Optical Coherence Tomography and Cardiac Outcomes in Patients with Acute Coronary Syndrome